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The effects of a pilot-scale steam decontamination system on the hygiene and sensory quality of chicken carcasses
Journal Pre-proof The effects of a pilot-scale steam decontamination system on the hygiene and sensory quality of chicken carcasses Cathrine F. Kure, Lars Axelsson, Mats Carlehög, Ingrid Måge, Merete R. Jensen, Askild Holck PII:
S0956-7135(19)30537-7
DOI:
https://doi.org/10.1016/j.foodcont.2019.106948
Reference:
JFCO 106948
To appear in:
Food Control
Received Date: 11 September 2019 Revised Date:
9 October 2019
Accepted Date: 10 October 2019
Please cite this article as: Kure C.F., Axelsson L., Carlehög M., Måge I., Jensen M.R. & Holck A., The effects of a pilot-scale steam decontamination system on the hygiene and sensory quality of chicken carcasses, Food Control (2019), doi: https://doi.org/10.1016/j.foodcont.2019.106948. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
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The effects of a pilot-scale steam decontamination system on the hygiene and sensory quality of
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chicken carcasses
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Cathrine F. Kure*, Lars Axelsson, Mats Carlehög, Ingrid Måge, Merete R. Jensen, and Askild Holck
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Nofima - Norwegian Institute of Food, Fisheries and Aquaculture Research, P. O. Box 210, N-1431
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Aas, Norway
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Key words: Salmonella Enteritidis, Campylobacter jejuni, chicken, decontamination, steam
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Author for correspondence
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*Cathrine F. Kure, Tel.: 0047 64970100, E-mail: [email protected]
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Declaration of interest: None
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Abstract Salmonella and Campylobacter represent the two most commonly reported zoonoses in EU
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and cause a significant health burden. The effects of a prototype steam treatment system
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(Deconizer) on reduction of aerobic bacteria, Salmonella Enteritidis and Campylobacter jejuni on
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chicken carcasses were investigated in the present study. In addition, the treated chicken carcasses
23
were subjected to sensory analysis. The system tested is intended to be integrated as part of chicken
24
production lines to give a short steam treatment to the carcasses during processing.
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Freshly slaughtered eviscerated chicken carcasses were transported from the slaughterhouse
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to a Pathogen Pilot Plant facility. The chicken carcasses were treated with steam in the Deconizer for
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3 s or 5 s at 95 °C or 120 °C. For determination of reduction of aerobic bacteria, the surface of
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chicken carcasses was sampled at three different places: breast, outer side of leg/thigh and wing on
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the left side of the carcasses before steam treatment (controls) and on the right side of the carcasses
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after steam treatment. For investigation of the reduction of S. Enteritidis and C. jejuni, a surface area
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of 2x5 cm2 was inoculated with 20 µl mix of the bacteria strains and spread over 10 cm2 on breasts,
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legs and wings on the left and right sides. Bacteria were subsequently sampled before steam
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treatments (left side) and after treatments (right side).
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The Deconizer steam treatment chamber substantially reduced aerobic bacteria, Salmonella
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and Campylobacter on chicken carcasses within a few seconds. The reduction was 1.22 - 3.33 log for
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aerobic bacteria, 1.36 - 3.05 log for Salmonella Enteritidis and 0.84 - 4.32 log for Campylobacter
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jejuni. Reductions of bacteria varied strongly with sampling place and treatment time.
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treatments for 5 s gave consistently higher reductions than 3 s at both 95 °C and 120 °C, on both
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breast, legs and wings, and the reduction on breast was higher than on legs and wings.
Heat
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The method will not impede the speed of poultry processing and gives only marginal sensory
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changes in the appearance of the carcasses. The method employs no chemicals and can easily be
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implemented in chicken facilities to enhance food safety. 2
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1. Introduction
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Foodborne diseases represent a huge health burden and continuous work is needed in order
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to reduce the incidences of foodborne outbreaks. Campylobacteriosis was by far the most commonly
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reported zoonosis in EU in 2017, representing almost 70% of the cases, and has been the most
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frequently reported of the zoonoses in EU since 2005 (EFSA/ECDC, 2018). The prevalence has been
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essentially unchanged over the period 2013 - 2017. About 24 % of the strong evidence food borne
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outbreaks caused by Campylobacter were linked to broiler meat and their products. The EU member
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states monitoring program on Campylobacter in animals showed that more than 12% of the sample
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units (single and batch samples) originated from broilers (EFSA/ECDC, 2018).The highest occurrences
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were observed in fresh meat from broilers with 37.4% positive units. As of January 1, 2018
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Regulation (EC) No. 2017/1495 amending Regulation (EC) No. 2073/2005 states that the limit of
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<1,000 cfu Campylobacter spp./g applies for poultry carcasses after chilling (European Union
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Commission, 2017).
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Salmonellosis was the second most frequently reported zoonosis in EU in 2017 representing
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almost 27 % of the cases (EFSA/ECDC, 2018). The EU notification rate has remained at the same level
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the last 5 years. About 2 % of the strong evidence food borne outbreaks were linked to Salmonella in
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broiler meat and their products. In total, 7.5 % of fresh chicken meat analysed tested positive for
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Salmonella. EU legislation requires absence of Salmonella in 25 g of pooled samples of neck skin of
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poultry carcasses of broilers and turkeys (Anon, 2005).
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According to the Food and Agriculture Organization of the United Nations (FAO), the average
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annual consumption of chicken meat pro capita worldwide increased from 10.2 kg in 1999 to 13.8 kg
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in 2015 (Bruinsma, 2015). The global meat consumption is projected to rise more than 4% per
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person over the next 10 years, and for poultry it is predicted to rise more than 10% (OECD/FAO,
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2016). As live poultry animals contain microorganisms on their skin, feathers, and in their digestive
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tract, contamination of the carcasses during slaughtering procedures can not be completely avoided
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when live animals are converted to meat for consumption. There is therefore a great interest in
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methods that could contribute to reducing the level of bacteria on carcasses, particularly harmful
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bacteria.
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Since chicken is one of the animals with highest incidence of both Campylobacter and
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Salmonella, different decontamination strategies have been tested to reduce these bacteria.
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Intervention strategies to control contamination during poultry slaughter have been reviewed
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(Buncic & Sofos, 2012; Loretz, Stephan, & Zweifel, 2010). Many methods for decontamination are
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allowed in the USA such as use of organic acids and salts thereof, fermentates, sorbates, chlorine
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compounds, cetylpyridinium chloride, ozone and washing with trisodium phosphates. Allowed
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compounds and strategies are listed by FDA (FDA, 2019). Decontaminations considered for use first
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need to be validated for their efficacy and then should be regularly verified for continuous
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effectiveness during implementation (see references in (Buncic & Sofos, 2012)). In the European
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Union (EU), the EC regulation No 853/2004 allows decontamination treatments to be considered if
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shown to be safe and effective and not to conceal poor hygiene practices. Decontamination must
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always be considered as part of an integrated food safety system. Decontamination interventions
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with other substances than water need prior approval in the EU (EFSA, 2010). So far the only
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compound approved for use is lactic acid up to 5 % on bovine carcasses (European Commission,
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2013). Still other compounds have been evaluated by EFSA, but are not approved for use.
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Freezing of broiler meat is efficient for reduction of Campylobacter (Rosenquist, Nielsen,
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Sommer, Norrung, & Christensen, 2003). More than 90% risk reduction can be obtained by freezing
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carcasses for 2-3 weeks. A 50-90% risk reduction can be achieved by freezing for 2-3 days (Boysen,
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Wechter, & Rosenquist, 2013; EFSA, 2011).
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The use of steam for decontamination or reduction of the natural flora has been explored by
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several authors. The main advantage of using steam is the large amount of heat transferred to the
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food when steam condenses, which increases the surface temperature rapidly. Steam at 100 °C has a
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greater heat content than the same amount of water at that temperature. In addition, steam has the
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ability to penetrate cavities, crevices and feather follicles (James, Goksoy, Corry, & James, 2000).
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Virtually complete elimination of microorganisms was achieved by exposing chicken carcasses with
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flowing steam (96-98 °C) for 3 min (Avens, et al., 2002). Steam treatment at 100 °C for 10 s reduced
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the natural flora by 1.65 log, however, the samples appeared to be partially cooked (James, et al.,
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2000), while insignificant reductions of total viable counts were obtained after steam treatment of
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broiler carcasses at 90 °C for 12 s (Whyte, McGill, & Collins, 2003). A 1.8 and 3.3 log reduction of
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Campylobacter jejuni was achieved when broiler carcasses were treated in steam cabinets for 10 s
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and 20 s, respectively, but in these cases the skin shrank and changed colour (James, et al., 2007).
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When disks of poultry skin were treated with superheated steam, more than 5 log reduction of
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Listeria innocua was obtained after 30 s of treatment (Kondjoyan & Portanguen, 2008). Differences in
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reduction between superheated and non-superheated steam were only detected after more than 10
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s treatment. The combination of steam and ultrasound treatment of broilers gave promising results
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with approximately 1.0 log reduction of Campylobacter and 0.7 log reduction in total viable count
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(Musavian, Krebs, Nonboe, Corry, & Purnell, 2014).
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In slaughterhouses chickens are processed at speeds up to 200 carcasses/min (James, et al.,
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2000). Optimal decontamination techniques should be an integrated part of the production line and
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not increase the production time significantly. In addition, the chicken should not show any
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undesired sensory changes after the treatment.
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The aim of this study was to evaluate the effect of a prototype steam treatment system
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(Deconizer) on reduction of aerobic bacteria, Salmonella Enteritidis and C. jejuni on chicken
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carcasses. The system is intended to be integrated as part of the chicken production line to give a
115
short steam treatment to the carcasses. In addition to microbial analyses, sensory analysis of the
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treated chicken carcasses was carried out.
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2. Material and methods
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2.1. Bacterial strains and culture preparation
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S. Enteritidis and C. jejuni strains used in decontamination experiments are listed in Table 1.
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The strains originated from poultry or culture collections. Rifampicin (Rif, Sigma-Aldrich, St. Louis,
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USA) resistant (RifR) derivatives were prepared by growing strains in liquid media containing 200
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µg/ml Rif as described by Heir et al. (Heir, et al., 2010). The Salmonella strains were maintained at 80
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°C in Tryptic soy broth (TSB, Oxoid Ltd, Basingstoke, UK) supplemented with 20% glycerol (v/v). For
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each experiment, the Salmonella strains were plated separately on tryptic soy agar (TSA) with 200
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µg/ml Rif and incubated 37 °C overnight. Two-three colonies from the TSA agar plates were
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transferred to TSB supplemented with 200 µg/ml Rif and incubated at 37 °C overnight. A 1:100
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dilution of the TSB culture was thereafter transferred to TSB with 200 µg/ml Rif, and incubated at 37
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°C overnight. Appropriate dilutions were prepared in peptone water, the strains were mixed in equal
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amounts and used for inoculation of the chicken carcasses. Campylobacter strains were stored at -80
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°C in Müller-Hinton (MH) supplemented with 20% glycerol (v/v). Strains were plated on MH agar
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supplemented with 100 µg/ml Rif and incubated in microaerophilic environment at 37 °C for 3 days.
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A 10µl loop of culture was transferred to MH broth with 100 µg/ml Rif in baffled Erlenmeyerflasks
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and incubated microaerophilicly at 37 °C with 150 rpm shaking for 3 days. One ml of the cultures
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was then transferred to 30 ml fresh MH-broth with 100 µg/ml Rif and incubated microaerophilicly in
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baffled Erlenmeyer flasks at 37 °C with 150 rpm shaking for 2 days. These cultures were used for the
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inoculation experiment. Appropriate dilutions were prepared in peptone water, the strains were
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mixed in equal amounts and used for inoculation of the chicken carcasses.
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2.2. Sample preparation and inoculation procedures
Freshly slaughtered eviscerated chicken carcasses were packaged warm in separate plastic
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bags and transported from the slaughterhouse to the Pathogen Pilot Plant facility (see below) in
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styrofoam boxes. The warm chicken carcasses were hung up on the processing line. For
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determination of aerobic bacteria, the surface of chicken carcasses was sampled at three different
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places: breast, outer side of leg/thigh and wing on the left side of the carcasses before steam
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treatment (controls) and on the right side of the carcasses after steam treatment. A surface area of
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2x5 cm2 was swabbed using FLOQswab swabs (Copan Diagnostics Inc., CA, USA) that were wetted in
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peptone water before use. After swabbing, the swabs were placed in 2 ml peptone water and kept
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refrigerated until plating. For comparison with swabbing, some chickens were analyzed by collecting
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skin samples. In these cases, 2x5 cm2 skin from before and after heat treatments was mixed
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separately with 10 ml peptone water and stomached for 1 min in a Smasher (AES Laboratoire,
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Chemunex, Combourg, France). Samples were kept refrigerated until plating.
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2.3. Inoculation of chicken carcasses with Salmonella and Campylobacter
The chicken carcasses were inoculated with 20 µl mix of the bacteria strains and spread over
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10 cm2 using an L-shape spreader at three different places: breast, outer side of leg/thigh and wing.
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Both on the left and right sides of the chicken were inoculated. The bacteria were left on the skin for
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five minutes before the left inoculated breast, leg/thigh and wing areas were swabbed with
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prewetted FLOQswab swabs. The swabs were placed in 2 ml peptone water for Salmonella or 2 ml
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MH broth for Campylobacter and kept refrigerated until plating. The Campylobacter containing
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swabs, kept in MH broth were stored microaerophilicly (Oxoid, CampyGen) in tubes until plating. The
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chickens were then subjected to steam treatment before the inoculated sites on the right side were
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sampled in the same manner.
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2.4. Steam treatments
The experimental apparatus (Deconizer) is an industrial scale decontamination equipment. The apparatus consists of a steam tunnel that is 6 m long, a control unit, a steam generator,
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superheaters, a steam exhaust system and a motorized conveyor to transport the chickens trough
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the steam tunnel. The Deconizer has a frame of steel and a chamber with Teflon covered plates. The
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central steam treatment cabinet is approximately 1.5 m long and provided with steam nozzles that
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lead the steam to the chickens passing through the cabinet. In addition, there are some steam
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nozzles at each end of the steam cabinet. The steam was generated in a Steamrator (Steamrator Oy,
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Finland) with a capacity of approx. 100 kW. The steam passes from the steam generator through
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superheaters that increased the temperature of the steam up to 120 °C (at atmospheric pressure). A
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sensor (Spiro TVA flowmeter) registered the pressure, energy use and quantity of steam. At normal
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settings the steam pressure was approx. 4.3 bar. Low speed (45 Hz) of the conveyor gave a speed
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that was equivalent to each chicken getting steam for 5 s. High speed (75 Hz) gave a speed gave 3 s
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steaming of the chickens. The Deconizer could be adjusted by changing temperature and pressure of
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the steam, varying opening of the nozzles and the distance from the nozzles to the carcasses. The
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experiments were performed in a Biosafety level 3 Pathogen Pilot Plant facility.
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2.5. Analysis of cells
After heat treatments, swabs were vortexed and bacteria plated on to total plate count agar
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(PCA) for total aerobic counts. Five hundred μl were plated directly on the agar plate. In addition,
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undiluted and 1:10 dilutions were plated using an automated plate spreader (Whitley Automatic
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Spiral Plater, Don Whitley Scientific Ltd., West Yorkshire, UK) and incubated at 20 °C for 4 days. The
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number of colonies were determined using an automatic plate reader. Swab samples from the
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Salmonella inoculated chicken carcasses were plated on TSA with 200 µg/ml Rif and incubated at 37
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°C for 1-2 days. Swab samples of the chicken carcasses inoculated with Campylobacter were plated
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on MH agar with 100 µg/ml Rif and incubated microaerophilicly (Oxoid™ CampyGen™ 3.5L Sachet,
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Thermo Fisher Scientific, Mass, USA) at 37 °C for 4 days. Since RifR strains were used, the background
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flora for the Salmonella and Campylobacter determinations were negligible. 8
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2.6. Sensory analysis
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Chicken carcasses treated in the steam cabinet and control chickens were stored in plastic
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bags at +4 °C for 1 day and 6 days before sensory analyses. A highly trained panel of 9 assessors (9
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women, aged 37-64 years) at Nofima performed a sensory descriptive analysis (DA) according to
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“Generic Descriptive Analysis” as described by Lawless & Heymann (Lawless & Heymann, 2010) and
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the ISO standard 13229 (Anon., 2016). The assessors are regularly tested and trained according to
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ISO standard 8586 (Anon., 2012), and the sensory laboratory follows the practice of ISO standards
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8589 (Anon, 2007). The assessors agreed upon seven attributes describing the chicken carcasses with
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skin: color hue, color intensity, whiteness, color uniformity, glossiness, degree of goose bumps and
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dried skin surface. For carcasses with breast skin removed, the same attributes were evaluated
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except for degree of goose bumps, which was omitted. Chicken carcasses were put on coded baking
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paper and set out in a sensory booth for evaluation. Each carcass was evaluated by each assessor
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with and without skin in two separate sessions, first session with skin and second session without
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skin (the same chickens where the skin was removed after the first session). All attributes were
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assessed on an unstructured line scale with labelled endpoints going from “no intensity” (1) to “high
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intensity” (9). Each assessor evaluated all samples at individual speed on a computer system for
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direct recording of data (EyeQuestion, Software Logic8 BV, Utrecht, The Netherlands) using tablets.
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The coded chicken samples, from 4 series and control and 5 replicates were evaluated and served in
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a randomized experimental design for each session, in total 25 samples per session. The DA was
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performed during two following weeks, first week 1 day of storage and week two 6 days of storage.
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In a pre-test session before the main test, the assessors were calibrated on samples that were
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considered the most different on the selected attributes typical for the chicken carcass samples to be
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tested.
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2.7. Experimental design and statistical analysis Four treatments were compared in the main experimental setup, following a 22 factorial
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design with factors Temperature (95°C or 120°C) and Time (3s or 5s), and three sites were sampled
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on every carcass (breast, leg/thigh and wing). Seven carcasses were treated in each experimental
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run, based on power estimations showing that a difference of one log could be detected with a
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power of 95% at alpha=0.05. Each treatment was repeated three times on different days, for each of
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Total aerobic bacteria, Salmonella and Campylobacter. In addition to the main experiment, some
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extra tests were run to investigate the effects of nozzle opening and distance from nozzles to carcass.
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Split-plot analysis of variance (ANOVA) models with fixed factors Temperature, Time and
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Sample site were fitted to each of the response variables Total aerobic bacteria, Salmonella and
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Campylobacter. All bacteria counts were transformed to log values before analysis. The analyses
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were performed in R (R_Core_Team, 2016). Details from the statistical analysis are presented in the
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supplemental material.
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Data from the sensory descriptive analysis were evaluated with mixed effects ANOVA, where
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product was considered fixed while the assessor and interaction effects including assessor were
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considered random. Tukey multiple comparison test was used to determine significant differences
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between products (P<0.05). The statistical software used for the sensory analysis was EyeOpenR
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(Logic8 BV).
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3. Results
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3.1. Reduction of aerobic bacteria on heat treated chicken carcasses
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Chicken carcasses were subjected a steam treatment of 95 °C for 5 s. Twenty one chickens were analysed for reduction of aerobic counts on the breast by swabbing, while seven were analysed 10
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by cutting and removing skin and extraction of the bacteria by stomaching. Both methods gave the
242
same reduction and the more convenient swabbing method was used in the experiments (see
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Supplemental Materials).
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Chicken carcasses with naturally occurring bacteria were steam treated in the Deconizer at
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different temperatures for different times (95 °C and 120 °C, for 3 s and 5 s). The surfaces of the
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chicken carcasses were swabbed at breast, leg/thigh and wing before and after the treatment. The
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steam treatments reduced the total bacteria count in the range 2.45 - 3.3 log on breast, 1.37 - 1.88
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log on legs and 1.22 - 1.78 log on wings depending on the conditions used (Table 2). The log
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reduction was significantly higher on breast compared to legs and wings, and the log reduction was
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significantly higher when the chickens were treated for 5 s compared to 3 s at the same temperature
251
(see statistical analysis, Supplemental Materials). There were no significant differences between the
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reductions at 120 °C compared to 95 °C for the same time treatments.
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The Deconizer system was tested by increasing the distance from the nozzles to the chicken
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carcasses in the steam chamber. A lower log reduction was observed for breast, but there was no
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statistically significant difference for legs and wings. The Deconizer was also tested with fully open
256
steam nozzles. A tendency for enhanced log reduction was seen when the nozzles were fully open.
257
Se Supplemental materials for details.
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259
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3.2. Reduction of Salmonella on heat treated chicken carcasses
Chicken carcasses were inoculated with S. Enteritidis. The steam treatments gave significant
261
reduction of Salmonella on breast, legs and wings (Table 2). The reductions of Salmonella were in the
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range 2.11 - 3.05 log on breast, 1.69 - 2.40 log on legs, and 1.36 - 1.92 log on wings. The reduction
263
was significantly higher on breast compared to legs and wings, and the log reduction was significantly
264
higher when the chickens were treated for 5 s compared to 3 s at the same temperature. There were 11
265
no significant differences between the reductions at 95 °C compared to 120 °C for the same time
266
treatments.
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3.3. Reduction of Campylobacter on heat treated chicken carcasses
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For chicken carcasses inoculated with Campylobacter, log reductions after steam treatments
270
were in the range 3.65 - 4.32 with 5 s treatment on breast, 2.76 - 3.18 log on legs and 2.45 - 2.65 log
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on wings (Table 2). Reductions for 3 s treatments were significantly lower. However, the reductions
272
were 1.7 log for breast , 1.34 - 1.96 log for legs, and 0.84 - 1.37 log for wings. There was a
273
statistically significant difference between experimental days for Campylobacter, which was adjusted
274
for by including it as a random factor in the model (see Supplemental Material). The ANOVA revealed
275
a significant interaction between inoculation site and time, caused by the fact that increasing the
276
time from 3 to 5 seconds has a larger effect on the breast than on the legs and wings (Suppl. Material
277
Figure. 4).
278
One series of chicken carcasses was treated twice in the chamber (2 x 5 s) at 120 °C. The
279
carcasses got a cooked appearance. Hence, there is an upper limit of treatment time possible before
280
visual changes become apparent.
281 282
The Enterobacteriaceae level on the chicken carcasses varied and often the levels were very low. It was therefore difficult to get good results for reduction of Enterobacteriaceae.
283
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285 286
3.4. Sensory evaluation
Chicken carcasses treated in the steam cabinet and control chickens were stored in plastic bags at 4 °C for 1 day and 6 days before analysing visually sensory properties of the chicken carcasses
12
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with and without skin (Figs. 1 and 2). After 1 and 6 days of storage the untreated chickens with skin
288
obtained a higher score on the attribute glossy appearance. There were some variations in several of
289
the other attributes as well, however they were small, and appeared not to be correlated with the
290
extent of treatments. For chickens without skin only small differences were detected.
291
292 293
4. Discussion The microbial reduction after steam treatment varied with where on the chicken the samples
294
were taken. The reductions were markedly higher on breast skin than on legs and wings for both
295
total aerobic bacteria, Salmonella and Campylobacter. The skin on the breast is thinner than on the
296
wings and legs where the skin also often is more folded. The temperature rise varies with skin
297
thickness with thinner skin reaching higher temperatures leading to enhanced heat reduction of
298
bacteria (Kondjoyan & Portanguen, 2008). The folds and crevices of the thicker skin and feather
299
follicles may provide protection for bacteria so they will not experience the same heat as those
300
exposed on the surface. Tentatively, one could argue that since breast skin passes directly in front of
301
the nozzles and are directly hit by the blowing steam while wings and legs are at 90 degrees angle
302
away from the nozzles, one would expect higher kill on the breast skin. This has, however, not been
303
systematically investigated. Likewise, we also do not know whether the steam treatment may also
304
give a mechanical effect when the steam blows directly on the breast compared to wings and legs.
305
Previously reported steam treatment experiments usually only give results from chicken breast skin,
306
so it is difficult to compare previous results with our reductions on thighs and wings.
307
Reductions of bacteria also varied strongly with treatment time. Heat treatments for 5 s
308
gave consistently higher reductions than 3 s at both 95 °C and 120 °C, on both breast, legs and wings.
309
Heating is perhaps the most common way of reducing bacteria and longer heat treatment will
310
normally give enhanced reduction of bacteria and hence the results are as expected. Previous
311
examinations on heat treatments report varying results depending on the time of the treatment.
13
312
Insignificant reductions of total viable bacteria, Enterobacteriaceae and thermophilic Campylobacter
313
were obtained after a steam treatment of 90 °C for 12s (Whyte, et al., 2003). When chicken breast
314
was treated for 100 °C for 10s, 1.65 log reduction of total viable bacteria was observed, but the skin
315
appeared cooked (James, et al., 2000). C. jejuni and E. coli were reduced by 1.8, 2.6 and 3.3 log and
316
1.7, 2.3 and 2.8 log after 10s, 12s and 20s treatments, respectively, but also here the skin appeared
317
cooked (James, et al., 2007). When chicken carcass skin was exposed to flowing steam at 96-98 °C for
318
3 min, < 10 aerobic microbes were present per cm2 (Avens, et al., 2002). The upper limit of steam
319
treatment depends on further treatment of the carcass. More intense steam treatments will lead to
320
a cooked appearance of the skin. This may be of importance if the chicken is later to be sold as raw
321
meat. If the meat is intended for further heat processing in the factory, it may not be important.
322
When chickens were exposed to a combination of heat (90-94 °C) and ultrasound (30-40 kHz), a 0.90
323
log reduction of Campylobacter was achieved (Musavian, et al., 2014).
324
Bacteria usually start dying at temperatures around 60 °C and are increasingly sensitive
325
above this temperature. For example, the D-value of E. coli is reduced from around 1 h to 2 min as
326
the temperature increases from 56 °C to 62 °C (USDA, 2019). Under steam treatments bacteria are
327
killed by the heat transferred from the steam. Much of the heat energy comes from the liberated
328
energy when water gas condenses on the surface of the colder chicken skin. Water gas at 100 °C
329
contains much more energy than the same amount of liquid water at the same temperature. Under a
330
traditional steam treatment, the hot steam contains a mix of water as gas and water droplets. The
331
intention of using superheated steam was to maximize the energy liberated on the chicken skin and
332
thereby obtaining a higher temperature and an enhanced reduction during the short treatment.
333
However, no additional reduction of bacteria was detected when using superheated steam
334
compared to non-superheated steam for the same times. Apparently, both temperatures used in the
335
study are far above inactivation temperature of the vegetative bacteria and thus no additional
336
reduction was detected. When disks of poultry skin were inoculated with L. innocua and then
337
subjected to steam at 95 °C and superheated steam at 400 - 450 °C, approx. 2.5 log reduction was 14
338
obtained after 10s regardless of the method used (Kondjoyan & Portanguen, 2008). After longer
339
treatments (20 - 45 s), the superheated steam treatments clearly gave higher reduction. The results
340
were variable and the rise in temperature appeared to be related to the thickness of the chicken skin.
341
In order to optimize the system and achieve as high log reduction as possible, the system was
342
tested with different distances from the nozzles to the chicken carcass in the chamber, and with
343
varying the opening of the nozzles for steam, to investigate if this could increase the log reduction
344
further. Increasing the distance from the nozzles to the chicken showed reduced log reduction on
345
breast but not on legs and wings. The distance from the nozzles to the chicken may therefore
346
influence on the reduction of bacteria. There were also seen a tendency for enhanced log reduction
347
when the nozzles where fully open. Only a few experiments where performed for this. Hence, this
348
needs to be investigated further in the development of the next generation Deconizer. One series
349
with chicken carcasses was treated two times in the chamber (2 x 5 s) at 120 °C. This gave cooked
350
appearance on the surface of the chicken and was therefore not investigated further.
351
Different authors obtain varying results after steam treatments due to different treatment
352
regimes, using different steam delivery equipment, different temperatures on the steam and
353
different treatment times. It is therefore difficult to compare directly results from different groups.
354
The amount of steam used and the initial temperature on the skin, whether refrigerated or warm,
355
simulating newly slaughtered chickens that are used may also influence the results. This is due to the
356
fact that refrigerated skin will reach a lower temperature during a treatment and in addition because
357
stationary phase cells on refrigerated samples are more heat resistant (Kaur, Ledward, Park, &
358
Robson, 1998). The Deconizer was efficient for reduction of both total aerobic bacteria, S. Enteritidis
359
and C. jejuni inoculated on the chicken breast with up to 3.30, 3.05 and 4.32 log reduction,
360
respectively, during a 5 s heat treatment. The high reduction, compared to previous results, was
361
probably caused by the efficient steam generation leading to a high heat transfer to the carcasses.
15
362
Another benefit of the Deconizer is the treatment capacity. It can be implemented on the slaughter
363
line without reduction of slaughtering efficiency.
364
The sensory analysis carried out on heat treated chicken at days 1 and 6 showed that the
365
changes in attributes generally were small and appeared to follow a random pattern. For the samples
366
analysed with skin, only glossy appearance was higher on untreated chicken carcasses. The
367
importance of this seem to be minor since the other parameters such as color tone, color strength,
368
whiteness, dryness and tightness of skin were close to their respective controls, and the consumer
369
will probably not experience glossiness alone as a parameter for treated or cooked chicken carcasses.
370
When the breast skin of heat-treated chicken was removed, and the breast muscles evaluated, only
371
minor non-systematic changes were recognized. In conclusion, there was only very minor sensory
372
changes on the treated chicken carcasses. Since doubling the exposure time to 10 s at 120 °C gave a
373
cooked appearance, the optimal treatment time must be carefully determined. From the sensory
374
analysis the shelf life of treated chickens appeared to be similar to that of untreated controls. We did
375
not do a microbial study on shelf life of treated carcasses. When chicken portions were subjected to
376
steam at 100 °C for 10 s, a 1.65 log reduction of the total viable bacteria were obtained (James, et al.,
377
2000). When comparing with untreated chicken portions, the cell counts of treated chicken remained
378
lower until day 3 of storage at 3 °C, but were essentially the same as those of untreated carcasses at
379
day 5, so no extension of the shelf-life was observed. However, from a food safety perspective
380
pathogens on the chickens would be substantially reduced by the treatment. In a quantitative risk
381
assessment of human campylobacteriosis associated with thermophilic Campylobacter species in
382
chickens, it was calculated that campylobacteriosis in conjunction with consumption of chicken meals
383
could be reduced 30 times by introducing a 2 log reduction of the number of Campylobacter on the
384
chicken carcasses (Rosenquist, et al., 2003).
385
In summary, we have shown that the Deconizer steam treatment chamber can substantially
386
reduce total aerobic bacteria, Salmonella and Campylobacter on chicken carcasses within a few
387
seconds in a steam chamber designed for implementation on a chicken slaughter line. The method 16
388
will not impede the speed of poultry processing and gives only marginal sensory changes in the
389
appearance of the carcasses. The method employs no chemicals and can be easily implemented in
390
the chicken facilities to enhance food safety.
391 392
ACKNOWLEDGMENTS
393
We thank the trained sensory panel at Nofima for carrying out the sensory evaluation, and Janina
394
Berg for excellent technical assistance. The work was funded by grants to the projects 248928,
395
221663 and 262306 financed by the Research Council of Norway, Ministry of Agriculture and Food
396
and the Research Levy on Agricultural Products, respectively.
397 398
SUPPLEMENTAL MATERIAL
399
Supplemental materials associated with this article can be found online at:
400
[URL to be completed by the publisher].
17
401
References
402
Anon. (2005). Commission regulation (EC) No 2073/2005 of November 2005 on microbiological
403 404 405 406 407 408 409 410
criteria for foodstuffs. Official Journal of the European Union, 338(1-26). Anon. (2007). ISO 8589 Sensory analysis - General guidance for the design of test rooms. Geneva, Switzerland. Anon. (2012). Sensory analysis - General guidance for selection, training and monitoring of selected sensory assessors and expert assessors. Geneva, Switzerland. Anon. (2016). ISO 13229 Sensory analysis - General guidance for establishing a sensory profile. Geneva, Switzerland: International Organization for Standardization. Avens, J. S., Albright, S. N., Morton, A. S., Prewitt, B. E., Kendall, P. A., & Sofos, J. N. (2002).
411
Destruction of microorganisms on chicken carcasses by steam and boiling water immersion.
412
Food Control, 13(6-7), 445-450.
413
Boysen, L., Wechter, N. S., & Rosenquist, H. (2013). Effects of decontamination at varying
414
contamination levels of Campylobacter jejuni on broiler meat. Poultry Science, 92(5), 1425-
415
1429.
416 417 418 419 420
Bruinsma, J. (2015). World agriculture: towards 2015/2030 an FAO perspective. http://www.fao.org/3/a-y4252e.pdf: FAO. Buncic, S., & Sofos, J. (2012). Interventions to control Salmonella contamination during poultry, cattle and pig slaughter. Food Research International, 45(2), 641-655. EFSA. (2010). Revision of the joint AFC/BIOHAZ guidance document on the submission of data for the
421
evaluation of the safety and efficacy of substances for the removal of microbial surface
422
contamination of foods of animal origin intended for human consumption. EFSA Journal,
423
8(4), 1544.
424
EFSA. (2011). Scientific Opinion on Campylobacter in broiler meat production: control options and
425
performance objectives and/or targets at different stages of the food chain. EFSA Journal,
426
9(4), 2105. 18
427 428 429
EFSA/ECDC. (2018). The European Union summary report on trends and sources of zoonoses, zoonotic agents and food-borne outbreaks in 2017. EFSA Journal, 16(12). European Commission. (2013). Regulations Commission Regulation (EU) No 101/2013 of 4 February
430
2013 concerning the use of lactic acid to reduce microbiological surface contamination on
431
bovine carcases. Official Journal of the European Union, L34.
432
European Union Commission. (2017). Regulations Commission Regulation (EU) 2017/1495 of 23
433
August 2017 amending Regulation (EC) No 2073/2005 as regards Campylobacter in broiler
434
carcases. Official Journal of the European Union, L218, 1-6.
435 436 437
FDA. (2019). Food Safety and Inspection Service New Technology Information Table. https://www.fda.gov/. Heir, E., Holck, A. L., Omer, M. K., Alvseike, O., Hoy, M., Mage, I., & Axelsson, L. (2010). Reduction of
438
verotoxigenic Escherichia coli by process and recipe optimisation in dry-fermented sausages.
439
International Journal of Food Microbiology, 141(3), 195-202.
440
James, C., Goksoy, E. O., Corry, J. E. L., & James, S. J. (2000). Surface pasteurisation of poultry meat
441
using steam at atmospheric pressure. Journal of Food Engineering, 45(2), 111-117.
442
James, C., James, S. J., Hannay, N., Purnell, G., Barbedo-Pinto, C., Yaman, H., Araujo, M., Gonzalez, M.
443
L., Calvo, J., Howell, M., & Corry, J. E. L. (2007). Decontamination of poultry carcasses using
444
steam or hot water in combination with rapid cooling, chilling or freezing of carcass surfaces.
445
International Journal of Food Microbiology, 114(2), 195-203.
446 447
Kaur, J., Ledward, D. A., Park, R. W. A., & Robson, R. L. (1998). Factors affecting the heat resistance of Escherichia coli O157 : H7. Letters in Applied Microbiology, 26(4), 325-330.
448
Kondjoyan, A., & Portanguen, S. (2008). Effect of superheated steam on the inactivation of Listeria
449
innocua surface-inoculated onto chicken skin. Journal of Food Engineering, 87(2), 162-171.
450 451
Lawless, H. T., & Heymann, H. (2010). Sensory evaluation of food - Principles and Practices (2nd ed.). New York: Springer.
19
452 453 454
Loretz, M., Stephan, R., & Zweifel, C. (2010). Antimicrobial activity of decontamination treatments for poultry carcasses: A literature survey. Food Control, 21(6), 791-804. Musavian, H. S., Krebs, N. H., Nonboe, U., Corry, J. E. L., & Purnell, G. (2014). Combined steam and
455
ultrasound treatment of broilers at slaughter: A promising intervention to significantly
456
reduce numbers of naturally occurring campylobacters on carcasses. International Journal of
457
Food Microbiology, 176, 23-28.
458 459 460 461
OECD/FAO. (2016). OECD-FAO Agricultural Outlook 2016-2025. In. Rome: OECD Publishing, Paris/FAO. R_Core_Team. (2016). R: A language and environment for statistical computing. In. Vienna, Austria: R Foundation for Statistical Computing.
462
Rosenquist, H., Nielsen, N. L., Sommer, H. M., Norrung, B., & Christensen, B. B. (2003). Quantitative
463
risk assessment of human campylobacteriosis associated with thermophilic Campylobacter
464
species in chickens. International Journal of Food Microbiology, 83(1), 87-103.
465
USDA. (2019). Pathogen Modeling Program (PMP) Online.
466
https://pmp.errc.ars.usda.gov/PMPOnline.aspx: United States Department of Agriculture
467
Agricultural Research Service.
468
Whyte, P., McGill, K., & Collins, J. D. (2003). An assessment of steam pasteurization and hot water
469
immersion treatments for the microbiological decontamination of broiler carcasses. Food
470
Microbiology, 20(1), 111-117.
471 472 473 474 475 476 477 478 20
479
Legend to figures
480 481
Figure 1. Sensory properties steam treated chickens with skin after (A) one day and (B) six days of
482
storage in plastic bags at 4 °C. Chickens were exposed to steam at indicated temperatures and times.
483
The intensity of different attributes were registered. 1 = low intensity, and 9 = high intensity. The
484
letters above the columns indicate grouping according to ANOVA and Tukey multiple comparison test
485
at (P<0.05). Samples with the same letter are considered being equal for the specific property.
486 487
Figure 2. Sensory properties steam treated chickens without skin after (A) one day and (B) six days of
488
storage in plastic bags at 4 °C. Chickens were exposed to steam at indicated temperatures and times.
489
The intensity of different attributes were registered. 1 = low intensity, and 9 = high intensity. The
490
letters above the columns indicate grouping according to ANOVA and Tukey multiple comparison test
491
at (P<0.05). Samples with the same letter are considered being equal for the specific property.
492 493
21
494
Table 1. Strains used in this study. Species
Strain/Serotype
Source
MF number RifR,1
Salmonella
1049-1-99
Norwegian Veterinary Institute,
3817
Enteritidis
Norway 61-358-1
Poultry, DTU Vet, National
3818
Veterinary Institute, Denmark
Campylobacter
C484, serotype 1
ATCC130762
3824
Poultry leg
6848
NCTC 11168-BN148Rif3
6856
jejuni
495
1
Reference number of strains after mutating to RifR.
496
2
497
3
American Type Culture Collection, Manassas, VA, USA Original strain from Public Health England, Culture Collection
22
498
Table 2. Mean reductions (log) of total aerobic bacteria on chicken carcasses and mean reductions (log) of Salmonella and
499
Campylobacter inoculated on chicken carcasses, after different steam treatments at three sampling sites
Aerobic bacteria
Salmonella
Campylobacter
500
Treatment
Breast1
Leg/thigh1
Wing1
95 °C 3 s
2.45 (0.70)
1.50 (0.54)
1.22 (0.67)
95 °C 5 s
3.30 (1.08)
1.62 (0.59)
1.70 (0.64)
120 °C 3 s
2.53 (1.03)
1.37 (0.58)
1.47 (0.67)
120 °C 5 s
3.17 (1.08)
1.88 (0.49)
1.78 (0.54)
95 °C 3 s
2.21 (0.40)
1.69 (0.59)
1.36 (0.27)
95 °C 5 s
2.94 (1.11)
2.40 (0.66)
1.90 (0.38)
120 °C 3 s
2.11 (0.77)
1.76 (0.53)
1.50 (0.29)
120 °C 5 s
3.05 (1.09)
2.19 (0.44)
1.92 (0.32)
95 °C 3 s
1.71 (1.26)
1.34 (0.90)
0.84 (0.81)
95 °C 5 s
4.32 (1.30)
2.76 (0.60)
2.65 (0.78)
120 °C 3 s
1.70 (1.10)
1.96 (1.37)
1.37 (1.40)
120 °C 5 s
3.65 (1.76)
3.18 (1.77)
2.45 (2.17)
1
Standard deviations in parentheses 23
501
Figure 1 A.
Control
95°C 3 s
95°C 5 s
120°C 3 s
120°C 5 s
9 8 A
Sensory intensity
7 6
AA
A
5
AAAA A
AB
A
AB AB
B
4
A
AA
BC
AA
B C
C
BCBC AA
3
A AA A
2
AB ABC C BC
1 Color hue 502 503
Color intensity
Whiteness
Color Glossiness uniformity
Goose bumps
Dried skin surface
Figure 1 B. Control
95°C 3 s
95°C 5 s
120°C 3 s
120°C 5 s
9 8 A
Sensory intensity
7 6
AAA
A AAB
B
BC AB C
A
5 4
AB
A
AB AB B AB
BC
B
CD D
B B AB
A AB ABAB
3
B
2
B
ABABAAB
1 Color hue 504
Color intensity
Whiteness
Color Glossiness uniformity
Goose bumps
Dried skin surface
24
505
Figure 2 A.
Control
95°C 3 s
95°C 5 s
120°C 3 s
120°C 5 s
9 8
Sensory intensity
7
A
A A A A
AB A ABC BC C
6 AB
5
A B B
A AB
A
A B
AB
A AB ABC BC C
4 3
A
2
B B B
B
1 Color hue
Color intensity Whiteness
506 507
Color uniformity
Glossiness
Dried skin surface
Figure 2 B.
Control
95°C 3 s
95°C 5 s
120°C 3 s
120°C 5 s
9 8
Sensory intensity
7 6
A
A
A A A
A B
A
5
B
B
AB
A A
A
A
A A A A
B B
AB BCBC
4
C
3 A ABABAB B
2 1 Color hue 508
Color intensity Whiteness
Color uniformity
Glossiness
Dried skin surface 25
Highlights
• • • •
The Deconizer steam treatment effectively reduced aerobic bacteria, Salmonella and Campylobacter with 1.62 log – 4.32 log Treatment time was 5s at 95 °C or 120 °C No negative sensory changes Can easely be implemented in existing production lines
Declaration of interest: None
S0956-7135(19)30537-7
DOI:
https://doi.org/10.1016/j.foodcont.2019.106948
Reference:
JFCO 106948
To appear in:
Food Control
Received Date: 11 September 2019 Revised Date:
9 October 2019
Accepted Date: 10 October 2019
Please cite this article as: Kure C.F., Axelsson L., Carlehög M., Måge I., Jensen M.R. & Holck A., The effects of a pilot-scale steam decontamination system on the hygiene and sensory quality of chicken carcasses, Food Control (2019), doi: https://doi.org/10.1016/j.foodcont.2019.106948. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
1
The effects of a pilot-scale steam decontamination system on the hygiene and sensory quality of
2
chicken carcasses
3 4
Cathrine F. Kure*, Lars Axelsson, Mats Carlehög, Ingrid Måge, Merete R. Jensen, and Askild Holck
5 6 7
Nofima - Norwegian Institute of Food, Fisheries and Aquaculture Research, P. O. Box 210, N-1431
8
Aas, Norway
9 10 11
Key words: Salmonella Enteritidis, Campylobacter jejuni, chicken, decontamination, steam
12 13 14
Author for correspondence
15
*Cathrine F. Kure, Tel.: 0047 64970100, E-mail: [email protected]
16 17
Declaration of interest: None
1
18 19
Abstract Salmonella and Campylobacter represent the two most commonly reported zoonoses in EU
20
and cause a significant health burden. The effects of a prototype steam treatment system
21
(Deconizer) on reduction of aerobic bacteria, Salmonella Enteritidis and Campylobacter jejuni on
22
chicken carcasses were investigated in the present study. In addition, the treated chicken carcasses
23
were subjected to sensory analysis. The system tested is intended to be integrated as part of chicken
24
production lines to give a short steam treatment to the carcasses during processing.
25
Freshly slaughtered eviscerated chicken carcasses were transported from the slaughterhouse
26
to a Pathogen Pilot Plant facility. The chicken carcasses were treated with steam in the Deconizer for
27
3 s or 5 s at 95 °C or 120 °C. For determination of reduction of aerobic bacteria, the surface of
28
chicken carcasses was sampled at three different places: breast, outer side of leg/thigh and wing on
29
the left side of the carcasses before steam treatment (controls) and on the right side of the carcasses
30
after steam treatment. For investigation of the reduction of S. Enteritidis and C. jejuni, a surface area
31
of 2x5 cm2 was inoculated with 20 µl mix of the bacteria strains and spread over 10 cm2 on breasts,
32
legs and wings on the left and right sides. Bacteria were subsequently sampled before steam
33
treatments (left side) and after treatments (right side).
34
The Deconizer steam treatment chamber substantially reduced aerobic bacteria, Salmonella
35
and Campylobacter on chicken carcasses within a few seconds. The reduction was 1.22 - 3.33 log for
36
aerobic bacteria, 1.36 - 3.05 log for Salmonella Enteritidis and 0.84 - 4.32 log for Campylobacter
37
jejuni. Reductions of bacteria varied strongly with sampling place and treatment time.
38
treatments for 5 s gave consistently higher reductions than 3 s at both 95 °C and 120 °C, on both
39
breast, legs and wings, and the reduction on breast was higher than on legs and wings.
Heat
40
The method will not impede the speed of poultry processing and gives only marginal sensory
41
changes in the appearance of the carcasses. The method employs no chemicals and can easily be
42
implemented in chicken facilities to enhance food safety. 2
43
1. Introduction
44
Foodborne diseases represent a huge health burden and continuous work is needed in order
45
to reduce the incidences of foodborne outbreaks. Campylobacteriosis was by far the most commonly
46
reported zoonosis in EU in 2017, representing almost 70% of the cases, and has been the most
47
frequently reported of the zoonoses in EU since 2005 (EFSA/ECDC, 2018). The prevalence has been
48
essentially unchanged over the period 2013 - 2017. About 24 % of the strong evidence food borne
49
outbreaks caused by Campylobacter were linked to broiler meat and their products. The EU member
50
states monitoring program on Campylobacter in animals showed that more than 12% of the sample
51
units (single and batch samples) originated from broilers (EFSA/ECDC, 2018).The highest occurrences
52
were observed in fresh meat from broilers with 37.4% positive units. As of January 1, 2018
53
Regulation (EC) No. 2017/1495 amending Regulation (EC) No. 2073/2005 states that the limit of
54
<1,000 cfu Campylobacter spp./g applies for poultry carcasses after chilling (European Union
55
Commission, 2017).
56
Salmonellosis was the second most frequently reported zoonosis in EU in 2017 representing
57
almost 27 % of the cases (EFSA/ECDC, 2018). The EU notification rate has remained at the same level
58
the last 5 years. About 2 % of the strong evidence food borne outbreaks were linked to Salmonella in
59
broiler meat and their products. In total, 7.5 % of fresh chicken meat analysed tested positive for
60
Salmonella. EU legislation requires absence of Salmonella in 25 g of pooled samples of neck skin of
61
poultry carcasses of broilers and turkeys (Anon, 2005).
62
According to the Food and Agriculture Organization of the United Nations (FAO), the average
63
annual consumption of chicken meat pro capita worldwide increased from 10.2 kg in 1999 to 13.8 kg
64
in 2015 (Bruinsma, 2015). The global meat consumption is projected to rise more than 4% per
65
person over the next 10 years, and for poultry it is predicted to rise more than 10% (OECD/FAO,
66
2016). As live poultry animals contain microorganisms on their skin, feathers, and in their digestive
67
tract, contamination of the carcasses during slaughtering procedures can not be completely avoided
68
when live animals are converted to meat for consumption. There is therefore a great interest in
3
69
methods that could contribute to reducing the level of bacteria on carcasses, particularly harmful
70
bacteria.
71
Since chicken is one of the animals with highest incidence of both Campylobacter and
72
Salmonella, different decontamination strategies have been tested to reduce these bacteria.
73
Intervention strategies to control contamination during poultry slaughter have been reviewed
74
(Buncic & Sofos, 2012; Loretz, Stephan, & Zweifel, 2010). Many methods for decontamination are
75
allowed in the USA such as use of organic acids and salts thereof, fermentates, sorbates, chlorine
76
compounds, cetylpyridinium chloride, ozone and washing with trisodium phosphates. Allowed
77
compounds and strategies are listed by FDA (FDA, 2019). Decontaminations considered for use first
78
need to be validated for their efficacy and then should be regularly verified for continuous
79
effectiveness during implementation (see references in (Buncic & Sofos, 2012)). In the European
80
Union (EU), the EC regulation No 853/2004 allows decontamination treatments to be considered if
81
shown to be safe and effective and not to conceal poor hygiene practices. Decontamination must
82
always be considered as part of an integrated food safety system. Decontamination interventions
83
with other substances than water need prior approval in the EU (EFSA, 2010). So far the only
84
compound approved for use is lactic acid up to 5 % on bovine carcasses (European Commission,
85
2013). Still other compounds have been evaluated by EFSA, but are not approved for use.
86
Freezing of broiler meat is efficient for reduction of Campylobacter (Rosenquist, Nielsen,
87
Sommer, Norrung, & Christensen, 2003). More than 90% risk reduction can be obtained by freezing
88
carcasses for 2-3 weeks. A 50-90% risk reduction can be achieved by freezing for 2-3 days (Boysen,
89
Wechter, & Rosenquist, 2013; EFSA, 2011).
90
The use of steam for decontamination or reduction of the natural flora has been explored by
91
several authors. The main advantage of using steam is the large amount of heat transferred to the
92
food when steam condenses, which increases the surface temperature rapidly. Steam at 100 °C has a
93
greater heat content than the same amount of water at that temperature. In addition, steam has the
94
ability to penetrate cavities, crevices and feather follicles (James, Goksoy, Corry, & James, 2000).
4
95
Virtually complete elimination of microorganisms was achieved by exposing chicken carcasses with
96
flowing steam (96-98 °C) for 3 min (Avens, et al., 2002). Steam treatment at 100 °C for 10 s reduced
97
the natural flora by 1.65 log, however, the samples appeared to be partially cooked (James, et al.,
98
2000), while insignificant reductions of total viable counts were obtained after steam treatment of
99
broiler carcasses at 90 °C for 12 s (Whyte, McGill, & Collins, 2003). A 1.8 and 3.3 log reduction of
100
Campylobacter jejuni was achieved when broiler carcasses were treated in steam cabinets for 10 s
101
and 20 s, respectively, but in these cases the skin shrank and changed colour (James, et al., 2007).
102
When disks of poultry skin were treated with superheated steam, more than 5 log reduction of
103
Listeria innocua was obtained after 30 s of treatment (Kondjoyan & Portanguen, 2008). Differences in
104
reduction between superheated and non-superheated steam were only detected after more than 10
105
s treatment. The combination of steam and ultrasound treatment of broilers gave promising results
106
with approximately 1.0 log reduction of Campylobacter and 0.7 log reduction in total viable count
107
(Musavian, Krebs, Nonboe, Corry, & Purnell, 2014).
108
In slaughterhouses chickens are processed at speeds up to 200 carcasses/min (James, et al.,
109
2000). Optimal decontamination techniques should be an integrated part of the production line and
110
not increase the production time significantly. In addition, the chicken should not show any
111
undesired sensory changes after the treatment.
112
The aim of this study was to evaluate the effect of a prototype steam treatment system
113
(Deconizer) on reduction of aerobic bacteria, Salmonella Enteritidis and C. jejuni on chicken
114
carcasses. The system is intended to be integrated as part of the chicken production line to give a
115
short steam treatment to the carcasses. In addition to microbial analyses, sensory analysis of the
116
treated chicken carcasses was carried out.
117 118
2. Material and methods
119
2.1. Bacterial strains and culture preparation
5
120
S. Enteritidis and C. jejuni strains used in decontamination experiments are listed in Table 1.
121
The strains originated from poultry or culture collections. Rifampicin (Rif, Sigma-Aldrich, St. Louis,
122
USA) resistant (RifR) derivatives were prepared by growing strains in liquid media containing 200
123
µg/ml Rif as described by Heir et al. (Heir, et al., 2010). The Salmonella strains were maintained at 80
124
°C in Tryptic soy broth (TSB, Oxoid Ltd, Basingstoke, UK) supplemented with 20% glycerol (v/v). For
125
each experiment, the Salmonella strains were plated separately on tryptic soy agar (TSA) with 200
126
µg/ml Rif and incubated 37 °C overnight. Two-three colonies from the TSA agar plates were
127
transferred to TSB supplemented with 200 µg/ml Rif and incubated at 37 °C overnight. A 1:100
128
dilution of the TSB culture was thereafter transferred to TSB with 200 µg/ml Rif, and incubated at 37
129
°C overnight. Appropriate dilutions were prepared in peptone water, the strains were mixed in equal
130
amounts and used for inoculation of the chicken carcasses. Campylobacter strains were stored at -80
131
°C in Müller-Hinton (MH) supplemented with 20% glycerol (v/v). Strains were plated on MH agar
132
supplemented with 100 µg/ml Rif and incubated in microaerophilic environment at 37 °C for 3 days.
133
A 10µl loop of culture was transferred to MH broth with 100 µg/ml Rif in baffled Erlenmeyerflasks
134
and incubated microaerophilicly at 37 °C with 150 rpm shaking for 3 days. One ml of the cultures
135
was then transferred to 30 ml fresh MH-broth with 100 µg/ml Rif and incubated microaerophilicly in
136
baffled Erlenmeyer flasks at 37 °C with 150 rpm shaking for 2 days. These cultures were used for the
137
inoculation experiment. Appropriate dilutions were prepared in peptone water, the strains were
138
mixed in equal amounts and used for inoculation of the chicken carcasses.
139 140
141
2.2. Sample preparation and inoculation procedures
Freshly slaughtered eviscerated chicken carcasses were packaged warm in separate plastic
142
bags and transported from the slaughterhouse to the Pathogen Pilot Plant facility (see below) in
143
styrofoam boxes. The warm chicken carcasses were hung up on the processing line. For
144
determination of aerobic bacteria, the surface of chicken carcasses was sampled at three different
6
145
places: breast, outer side of leg/thigh and wing on the left side of the carcasses before steam
146
treatment (controls) and on the right side of the carcasses after steam treatment. A surface area of
147
2x5 cm2 was swabbed using FLOQswab swabs (Copan Diagnostics Inc., CA, USA) that were wetted in
148
peptone water before use. After swabbing, the swabs were placed in 2 ml peptone water and kept
149
refrigerated until plating. For comparison with swabbing, some chickens were analyzed by collecting
150
skin samples. In these cases, 2x5 cm2 skin from before and after heat treatments was mixed
151
separately with 10 ml peptone water and stomached for 1 min in a Smasher (AES Laboratoire,
152
Chemunex, Combourg, France). Samples were kept refrigerated until plating.
153
154
155
2.3. Inoculation of chicken carcasses with Salmonella and Campylobacter
The chicken carcasses were inoculated with 20 µl mix of the bacteria strains and spread over
156
10 cm2 using an L-shape spreader at three different places: breast, outer side of leg/thigh and wing.
157
Both on the left and right sides of the chicken were inoculated. The bacteria were left on the skin for
158
five minutes before the left inoculated breast, leg/thigh and wing areas were swabbed with
159
prewetted FLOQswab swabs. The swabs were placed in 2 ml peptone water for Salmonella or 2 ml
160
MH broth for Campylobacter and kept refrigerated until plating. The Campylobacter containing
161
swabs, kept in MH broth were stored microaerophilicly (Oxoid, CampyGen) in tubes until plating. The
162
chickens were then subjected to steam treatment before the inoculated sites on the right side were
163
sampled in the same manner.
164
165
166 167
2.4. Steam treatments
The experimental apparatus (Deconizer) is an industrial scale decontamination equipment. The apparatus consists of a steam tunnel that is 6 m long, a control unit, a steam generator,
7
168
superheaters, a steam exhaust system and a motorized conveyor to transport the chickens trough
169
the steam tunnel. The Deconizer has a frame of steel and a chamber with Teflon covered plates. The
170
central steam treatment cabinet is approximately 1.5 m long and provided with steam nozzles that
171
lead the steam to the chickens passing through the cabinet. In addition, there are some steam
172
nozzles at each end of the steam cabinet. The steam was generated in a Steamrator (Steamrator Oy,
173
Finland) with a capacity of approx. 100 kW. The steam passes from the steam generator through
174
superheaters that increased the temperature of the steam up to 120 °C (at atmospheric pressure). A
175
sensor (Spiro TVA flowmeter) registered the pressure, energy use and quantity of steam. At normal
176
settings the steam pressure was approx. 4.3 bar. Low speed (45 Hz) of the conveyor gave a speed
177
that was equivalent to each chicken getting steam for 5 s. High speed (75 Hz) gave a speed gave 3 s
178
steaming of the chickens. The Deconizer could be adjusted by changing temperature and pressure of
179
the steam, varying opening of the nozzles and the distance from the nozzles to the carcasses. The
180
experiments were performed in a Biosafety level 3 Pathogen Pilot Plant facility.
181
182
183
2.5. Analysis of cells
After heat treatments, swabs were vortexed and bacteria plated on to total plate count agar
184
(PCA) for total aerobic counts. Five hundred μl were plated directly on the agar plate. In addition,
185
undiluted and 1:10 dilutions were plated using an automated plate spreader (Whitley Automatic
186
Spiral Plater, Don Whitley Scientific Ltd., West Yorkshire, UK) and incubated at 20 °C for 4 days. The
187
number of colonies were determined using an automatic plate reader. Swab samples from the
188
Salmonella inoculated chicken carcasses were plated on TSA with 200 µg/ml Rif and incubated at 37
189
°C for 1-2 days. Swab samples of the chicken carcasses inoculated with Campylobacter were plated
190
on MH agar with 100 µg/ml Rif and incubated microaerophilicly (Oxoid™ CampyGen™ 3.5L Sachet,
191
Thermo Fisher Scientific, Mass, USA) at 37 °C for 4 days. Since RifR strains were used, the background
192
flora for the Salmonella and Campylobacter determinations were negligible. 8
193
194
2.6. Sensory analysis
195
Chicken carcasses treated in the steam cabinet and control chickens were stored in plastic
196
bags at +4 °C for 1 day and 6 days before sensory analyses. A highly trained panel of 9 assessors (9
197
women, aged 37-64 years) at Nofima performed a sensory descriptive analysis (DA) according to
198
“Generic Descriptive Analysis” as described by Lawless & Heymann (Lawless & Heymann, 2010) and
199
the ISO standard 13229 (Anon., 2016). The assessors are regularly tested and trained according to
200
ISO standard 8586 (Anon., 2012), and the sensory laboratory follows the practice of ISO standards
201
8589 (Anon, 2007). The assessors agreed upon seven attributes describing the chicken carcasses with
202
skin: color hue, color intensity, whiteness, color uniformity, glossiness, degree of goose bumps and
203
dried skin surface. For carcasses with breast skin removed, the same attributes were evaluated
204
except for degree of goose bumps, which was omitted. Chicken carcasses were put on coded baking
205
paper and set out in a sensory booth for evaluation. Each carcass was evaluated by each assessor
206
with and without skin in two separate sessions, first session with skin and second session without
207
skin (the same chickens where the skin was removed after the first session). All attributes were
208
assessed on an unstructured line scale with labelled endpoints going from “no intensity” (1) to “high
209
intensity” (9). Each assessor evaluated all samples at individual speed on a computer system for
210
direct recording of data (EyeQuestion, Software Logic8 BV, Utrecht, The Netherlands) using tablets.
211
The coded chicken samples, from 4 series and control and 5 replicates were evaluated and served in
212
a randomized experimental design for each session, in total 25 samples per session. The DA was
213
performed during two following weeks, first week 1 day of storage and week two 6 days of storage.
214
In a pre-test session before the main test, the assessors were calibrated on samples that were
215
considered the most different on the selected attributes typical for the chicken carcass samples to be
216
tested.
217
9
218
219
2.7. Experimental design and statistical analysis Four treatments were compared in the main experimental setup, following a 22 factorial
220
design with factors Temperature (95°C or 120°C) and Time (3s or 5s), and three sites were sampled
221
on every carcass (breast, leg/thigh and wing). Seven carcasses were treated in each experimental
222
run, based on power estimations showing that a difference of one log could be detected with a
223
power of 95% at alpha=0.05. Each treatment was repeated three times on different days, for each of
224
Total aerobic bacteria, Salmonella and Campylobacter. In addition to the main experiment, some
225
extra tests were run to investigate the effects of nozzle opening and distance from nozzles to carcass.
226
Split-plot analysis of variance (ANOVA) models with fixed factors Temperature, Time and
227
Sample site were fitted to each of the response variables Total aerobic bacteria, Salmonella and
228
Campylobacter. All bacteria counts were transformed to log values before analysis. The analyses
229
were performed in R (R_Core_Team, 2016). Details from the statistical analysis are presented in the
230
supplemental material.
231
Data from the sensory descriptive analysis were evaluated with mixed effects ANOVA, where
232
product was considered fixed while the assessor and interaction effects including assessor were
233
considered random. Tukey multiple comparison test was used to determine significant differences
234
between products (P<0.05). The statistical software used for the sensory analysis was EyeOpenR
235
(Logic8 BV).
236
237
3. Results
238
3.1. Reduction of aerobic bacteria on heat treated chicken carcasses
239 240
Chicken carcasses were subjected a steam treatment of 95 °C for 5 s. Twenty one chickens were analysed for reduction of aerobic counts on the breast by swabbing, while seven were analysed 10
241
by cutting and removing skin and extraction of the bacteria by stomaching. Both methods gave the
242
same reduction and the more convenient swabbing method was used in the experiments (see
243
Supplemental Materials).
244
Chicken carcasses with naturally occurring bacteria were steam treated in the Deconizer at
245
different temperatures for different times (95 °C and 120 °C, for 3 s and 5 s). The surfaces of the
246
chicken carcasses were swabbed at breast, leg/thigh and wing before and after the treatment. The
247
steam treatments reduced the total bacteria count in the range 2.45 - 3.3 log on breast, 1.37 - 1.88
248
log on legs and 1.22 - 1.78 log on wings depending on the conditions used (Table 2). The log
249
reduction was significantly higher on breast compared to legs and wings, and the log reduction was
250
significantly higher when the chickens were treated for 5 s compared to 3 s at the same temperature
251
(see statistical analysis, Supplemental Materials). There were no significant differences between the
252
reductions at 120 °C compared to 95 °C for the same time treatments.
253
The Deconizer system was tested by increasing the distance from the nozzles to the chicken
254
carcasses in the steam chamber. A lower log reduction was observed for breast, but there was no
255
statistically significant difference for legs and wings. The Deconizer was also tested with fully open
256
steam nozzles. A tendency for enhanced log reduction was seen when the nozzles were fully open.
257
Se Supplemental materials for details.
258
259
260
3.2. Reduction of Salmonella on heat treated chicken carcasses
Chicken carcasses were inoculated with S. Enteritidis. The steam treatments gave significant
261
reduction of Salmonella on breast, legs and wings (Table 2). The reductions of Salmonella were in the
262
range 2.11 - 3.05 log on breast, 1.69 - 2.40 log on legs, and 1.36 - 1.92 log on wings. The reduction
263
was significantly higher on breast compared to legs and wings, and the log reduction was significantly
264
higher when the chickens were treated for 5 s compared to 3 s at the same temperature. There were 11
265
no significant differences between the reductions at 95 °C compared to 120 °C for the same time
266
treatments.
267
268
3.3. Reduction of Campylobacter on heat treated chicken carcasses
269
For chicken carcasses inoculated with Campylobacter, log reductions after steam treatments
270
were in the range 3.65 - 4.32 with 5 s treatment on breast, 2.76 - 3.18 log on legs and 2.45 - 2.65 log
271
on wings (Table 2). Reductions for 3 s treatments were significantly lower. However, the reductions
272
were 1.7 log for breast , 1.34 - 1.96 log for legs, and 0.84 - 1.37 log for wings. There was a
273
statistically significant difference between experimental days for Campylobacter, which was adjusted
274
for by including it as a random factor in the model (see Supplemental Material). The ANOVA revealed
275
a significant interaction between inoculation site and time, caused by the fact that increasing the
276
time from 3 to 5 seconds has a larger effect on the breast than on the legs and wings (Suppl. Material
277
Figure. 4).
278
One series of chicken carcasses was treated twice in the chamber (2 x 5 s) at 120 °C. The
279
carcasses got a cooked appearance. Hence, there is an upper limit of treatment time possible before
280
visual changes become apparent.
281 282
The Enterobacteriaceae level on the chicken carcasses varied and often the levels were very low. It was therefore difficult to get good results for reduction of Enterobacteriaceae.
283
284
285 286
3.4. Sensory evaluation
Chicken carcasses treated in the steam cabinet and control chickens were stored in plastic bags at 4 °C for 1 day and 6 days before analysing visually sensory properties of the chicken carcasses
12
287
with and without skin (Figs. 1 and 2). After 1 and 6 days of storage the untreated chickens with skin
288
obtained a higher score on the attribute glossy appearance. There were some variations in several of
289
the other attributes as well, however they were small, and appeared not to be correlated with the
290
extent of treatments. For chickens without skin only small differences were detected.
291
292 293
4. Discussion The microbial reduction after steam treatment varied with where on the chicken the samples
294
were taken. The reductions were markedly higher on breast skin than on legs and wings for both
295
total aerobic bacteria, Salmonella and Campylobacter. The skin on the breast is thinner than on the
296
wings and legs where the skin also often is more folded. The temperature rise varies with skin
297
thickness with thinner skin reaching higher temperatures leading to enhanced heat reduction of
298
bacteria (Kondjoyan & Portanguen, 2008). The folds and crevices of the thicker skin and feather
299
follicles may provide protection for bacteria so they will not experience the same heat as those
300
exposed on the surface. Tentatively, one could argue that since breast skin passes directly in front of
301
the nozzles and are directly hit by the blowing steam while wings and legs are at 90 degrees angle
302
away from the nozzles, one would expect higher kill on the breast skin. This has, however, not been
303
systematically investigated. Likewise, we also do not know whether the steam treatment may also
304
give a mechanical effect when the steam blows directly on the breast compared to wings and legs.
305
Previously reported steam treatment experiments usually only give results from chicken breast skin,
306
so it is difficult to compare previous results with our reductions on thighs and wings.
307
Reductions of bacteria also varied strongly with treatment time. Heat treatments for 5 s
308
gave consistently higher reductions than 3 s at both 95 °C and 120 °C, on both breast, legs and wings.
309
Heating is perhaps the most common way of reducing bacteria and longer heat treatment will
310
normally give enhanced reduction of bacteria and hence the results are as expected. Previous
311
examinations on heat treatments report varying results depending on the time of the treatment.
13
312
Insignificant reductions of total viable bacteria, Enterobacteriaceae and thermophilic Campylobacter
313
were obtained after a steam treatment of 90 °C for 12s (Whyte, et al., 2003). When chicken breast
314
was treated for 100 °C for 10s, 1.65 log reduction of total viable bacteria was observed, but the skin
315
appeared cooked (James, et al., 2000). C. jejuni and E. coli were reduced by 1.8, 2.6 and 3.3 log and
316
1.7, 2.3 and 2.8 log after 10s, 12s and 20s treatments, respectively, but also here the skin appeared
317
cooked (James, et al., 2007). When chicken carcass skin was exposed to flowing steam at 96-98 °C for
318
3 min, < 10 aerobic microbes were present per cm2 (Avens, et al., 2002). The upper limit of steam
319
treatment depends on further treatment of the carcass. More intense steam treatments will lead to
320
a cooked appearance of the skin. This may be of importance if the chicken is later to be sold as raw
321
meat. If the meat is intended for further heat processing in the factory, it may not be important.
322
When chickens were exposed to a combination of heat (90-94 °C) and ultrasound (30-40 kHz), a 0.90
323
log reduction of Campylobacter was achieved (Musavian, et al., 2014).
324
Bacteria usually start dying at temperatures around 60 °C and are increasingly sensitive
325
above this temperature. For example, the D-value of E. coli is reduced from around 1 h to 2 min as
326
the temperature increases from 56 °C to 62 °C (USDA, 2019). Under steam treatments bacteria are
327
killed by the heat transferred from the steam. Much of the heat energy comes from the liberated
328
energy when water gas condenses on the surface of the colder chicken skin. Water gas at 100 °C
329
contains much more energy than the same amount of liquid water at the same temperature. Under a
330
traditional steam treatment, the hot steam contains a mix of water as gas and water droplets. The
331
intention of using superheated steam was to maximize the energy liberated on the chicken skin and
332
thereby obtaining a higher temperature and an enhanced reduction during the short treatment.
333
However, no additional reduction of bacteria was detected when using superheated steam
334
compared to non-superheated steam for the same times. Apparently, both temperatures used in the
335
study are far above inactivation temperature of the vegetative bacteria and thus no additional
336
reduction was detected. When disks of poultry skin were inoculated with L. innocua and then
337
subjected to steam at 95 °C and superheated steam at 400 - 450 °C, approx. 2.5 log reduction was 14
338
obtained after 10s regardless of the method used (Kondjoyan & Portanguen, 2008). After longer
339
treatments (20 - 45 s), the superheated steam treatments clearly gave higher reduction. The results
340
were variable and the rise in temperature appeared to be related to the thickness of the chicken skin.
341
In order to optimize the system and achieve as high log reduction as possible, the system was
342
tested with different distances from the nozzles to the chicken carcass in the chamber, and with
343
varying the opening of the nozzles for steam, to investigate if this could increase the log reduction
344
further. Increasing the distance from the nozzles to the chicken showed reduced log reduction on
345
breast but not on legs and wings. The distance from the nozzles to the chicken may therefore
346
influence on the reduction of bacteria. There were also seen a tendency for enhanced log reduction
347
when the nozzles where fully open. Only a few experiments where performed for this. Hence, this
348
needs to be investigated further in the development of the next generation Deconizer. One series
349
with chicken carcasses was treated two times in the chamber (2 x 5 s) at 120 °C. This gave cooked
350
appearance on the surface of the chicken and was therefore not investigated further.
351
Different authors obtain varying results after steam treatments due to different treatment
352
regimes, using different steam delivery equipment, different temperatures on the steam and
353
different treatment times. It is therefore difficult to compare directly results from different groups.
354
The amount of steam used and the initial temperature on the skin, whether refrigerated or warm,
355
simulating newly slaughtered chickens that are used may also influence the results. This is due to the
356
fact that refrigerated skin will reach a lower temperature during a treatment and in addition because
357
stationary phase cells on refrigerated samples are more heat resistant (Kaur, Ledward, Park, &
358
Robson, 1998). The Deconizer was efficient for reduction of both total aerobic bacteria, S. Enteritidis
359
and C. jejuni inoculated on the chicken breast with up to 3.30, 3.05 and 4.32 log reduction,
360
respectively, during a 5 s heat treatment. The high reduction, compared to previous results, was
361
probably caused by the efficient steam generation leading to a high heat transfer to the carcasses.
15
362
Another benefit of the Deconizer is the treatment capacity. It can be implemented on the slaughter
363
line without reduction of slaughtering efficiency.
364
The sensory analysis carried out on heat treated chicken at days 1 and 6 showed that the
365
changes in attributes generally were small and appeared to follow a random pattern. For the samples
366
analysed with skin, only glossy appearance was higher on untreated chicken carcasses. The
367
importance of this seem to be minor since the other parameters such as color tone, color strength,
368
whiteness, dryness and tightness of skin were close to their respective controls, and the consumer
369
will probably not experience glossiness alone as a parameter for treated or cooked chicken carcasses.
370
When the breast skin of heat-treated chicken was removed, and the breast muscles evaluated, only
371
minor non-systematic changes were recognized. In conclusion, there was only very minor sensory
372
changes on the treated chicken carcasses. Since doubling the exposure time to 10 s at 120 °C gave a
373
cooked appearance, the optimal treatment time must be carefully determined. From the sensory
374
analysis the shelf life of treated chickens appeared to be similar to that of untreated controls. We did
375
not do a microbial study on shelf life of treated carcasses. When chicken portions were subjected to
376
steam at 100 °C for 10 s, a 1.65 log reduction of the total viable bacteria were obtained (James, et al.,
377
2000). When comparing with untreated chicken portions, the cell counts of treated chicken remained
378
lower until day 3 of storage at 3 °C, but were essentially the same as those of untreated carcasses at
379
day 5, so no extension of the shelf-life was observed. However, from a food safety perspective
380
pathogens on the chickens would be substantially reduced by the treatment. In a quantitative risk
381
assessment of human campylobacteriosis associated with thermophilic Campylobacter species in
382
chickens, it was calculated that campylobacteriosis in conjunction with consumption of chicken meals
383
could be reduced 30 times by introducing a 2 log reduction of the number of Campylobacter on the
384
chicken carcasses (Rosenquist, et al., 2003).
385
In summary, we have shown that the Deconizer steam treatment chamber can substantially
386
reduce total aerobic bacteria, Salmonella and Campylobacter on chicken carcasses within a few
387
seconds in a steam chamber designed for implementation on a chicken slaughter line. The method 16
388
will not impede the speed of poultry processing and gives only marginal sensory changes in the
389
appearance of the carcasses. The method employs no chemicals and can be easily implemented in
390
the chicken facilities to enhance food safety.
391 392
ACKNOWLEDGMENTS
393
We thank the trained sensory panel at Nofima for carrying out the sensory evaluation, and Janina
394
Berg for excellent technical assistance. The work was funded by grants to the projects 248928,
395
221663 and 262306 financed by the Research Council of Norway, Ministry of Agriculture and Food
396
and the Research Levy on Agricultural Products, respectively.
397 398
SUPPLEMENTAL MATERIAL
399
Supplemental materials associated with this article can be found online at:
400
[URL to be completed by the publisher].
17
401
References
402
Anon. (2005). Commission regulation (EC) No 2073/2005 of November 2005 on microbiological
403 404 405 406 407 408 409 410
criteria for foodstuffs. Official Journal of the European Union, 338(1-26). Anon. (2007). ISO 8589 Sensory analysis - General guidance for the design of test rooms. Geneva, Switzerland. Anon. (2012). Sensory analysis - General guidance for selection, training and monitoring of selected sensory assessors and expert assessors. Geneva, Switzerland. Anon. (2016). ISO 13229 Sensory analysis - General guidance for establishing a sensory profile. Geneva, Switzerland: International Organization for Standardization. Avens, J. S., Albright, S. N., Morton, A. S., Prewitt, B. E., Kendall, P. A., & Sofos, J. N. (2002).
411
Destruction of microorganisms on chicken carcasses by steam and boiling water immersion.
412
Food Control, 13(6-7), 445-450.
413
Boysen, L., Wechter, N. S., & Rosenquist, H. (2013). Effects of decontamination at varying
414
contamination levels of Campylobacter jejuni on broiler meat. Poultry Science, 92(5), 1425-
415
1429.
416 417 418 419 420
Bruinsma, J. (2015). World agriculture: towards 2015/2030 an FAO perspective. http://www.fao.org/3/a-y4252e.pdf: FAO. Buncic, S., & Sofos, J. (2012). Interventions to control Salmonella contamination during poultry, cattle and pig slaughter. Food Research International, 45(2), 641-655. EFSA. (2010). Revision of the joint AFC/BIOHAZ guidance document on the submission of data for the
421
evaluation of the safety and efficacy of substances for the removal of microbial surface
422
contamination of foods of animal origin intended for human consumption. EFSA Journal,
423
8(4), 1544.
424
EFSA. (2011). Scientific Opinion on Campylobacter in broiler meat production: control options and
425
performance objectives and/or targets at different stages of the food chain. EFSA Journal,
426
9(4), 2105. 18
427 428 429
EFSA/ECDC. (2018). The European Union summary report on trends and sources of zoonoses, zoonotic agents and food-borne outbreaks in 2017. EFSA Journal, 16(12). European Commission. (2013). Regulations Commission Regulation (EU) No 101/2013 of 4 February
430
2013 concerning the use of lactic acid to reduce microbiological surface contamination on
431
bovine carcases. Official Journal of the European Union, L34.
432
European Union Commission. (2017). Regulations Commission Regulation (EU) 2017/1495 of 23
433
August 2017 amending Regulation (EC) No 2073/2005 as regards Campylobacter in broiler
434
carcases. Official Journal of the European Union, L218, 1-6.
435 436 437
FDA. (2019). Food Safety and Inspection Service New Technology Information Table. https://www.fda.gov/. Heir, E., Holck, A. L., Omer, M. K., Alvseike, O., Hoy, M., Mage, I., & Axelsson, L. (2010). Reduction of
438
verotoxigenic Escherichia coli by process and recipe optimisation in dry-fermented sausages.
439
International Journal of Food Microbiology, 141(3), 195-202.
440
James, C., Goksoy, E. O., Corry, J. E. L., & James, S. J. (2000). Surface pasteurisation of poultry meat
441
using steam at atmospheric pressure. Journal of Food Engineering, 45(2), 111-117.
442
James, C., James, S. J., Hannay, N., Purnell, G., Barbedo-Pinto, C., Yaman, H., Araujo, M., Gonzalez, M.
443
L., Calvo, J., Howell, M., & Corry, J. E. L. (2007). Decontamination of poultry carcasses using
444
steam or hot water in combination with rapid cooling, chilling or freezing of carcass surfaces.
445
International Journal of Food Microbiology, 114(2), 195-203.
446 447
Kaur, J., Ledward, D. A., Park, R. W. A., & Robson, R. L. (1998). Factors affecting the heat resistance of Escherichia coli O157 : H7. Letters in Applied Microbiology, 26(4), 325-330.
448
Kondjoyan, A., & Portanguen, S. (2008). Effect of superheated steam on the inactivation of Listeria
449
innocua surface-inoculated onto chicken skin. Journal of Food Engineering, 87(2), 162-171.
450 451
Lawless, H. T., & Heymann, H. (2010). Sensory evaluation of food - Principles and Practices (2nd ed.). New York: Springer.
19
452 453 454
Loretz, M., Stephan, R., & Zweifel, C. (2010). Antimicrobial activity of decontamination treatments for poultry carcasses: A literature survey. Food Control, 21(6), 791-804. Musavian, H. S., Krebs, N. H., Nonboe, U., Corry, J. E. L., & Purnell, G. (2014). Combined steam and
455
ultrasound treatment of broilers at slaughter: A promising intervention to significantly
456
reduce numbers of naturally occurring campylobacters on carcasses. International Journal of
457
Food Microbiology, 176, 23-28.
458 459 460 461
OECD/FAO. (2016). OECD-FAO Agricultural Outlook 2016-2025. In. Rome: OECD Publishing, Paris/FAO. R_Core_Team. (2016). R: A language and environment for statistical computing. In. Vienna, Austria: R Foundation for Statistical Computing.
462
Rosenquist, H., Nielsen, N. L., Sommer, H. M., Norrung, B., & Christensen, B. B. (2003). Quantitative
463
risk assessment of human campylobacteriosis associated with thermophilic Campylobacter
464
species in chickens. International Journal of Food Microbiology, 83(1), 87-103.
465
USDA. (2019). Pathogen Modeling Program (PMP) Online.
466
https://pmp.errc.ars.usda.gov/PMPOnline.aspx: United States Department of Agriculture
467
Agricultural Research Service.
468
Whyte, P., McGill, K., & Collins, J. D. (2003). An assessment of steam pasteurization and hot water
469
immersion treatments for the microbiological decontamination of broiler carcasses. Food
470
Microbiology, 20(1), 111-117.
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Legend to figures
480 481
Figure 1. Sensory properties steam treated chickens with skin after (A) one day and (B) six days of
482
storage in plastic bags at 4 °C. Chickens were exposed to steam at indicated temperatures and times.
483
The intensity of different attributes were registered. 1 = low intensity, and 9 = high intensity. The
484
letters above the columns indicate grouping according to ANOVA and Tukey multiple comparison test
485
at (P<0.05). Samples with the same letter are considered being equal for the specific property.
486 487
Figure 2. Sensory properties steam treated chickens without skin after (A) one day and (B) six days of
488
storage in plastic bags at 4 °C. Chickens were exposed to steam at indicated temperatures and times.
489
The intensity of different attributes were registered. 1 = low intensity, and 9 = high intensity. The
490
letters above the columns indicate grouping according to ANOVA and Tukey multiple comparison test
491
at (P<0.05). Samples with the same letter are considered being equal for the specific property.
492 493
21
494
Table 1. Strains used in this study. Species
Strain/Serotype
Source
MF number RifR,1
Salmonella
1049-1-99
Norwegian Veterinary Institute,
3817
Enteritidis
Norway 61-358-1
Poultry, DTU Vet, National
3818
Veterinary Institute, Denmark
Campylobacter
C484, serotype 1
ATCC130762
3824
Poultry leg
6848
NCTC 11168-BN148Rif3
6856
jejuni
495
1
Reference number of strains after mutating to RifR.
496
2
497
3
American Type Culture Collection, Manassas, VA, USA Original strain from Public Health England, Culture Collection
22
498
Table 2. Mean reductions (log) of total aerobic bacteria on chicken carcasses and mean reductions (log) of Salmonella and
499
Campylobacter inoculated on chicken carcasses, after different steam treatments at three sampling sites
Aerobic bacteria
Salmonella
Campylobacter
500
Treatment
Breast1
Leg/thigh1
Wing1
95 °C 3 s
2.45 (0.70)
1.50 (0.54)
1.22 (0.67)
95 °C 5 s
3.30 (1.08)
1.62 (0.59)
1.70 (0.64)
120 °C 3 s
2.53 (1.03)
1.37 (0.58)
1.47 (0.67)
120 °C 5 s
3.17 (1.08)
1.88 (0.49)
1.78 (0.54)
95 °C 3 s
2.21 (0.40)
1.69 (0.59)
1.36 (0.27)
95 °C 5 s
2.94 (1.11)
2.40 (0.66)
1.90 (0.38)
120 °C 3 s
2.11 (0.77)
1.76 (0.53)
1.50 (0.29)
120 °C 5 s
3.05 (1.09)
2.19 (0.44)
1.92 (0.32)
95 °C 3 s
1.71 (1.26)
1.34 (0.90)
0.84 (0.81)
95 °C 5 s
4.32 (1.30)
2.76 (0.60)
2.65 (0.78)
120 °C 3 s
1.70 (1.10)
1.96 (1.37)
1.37 (1.40)
120 °C 5 s
3.65 (1.76)
3.18 (1.77)
2.45 (2.17)
1
Standard deviations in parentheses 23
501
Figure 1 A.
Control
95°C 3 s
95°C 5 s
120°C 3 s
120°C 5 s
9 8 A
Sensory intensity
7 6
AA
A
5
AAAA A
AB
A
AB AB
B
4
A
AA
BC
AA
B C
C
BCBC AA
3
A AA A
2
AB ABC C BC
1 Color hue 502 503
Color intensity
Whiteness
Color Glossiness uniformity
Goose bumps
Dried skin surface
Figure 1 B. Control
95°C 3 s
95°C 5 s
120°C 3 s
120°C 5 s
9 8 A
Sensory intensity
7 6
AAA
A AAB
B
BC AB C
A
5 4
AB
A
AB AB B AB
BC
B
CD D
B B AB
A AB ABAB
3
B
2
B
ABABAAB
1 Color hue 504
Color intensity
Whiteness
Color Glossiness uniformity
Goose bumps
Dried skin surface
24
505
Figure 2 A.
Control
95°C 3 s
95°C 5 s
120°C 3 s
120°C 5 s
9 8
Sensory intensity
7
A
A A A A
AB A ABC BC C
6 AB
5
A B B
A AB
A
A B
AB
A AB ABC BC C
4 3
A
2
B B B
B
1 Color hue
Color intensity Whiteness
506 507
Color uniformity
Glossiness
Dried skin surface
Figure 2 B.
Control
95°C 3 s
95°C 5 s
120°C 3 s
120°C 5 s
9 8
Sensory intensity
7 6
A
A
A A A
A B
A
5
B
B
AB
A A
A
A
A A A A
B B
AB BCBC
4
C
3 A ABABAB B
2 1 Color hue 508
Color intensity Whiteness
Color uniformity
Glossiness
Dried skin surface 25
Highlights
• • • •
The Deconizer steam treatment effectively reduced aerobic bacteria, Salmonella and Campylobacter with 1.62 log – 4.32 log Treatment time was 5s at 95 °C or 120 °C No negative sensory changes Can easely be implemented in existing production lines
Declaration of interest: None