- Email: [email protected]
Efficacy of some antimicrobial treatments compared to sodium hypochlorite on physical, physiological and microbial quality of fresh-cut melons (Cucumis melo L. var. inodorus)
LWT - Food Science and Technology 59 (2014) 1146e1151
Contents lists available at ScienceDirect
LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt
Efficacy of some antimicrobial treatments compared to sodium hypochlorite on physical, physiological and microbial quality of fresh-cut melons (Cucumis melo L. var. inodorus) Tuba Dilmaçünal a, *, Derya Erbas¸ a, Mehmet Ali Koyuncu a, Cemile Ebru Onursal b, Hakan Kuleas¸an c a b c
Suleyman Demirel University, Faculty of Agriculture, Department of Horticulture, 32260, Isparta, Turkey irdir Horticultural Research Institute, 32500, Isparta, Turkey Eg Suleyman Demirel University, Faculty of Engineering, Department of Food Technology, 32260, Isparta, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 April 2013 Received in revised form 30 June 2014 Accepted 24 July 2014 Available online 2 August 2014
aç’ melons (Cucumis melo L. var. inodorus cv. ‘Kırkag aç’) were hand-harvested at a Turkish-type ‘Kırkag commercial harvest maturity stage from a greenhouse in Turkey (Antalya). Fruits were divided into four groups for the experiments: 1. Control (C), 2. Hazelnut oil (HO), 3. Gaseous Ozone (GO), and 4. NaClO. After the treatments, slices were placed immediately to lidded plastic boxes (500 g capacity) and stored in a cold room at 5 C and 90 ± 5% relative humidity for 12 days. Fruits were evaluated at three-day intervals for microbial enumeration, firmness, flesh color, titratable acidity (TA), pH, soluble solid content (SSC), weight loss, sensorial attributes (external appearance, taste-flavor and translucency), respiration rate and ethylene production. The integrity of the slices treated with GO was preserved better than those of the others and no juice leakage was observed during storage. According to the results, especially for microbial and sensorial attributes, control, NaClO and HO treated melon slices were preserved their quality for six days, whereas GO treated samples were stored for nine days with good quality. © 2014 Elsevier Ltd. All rights reserved.
Keywords: Cold storage Gaseous ozone Hazelnut oil aç Kırkag Sodium hypochlorite
1. Introduction The melon is one of the most economically important and widely cultivated crops in the world, and Turkey is the second largest producer after China, producing 1,708,415 million t annually (Anonymous, 2014a). The European and American melon markets are dominated by two major cultivar types differing in quality attributes and postharvest behavior. Cantaloupensis and Reticulatus groups include the very aromatic, climacteric, and fast senescing cantaloupes and muskmelons; Inodorus group includes the less aromatic, non-climacteric, slow senescing melons (Amaro, Beaulieu, Grimm, Stein, & Almeida, 2012). aç (Cucumis melo L. var. inodorus) is one of the commonly Kırkag grown melon cultivars, particularly in the Aegean and the Central lu, & S¸engül, Anatolia regions of Turkey (Yıldırım, Halloran, Çavus¸og 2009). It has generally light green skin color with dark green spots at first, yellow at maturity (Sensoy, Büyükalaca, & Abak, 2007). Its
* Corresponding author. Tel.: þ90 246 2113923; fax: þ90 246 2118696. E-mail addresses: [email protected], [email protected] (T. Dilmaçünal). http://dx.doi.org/10.1016/j.lwt.2014.07.033 0023-6438/© 2014 Elsevier Ltd. All rights reserved.
fruit flesh is sweet and delicious and they are more resistant to transportation and postharvest resting than many other cultivars aç melons has (Yıldırım et al., 2009). Exportation value of Kırkag gained importance in recent years thanks to its high quality characteristics (Anonymous, 2014b). Fresh-cut processing of fruit and vegetables is well known to promote faster deterioration in comparison with their intact counterparts. In particular, microbial growth and development of biochemical reactions on wounded plant tissues are responsible for safety and quality degradation of the product, which translate not only in food spoilage but also in risk for foodborn illness (Manzocco, Pieve, & Maifreni, 2011). Safe production methods and proper disinfection/decontamination procedures are therefore critical steps in ensuring the safety of ready-to-eat fresh fruit and vege as, 2011). tables (Abadias, Alegre, Usall, Torres, & Vin Chlorine is the most common sanitizer used in fresh-cut fruit and vegetable production (Anonymous, 2014c). The common form of chlorine used in the fresh production industry is sodium hypochlorite (NaClO). The use of hypochlorite-based systems for fresh product washing is already prohibited in various European Union countries because of the risk of a range of cancers (Silveira, Conesa,
T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151
s, 2008). Additionally, on fresh-cut melon cubes, Aguayo, & Arte chlorine resulted in less than a 90% reduction in viable cells of n ez, Cantwell, & Suslow, several strains of Salmonella (Selma, Iba 2008). The concept of using multiple intervention methods or various preservation technologies that are healthier for consumers n ez, Allende, Cantwell, is increasing in their importance (Selma, Iba & Suslow, 2008). Therefore, there is much interest in developing safer and more effective sanitizers for fruit and vegetable (Abadias et al., 2011). The use of ozone gaseous has been suggested as an alternative to reduce microbial populations on melon before cutn ez, Cantwell, et al., 2008). Hazelnut oil (Oleum ting (Selma, Iba Coryli) is an edible oil extracted from hazelnut (Corylus avellana L.) fruit seeds without heat treatment and chemical application, naturally by cold pressing method by a firm operating in Turkey. It contains essential fatty acids (Omega-3, 6 and 9) as well as vitamin E. Vitamin E is a good antioxidant and has beneficial impacts in lowering cholesterol and protecting cardiovascular health and it can be used as an alternative in reducing microbial populations and quality losses. The aim of this work was to evaluate the efficacy of some treatments compared to NaClO in reducing microbial populations aç’ and remaining the quality of cold stored fresh-cut ‘Kırkag melons. 2. Materials and methods 2.1. Plant material aç’ (Cucumis melo L. var. inodorus Turkish-type melons cv. ‘Kırkag aç’), grown under greenhouse conditions in the Medicv. ‘Kırkag terranean region of Turkey (Antalya), were hand-harvested in June at the commercial harvest maturity stage and transported immediately to the laboratory. Melons were inspected carefully and fruit with no visual defects and uniform in shape and size were selected. Fruit skin color was yellow on green spotted, wrinkled and medium-thick and resistant to transporting and have a long shelf life. Fruit flesh color was white-cream, juicy, delicious and sweet. The average weight of fruits was 3350 g, average fruit diameter was 23.5 cm and average fruit length was 23.25 cm. 2.2. Storage conditions Fruits were transported immediately to the laboratory and all fruits and dipping water were chilled to 5 C overnight before processing on the following morning. Disposable gloves were worn during preparation of the fruits. Chopping boards and knives were disinfected with sodium hypochlorite (NaClO), washed with tap water, sanitized with ethyl alcohol and air-dried immediately before use. Also workbench and boxes were sanitized with ethyl alcohol. In a clean cold room, at 5 C, whole unprocessed melons (12 melons for each treatment, totally 48 melons for all experiments) were washed with tap water at 5 C, drained and dried with blotting paper before the treatments. All unprocessed melons were dipped into distilled water (DW) at 5 C for 2 min, drained and dried with blotting paper, peeled, halved, cored and hand cut to obtain trapezoidal sections (3.0 ± 0.4 cm of wide, 4.0 ± 0.5 of length) before the treatments except NaClO treatment. Unprocessed melons, prepared for NaClO treatment, were dipped into NaClO solution (200 mL/L, pH 6.5) at 5 C for 2 min drained and dried with blotting paper, peeled, halved, cored and hand cut to obtain trapezoidal sections (3.0 ± 0.4 cm of wide, 4.0 ± 0.5 of length). After dipping, fruits were prepared for the experiments: 1. Control (C): Slices were dipped into DW for thirty seconds. 2. Hazelnut oil (HO): HO was put into a sprayer and sprayed on melon slices. HO was extracted from hazelnut (Corylus avellana L.) fruit
1147
seeds without heat treatment and chemical application, naturally by cold pressing method by a firm operating in Turkey. HO contains essential fatty acids (Omega-3, 6 and 9) and also, vitamin E. HO is a good antioxidant and has positive impacts in lowering cholesterol and protecting cardiovascular health. 3. Gaseous Ozone (GO): Slices were treated with 6.34 mg/m3 gaseous ozone by an ozone generator (OPAL, OGHe03, Turkey) in a glass gas tight cabinet for 3 h 4. Sodium hypochlorite (NaClO): Slices were dipped into NaClO solution (150 mL/L, pH 6.5) at 5 C for thirty seconds. After the treatments, slices (22 ± 2 slices per each boxes) were placed immediately to lidded plastic boxes (500 g capacity) and stored in a cold room at 5 C temperature and 90 ± 5% relative humidity for 12 days. The experiment was set up with 3 replication, each package was regarded as a replication, and totally 60 boxes of melon slices were used during analyzing periods. Melon slices were analyzed initially (initial analyses were made after the treatments) and at three-day intervals for microbial enumeration, flesh firmness, flesh color, titratable acidity (TA), pH, soluble solid content (SSC), weight loss, sensorial attributes (external appearance, tasteflavor and translucency), respiration rate and ethylene production during storage.
2.3. Physical and chemical analyses Analyses were made initially and at three-day intervals during cold storage. Fruit firmness was determined using a digital texture machine (AMETEK LLOYD Instruments LF-Plus Tensile Tester, England) and measured via compression using a 50 N load cell and a stainless steel, 5.1 mm diameter cylindrical probe with a constant speed of 100 mm/min at harvest date and during storage period. The maximum force (N) generated during the probe travel was used for data analysis. Fruit flesh color was determined using a chromameter (Minolta CR-300, Minolta Ramsey, NJ, USA). The dimensions L*, a*, and b* were obtained, and the L*, C* and h values were used to determine the color of melon slices. L* indicates lightness and is the same as the L*a*b* color space, C* is chroma, and h is the hue angle. The value of C* is 0 at the center and increases according to the distance from the center. Hue angle is defined as starting at the þa* axis and is expresses in degrees; 0 would be þa* (red), 90 would be þb* (yellow), 180 would be a*(green) and 270 would be b* (blue). The hue angle was calculated (h ¼ arctan b*/a*) and expressed in degrees ( ). Saturation index, or Table 1 aç melon slices stored for 12 days at Microbial counts (log cfu/g) of fresh-cut Kırkag 5 C. Days
GOb
Control
Aerobic bacteria 0 3.32 ± 0.03 3 4.39 ± 0.07 6 4.73 ± 0.13 9 6.61 ± 0.36 12 7.08 ± 0.17
aAa bA cA dA eA
3.23 3.71 4.51 4.78 5.06
Yeast and molds 0 2.56 ± 0.23 3 2.74 ± 0.13 6 3.16 ± 0.09 9 4.36 ± 0.31 12 4.92 ± 0.06
aA aA aA bA bA
0 0 0 0 0
aB aB aB aB aB
HOc ± ± ± ± ±
0.10 0.12 0.23 0.10 0.06
aA bB cA cdB dB
NaClOd
3.35 4.87 5.24 5.42 5.83
± ± ± ± ±
0.10 0.23 0.08 0.30 0.11
aAB bA bcB cdC dC
3.63 4.40 4.84 6.22 6.84
± ± ± ± ±
0.08 0.26 0.03 0.06 0.12
aB bA cA dAC eA
2.10 2.40 2.69 3.01 3.31
± ± ± ± ±
0.17 0.17 0.09 0.11 0.08
aC abAC bcC cdC dC
0 aB 2.15 ± 3.21 ± 3.32 ± 4.13 ±
0.28 0.16 0.50 0.09
bC bcA cC cD
GO: Gaseous ozone, HO: Hazelnut oil, NaClO: Sodium hypochlorite. a Capital letters in lines show comparisons between applications and small letters in columns show comparisons between storage periods. Same letters in lines or columns indicates no significance at p < 0.05, n ¼ 3, Tukey. b GO: Gaseous ozone. c HO: Hazelnut oil. d NaClO: Sodium hypochlorite.
1148
T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151
Table 2 The quality attributes (weight loss, firmness, soluble solid contents (SSC), titratable acidity (TA), pH, ethylene production, respiration rate, taste- flavor, external appearance, aç melon slices stored for 12 days at 5 C. color (L*, C*, h and DE*)) of fresh-cut Kırkag Treatments
Control
Storage period (days)
0 3 6 9 12 0 NaClOd 3 6 9 12 e HO 0 3 6 9 12 f GO 0 3 6 9 12 Storage period (SP) Treatment (T) T SP
Weight loss
Firmness
e 0.003 0.034 0.027 0.028 e 0.163 0.051 0.038 0.204 e 0.000 0.015 0.042 0.417 e 0.482 0.391 0.417 0.300 ** ** **
5.88 3.73 4.87 4.54 3.15 5.21 4.11 4.09 4.38 4.07 4.94 3.89 3.38 2.36 2.97 4.02 4.09 4.35 4.06 4.29 ** ** **
SSC
6.25 7.32 7.92 7.35 7.27 6.83 6.25 6.43 5.63 6.33 7.35 6.45 7.82 8.32 8.5 7.45 6.73 7.58 6.68 6.85 ns **b ns
TA
0.090 0.100 0.127 0.125 0.121 0.100 0.097 0.101 0.098 0.134 0.090 0.107 0.108 0.120 0.113 0.080 0.113 0.110 0.114 0.133 ** nsc *a
pH
5.44 5.55 5.41 5.40 5.40 5.44 5.48 5.44 5.45 5.08 5.66 5.47 5.49 5.82 5.61 5.60 5.38 5.40 5.56 5.20 ** ** **
Ethylene production
Respiration rate
Taste-flavor (1e5 scale)
External appearance (1e9 scale)
L* (lightness)
C* (chroma)
h (hue angle)
DE
0.801 1.733 1.397 2.619 1.207 0.955 1.841 1.057 0.759 0.278 2.354 1.072 1.108 1.455 0.642 1.022 0.650 1.016 1.274 1.242 ns ns *
0.017 1.797 1.351 1.323 1.991 0.020 1.540 1.455 1.131 0.976 0.019 2.414 2.105 2.573 1.078 0.020 0.560 1.198 1.258 0.930 ** * ns
5.00 4.93 4.21 1.92 1.00 5.00 3.17 3.13 1.83 1.33 5.00 3.39 2.93 2.33 1.89 5.00 4.13 2.92 2.87 2.50 ** ** **
9.00 8.73 8.46 4.75 1.00 9.00 8.80 8.46 5.83 3.38 9.00 8.33 7.39 4.83 4.72 9.00 8.87 8.54 5.75 5.29 ** ** **
76.32 73.25 74.71 74.33 69.34 73.13 70.32 72.00 75.02 70.37 73.12 73.51 74.04 70.82 73.22 71.36 73.86 70.25 72.95 75.60 ns ns *
11.77 10.64 10.27 9.23 8.52 10.35 10.07 10.63 9.74 9.38 12.75 12.32 11.26 12.06 10.73 10.39 10.63 11.43 10.61 10.02 * * *
111.93 110.96 110.27 111.39 109.66 112.28 112.09 112.89 111.66 110.87 112.18 111.55 111.16 109.39 110.42 111.51 111.41 112.39 111.02 112.70 ns * ns
e 3.37 3.12 3.65 10.55 e 1.92 1.35 2.01 1.05 e 1.69 4.15 1.66 1.55 e 2.13 2.03 2.30 2.90 ** ** **
(Delta E)
a *: p < 0.05; b**: p < 0.01; cns: not significant, n ¼ 3. Scale of external appearance: 1e9: 1e4: poor, 5: marketable, 7e8: good, 9: excellent; Scale of taste-flavor: 1e5: 1: very poor, 2: poor, 3: mild, 4: good, 5: excellent. d NaClO: Sodium hypochlorite. e HO: Hazelnut oil. f GO: Gaseous ozone.
purity of color (chroma), was also calculated [C* ¼ ((a*)2 þ (b*)2)1/2] and expressed numerically. Also, fruit flesh color was represented * ¼ ððL* L* Þ2 þ ða* a* Þ2 þ ðb* b* Þ2 Þ1=2 as color difference ½DEab 2 1 2 1 2 1 in Table 2. Weight loss was expressed as the percentage of loss of weight with respect to the initial weight. The soluble solid content (SSC) was measured using a digital refractometer (Atago Pocket PAL-1, Tokyo, Japan) and SSC was expressed as percentage of soluble solids per 100 g fresh weight. Titratable acidity (TA) was determined by a digital pH meter (Hanna Instruments HI 9231, Italy) and titrimeter (Isolab Digitrate, Germany), and expressed as percentage of grams of malic acid equivalent per 100 g fresh weight and pH was measured by a digital pH meter (Hanna Instruments HI 9231, Italy). For respiration measurements, the static system described by Saltveit (2004) was used. Respiration rate and ethylene production were determined by gas chromatography. Samples were put in a gas tight glass jars at room temperature at harvest date and three-day intervals during storage. Gas sample was taken from the jars at the end of the 4 h. Measurements were made in split/splitless (S/SL) of inlet in split mode with gas sampling valve with 1-mL gas sample by using fused silica capilar column (GS-GASPRO, 30 m 0.32 mm I.D., U.S.A), with thermal conductivity detector (TCD) for respiration rate measurements and flame ionization detector (FID) for ethylene production measurements by Agilent GC-6890N (U.S.A and Canada) model gas chromatography (GC) and Chemstation A.09.03 [1417] software. Carrier gas flow was 1.7 mL/min in stable flow mode. The temperature of the oven, TCD and FID detectors were 40 C (isothermal), 250 C and 250 C, respectively (Dilmaçünal, 2009, p. 188).
buffered saline (PBS) and homogenized in a stomacher (BagMixer 400, USA) for thirty seconds. After homogenization, samples were serially diluted in sterile PBS. After dilutions were made, 0.1 mL sample from each dilution was plated on proper media plates in triplicate. Plate count agar (PCA, Merck, Germany) was used for the determination of total aerobic bacteria. The plates were incubated at 30 C for 24e48 h (Maturin & Peeler, 2001; Anonymous, 2014d). Yeasts and molds were counted on Malt Extract Agar (MEA, Merck, Germany). The pH of MEA plates was adjusted to 3.5 and 50 mg/L chloramphenicol was added to suppress undesired bacterial growth. PDA plates were incubated at 25 C for 48e72 h (Thomas, Stack, Mislivec, Koch & Bandler, 2001; Anonymous, 2012). After incubation, plates were counted and data was analyzed. 2.5. Sensorial attributes External appearance of fresh-cut melons was evaluated using a scale of 1e9: 1e4: poor, 5: marketable, 7e8: good, 9: excellent. Taste and flavor of melon slices were evaluated using a scale of 1e5: 1: very poor, 2: poor, 3: mild, 4: good, 5: excellent. Translucency was evaluated by counting deteriorated melon slices and expressed as a percentage of the total number of slices. The analyses were conducted by a panel of 15 (age range of 30, 8 women and 7 men) trained judges. They were trained before the sensorial analyses at postharvest physiology laboratory for the evaluation of the sensory quality characteristics of fruits. 2.6. Experimental design and statistical analyses
2.4. Microbial enumeration In order to determine the number of microorganisms, 25 g of melon sample was added into 225 mL of 1 g/100 mL phosphate-
The experiment followed a completely randomized design with 3 replication and each package was regarded as a replication. The differences between the mean of the groups was determined by Tukey. All analyses were performed using the Minitab® 15 statistics
T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151
software (Minitab Inc. USA). Microbial counts were first subjected to logarithmic conversion. The analysis of covariance was used to decide whether significant differences (p < 0.05) existed among treatments. 3. Results and discussion 3.1. Microbial enumeration The effect of storage period and treatments on the number of microorganisms was statistically significant (p < 0.05). GO was determined to be the most effective treatment for the inhibition of both bacteria and fungi in fresh-cut melon samples during storage. Its effect on yeasts and molds was significantly above other treatments. While GO totally inhibited the growth of yeasts and molds, the number of bacteria increased to serious numbers during 12 day storage. Although, NaClO limited the growth of yeasts and molds, the level of inhibition was not comparable to that of GO. The treatment prevented the growth of bacteria at initial period. On the other hand the total number of bacteria increased to higher numbers after 3 days showing that NaClO treatment affected only bacterial cells in vegetative forms but not bacterial spores. After initial period spores germinated and became vegetative again. The number of yeasts and molds were 4.13 log cfu/g after 12 days. Inhibitory effect of HO on both bacteria and fungi was astonishing. It was determined that degree of inhibition was better when compared to NaClO treatment (Table 1). Microbial quality of freshcut melons during storage is depended on some factors such as genotype, maturity, soluble solid content, packaging material and storage temperature (Roller & Seedhar, 2002; Saftner, Bai, Abbott, & Lee, 2003). Maximum required microbial limit set by Turkish legislations (Anonymous, 2012) for mesophilic aerobic bacterial growth (107 cfu/g) was not exceeded in this study after 12 days of storage at 5 C by all experimental groups except control group (Table 1). Saftner, Abbott, Lester, and Vinyard (2006) reported that microbial population tended to increase in stored melons after 2 days and a rapid increase was found after 5 days of storage. The efficacy of decontamination methods is reflected in the microbiological reduction obtained and, even more important, in the maintenance of this reduction during storage (Abadias et al., 2011). GO treatment was determined to be the most effective method for the inhibition of both bacteria and fungi in fresh-cut melon samples during storage. Its effect on yeasts and molds was significantly above of the other applications. While GO totally inhibited the growth of yeasts and molds, the number of bacteria increased to serious numbers on day 12 of storage. Similar inhibitory effect of edible alginates on fungi was also reported by Raybaudi-Massilia, Mosqueda-Melgar, and Martin-Belloso (2008). However the effect of alginates on bacterial species was not that strong. Aguayo, s (2003) stated that the number of bacteria after Allende, and Arte 14 days of storage in modified atmosphere packaged melons were more than 107 cfu/g. The number of yeasts recorded in their study was similar to our findings. Inhibitory effect of HO on both bacteria and fungi was better when compared to NaClO. It can be explained by strong binding and coating effect of HO. The oil forms a layer on the surface of melon slices which prevents accession of microbial cells to nutrients. The coating effect may also limit the oxygen intake of aerobic microorganisms. Being a common food without any putative effect is another feature of edible oil which can be used as a coating material for fresh-cut fruits. 3.2. Firmness The melon slices became softer compared to harvest date in all treatments with increasing storage period except the GO treatment.
1149
Control group displayed the highest firmness loss (46.43 N/100 N), followed by HO (39.88 N/100 N), and NaClO (21.88 N/100 N) (Table 2). The melon slices treated with HO had a greasy texture especially in last days of storage. One of the important effects of ozone in cold storage is to slow down the fruit and vegetable ripening process (Xu, 1999). Likewise, GO treated melon slices with high flesh firmness values also showed low ethylene production during cold storage (Table 2). The obtained results are similar to the n, Cantwell, and Barrett (1999), who refindings by Luna-Guzma ported that samples treated with gaseous ozone seemed to hold firmness better than other treatments throughout 9 days of storage. n ez, Cantwell, et al. (2008) found similar results in cold Selma, Iba storage of melon slices. 3.3. Weight loss Weight loss of slices was at low values in all treatments at the end of the storage. GO treated slices displayed highest moisture loss (0.30 g/100 g) at day 12 than those of the others, followed by NaClO (0.20 g/100 g). The lowest weight loss (0.01 g/100 g) was obtained in HO treated slices at day 12. Also, control group displayed low weight loss (0.03 g/100 g) at the end of the storage (Table 2). Freshcut vegetables are highly perishable, because internal tissues are exposed and generally lack skin or cuticle as a protective covering and the metabolism of the tissue accelerated by the physical damage caused by the fresh-cut processing (Watada & Qi, 1999). Also, the fact of presenting a great exposed surface area induces a s, higher dehydration, and consequently a high weight loss (Arte mez, & Arte s-Herna ndez, 2007). Sliced melons of all treatGo ments exposed to air during experimental preparation, handling, washing, dipping and packaging, but the slices in GO treatment exposed to air for longer period than those of the others during the gaseous ozone treatment. Therefore, the weight loss of the slices was higher in GO treatment than control, NaClO and HO treatments. The HO was covered over all surfaces of melon slices. The moisture loss of the slices was prevented thanks to this thin layer. Consequently, the lowest weight loss was obtained in HO (0.01 g/ 100 g) treated slices at day 12. However, the weight loss of HO treated slices was 0.04 at day 9. The high moisture loss after day 9 maybe caused to decrease the water content of the slices and slowed down the decreasing in weight loss at day 12. Also, melon slices in control group showed low weight loss at the end of the storage. We considered that treated melon slices had to contact to air more than the control group during the treatments. Therefore, the moisture loss of the melon slices in control group displayed lower values than those of the others (Table 2). 3.4. Respiration rate and ethylene production According to average values, the respiration rate of melon slices in GO treatment displayed lowest value (0.61 mLCO2/kg h) while the highest value (1.43 mLCO2/kg h) was obtained in NaClO treatment. The ethylene production of the melon slices showed lowest value (0.98 mL/kg h) in HO treatment followed by GO (1.04 mL/kg h) and NaClO (1.33 mL/kg h) treatments, while control group displayed the highest value (1.55 mL/kg h) according to average values (Table 2). Among the different plant hormones which are involved in fruit development, ethylene has the main role during melon fruit soft~ ez-Palenius, 2005, p. 215). Luna-Guzm ening (Nun an et al. (1999) reported that an increasing in respiration rate after day 6 could be due to microbial growth. Likewise, according to average values, control group had the highest values of ethylene production (Table 2) with highest level of microbial spoilage at the end of the storage (Table 1).
1150
T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151
3.5. Titratable acidity and pH During storage, a little fluctuation in titratable acidity (TA) and pH values were found in all treatments. In general, TA values tend to decrease and pH values tend to increase compared to initial values to the end of the storage. On the contrary of the general manner, a reverse tendency was obtained in TA and pH values of all treatments during storage. The TA values were increased and pH values were decreased compared to initial values at the end of the storage (Table 2). In general, an increase in pH and a decrease in TA values are observed; however, in some cases a reverse tendency is observed during the last days of storage (Aguayo et al., 2003). The reverse tendency in TA and pH values of the melon slices found during storage (Table 2) was probably due to microbial growth (Aguayo et al., 2003). 3.6. Soluble solid content While the soluble solid contents of the melon slices showed an increase in control and HO treatments, a reduction was found in NaClO and GO treatments compared to initial values. HO treated slices were displayed the highest value (8.58 g/100 g) while the lowest value (6.33 g/100 g) was obtained in NaClO treatment (Table 2). Beaulieu, Ingber, and Lea (2011) found roughly 15% soluble solids loss in melon cubes and thin-slices. Similar to our s (2010) found a reduction and findings, Silveira, Aguayo, and Arte changes in the levels of soluble solid contents with storage time and the researchers based upon this case to influencing of this parameter by the kind of sanitizer. Likewise the soluble solid contents of the melon slices displayed a reduction in GO and NaClO treatments while an increase was found in control and HO treatment compared to initial values (Table 2). 3.7. Flesh color No tissue browning was observed, but yellow color of samples displayed differences depending on treatments throughout storage. Black spot was observed at high levels at day 12 in control group and this caused to a darkening in yellow color of slices. The melon slices in control group were less bright, duller and displayed dark yellow color than the other treatments. GO treated slices were brighter, more vivid and displayed light yellow color than HO, NaClO and control. A very obvious color difference (DE) was determined in control group (Table 2). Color of fresh-cut produce is probably the main quality attribute considered by consumers. Research in the past few years has focused on the prevention of s et al., 2007). No tissue browning was observed discoloration (Arte and yellow color of samples was kept stable throughout storage in all treatments except control. GO treated slices were appeared more vivid and bright at day 12 than those of the others (Table 2). n ez, The obtained results are similar to the findings by Selma, Iba Cantwell, et al. (2008), who reported that gaseous ozone treatment notably affected the color of fresh-cut melon during storage. 3.8. Sensorial attributes From the sensory quality point of view, melon slices in GO treatment were found marketable in day 12 when the external appearance (5.29 points) and taste and flavor (2.50 points) were taken into account together (Table 2). However, according to microbial enumeration results (Table 1), it can be suggested that GO treated slices were marketable for 9 days with good quality. At day 9, the external appearances of the slices in control and NaClO treatment were still acceptable (4.75 and 5.83 points, respectively) from the consumer point of view. However, the taste and flavor
values of the samples were significantly decreased after day 6 and evaluated as poor at day 9. HO treated slices lost their marketable quality at day 9 (3.83 points) and taste and flavor was evaluated as poor (2.33 points) at the same day. So, the melon slices in control, NaClO and HO treatments were found marketable with good quality for 6 days (Table 2). Neither browning of tissues nor black spot was observed in all treatments except control group during storage. Control group showed high level of black spot at day 12. Translucency was not observed in all treatments for 6 days of storage. However, with the prolonged storage life, a slight increase in translucency was observed at day 9 in control (14.3 slices/100 slices), NaClO (22.2 slices/100 slices) and HO treatments (25 slices/ 100 slices). At day 12, translucency was observed in all treatments except GO. Translucency was observed at high levels in NaClO (23.15 slices/100 slices) and HO (27.38 slices/100 slices) treatments and being more evident in samples of control group (33.76 slices/ 100 slices) at the end of the storage (data were not given). Very little amount of juice leakage was observed in NaClO treatment while control and HO treated slices showed much juice leakage at day 12. The integrity of the slices treated with GO preserved better than the others and no juice leakage was observed during storage. The shelf-life of fresh-cut products tends to be very short and even few days of its extension could represent a remarkable advantage for the companies operating in the sector (Manzocco et al., 2011). Delay of spoilage and improvement of sensorial attributes of fresh-cut fruit and vegetables, may also be interesting from lez-Aguilar, & Dela commercial point of view (Ayala-Zavala, Gonza nchez, 2009). Sensory and microbiological quality of the GO Toro-Sa treated samples were at acceptable quality during 9 days of storage (Tables 1 and 2). The obtained results are similar to the findings by n ez, Cantwell, et al. (2008), who reported that the freshSelma, Iba cut melon samples treated with ozone maintained a good visual quality, aroma and firmness. The ozone treatment was found to be better than the chlorine and other organic acid treatments in maintaining the sensory quality of fresh-cut green lettuce (Yadav, 2010). In our research, a greasy texture and slight off-odor was perceived in the HO treated slices. The chemical reactivity of natural antimicrobial agents with fresh fruits and vegetables and package matrix, could significantly affect the sensorial properties of produce (Ayala-Zavala et al., 2009). Next to firmness, the high rate of translucency compared to intact fruit is also an important quality issue for fresh-cut melon. Tissue water soaking or translucency and juice leakage are major factors limiting the longevity and quality of fresh-cut fruits (Guo et al., 2011). Translucency as a symptom of senescence and that all treatments that accelerate ripening, such as high temperatures of storage, prolonged storage time, unwashed cut melon, air atmosphere, using blunt blade for cutting, kind of cut (cylinders compared to trapezoid sections), also increase translucency (Aguayo et al., 2003). Oms-Oliu, Soliva-Fortuny, and Martín-Belloso (2007) reported that translucency may be a consequence of an advanced stage of ripeness, treatments that accelerate ripening or high storage temperatures. Cold storage combined with gaseous ozone and modified atmosphere packaging slowed down the ripening process of the slices during the storage. So, the translucency was successfully prevented by GO treatment during cold storage. It was possible that translucency symptoms were also caused by other factors such as sugar content (Guo et al., 2011). Likewise, high level of sugar content (Table 2) with high level of translucency was observed in control and HO treatment at the end of the storage. 4. Conclusion It was shown with this research that GO treatment was the most effective method and HO was as effective as sodium hypochlorite in
T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151
reducing microbial populations and preserving the quality of freshcut melon during cold storage. References as, I. (2011). Evaluation of alternative Abadias, M., Alegre, I., Usall, J., Torres, R., & Vin sanitizers to chlorine disinfection for reducing foodborne pathogens in freshcut apple. Postharvest Biology and Technology, 59, 289e297. s, F. (2003). Keeping quality and safety of minimally Aguayo, E., Allende, A., & Arte fresh processed melon. European Food Research and Technology, 216, 494e499. Amaro, A. L., Beaulieu, J. C., Grimm, C. C., Stein, R. E., & Almeida, D. P. F. (2012). Effect of oxygen on aroma volatiles and quality of fresh-cut cantaloupe and honeydew melons. Food Chemistry, 130, 49e57. Anonymous. (2012). Turkish national standards. Microbiology section. General guidelines for enumeration of yeasts and molds. Colony counting technique at 25 C. Ankara: Turkish Standards Institute. TS 6580-ISO 7954. Anonymous. (2014d). Turkish National Standards. Microbiology Section. Food and animal feed. General guidelines for enumeration of mesophillic aerobic bacteria. Colony counting technique at 30 C. Ankara: Turkish Standards Institute. TS 7703 EN ISO 4833. Anonymous. (2014a). Food and Agriculture Organization of the United Nations. FAOSTAT-Agriculture. http://www.fao.org/waicent/portal/statistics_en.asp, 06.08.2014. Anonymous. (2014c). Strong oxidizers present alternatives to chlorine washes. FreshCUT Magazine. http://freshcut.com/index.php/magazine/article/1224. Great American Media Services. 06.08.2014. aç kavunları. Dünyada ve Ülkemizde kavunun yeri. http:// Anonymous. (2014b). Kırkag www.kirkagackavunlari.com/dunyadakavununyeri.asp, 06.08.2014. s, F., Go mez, P. A., & Arte s-Hern Arte andez, F. (2007). Physical, physiological and microbial deterioration of minimally fresh processed fruits and vegetables. Food Science and Technology International, 13(3), 177e188. lez-Aguilar, G. A., & Del-Toro-Sa nchez, L. (2009). Enhancing Ayala-Zavala, J. F., Gonza safety and aroma appealing of fresh-cut fruits and vegetables using the antimicrobial and aromatic power of essential oils. Journal of Food Science, 74(7), 84e91. Beaulieu, J. C., Ingber, B. F., & Lea, J. M. (2011). Physiological, volatile, and SEM surface effects resulting from cutting and dipping treatments in cantaloupe. Journal of Food Science, 76(7), 415e422. Dilmaçünal, T. (2009). Normal and controlled atmosphere storage of some apple cultivars grown in organic and conventional farming conditions (PhD thesis). Süleyman Demirel University (in Turkish). Guo, Q., Cheng, L., Wang, J., Che, F., Zhang, P., & Wu, B. (2011). Quality characteristics of fresh-cut ‘Hami’ melon treated with 1-methylcyclopropene. African Journal of Biotechnology, 10(79), 18200e18209. Luna-Guzm an, I., Cantwell, M., & Barrett, D. M. (1999). Fresh-cut cantaloupe: effects of CaCl2 dips and heat treatments on firmness and metabolic activity. Postharvest Biology and Technology, 17, 201e213. Manzocco, L., Pieve, S. D., & Maifreni, M. (2011). Impact of UV-C light on safety and quality of fresh-cut melon. Innovative Food Science and Emerging Technologies, 12, 13e17. Maturin, L., & Peeler, J. T. (2001). Aerobic plate count. Bacteriological analytical manual (8th edition). chapter 3. ~ ez-Palenius, H. G. (2005). Transformation of ‘Galia’ melon to improve fruit quality. Nun A dissertation presented to the graduate school of the University of Florida in
1151
partial fulfillment of the requirements for the degree of doctor of philosophy. University of Florida. Oms-Oliu, G., Soliva-Fortuny, R., & Martín-Belloso, O. (2007). Effect of ripeness on the shelf-life of fresh-cut melon preserved by modified atmosphere packaging. European Food Research and Technology, 225, 301e311. Raybaudi-Massilia, R., Mosqueda-Melgar, J., & Martin-Belloso, O. (2008). Edible alginate-based coating as carrier of antimicrobials to improve shelf-life and safety of fresh-cut melon. International Journal of Food Microbiology, 121, 313e327. Roller, S., & Seedhar, P. (2002). Carvacrol and cinnamic acid inhibit microbial growth in fresh- cut melon and kiwifruit at 4 and 8 C. Letters in Applied Microbiology, 35, 390e394. Saftner, R., Bai, J., Abbott, J. A., & Lee, Y. S. (2003). Sanitary dips with calcium propionate, calcium chloride, or a calcium amino acid chelate maintain quality and shelf stability of fresh-cut honeydew chunks. Postharvest Biology and Technology, 29, 257e269. Saftner, R., Abbott, J. A., Lester, G., & Vinyard, B. (2006). Sensory and analytical comparison of orange-fleshed honeydew to cantaloupe and green-fleshed honeydew for fresh-cut chunks. Postharvest Biology and Technology, 42, 150e160. Saltveit, M. E. (2004). Respiratory metabolism. In The commercial storage of fruits, vegetables, and florist and nursery stocks. Agriculture handbook number 66 http://usna.usda.gov/hb66/019respiration.pdf (viewed on 2nd April 2013). n ez, A. M., Allende, A., Cantwell, M., & Suslow, T. (2008). Effect of Selma, M. V., Iba gaseous ozone and hot water on microbial and sensory quality of cantaloupe and potential transference of Escherichia coli O157:H7 during cutting. Food Microbiology, 25, 162e168. n ez, A. M., Cantwell, M., & Suslow, T. (2008b). Reduction by gaseous Selma, M. V., Iba ozone of Salmonella and microbial flora associated with fresh-cut cantaloupe. Food Microbiology, 25, 558e565. Sensoy, S., Büyükalaca, S., & Abak, K. (2007). Evaluation of genetic diversity in Turkish melons (Cucumis melo L.) based on phenotypic characters and RAPD markers. Genetic Resources and Crop Evolution, 54, 1351e1365. http://dx.doi.org/ 10.1007/s10722-006-9120-6. s, F. (2008). Alternative sanitizers to Silveira, A. C., Conesa, A., Aguayo, E., & Arte chlorine for use on fresh-cut “Galia” (Cucumis melo var. catalupensis) melon. Journal of Food Science, 73(9), 405e411. s, F. (2010). Emerging sanitizers and clean room Silveira, A. C., Aguayo, E., & Arte packaging for improving the microbial quality of fresh-cut ‘Galia’ melon. Food Control, 21, 863e871. Thomas, V., Stack, M. E., Mislivec, P. B., Koch, A., & Bandler, R. (2001). Yeasts, molds and mycotoxins. Bacteriological analytical manual (8th edition). chapter 18. Xu, L. (1999). Use of ozone to improve the safety of fresh fruits and vegetables. Food Technology, 53(10), 58e63. Watada, A. E., & Qi, L. (1999). Quality control of minimally-processed vegetables. In J. M. Lee, K. C. Gross, A. E. Watada, & S. K. Lee (Eds.), Acta Horticulturae: Vol. 483. Proc. Int. Symp. on Quality of fresh and fermented vegetables (pp. 209e220). Yadav, L. (2010). The effect of ozone on the growth and development of selected food spoilage fungi. ISBN-10:1-59942-352-9, ISBN-13: 978-1-59942-352-4. Dissertation.com, Boca Raton, Florida, U.S.A http://www.bookpump.com/dps/pdfb/9423529b.pdf. lu, S¸., & S¸engül, N. (2009). Effects of different Yıldırım, O., Halloran, N., Çavus¸og irrigation programs on the growth, yield, and fruit quality of drip-irrigated melon. Turkish Journal of Agriculture and Forestry, 33, 243e255.
Contents lists available at ScienceDirect
LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt
Efficacy of some antimicrobial treatments compared to sodium hypochlorite on physical, physiological and microbial quality of fresh-cut melons (Cucumis melo L. var. inodorus) Tuba Dilmaçünal a, *, Derya Erbas¸ a, Mehmet Ali Koyuncu a, Cemile Ebru Onursal b, Hakan Kuleas¸an c a b c
Suleyman Demirel University, Faculty of Agriculture, Department of Horticulture, 32260, Isparta, Turkey irdir Horticultural Research Institute, 32500, Isparta, Turkey Eg Suleyman Demirel University, Faculty of Engineering, Department of Food Technology, 32260, Isparta, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history: Received 5 April 2013 Received in revised form 30 June 2014 Accepted 24 July 2014 Available online 2 August 2014
aç’ melons (Cucumis melo L. var. inodorus cv. ‘Kırkag aç’) were hand-harvested at a Turkish-type ‘Kırkag commercial harvest maturity stage from a greenhouse in Turkey (Antalya). Fruits were divided into four groups for the experiments: 1. Control (C), 2. Hazelnut oil (HO), 3. Gaseous Ozone (GO), and 4. NaClO. After the treatments, slices were placed immediately to lidded plastic boxes (500 g capacity) and stored in a cold room at 5 C and 90 ± 5% relative humidity for 12 days. Fruits were evaluated at three-day intervals for microbial enumeration, firmness, flesh color, titratable acidity (TA), pH, soluble solid content (SSC), weight loss, sensorial attributes (external appearance, taste-flavor and translucency), respiration rate and ethylene production. The integrity of the slices treated with GO was preserved better than those of the others and no juice leakage was observed during storage. According to the results, especially for microbial and sensorial attributes, control, NaClO and HO treated melon slices were preserved their quality for six days, whereas GO treated samples were stored for nine days with good quality. © 2014 Elsevier Ltd. All rights reserved.
Keywords: Cold storage Gaseous ozone Hazelnut oil aç Kırkag Sodium hypochlorite
1. Introduction The melon is one of the most economically important and widely cultivated crops in the world, and Turkey is the second largest producer after China, producing 1,708,415 million t annually (Anonymous, 2014a). The European and American melon markets are dominated by two major cultivar types differing in quality attributes and postharvest behavior. Cantaloupensis and Reticulatus groups include the very aromatic, climacteric, and fast senescing cantaloupes and muskmelons; Inodorus group includes the less aromatic, non-climacteric, slow senescing melons (Amaro, Beaulieu, Grimm, Stein, & Almeida, 2012). aç (Cucumis melo L. var. inodorus) is one of the commonly Kırkag grown melon cultivars, particularly in the Aegean and the Central lu, & S¸engül, Anatolia regions of Turkey (Yıldırım, Halloran, Çavus¸og 2009). It has generally light green skin color with dark green spots at first, yellow at maturity (Sensoy, Büyükalaca, & Abak, 2007). Its
* Corresponding author. Tel.: þ90 246 2113923; fax: þ90 246 2118696. E-mail addresses: [email protected], [email protected] (T. Dilmaçünal). http://dx.doi.org/10.1016/j.lwt.2014.07.033 0023-6438/© 2014 Elsevier Ltd. All rights reserved.
fruit flesh is sweet and delicious and they are more resistant to transportation and postharvest resting than many other cultivars aç melons has (Yıldırım et al., 2009). Exportation value of Kırkag gained importance in recent years thanks to its high quality characteristics (Anonymous, 2014b). Fresh-cut processing of fruit and vegetables is well known to promote faster deterioration in comparison with their intact counterparts. In particular, microbial growth and development of biochemical reactions on wounded plant tissues are responsible for safety and quality degradation of the product, which translate not only in food spoilage but also in risk for foodborn illness (Manzocco, Pieve, & Maifreni, 2011). Safe production methods and proper disinfection/decontamination procedures are therefore critical steps in ensuring the safety of ready-to-eat fresh fruit and vege as, 2011). tables (Abadias, Alegre, Usall, Torres, & Vin Chlorine is the most common sanitizer used in fresh-cut fruit and vegetable production (Anonymous, 2014c). The common form of chlorine used in the fresh production industry is sodium hypochlorite (NaClO). The use of hypochlorite-based systems for fresh product washing is already prohibited in various European Union countries because of the risk of a range of cancers (Silveira, Conesa,
T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151
s, 2008). Additionally, on fresh-cut melon cubes, Aguayo, & Arte chlorine resulted in less than a 90% reduction in viable cells of n ez, Cantwell, & Suslow, several strains of Salmonella (Selma, Iba 2008). The concept of using multiple intervention methods or various preservation technologies that are healthier for consumers n ez, Allende, Cantwell, is increasing in their importance (Selma, Iba & Suslow, 2008). Therefore, there is much interest in developing safer and more effective sanitizers for fruit and vegetable (Abadias et al., 2011). The use of ozone gaseous has been suggested as an alternative to reduce microbial populations on melon before cutn ez, Cantwell, et al., 2008). Hazelnut oil (Oleum ting (Selma, Iba Coryli) is an edible oil extracted from hazelnut (Corylus avellana L.) fruit seeds without heat treatment and chemical application, naturally by cold pressing method by a firm operating in Turkey. It contains essential fatty acids (Omega-3, 6 and 9) as well as vitamin E. Vitamin E is a good antioxidant and has beneficial impacts in lowering cholesterol and protecting cardiovascular health and it can be used as an alternative in reducing microbial populations and quality losses. The aim of this work was to evaluate the efficacy of some treatments compared to NaClO in reducing microbial populations aç’ and remaining the quality of cold stored fresh-cut ‘Kırkag melons. 2. Materials and methods 2.1. Plant material aç’ (Cucumis melo L. var. inodorus Turkish-type melons cv. ‘Kırkag aç’), grown under greenhouse conditions in the Medicv. ‘Kırkag terranean region of Turkey (Antalya), were hand-harvested in June at the commercial harvest maturity stage and transported immediately to the laboratory. Melons were inspected carefully and fruit with no visual defects and uniform in shape and size were selected. Fruit skin color was yellow on green spotted, wrinkled and medium-thick and resistant to transporting and have a long shelf life. Fruit flesh color was white-cream, juicy, delicious and sweet. The average weight of fruits was 3350 g, average fruit diameter was 23.5 cm and average fruit length was 23.25 cm. 2.2. Storage conditions Fruits were transported immediately to the laboratory and all fruits and dipping water were chilled to 5 C overnight before processing on the following morning. Disposable gloves were worn during preparation of the fruits. Chopping boards and knives were disinfected with sodium hypochlorite (NaClO), washed with tap water, sanitized with ethyl alcohol and air-dried immediately before use. Also workbench and boxes were sanitized with ethyl alcohol. In a clean cold room, at 5 C, whole unprocessed melons (12 melons for each treatment, totally 48 melons for all experiments) were washed with tap water at 5 C, drained and dried with blotting paper before the treatments. All unprocessed melons were dipped into distilled water (DW) at 5 C for 2 min, drained and dried with blotting paper, peeled, halved, cored and hand cut to obtain trapezoidal sections (3.0 ± 0.4 cm of wide, 4.0 ± 0.5 of length) before the treatments except NaClO treatment. Unprocessed melons, prepared for NaClO treatment, were dipped into NaClO solution (200 mL/L, pH 6.5) at 5 C for 2 min drained and dried with blotting paper, peeled, halved, cored and hand cut to obtain trapezoidal sections (3.0 ± 0.4 cm of wide, 4.0 ± 0.5 of length). After dipping, fruits were prepared for the experiments: 1. Control (C): Slices were dipped into DW for thirty seconds. 2. Hazelnut oil (HO): HO was put into a sprayer and sprayed on melon slices. HO was extracted from hazelnut (Corylus avellana L.) fruit
1147
seeds without heat treatment and chemical application, naturally by cold pressing method by a firm operating in Turkey. HO contains essential fatty acids (Omega-3, 6 and 9) and also, vitamin E. HO is a good antioxidant and has positive impacts in lowering cholesterol and protecting cardiovascular health. 3. Gaseous Ozone (GO): Slices were treated with 6.34 mg/m3 gaseous ozone by an ozone generator (OPAL, OGHe03, Turkey) in a glass gas tight cabinet for 3 h 4. Sodium hypochlorite (NaClO): Slices were dipped into NaClO solution (150 mL/L, pH 6.5) at 5 C for thirty seconds. After the treatments, slices (22 ± 2 slices per each boxes) were placed immediately to lidded plastic boxes (500 g capacity) and stored in a cold room at 5 C temperature and 90 ± 5% relative humidity for 12 days. The experiment was set up with 3 replication, each package was regarded as a replication, and totally 60 boxes of melon slices were used during analyzing periods. Melon slices were analyzed initially (initial analyses were made after the treatments) and at three-day intervals for microbial enumeration, flesh firmness, flesh color, titratable acidity (TA), pH, soluble solid content (SSC), weight loss, sensorial attributes (external appearance, tasteflavor and translucency), respiration rate and ethylene production during storage.
2.3. Physical and chemical analyses Analyses were made initially and at three-day intervals during cold storage. Fruit firmness was determined using a digital texture machine (AMETEK LLOYD Instruments LF-Plus Tensile Tester, England) and measured via compression using a 50 N load cell and a stainless steel, 5.1 mm diameter cylindrical probe with a constant speed of 100 mm/min at harvest date and during storage period. The maximum force (N) generated during the probe travel was used for data analysis. Fruit flesh color was determined using a chromameter (Minolta CR-300, Minolta Ramsey, NJ, USA). The dimensions L*, a*, and b* were obtained, and the L*, C* and h values were used to determine the color of melon slices. L* indicates lightness and is the same as the L*a*b* color space, C* is chroma, and h is the hue angle. The value of C* is 0 at the center and increases according to the distance from the center. Hue angle is defined as starting at the þa* axis and is expresses in degrees; 0 would be þa* (red), 90 would be þb* (yellow), 180 would be a*(green) and 270 would be b* (blue). The hue angle was calculated (h ¼ arctan b*/a*) and expressed in degrees ( ). Saturation index, or Table 1 aç melon slices stored for 12 days at Microbial counts (log cfu/g) of fresh-cut Kırkag 5 C. Days
GOb
Control
Aerobic bacteria 0 3.32 ± 0.03 3 4.39 ± 0.07 6 4.73 ± 0.13 9 6.61 ± 0.36 12 7.08 ± 0.17
aAa bA cA dA eA
3.23 3.71 4.51 4.78 5.06
Yeast and molds 0 2.56 ± 0.23 3 2.74 ± 0.13 6 3.16 ± 0.09 9 4.36 ± 0.31 12 4.92 ± 0.06
aA aA aA bA bA
0 0 0 0 0
aB aB aB aB aB
HOc ± ± ± ± ±
0.10 0.12 0.23 0.10 0.06
aA bB cA cdB dB
NaClOd
3.35 4.87 5.24 5.42 5.83
± ± ± ± ±
0.10 0.23 0.08 0.30 0.11
aAB bA bcB cdC dC
3.63 4.40 4.84 6.22 6.84
± ± ± ± ±
0.08 0.26 0.03 0.06 0.12
aB bA cA dAC eA
2.10 2.40 2.69 3.01 3.31
± ± ± ± ±
0.17 0.17 0.09 0.11 0.08
aC abAC bcC cdC dC
0 aB 2.15 ± 3.21 ± 3.32 ± 4.13 ±
0.28 0.16 0.50 0.09
bC bcA cC cD
GO: Gaseous ozone, HO: Hazelnut oil, NaClO: Sodium hypochlorite. a Capital letters in lines show comparisons between applications and small letters in columns show comparisons between storage periods. Same letters in lines or columns indicates no significance at p < 0.05, n ¼ 3, Tukey. b GO: Gaseous ozone. c HO: Hazelnut oil. d NaClO: Sodium hypochlorite.
1148
T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151
Table 2 The quality attributes (weight loss, firmness, soluble solid contents (SSC), titratable acidity (TA), pH, ethylene production, respiration rate, taste- flavor, external appearance, aç melon slices stored for 12 days at 5 C. color (L*, C*, h and DE*)) of fresh-cut Kırkag Treatments
Control
Storage period (days)
0 3 6 9 12 0 NaClOd 3 6 9 12 e HO 0 3 6 9 12 f GO 0 3 6 9 12 Storage period (SP) Treatment (T) T SP
Weight loss
Firmness
e 0.003 0.034 0.027 0.028 e 0.163 0.051 0.038 0.204 e 0.000 0.015 0.042 0.417 e 0.482 0.391 0.417 0.300 ** ** **
5.88 3.73 4.87 4.54 3.15 5.21 4.11 4.09 4.38 4.07 4.94 3.89 3.38 2.36 2.97 4.02 4.09 4.35 4.06 4.29 ** ** **
SSC
6.25 7.32 7.92 7.35 7.27 6.83 6.25 6.43 5.63 6.33 7.35 6.45 7.82 8.32 8.5 7.45 6.73 7.58 6.68 6.85 ns **b ns
TA
0.090 0.100 0.127 0.125 0.121 0.100 0.097 0.101 0.098 0.134 0.090 0.107 0.108 0.120 0.113 0.080 0.113 0.110 0.114 0.133 ** nsc *a
pH
5.44 5.55 5.41 5.40 5.40 5.44 5.48 5.44 5.45 5.08 5.66 5.47 5.49 5.82 5.61 5.60 5.38 5.40 5.56 5.20 ** ** **
Ethylene production
Respiration rate
Taste-flavor (1e5 scale)
External appearance (1e9 scale)
L* (lightness)
C* (chroma)
h (hue angle)
DE
0.801 1.733 1.397 2.619 1.207 0.955 1.841 1.057 0.759 0.278 2.354 1.072 1.108 1.455 0.642 1.022 0.650 1.016 1.274 1.242 ns ns *
0.017 1.797 1.351 1.323 1.991 0.020 1.540 1.455 1.131 0.976 0.019 2.414 2.105 2.573 1.078 0.020 0.560 1.198 1.258 0.930 ** * ns
5.00 4.93 4.21 1.92 1.00 5.00 3.17 3.13 1.83 1.33 5.00 3.39 2.93 2.33 1.89 5.00 4.13 2.92 2.87 2.50 ** ** **
9.00 8.73 8.46 4.75 1.00 9.00 8.80 8.46 5.83 3.38 9.00 8.33 7.39 4.83 4.72 9.00 8.87 8.54 5.75 5.29 ** ** **
76.32 73.25 74.71 74.33 69.34 73.13 70.32 72.00 75.02 70.37 73.12 73.51 74.04 70.82 73.22 71.36 73.86 70.25 72.95 75.60 ns ns *
11.77 10.64 10.27 9.23 8.52 10.35 10.07 10.63 9.74 9.38 12.75 12.32 11.26 12.06 10.73 10.39 10.63 11.43 10.61 10.02 * * *
111.93 110.96 110.27 111.39 109.66 112.28 112.09 112.89 111.66 110.87 112.18 111.55 111.16 109.39 110.42 111.51 111.41 112.39 111.02 112.70 ns * ns
e 3.37 3.12 3.65 10.55 e 1.92 1.35 2.01 1.05 e 1.69 4.15 1.66 1.55 e 2.13 2.03 2.30 2.90 ** ** **
(Delta E)
a *: p < 0.05; b**: p < 0.01; cns: not significant, n ¼ 3. Scale of external appearance: 1e9: 1e4: poor, 5: marketable, 7e8: good, 9: excellent; Scale of taste-flavor: 1e5: 1: very poor, 2: poor, 3: mild, 4: good, 5: excellent. d NaClO: Sodium hypochlorite. e HO: Hazelnut oil. f GO: Gaseous ozone.
purity of color (chroma), was also calculated [C* ¼ ((a*)2 þ (b*)2)1/2] and expressed numerically. Also, fruit flesh color was represented * ¼ ððL* L* Þ2 þ ða* a* Þ2 þ ðb* b* Þ2 Þ1=2 as color difference ½DEab 2 1 2 1 2 1 in Table 2. Weight loss was expressed as the percentage of loss of weight with respect to the initial weight. The soluble solid content (SSC) was measured using a digital refractometer (Atago Pocket PAL-1, Tokyo, Japan) and SSC was expressed as percentage of soluble solids per 100 g fresh weight. Titratable acidity (TA) was determined by a digital pH meter (Hanna Instruments HI 9231, Italy) and titrimeter (Isolab Digitrate, Germany), and expressed as percentage of grams of malic acid equivalent per 100 g fresh weight and pH was measured by a digital pH meter (Hanna Instruments HI 9231, Italy). For respiration measurements, the static system described by Saltveit (2004) was used. Respiration rate and ethylene production were determined by gas chromatography. Samples were put in a gas tight glass jars at room temperature at harvest date and three-day intervals during storage. Gas sample was taken from the jars at the end of the 4 h. Measurements were made in split/splitless (S/SL) of inlet in split mode with gas sampling valve with 1-mL gas sample by using fused silica capilar column (GS-GASPRO, 30 m 0.32 mm I.D., U.S.A), with thermal conductivity detector (TCD) for respiration rate measurements and flame ionization detector (FID) for ethylene production measurements by Agilent GC-6890N (U.S.A and Canada) model gas chromatography (GC) and Chemstation A.09.03 [1417] software. Carrier gas flow was 1.7 mL/min in stable flow mode. The temperature of the oven, TCD and FID detectors were 40 C (isothermal), 250 C and 250 C, respectively (Dilmaçünal, 2009, p. 188).
buffered saline (PBS) and homogenized in a stomacher (BagMixer 400, USA) for thirty seconds. After homogenization, samples were serially diluted in sterile PBS. After dilutions were made, 0.1 mL sample from each dilution was plated on proper media plates in triplicate. Plate count agar (PCA, Merck, Germany) was used for the determination of total aerobic bacteria. The plates were incubated at 30 C for 24e48 h (Maturin & Peeler, 2001; Anonymous, 2014d). Yeasts and molds were counted on Malt Extract Agar (MEA, Merck, Germany). The pH of MEA plates was adjusted to 3.5 and 50 mg/L chloramphenicol was added to suppress undesired bacterial growth. PDA plates were incubated at 25 C for 48e72 h (Thomas, Stack, Mislivec, Koch & Bandler, 2001; Anonymous, 2012). After incubation, plates were counted and data was analyzed. 2.5. Sensorial attributes External appearance of fresh-cut melons was evaluated using a scale of 1e9: 1e4: poor, 5: marketable, 7e8: good, 9: excellent. Taste and flavor of melon slices were evaluated using a scale of 1e5: 1: very poor, 2: poor, 3: mild, 4: good, 5: excellent. Translucency was evaluated by counting deteriorated melon slices and expressed as a percentage of the total number of slices. The analyses were conducted by a panel of 15 (age range of 30, 8 women and 7 men) trained judges. They were trained before the sensorial analyses at postharvest physiology laboratory for the evaluation of the sensory quality characteristics of fruits. 2.6. Experimental design and statistical analyses
2.4. Microbial enumeration In order to determine the number of microorganisms, 25 g of melon sample was added into 225 mL of 1 g/100 mL phosphate-
The experiment followed a completely randomized design with 3 replication and each package was regarded as a replication. The differences between the mean of the groups was determined by Tukey. All analyses were performed using the Minitab® 15 statistics
T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151
software (Minitab Inc. USA). Microbial counts were first subjected to logarithmic conversion. The analysis of covariance was used to decide whether significant differences (p < 0.05) existed among treatments. 3. Results and discussion 3.1. Microbial enumeration The effect of storage period and treatments on the number of microorganisms was statistically significant (p < 0.05). GO was determined to be the most effective treatment for the inhibition of both bacteria and fungi in fresh-cut melon samples during storage. Its effect on yeasts and molds was significantly above other treatments. While GO totally inhibited the growth of yeasts and molds, the number of bacteria increased to serious numbers during 12 day storage. Although, NaClO limited the growth of yeasts and molds, the level of inhibition was not comparable to that of GO. The treatment prevented the growth of bacteria at initial period. On the other hand the total number of bacteria increased to higher numbers after 3 days showing that NaClO treatment affected only bacterial cells in vegetative forms but not bacterial spores. After initial period spores germinated and became vegetative again. The number of yeasts and molds were 4.13 log cfu/g after 12 days. Inhibitory effect of HO on both bacteria and fungi was astonishing. It was determined that degree of inhibition was better when compared to NaClO treatment (Table 1). Microbial quality of freshcut melons during storage is depended on some factors such as genotype, maturity, soluble solid content, packaging material and storage temperature (Roller & Seedhar, 2002; Saftner, Bai, Abbott, & Lee, 2003). Maximum required microbial limit set by Turkish legislations (Anonymous, 2012) for mesophilic aerobic bacterial growth (107 cfu/g) was not exceeded in this study after 12 days of storage at 5 C by all experimental groups except control group (Table 1). Saftner, Abbott, Lester, and Vinyard (2006) reported that microbial population tended to increase in stored melons after 2 days and a rapid increase was found after 5 days of storage. The efficacy of decontamination methods is reflected in the microbiological reduction obtained and, even more important, in the maintenance of this reduction during storage (Abadias et al., 2011). GO treatment was determined to be the most effective method for the inhibition of both bacteria and fungi in fresh-cut melon samples during storage. Its effect on yeasts and molds was significantly above of the other applications. While GO totally inhibited the growth of yeasts and molds, the number of bacteria increased to serious numbers on day 12 of storage. Similar inhibitory effect of edible alginates on fungi was also reported by Raybaudi-Massilia, Mosqueda-Melgar, and Martin-Belloso (2008). However the effect of alginates on bacterial species was not that strong. Aguayo, s (2003) stated that the number of bacteria after Allende, and Arte 14 days of storage in modified atmosphere packaged melons were more than 107 cfu/g. The number of yeasts recorded in their study was similar to our findings. Inhibitory effect of HO on both bacteria and fungi was better when compared to NaClO. It can be explained by strong binding and coating effect of HO. The oil forms a layer on the surface of melon slices which prevents accession of microbial cells to nutrients. The coating effect may also limit the oxygen intake of aerobic microorganisms. Being a common food without any putative effect is another feature of edible oil which can be used as a coating material for fresh-cut fruits. 3.2. Firmness The melon slices became softer compared to harvest date in all treatments with increasing storage period except the GO treatment.
1149
Control group displayed the highest firmness loss (46.43 N/100 N), followed by HO (39.88 N/100 N), and NaClO (21.88 N/100 N) (Table 2). The melon slices treated with HO had a greasy texture especially in last days of storage. One of the important effects of ozone in cold storage is to slow down the fruit and vegetable ripening process (Xu, 1999). Likewise, GO treated melon slices with high flesh firmness values also showed low ethylene production during cold storage (Table 2). The obtained results are similar to the n, Cantwell, and Barrett (1999), who refindings by Luna-Guzma ported that samples treated with gaseous ozone seemed to hold firmness better than other treatments throughout 9 days of storage. n ez, Cantwell, et al. (2008) found similar results in cold Selma, Iba storage of melon slices. 3.3. Weight loss Weight loss of slices was at low values in all treatments at the end of the storage. GO treated slices displayed highest moisture loss (0.30 g/100 g) at day 12 than those of the others, followed by NaClO (0.20 g/100 g). The lowest weight loss (0.01 g/100 g) was obtained in HO treated slices at day 12. Also, control group displayed low weight loss (0.03 g/100 g) at the end of the storage (Table 2). Freshcut vegetables are highly perishable, because internal tissues are exposed and generally lack skin or cuticle as a protective covering and the metabolism of the tissue accelerated by the physical damage caused by the fresh-cut processing (Watada & Qi, 1999). Also, the fact of presenting a great exposed surface area induces a s, higher dehydration, and consequently a high weight loss (Arte mez, & Arte s-Herna ndez, 2007). Sliced melons of all treatGo ments exposed to air during experimental preparation, handling, washing, dipping and packaging, but the slices in GO treatment exposed to air for longer period than those of the others during the gaseous ozone treatment. Therefore, the weight loss of the slices was higher in GO treatment than control, NaClO and HO treatments. The HO was covered over all surfaces of melon slices. The moisture loss of the slices was prevented thanks to this thin layer. Consequently, the lowest weight loss was obtained in HO (0.01 g/ 100 g) treated slices at day 12. However, the weight loss of HO treated slices was 0.04 at day 9. The high moisture loss after day 9 maybe caused to decrease the water content of the slices and slowed down the decreasing in weight loss at day 12. Also, melon slices in control group showed low weight loss at the end of the storage. We considered that treated melon slices had to contact to air more than the control group during the treatments. Therefore, the moisture loss of the melon slices in control group displayed lower values than those of the others (Table 2). 3.4. Respiration rate and ethylene production According to average values, the respiration rate of melon slices in GO treatment displayed lowest value (0.61 mLCO2/kg h) while the highest value (1.43 mLCO2/kg h) was obtained in NaClO treatment. The ethylene production of the melon slices showed lowest value (0.98 mL/kg h) in HO treatment followed by GO (1.04 mL/kg h) and NaClO (1.33 mL/kg h) treatments, while control group displayed the highest value (1.55 mL/kg h) according to average values (Table 2). Among the different plant hormones which are involved in fruit development, ethylene has the main role during melon fruit soft~ ez-Palenius, 2005, p. 215). Luna-Guzm ening (Nun an et al. (1999) reported that an increasing in respiration rate after day 6 could be due to microbial growth. Likewise, according to average values, control group had the highest values of ethylene production (Table 2) with highest level of microbial spoilage at the end of the storage (Table 1).
1150
T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151
3.5. Titratable acidity and pH During storage, a little fluctuation in titratable acidity (TA) and pH values were found in all treatments. In general, TA values tend to decrease and pH values tend to increase compared to initial values to the end of the storage. On the contrary of the general manner, a reverse tendency was obtained in TA and pH values of all treatments during storage. The TA values were increased and pH values were decreased compared to initial values at the end of the storage (Table 2). In general, an increase in pH and a decrease in TA values are observed; however, in some cases a reverse tendency is observed during the last days of storage (Aguayo et al., 2003). The reverse tendency in TA and pH values of the melon slices found during storage (Table 2) was probably due to microbial growth (Aguayo et al., 2003). 3.6. Soluble solid content While the soluble solid contents of the melon slices showed an increase in control and HO treatments, a reduction was found in NaClO and GO treatments compared to initial values. HO treated slices were displayed the highest value (8.58 g/100 g) while the lowest value (6.33 g/100 g) was obtained in NaClO treatment (Table 2). Beaulieu, Ingber, and Lea (2011) found roughly 15% soluble solids loss in melon cubes and thin-slices. Similar to our s (2010) found a reduction and findings, Silveira, Aguayo, and Arte changes in the levels of soluble solid contents with storage time and the researchers based upon this case to influencing of this parameter by the kind of sanitizer. Likewise the soluble solid contents of the melon slices displayed a reduction in GO and NaClO treatments while an increase was found in control and HO treatment compared to initial values (Table 2). 3.7. Flesh color No tissue browning was observed, but yellow color of samples displayed differences depending on treatments throughout storage. Black spot was observed at high levels at day 12 in control group and this caused to a darkening in yellow color of slices. The melon slices in control group were less bright, duller and displayed dark yellow color than the other treatments. GO treated slices were brighter, more vivid and displayed light yellow color than HO, NaClO and control. A very obvious color difference (DE) was determined in control group (Table 2). Color of fresh-cut produce is probably the main quality attribute considered by consumers. Research in the past few years has focused on the prevention of s et al., 2007). No tissue browning was observed discoloration (Arte and yellow color of samples was kept stable throughout storage in all treatments except control. GO treated slices were appeared more vivid and bright at day 12 than those of the others (Table 2). n ez, The obtained results are similar to the findings by Selma, Iba Cantwell, et al. (2008), who reported that gaseous ozone treatment notably affected the color of fresh-cut melon during storage. 3.8. Sensorial attributes From the sensory quality point of view, melon slices in GO treatment were found marketable in day 12 when the external appearance (5.29 points) and taste and flavor (2.50 points) were taken into account together (Table 2). However, according to microbial enumeration results (Table 1), it can be suggested that GO treated slices were marketable for 9 days with good quality. At day 9, the external appearances of the slices in control and NaClO treatment were still acceptable (4.75 and 5.83 points, respectively) from the consumer point of view. However, the taste and flavor
values of the samples were significantly decreased after day 6 and evaluated as poor at day 9. HO treated slices lost their marketable quality at day 9 (3.83 points) and taste and flavor was evaluated as poor (2.33 points) at the same day. So, the melon slices in control, NaClO and HO treatments were found marketable with good quality for 6 days (Table 2). Neither browning of tissues nor black spot was observed in all treatments except control group during storage. Control group showed high level of black spot at day 12. Translucency was not observed in all treatments for 6 days of storage. However, with the prolonged storage life, a slight increase in translucency was observed at day 9 in control (14.3 slices/100 slices), NaClO (22.2 slices/100 slices) and HO treatments (25 slices/ 100 slices). At day 12, translucency was observed in all treatments except GO. Translucency was observed at high levels in NaClO (23.15 slices/100 slices) and HO (27.38 slices/100 slices) treatments and being more evident in samples of control group (33.76 slices/ 100 slices) at the end of the storage (data were not given). Very little amount of juice leakage was observed in NaClO treatment while control and HO treated slices showed much juice leakage at day 12. The integrity of the slices treated with GO preserved better than the others and no juice leakage was observed during storage. The shelf-life of fresh-cut products tends to be very short and even few days of its extension could represent a remarkable advantage for the companies operating in the sector (Manzocco et al., 2011). Delay of spoilage and improvement of sensorial attributes of fresh-cut fruit and vegetables, may also be interesting from lez-Aguilar, & Dela commercial point of view (Ayala-Zavala, Gonza nchez, 2009). Sensory and microbiological quality of the GO Toro-Sa treated samples were at acceptable quality during 9 days of storage (Tables 1 and 2). The obtained results are similar to the findings by n ez, Cantwell, et al. (2008), who reported that the freshSelma, Iba cut melon samples treated with ozone maintained a good visual quality, aroma and firmness. The ozone treatment was found to be better than the chlorine and other organic acid treatments in maintaining the sensory quality of fresh-cut green lettuce (Yadav, 2010). In our research, a greasy texture and slight off-odor was perceived in the HO treated slices. The chemical reactivity of natural antimicrobial agents with fresh fruits and vegetables and package matrix, could significantly affect the sensorial properties of produce (Ayala-Zavala et al., 2009). Next to firmness, the high rate of translucency compared to intact fruit is also an important quality issue for fresh-cut melon. Tissue water soaking or translucency and juice leakage are major factors limiting the longevity and quality of fresh-cut fruits (Guo et al., 2011). Translucency as a symptom of senescence and that all treatments that accelerate ripening, such as high temperatures of storage, prolonged storage time, unwashed cut melon, air atmosphere, using blunt blade for cutting, kind of cut (cylinders compared to trapezoid sections), also increase translucency (Aguayo et al., 2003). Oms-Oliu, Soliva-Fortuny, and Martín-Belloso (2007) reported that translucency may be a consequence of an advanced stage of ripeness, treatments that accelerate ripening or high storage temperatures. Cold storage combined with gaseous ozone and modified atmosphere packaging slowed down the ripening process of the slices during the storage. So, the translucency was successfully prevented by GO treatment during cold storage. It was possible that translucency symptoms were also caused by other factors such as sugar content (Guo et al., 2011). Likewise, high level of sugar content (Table 2) with high level of translucency was observed in control and HO treatment at the end of the storage. 4. Conclusion It was shown with this research that GO treatment was the most effective method and HO was as effective as sodium hypochlorite in
T. Dilmaçünal et al. / LWT - Food Science and Technology 59 (2014) 1146e1151
reducing microbial populations and preserving the quality of freshcut melon during cold storage. References as, I. (2011). Evaluation of alternative Abadias, M., Alegre, I., Usall, J., Torres, R., & Vin sanitizers to chlorine disinfection for reducing foodborne pathogens in freshcut apple. Postharvest Biology and Technology, 59, 289e297. s, F. (2003). Keeping quality and safety of minimally Aguayo, E., Allende, A., & Arte fresh processed melon. European Food Research and Technology, 216, 494e499. Amaro, A. L., Beaulieu, J. C., Grimm, C. C., Stein, R. E., & Almeida, D. P. F. (2012). Effect of oxygen on aroma volatiles and quality of fresh-cut cantaloupe and honeydew melons. Food Chemistry, 130, 49e57. Anonymous. (2012). Turkish national standards. Microbiology section. General guidelines for enumeration of yeasts and molds. Colony counting technique at 25 C. Ankara: Turkish Standards Institute. TS 6580-ISO 7954. Anonymous. (2014d). Turkish National Standards. Microbiology Section. Food and animal feed. General guidelines for enumeration of mesophillic aerobic bacteria. Colony counting technique at 30 C. Ankara: Turkish Standards Institute. TS 7703 EN ISO 4833. Anonymous. (2014a). Food and Agriculture Organization of the United Nations. FAOSTAT-Agriculture. http://www.fao.org/waicent/portal/statistics_en.asp, 06.08.2014. Anonymous. (2014c). Strong oxidizers present alternatives to chlorine washes. FreshCUT Magazine. http://freshcut.com/index.php/magazine/article/1224. Great American Media Services. 06.08.2014. aç kavunları. Dünyada ve Ülkemizde kavunun yeri. http:// Anonymous. (2014b). Kırkag www.kirkagackavunlari.com/dunyadakavununyeri.asp, 06.08.2014. s, F., Go mez, P. A., & Arte s-Hern Arte andez, F. (2007). Physical, physiological and microbial deterioration of minimally fresh processed fruits and vegetables. Food Science and Technology International, 13(3), 177e188. lez-Aguilar, G. A., & Del-Toro-Sa nchez, L. (2009). Enhancing Ayala-Zavala, J. F., Gonza safety and aroma appealing of fresh-cut fruits and vegetables using the antimicrobial and aromatic power of essential oils. Journal of Food Science, 74(7), 84e91. Beaulieu, J. C., Ingber, B. F., & Lea, J. M. (2011). Physiological, volatile, and SEM surface effects resulting from cutting and dipping treatments in cantaloupe. Journal of Food Science, 76(7), 415e422. Dilmaçünal, T. (2009). Normal and controlled atmosphere storage of some apple cultivars grown in organic and conventional farming conditions (PhD thesis). Süleyman Demirel University (in Turkish). Guo, Q., Cheng, L., Wang, J., Che, F., Zhang, P., & Wu, B. (2011). Quality characteristics of fresh-cut ‘Hami’ melon treated with 1-methylcyclopropene. African Journal of Biotechnology, 10(79), 18200e18209. Luna-Guzm an, I., Cantwell, M., & Barrett, D. M. (1999). Fresh-cut cantaloupe: effects of CaCl2 dips and heat treatments on firmness and metabolic activity. Postharvest Biology and Technology, 17, 201e213. Manzocco, L., Pieve, S. D., & Maifreni, M. (2011). Impact of UV-C light on safety and quality of fresh-cut melon. Innovative Food Science and Emerging Technologies, 12, 13e17. Maturin, L., & Peeler, J. T. (2001). Aerobic plate count. Bacteriological analytical manual (8th edition). chapter 3. ~ ez-Palenius, H. G. (2005). Transformation of ‘Galia’ melon to improve fruit quality. Nun A dissertation presented to the graduate school of the University of Florida in
1151
partial fulfillment of the requirements for the degree of doctor of philosophy. University of Florida. Oms-Oliu, G., Soliva-Fortuny, R., & Martín-Belloso, O. (2007). Effect of ripeness on the shelf-life of fresh-cut melon preserved by modified atmosphere packaging. European Food Research and Technology, 225, 301e311. Raybaudi-Massilia, R., Mosqueda-Melgar, J., & Martin-Belloso, O. (2008). Edible alginate-based coating as carrier of antimicrobials to improve shelf-life and safety of fresh-cut melon. International Journal of Food Microbiology, 121, 313e327. Roller, S., & Seedhar, P. (2002). Carvacrol and cinnamic acid inhibit microbial growth in fresh- cut melon and kiwifruit at 4 and 8 C. Letters in Applied Microbiology, 35, 390e394. Saftner, R., Bai, J., Abbott, J. A., & Lee, Y. S. (2003). Sanitary dips with calcium propionate, calcium chloride, or a calcium amino acid chelate maintain quality and shelf stability of fresh-cut honeydew chunks. Postharvest Biology and Technology, 29, 257e269. Saftner, R., Abbott, J. A., Lester, G., & Vinyard, B. (2006). Sensory and analytical comparison of orange-fleshed honeydew to cantaloupe and green-fleshed honeydew for fresh-cut chunks. Postharvest Biology and Technology, 42, 150e160. Saltveit, M. E. (2004). Respiratory metabolism. In The commercial storage of fruits, vegetables, and florist and nursery stocks. Agriculture handbook number 66 http://usna.usda.gov/hb66/019respiration.pdf (viewed on 2nd April 2013). n ez, A. M., Allende, A., Cantwell, M., & Suslow, T. (2008). Effect of Selma, M. V., Iba gaseous ozone and hot water on microbial and sensory quality of cantaloupe and potential transference of Escherichia coli O157:H7 during cutting. Food Microbiology, 25, 162e168. n ez, A. M., Cantwell, M., & Suslow, T. (2008b). Reduction by gaseous Selma, M. V., Iba ozone of Salmonella and microbial flora associated with fresh-cut cantaloupe. Food Microbiology, 25, 558e565. Sensoy, S., Büyükalaca, S., & Abak, K. (2007). Evaluation of genetic diversity in Turkish melons (Cucumis melo L.) based on phenotypic characters and RAPD markers. Genetic Resources and Crop Evolution, 54, 1351e1365. http://dx.doi.org/ 10.1007/s10722-006-9120-6. s, F. (2008). Alternative sanitizers to Silveira, A. C., Conesa, A., Aguayo, E., & Arte chlorine for use on fresh-cut “Galia” (Cucumis melo var. catalupensis) melon. Journal of Food Science, 73(9), 405e411. s, F. (2010). Emerging sanitizers and clean room Silveira, A. C., Aguayo, E., & Arte packaging for improving the microbial quality of fresh-cut ‘Galia’ melon. Food Control, 21, 863e871. Thomas, V., Stack, M. E., Mislivec, P. B., Koch, A., & Bandler, R. (2001). Yeasts, molds and mycotoxins. Bacteriological analytical manual (8th edition). chapter 18. Xu, L. (1999). Use of ozone to improve the safety of fresh fruits and vegetables. Food Technology, 53(10), 58e63. Watada, A. E., & Qi, L. (1999). Quality control of minimally-processed vegetables. In J. M. Lee, K. C. Gross, A. E. Watada, & S. K. Lee (Eds.), Acta Horticulturae: Vol. 483. Proc. Int. Symp. on Quality of fresh and fermented vegetables (pp. 209e220). Yadav, L. (2010). The effect of ozone on the growth and development of selected food spoilage fungi. ISBN-10:1-59942-352-9, ISBN-13: 978-1-59942-352-4. Dissertation.com, Boca Raton, Florida, U.S.A http://www.bookpump.com/dps/pdfb/9423529b.pdf. lu, S¸., & S¸engül, N. (2009). Effects of different Yıldırım, O., Halloran, N., Çavus¸og irrigation programs on the growth, yield, and fruit quality of drip-irrigated melon. Turkish Journal of Agriculture and Forestry, 33, 243e255.