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New packaging strategies to preserve fresh-cut artichoke quality during refrigerated storage
Innovative Food Science and Emerging Technologies 10 (2009) 128–133
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Innovative Food Science and Emerging Technologies j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i f s e t
New packaging strategies to preserve fresh-cut artichoke quality during refrigerated storage M.A. Del Nobile a,c,⁎, A. Conte a, C. Scrocco a, J. Laverse a, I. Brescia a, G. Conversa b,c, A. Elia b,c a b c
Department of Food Science, University of Foggia, Via Napoli, 25 — 71100 Foggia, Italy Department of Agro-Environmental Science, Chemistry and Plant Protection, University of Foggia, via Napoli 25, 71100 Foggia, Italy Istituto per la Ricerca e le Applicazioni Biotecnologiche per la Sicurezza e la Valorizzazione dei Prodotti Tipici e di Qualità — BIOAGROMED, Università degli Studi di Foggia, Via Napoli, 25 — 71100 Foggia, Italy
A R T I C L E
I N F O
Article history: Received 14 March 2008 Accepted 22 June 2008 Keywords: Artichoke Biodegradable packaging Microbial characteristics Pre-treatments Sensory characteristics Shelf life
A B S T R A C T The influence of both post-harvest treatments and film permeability on the quality loss kinetic of minimally processed artichokes is assessed in this study. In particular, fresh-cut artichoke heads were subjected to dipping in citric acid/calcium chloride water solution, and coating with citric acid loaded sodium alginate, respectively. Three different packaging materials were used: a polyester-based biodegradable film, an aluminum-based multilayer film, and a commercially available oriented polypropylene film. Artichokes quality loss kinetic during storage was determined by monitoring produce appearance, weight loss, pH, and viable cell load of the main spoilage microorganisms. Results suggest that among the selected treatments, coating shows the best performance in terms of artichokes shelf life. As far as the packaging material is concerned, the biodegradable film tested in this work seems to be the most suitable packaging to preserve the quality of the coated fresh-cut produce. Industrial relevance: Fresh-cut vegetables market has grown rapidly in recent years as a result of changes in consumer attitudes. There is a real need to find methods for preservation of minimally processed food products that can gain widespread acceptance by the industry. This paper suggests effective packaging solutions to delay the quality decay kinetic of fresh-cut artichokes. Moreover, the present study proposes a new “green packaging system” that could emphasize the relevance of the obtained results due to the increased attention to the environmental impact. © 2008 Elsevier Ltd. All rights reserved.
1. Introduction The artichoke (Cynara cardunculus L. subsp. scolymus (L.) Hayek) is a perennial rosette plant grown throughout the world for its large, fleshy heads (Conti, Abbate, Alessandrini & Blasi, 2005). Most of its culture (about 90%) is concentrated in the countries bordering the Mediterranean Basin mainly in Italy (50 000 ha), Spain (17 000 ha) and France (10 000 ha) (FAO, 2008). The edible portions are the fleshy bases of the bracts, the thick, fleshy receptacle on which the bracts are borne, and the flower primordia. It is reputed that this vegetable has a marked anti-oxidative and health protective potential (Adzet, Camarasa & Laguna, 1987; Jimenez-Escrig, Gragsted, Daneshvar, Pulido & Saura-Calixto, 2003; Perez-Garcia, Adzet & Canigueral, 2000; Wang et al., 2003). To make artichokes as minimally processed products would be very convenient for its commercialization, reducing transport costs, storage space and preparation time (Yommi, Giletto, Horvitz & Lòpez-Camelo, 2001). However, very few works are reported in the literature on fresh-
cut heads, because the technologies successfully applied for other fresh-cut vegetables cannot be entirely used for artichokes, due to rapid enzymatic browning occurring after cutting (Giménez, Olarte et al., 2003). The most successful strategies aimed to prevent browning occurring on fresh-cut fruit and vegetables are based on treatments with reducing agents, acidifying agents, chelating substances and calcium solutions (Martin-Diana et al., 2007; Ragaert, Devlieghere & Debevere, 2007; Rico, Martín-Diana, Barat & Barry-Ryan, 2007). In addition to enzymatic browning, artichokes weight loss is another phenomenon that negatively influences its marketability. The dehydration depends on many factors including the temperature and relative humidity of the storage room, the air movement and the packaging material. The weight loss is a natural consequence of the catabolism of horticultural products, catalysed by enzymes and accelerated by cutting and slicing. The decrease in weight may be attributed to respiration and other senescence-related metabolic processes during storage (Watada & Qi, 1999). There are studies that propose edible coatings, in combination with active compounds, to
⁎ Corresponding author. Department of Food Science, University of Foggia, Via Napoli, 25 — 71100, Foggia, Italy. Tel./fax: +39 881 589 242. E-mail address: [email protected] (M.A. Del Nobile). 1466-8564/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ifset.2008.06.005
M.A. Del Nobile et al. / Innovative Food Science and Emerging Technologies 10 (2009) 128–133
delay browning and water loss (Park, 1999). Among the renewable sources to produce edible coating the polysaccharides-based materials are the most diffused because they are abundant, cheap and easy to use (Devlieghere, Vermeulen & Debevere, 2004; Lee, Park, Lee & Choi, 2003). In Apulia, the most important Italian region for artichoke production, there are widely cropped early cultivars such as ‘Violetto di Sicilia’ or ‘Brindisino’, a “Catanese type”; the autumn–winter production is normally destined to the fresh consumption, while that harvested during the spring period is used by the processing industry. The industrial preparation of artichoke heads is done by eliminating the inedible fibermost parts (external bracts and the apex of inner ones) resulting in 20% of product-useful. Recently a new “seed” propagated cultivar (‘Madrigal’) has been launched for processing purposes, which is characterized by more tender, less fibrous and greener bracts compared with the traditional cultivars. There is growing pressure in the fresh fruit and vegetables packaging sector to replace the petrochemical based packaging films with more environmentally-friendly biodegradable materials (Tharanathan, 2003). Biologically-based packaging contains raw materials originated from agricultural sources, produced from renewable raw materials such as starch and bio-derived monomers (Koide & Shi, 2007). Although biodegradable and renewable films are more expensive than the petrochemical films, they have the advantage to be biopolymers (Avella et al., 2005). Among the biopolymers, films made from starch are the most developed. The interest in this kind of new materials is linked to the usefulness and suitability in many applications (Bastioli, 1997); however, due to their low barrier proprieties to low molecular weight compounds, the application in food packaging is still limited. In fact, the permeability coefficient of a polymeric matrix intended for food packaging applications is strictly related to the shelf life of packed food (Del Nobile, Licciardello, Scrocco, Muratore & Zappa, 2007; Muratore, Del Nobile, Buonocore, Lanza & Nicolosi, 2005). The purpose of this study is to evaluate industrial yield performance and the influence of post-harvest treatments and film permeability on the quality loss of minimally processed artichokes of cv. Madrigal during storage at 4 °C. Sensorial, microbial and physicochemical parameters were monitored to assess the best packaging conditions to preserve the fresh-cut artichokes quality.
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point of cut of the bract (60 or 70% of the height of the head), in parallel to this and in middle position with respect to the breadth of the bract. 2.3. Samples packaging From the heads the inedible parts (leaves, stalks and outer bracts) were removed according to the procedure reported above. The artichoke heads were washed with tap water and treated for 30 s with chlorinated water (20 mL/L) (pH = 9.06). The excess water was then eliminated by manual centrifugation. Before packaging, the fresh-cut artichokes were subjected to two different treatments: a) Dipping (Dip): fresh-cut artichokes were dipped for 1 min into a solution containing citric acid (1%, w/v) and calcium chloride (CaCl2) (10%, w/v) (pH= 0.10). b) Coating (Coat): fresh-cut artichokes were dipped into sodium alginate solution (5%, w/v) to obtain a coating of about 100 μm. The sodium alginate solution was prepared by dissolving sodium alginic acid in distilled water at 100 °C for 2 h. A 1% (w/v) of citric acid solution was added to the above alginic solution (pH = 9.27). The coated fresh-cut samples were immersed into a 10% (w/v) calcium chloride (CaCl2) solution for 1 min (pH = 9.33). Sodium alginic acid and CaCl2 were provided by Sigma-Aldrich Co. Inc. (USA), Citric Acid Anhydrous by Baker (Holland). After dipping or coating treatment, 50 g of cut artichokes were packaged in different bags with a surface area of 396 cm2: a multilayer film obtained by laminating an aluminum foil with a polyethylene film (All-PE, thickness 133 μm), kindly supplied by Goglio (Daverio, Varese, Italy); a biodegradable monolayer film based on a blend of biodegradable polyesters (NVT2, thickness 25 μm) kindly provided by Novamont (Novara, Italy), and an Oriented Polypropylene film (OPP thickness 20 μm) kindly provided by Metalvuoto (Milano, Italy). Bags were hermetically sealed. Samples simply washed in chlorinated water were also packaged in the three different bags, to be used as control (Cntr). All bags were stored at 4 °C for 6 days. To better explain the adopted experimental method, a flow chart of the samples preparation procedure is reported in the following.
2. Experimental 2.1. Raw material ‘Madrigal’ (Nunhems) artichokes were collected in an experimental field of Nunhems in the area of Foggia from plants raised by “seeds” transplanted the preceding summer. ‘Madrigal’ artichokes are a new “seed” propagated cultivar characterized by a pale green color of the external bracts, with a good yield of uniform heads concentrated exclusively in the spring period. After harvesting, the fresh produce was directly transported from the field to the laboratory. 2.2. Artichokes morphological characterization A number of 30 heads, uniform in size and weight, at the optimal stage for processing were selected. Heads were deprived of the floral stalk and the equatorial diameter and the height were measured. Heads were further processed by applying a cut to the top part at 60% and at 70% of its total height for removing the inedible leathery apex of the bracts, and by eliminating the outermost and the hardest bracts (15–20). In order to achieve the optimal degree of tenderness, starting from the subsequent bract, every single bract was subjected to the measure of the cutting force, until reaching the cutting force of 35 N, which was previously set as optimal tenderness threshold value. A penetrometer with a prismatic body (3 mm width and 10 mm length) was used and the force was measured 5 mm below the transversal
2.4. Weight loss The percentage weight loss was determined according to the following Eq. (1): kWLðt Þ ¼
W0 −Wðt Þ d100 W0
ð1Þ
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M.A. Del Nobile et al. / Innovative Food Science and Emerging Technologies 10 (2009) 128–133
where: %WL(t) is the percentage weight loss at time t, W0 is the initial sample weight and W(t) is sample weight at time t. A digital precision balance (±0.1 g) (Gibertini Europe, Italy) was used to determine the product weight.
conditioning time, 1 mL of the gas contained in the bags was sampled and injected in the GC-TCD system.
2.5. Microbiological analyses
The results were compared by one-way variance analysis (ANOVA). A Duncan's multiple range test, with the option of homogeneous groups (P b 0.05), was used to determine significance between treatments. STATISTICA 7.1 for Windows (StatSoft, Inc, Tulsa, OK, USA) was used for this purpose.
An aliquot of 10 g of artichokes was removed from each package and homogenized with 90 mL of a sterile saline solution (0.9%) mixed in a Sterilmixer II (International PBI, Milan, Italy) for 2 min. Decimal dilutions of artichokes homogenates were performed, and microbiological counts of total mesophilic and psychrotrophic bacteria, total coliforms, yeast and moulds were determined. The following media and the incubation conditions were used: spread plating onto plate count agar (Oxoid), plates incubated at 30 °C for 48 h for total mesophilic bacteria; pour plating in violet red bile agar (Oxoid), incubated at 37 °C for 24 h for total coliforms; spread plating onto plate count agar (Oxoid) plates incubated at 7 °C for 10 days for psychrotrophs; spread plating onto sabouraud dextrose agar (Oxoid), supplemented with chloramphenycol (0.1 g L− 1) plates incubated at 25 °C for 5 days for yeast and moulds. The analyses were carried out twice.
2.9. Statistical analysis
3. Results and discussion The quality of minimally processed artichokes depends on several quality sub-indices, among which product appearance, weight loss, pH, and microbiological stability are the most important for this specific crop. In fact, due to the rapid decrease in the fresh-cut artichokes quality observed during refrigerated storage (Giménez et al., 2003), the produce respiratory activity does not affect, to a great extent, its degree of acceptability. Therefore, the quality loss kinetic of ready-to-use artichokes was determined by monitoring the above quality sub-indices for about 6 days. Results are presented in the following.
2.6. pH evaluation 3.1. Film barrier properties pH was evaluated twice on the homogenated artichoke by a pHmetre (Crison Instruments, Barcelona, Spain). 2.7. Sensory evaluation A sensorial test was run to determine packed artichokes whole quality as determined by its appearance. A panel of seven judges assessed the sensory characteristics of the investigated fresh-cut produce during the entire observation period, according to the procedure reported in the literature by Giménez et al. (2003). Freshcut produce was used as control (score = 5). The products were presented on coded plastic dishes. The intensity of the evaluated general appearance was indicated on a scale from 1 to 5, where 1– 2 = very poor, 3–4 = fair, and 5 = excellent. The sensory evaluation was used to determine the shelf life of packed produce. Scores below 3 for any of the attributes assessed were considered as an indication of food product unacceptability. During the test sessions, the sample presentation order was randomized.
Carbon dioxide permeation test was run on the package made of the All-PE film used in this investigation. The package was tested in place of the film because aluminum foil can rupture during thermal sealing of the package, reducing its barrier properties. After 28 days no passage of carbon dioxide through the package was detected. Based on this result, it can be assumed that for the investigation period the All-PE film used can be considered as impermeable to low molecular weight compounds. The measured values of Water Vapor Transmission Rate of the investigated films are 760 ± 5.00 g/m2 the number must be put as apex day and 0.61 ± 0.06 g/m2 day, respectively for NVT2 and OPP. It is worth noting that permeability tests were conducted at 23 °C instead of 4 °C (the temperature at which the quality decay tests were conducted). This is because it was not possible to reach temperatures as low as 4 °C with the apparatus used to measure the permeability of the investigated films. Therefore, these values must be considered only for comparative purpose. 3.2. Raw material characterization
2.8. Permeation tests The Water Vapor Transmission Rate of OPP and NVT2 films was determined by means of Permatran (Mocon, Model W 3/31, Neuwied, Germany). Samples with a surface area of 5 cm2 were tested at 23 °C and 85% of relative humidity. A flow rate of 100 mL/min of nitrogen was used. The CO2 permeability of All-PE film was measured using a gas chromatography HP 5890 with a Thermal Conductivity Detector (TCD). Eight bags were conditioned in a CO2 saturated ambient at 23 °C and 0% of relative humidity, according to the following conditions: 3 bags at 5 days; 3 bags at 7 days; 2 bags at 28 days. At the end of the
Before processing, the artichokes were physically characterized in order to assess the optimal preparation of the heads and to evaluate the yield performances of the cultivar, when processed. The ‘Madrigal’ artichoke heads weighed on average 126 g. They showed a globe shape, with height/equatorial diameter ratio of 1.1, and a total number of 82 bracts. The first optimal bract in terms of tenderness (with a cutting resistance less than 35 N) was the 34th and the 28th for the cutting at 70% and 60%, respectively (Table 1). As expected, with the lowest cut it was possible to eliminate 7 leaves less in order to reach the targeted tenderness level. However, no differences were observed between the two cutting heights in processed yield and in total waste production,
Table 1 Effect of cutting point height of head apex on produce performance Height of apex removal
35-N bract (n.)a
Head processed weight (g)
Head waste (g)
Remaining bracts after processing (n.)
Produce yield (kg/kg)
Heads per kg of produce (n.)
60% ht. max 70% ht. max Significanceb
27.7 33.9 ⁎⁎
43.0 43.6 Ns
82.6 84.6 ns
47.2 38.2 ⁎
0.34 0.36 ns
23.3 22.9 ns
a b
Represent position on the receptacle of the first bract that showed a cutting force lower or equal to 35 N (1 = the outermost bract of the head). ns, ⁎, and ⁎⁎: not significant or significant at P b 0.05 and P b 0.01, respectively.
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3.4. Sensory evaluation Fig. 2 shows the fresh-cut artichokes visual quality plotted as a function of the storage time for all the investigated samples. As can be inferred from the above data, Cntr sample has a shelf life ranging from 1 to 2 days, depending on the packaging film. In particular, sample packed in All-PE film and in NVT2 show a shelf life of 1 day, whereas a shelf life of 2 days was measured for Cntr sample packed in OPP film. A slightly higher shelf life was recorded for Dip sample, reaching 3 days in All-PE and NVT2. The above evidence is in agreement with what reported in the literature, where it is showed that dipping in water solution of citric acid and calcium chloride can delay the browning kinetic of several fresh-cut produce (Lee et al., 2003; Martin-Diana et al., 2007; Rico et al., 2007). Coated artichokes show the best results among the investigated samples, because they maintained for more time a good quality level, probably due to the fact that coating, with added anti-browning agents, provides a semi-permeable barrier that reduces water loss and oxidative reaction rate, that play the major role in determining product acceptability (Park, 1999). It is worth noting that after 3 days of storage, all samples lost their typical color, and their consistency slightly changed. Moreover, spots, moulds and general browning appeared. It
Fig. 1. Effect of treatments and packaging films on percentage weight loss of the investigated fresh-cut artichokes.
due to the compensation of the portion eliminated by the lower cut with the higher number of bracts remaining on the receptacle (Table 1). As average from a kilogram of raw material they were obtained 350 g of produce and they were necessary about 23 raw artichokes to obtain 1 kg of processed produce. As average, the industrial yield for the European cultivars ranges between 20 and 22% of the raw material (Lahoz et al., 2004), it is noteworthy that in ‘Madrigal’ it was 35%. 3.3. Weight loss Fig. 1 shows the time course, during the refrigerated storage, of weight loss for all samples investigated in this study. As expected, weight loss increases with time for all samples due to packed produce dehydration. Data shown in Fig. 1 also highlight that produce dehydration kinetic is strongly related to the packaging film water vapor barrier properties. In fact, the highest weight loss values were recorded for samples packed in NVT2 film, which has lower water vapor barrier properties than OPP film. No statistically significant differences between artichokes packed with All-PE and OPP were observed. In fact, both films have good water vapor barrier properties. Regarding the treatments tested in this investigation prior to packaging, it is worth noting that they do not seem to influence, to a great extent, the minimally processed artichoke dehydration kinetic.
Fig. 2. Influence of treatments and packaging films on the general appearance of the investigated fresh-cut artichokes.
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Table 2 Total mesophilic load (log CFU/g) of artichokes samples before and after storage as affected by pre-treatments and packaging films
Table 4 Total psychrotrophic load (log CFU/g) of artichokes samples before and after storage as affected by pre-treatments and packaging films
Pre-treatments
Pre-treatments
Initial count
Final count
Initial count
Packaging films
Control Dipping Coating
5.231
Final count Packaging films
All-PE
NVT2
OPP
6.84a,2 6.81a,3 6.81a,2
6.62a,2 7.33c,4 6.99b,2
7.24b,2 6.16a,2 6.92b,2
Control Dipping Coating
4.211
All-PE
NVT2
OPP
6.10a,2,3 6.04a,2 5.92a,2
6.22a,3 6.24a,2 5.65a,2
5.59a,2 5.94b,2 5.94b,2
Means in the same column with different superscript letters are significantly different (P b 0.05). Means in the rows with different superscript numbers are significantly different (P b 0.05).
Means in the same column with different superscript letters are significantly different (P b 0.05). Means in the rows with different superscript numbers are significantly different (P b 0.05).
was also observed that the dehydrated appearance of samples packed in NVT2 was particularly significant after day 3. The above evidence is in agreement with what reported above, where it has been observed that, regardless the pre-treatment used in this investigation, samples packed in NVT2 film show the highest percentage of weight loss. In summary, results underline that an increase in shelf life was obtained for both treated samples (i.e., Coat and Dip samples), if compared to the control. Shelf life increase ranges from 50 to 200% depending on the pre-treatment and on the packaging film barrier properties. In particular, coating together with packaging in NVT2 film seems to represent the better strategy to preserve the quality of artichokes. In fact, this is the sole sample that obtained the highest score after 2 day storage.
Table 5 Total coliforms (log CFU/g) of artichokes samples before and after storage as affected by pre-treatments and packaging films
3.5. Microbiological analyses The cell loads of the main spoilage microorganisms steadily increase with storage time (data not shown). The recorded cell loads on untreated artichokes are in agreement to what reported by Giménez et al. (2003) on minimally processed ‘Blanca de Tudela’ fresh-cut produce. For the sake of comparison, the initial and final cell loads of the investigated spoilage fungi and bacteria are listed in Tables 2 to 5. It seems that coated artichokes packaged in the NVT2 film maintain a higher microbial stability than other samples. However, even though one-way variance analysis shows some statistically significant differences between the investigated samples, the differences do not exceed one order of magnitude, suggesting that either treatments (i.e. dipping and coating) or polymeric films do not affect, to a great extent, the growth cycle of the monitored microbial groups. Moreover, it is worth noting that the microbial quality of the fresh-cut produce tested in this work can be considered more than acceptable, because the maximum cell load (i.e., that measured after 6 day storage) never exceed the threshold (5 × 107 CFU/g) imposed by French Regulation for fresh-cut vegetables (Ministere de l'Economie des Finances et du Budget, 1988), probably due to good quality of the raw materials (Francis, Thomas, & O'Beirne, 1999). The pH remained fairly constant during the entire observation period in all investigated samples. It ranged between 5.3 and 5.8, suggesting that it could not be considered responsible for artichokes
Table 3 Total yeasts load (log CFU/g) of artichokes samples before and after storage as affected by pre-treatments and packaging films Pre-treatments
Initial count
3.291
Initial count
Final count Packaging films
Control Dipping Coating
3.531
All-PE
NVT2
OPP
4.96a,4 5.35b,4 5.44b,4
4.26b,3 3.11a,2 4.32b,2
3.93a,2 4.06a,3 4.69b,3
Means in the same column with different superscript letters are significantly different (P b 0.05). Means in the rows with different superscript numbers are significantly different (P b 0.05).
quality loss. In fact, the recorded pH values are in agreement with those reported on packaged fresh-cut artichokes by Giménez et al. (2003). 4. Conclusions “Madrigal” artichokes proved to have suitable characteristics for industrial processing in terms of produce yield. The quality decay kinetic of fresh-cut artichokes during refrigerated storage, as affected by both post-harvest treatments and film barrier properties, was addressed. Two treatments, such as dipping in active solution and coating with active sodium alginate, were combined with three different packaging materials. Produce appearance, weight loss, pH, and viable cell load of the main spoilage microorganisms were monitored during storage to determine the artichoke quality loss kinetic. Results indicate that coated fresh-cut Madrigal artichokes packed in NVT2 film guarantee a shelf life of 3 days, which compared to the control sample packed in the same film, corresponds to an increase in the shelf life value of 200%. A shelf life of about 3 days seems to be enough for produce distribution to the local markets. In addition, the developed packaging strategy is characterized by a low environmental impact that could increase its potential industrial application. Acknowledgement This work was financially supported by Ministero dell'Istruzione, dell'Università e della Ricerca Scientifica e Tecnologica (MIUR) by the program “Grandi progetti Strategici (PNR 2005–2007)” — Title: “Qualità distintiva Made in Italy”.
Final count
References
Packaging films
Control Dipping Coating
Pre-treatments
All-PE
NVT2
OPP
6.32a,2 6.34a,3 6.28a,3
6.08b,2 6.68c,3 4.77a,2
6.80c,3 5.10a,2 6.03b,3
Means in the same column with different superscript letters are significantly different (P b 0.05). Means in the rows with different superscript numbers are significantly different (P b 0.05).
Adzet, T., Camarasa, J., & Laguna, C. J. (1987). Hepatoprotective activity of polyphenolic compounds from Cynara scolymus against CCl4 toxicity in isolated rat hepatocytes. Journal of Natural Products, 50, 612−617. Avella, M., De Vlieger, J. J., Errico, M. E., Fischer, S., Vacca, P., & Volpe, M. G. (2005). Biodegradable starch/clay nanocomposite films for food packaging applications. Food Chemistry, 93, 467−474. Bastioli, C. (1997). In L. Aaron, A. L. Brody, & K. S. Marsh (Eds.), The Wiley Encyclopedia of Packaging Technology (pp. pp. 77−83). (2nd ed.). John Wiley & Sons.
M.A. Del Nobile et al. / Innovative Food Science and Emerging Technologies 10 (2009) 128–133 Conti, F., Abbate, G., Alessandrini, A., & Blasi, C. (2005). An Annotated Checklist of the Italian Vascular Flora (pp. pp. 428). (1st ed.). Roma: Palombi Ed. Del Nobile, M. A., Licciardello, F., Scrocco, C., Muratore, G., & Zappa, M. (2007). Design of plastic packages for minimally processed fruits. Journal of Food Engineering, 79, 217−224. Devlieghere, F., Vermeulen, A., & Debevere, J. (2004). Chitosan: Antimicrobial activity, interactions with food components and applicability as a coating on fruit and vegetables. Food Microbiology, 21, 703−714. FAO (2008). FAO Statistics Division. URL. http://faostat.fao.org/site/567/DesktopDefault. aspx?PageID=567 (access date 08 January 2008). Francis, G. A., Thomas, C., & O'Beirne, D. (1999). The microbiological safety of minimally processed vegetables. International Journal of Food Science & Technology, 34, 1−22. Giménez, M., Olarte, C., Sanz, S., Lomas, C., Echàvarri, J. F., & Ayala, F. (2003). Relation between spoilage and microbiological quality in minimally processed artichoke packaged with different films. Food Microbiology, 20, 231−242. Jimenez-Escrig, A., Gragsted, L. O., Daneshvar, B., Pulido, R., & Saura-Calixto, F. (2003). In vitro antioxidant activities of edible artichoke and effect on biomarkers of antioxidants in rats. Journal Agricultural & Food Chemistry, 51, 5540−5545. Koide, S., & Shi, J. (2007). Microbial and quality evaluation of green peppers stored in biodegradable film packaging. Food Contaminants, 18, 1121−1125. Lahoz, I., Malumbres, A., Macua, J. I., Bozal, J. M., Urmentea, I., & Arrondo, M. A. (2004). Agricultural and industrial study of the principal European varieties of artichoke in Navarra. Acta Horticulturae, 660, 531−537. Lee, Y. J., Park, H. J., Lee, C. Y., & Choi, W. Y. (2003). Extending shelf life of minimally processed apples with edible coatings and antibrowning agents. LebensmittelWissenschaft und-Technologie, 36, 323−329. Martin-Diana, A. B., Rico, D., Frias, J. M., Barat, J. M., Henehan, G. T. M., & Barry-Ryan, C. (2007). Calcium for extending the shelf life of fresh whole and minimally processed fruits and vegetables: A review. Trends in Food Science & Technology, 18, 210−218.
133
Muratore, G., Del Nobile, M. A., Buonocore, G. G., Lanza, C. M., & Nicolosi, A. C. (2005). The influence of using biodegradable packaging films on the quality decay kinetic of plum tomato (Pomodorino Datterino). Journal of Food Engineering, 67, 393−399. Ministere de l'Economie des Finances et du Budget (1988). Marché consommation, Produits vegetaux prets a l'emploi dits de la “IVemme Gamme”: Guide de bonnes pratique hygieniques. J. Off. De la Republic Francaise, 1621−1629. Park, H. J. (1999). Development of advances edible coatings for fruits. Trends in Food Science & Technology, 10, 254−260. Perez-Garcia, F., Adzet, T., & Canigueral, S. (2000). Activity of artichokes leaf extract as reactive oxygen species in human leukocytes. Free Radical Research, 33, 661−665. Ragaert, P., Devlieghere, F., & Debevere, J. (2007). Role of microbiological and physiological spoilage mechanisms during storage of minimally processed vegetables. Postharvest Biology & Technology, 44, 185−194. Rico, D., Martín-Diana, A. B., Barat, J. M., & Barry-Ryan, C. (2007). Extending and measuring the quality of fresh-cut fruit and vegetables: A review. Trends in Food Science & Technology, 18, 373−386. Tharanathan, R. N. (2003). Biodegradable films and composite coatings: Past, present and future. Trends in Food Science & Technology, 14, 71−78. Wang, M., Simon, J. E., Aviles, I. F., He, K., Zheng, Q. Y., & Tadmor, Y. (2003). Analysis of antioxidative phenolics compounds in artichoke. Journal Agricultural & Food Chemistry, 51, 601−608. Watada, A. E., & Qi, L. (1999). Quality of fresh-cut produce. Postharvest Biology & Technology, 15, 201−205. Yommi, A., Giletto, C., Horvitz, S., & Lòpez Camelo, A. (2001). Effects of temperature and semi-permeable films on quality of stored artichokes (Cynara scolymus L.). Acta Horticulturae, 553, 619−620.
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Innovative Food Science and Emerging Technologies j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i f s e t
New packaging strategies to preserve fresh-cut artichoke quality during refrigerated storage M.A. Del Nobile a,c,⁎, A. Conte a, C. Scrocco a, J. Laverse a, I. Brescia a, G. Conversa b,c, A. Elia b,c a b c
Department of Food Science, University of Foggia, Via Napoli, 25 — 71100 Foggia, Italy Department of Agro-Environmental Science, Chemistry and Plant Protection, University of Foggia, via Napoli 25, 71100 Foggia, Italy Istituto per la Ricerca e le Applicazioni Biotecnologiche per la Sicurezza e la Valorizzazione dei Prodotti Tipici e di Qualità — BIOAGROMED, Università degli Studi di Foggia, Via Napoli, 25 — 71100 Foggia, Italy
A R T I C L E
I N F O
Article history: Received 14 March 2008 Accepted 22 June 2008 Keywords: Artichoke Biodegradable packaging Microbial characteristics Pre-treatments Sensory characteristics Shelf life
A B S T R A C T The influence of both post-harvest treatments and film permeability on the quality loss kinetic of minimally processed artichokes is assessed in this study. In particular, fresh-cut artichoke heads were subjected to dipping in citric acid/calcium chloride water solution, and coating with citric acid loaded sodium alginate, respectively. Three different packaging materials were used: a polyester-based biodegradable film, an aluminum-based multilayer film, and a commercially available oriented polypropylene film. Artichokes quality loss kinetic during storage was determined by monitoring produce appearance, weight loss, pH, and viable cell load of the main spoilage microorganisms. Results suggest that among the selected treatments, coating shows the best performance in terms of artichokes shelf life. As far as the packaging material is concerned, the biodegradable film tested in this work seems to be the most suitable packaging to preserve the quality of the coated fresh-cut produce. Industrial relevance: Fresh-cut vegetables market has grown rapidly in recent years as a result of changes in consumer attitudes. There is a real need to find methods for preservation of minimally processed food products that can gain widespread acceptance by the industry. This paper suggests effective packaging solutions to delay the quality decay kinetic of fresh-cut artichokes. Moreover, the present study proposes a new “green packaging system” that could emphasize the relevance of the obtained results due to the increased attention to the environmental impact. © 2008 Elsevier Ltd. All rights reserved.
1. Introduction The artichoke (Cynara cardunculus L. subsp. scolymus (L.) Hayek) is a perennial rosette plant grown throughout the world for its large, fleshy heads (Conti, Abbate, Alessandrini & Blasi, 2005). Most of its culture (about 90%) is concentrated in the countries bordering the Mediterranean Basin mainly in Italy (50 000 ha), Spain (17 000 ha) and France (10 000 ha) (FAO, 2008). The edible portions are the fleshy bases of the bracts, the thick, fleshy receptacle on which the bracts are borne, and the flower primordia. It is reputed that this vegetable has a marked anti-oxidative and health protective potential (Adzet, Camarasa & Laguna, 1987; Jimenez-Escrig, Gragsted, Daneshvar, Pulido & Saura-Calixto, 2003; Perez-Garcia, Adzet & Canigueral, 2000; Wang et al., 2003). To make artichokes as minimally processed products would be very convenient for its commercialization, reducing transport costs, storage space and preparation time (Yommi, Giletto, Horvitz & Lòpez-Camelo, 2001). However, very few works are reported in the literature on fresh-
cut heads, because the technologies successfully applied for other fresh-cut vegetables cannot be entirely used for artichokes, due to rapid enzymatic browning occurring after cutting (Giménez, Olarte et al., 2003). The most successful strategies aimed to prevent browning occurring on fresh-cut fruit and vegetables are based on treatments with reducing agents, acidifying agents, chelating substances and calcium solutions (Martin-Diana et al., 2007; Ragaert, Devlieghere & Debevere, 2007; Rico, Martín-Diana, Barat & Barry-Ryan, 2007). In addition to enzymatic browning, artichokes weight loss is another phenomenon that negatively influences its marketability. The dehydration depends on many factors including the temperature and relative humidity of the storage room, the air movement and the packaging material. The weight loss is a natural consequence of the catabolism of horticultural products, catalysed by enzymes and accelerated by cutting and slicing. The decrease in weight may be attributed to respiration and other senescence-related metabolic processes during storage (Watada & Qi, 1999). There are studies that propose edible coatings, in combination with active compounds, to
⁎ Corresponding author. Department of Food Science, University of Foggia, Via Napoli, 25 — 71100, Foggia, Italy. Tel./fax: +39 881 589 242. E-mail address: [email protected] (M.A. Del Nobile). 1466-8564/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.ifset.2008.06.005
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delay browning and water loss (Park, 1999). Among the renewable sources to produce edible coating the polysaccharides-based materials are the most diffused because they are abundant, cheap and easy to use (Devlieghere, Vermeulen & Debevere, 2004; Lee, Park, Lee & Choi, 2003). In Apulia, the most important Italian region for artichoke production, there are widely cropped early cultivars such as ‘Violetto di Sicilia’ or ‘Brindisino’, a “Catanese type”; the autumn–winter production is normally destined to the fresh consumption, while that harvested during the spring period is used by the processing industry. The industrial preparation of artichoke heads is done by eliminating the inedible fibermost parts (external bracts and the apex of inner ones) resulting in 20% of product-useful. Recently a new “seed” propagated cultivar (‘Madrigal’) has been launched for processing purposes, which is characterized by more tender, less fibrous and greener bracts compared with the traditional cultivars. There is growing pressure in the fresh fruit and vegetables packaging sector to replace the petrochemical based packaging films with more environmentally-friendly biodegradable materials (Tharanathan, 2003). Biologically-based packaging contains raw materials originated from agricultural sources, produced from renewable raw materials such as starch and bio-derived monomers (Koide & Shi, 2007). Although biodegradable and renewable films are more expensive than the petrochemical films, they have the advantage to be biopolymers (Avella et al., 2005). Among the biopolymers, films made from starch are the most developed. The interest in this kind of new materials is linked to the usefulness and suitability in many applications (Bastioli, 1997); however, due to their low barrier proprieties to low molecular weight compounds, the application in food packaging is still limited. In fact, the permeability coefficient of a polymeric matrix intended for food packaging applications is strictly related to the shelf life of packed food (Del Nobile, Licciardello, Scrocco, Muratore & Zappa, 2007; Muratore, Del Nobile, Buonocore, Lanza & Nicolosi, 2005). The purpose of this study is to evaluate industrial yield performance and the influence of post-harvest treatments and film permeability on the quality loss of minimally processed artichokes of cv. Madrigal during storage at 4 °C. Sensorial, microbial and physicochemical parameters were monitored to assess the best packaging conditions to preserve the fresh-cut artichokes quality.
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point of cut of the bract (60 or 70% of the height of the head), in parallel to this and in middle position with respect to the breadth of the bract. 2.3. Samples packaging From the heads the inedible parts (leaves, stalks and outer bracts) were removed according to the procedure reported above. The artichoke heads were washed with tap water and treated for 30 s with chlorinated water (20 mL/L) (pH = 9.06). The excess water was then eliminated by manual centrifugation. Before packaging, the fresh-cut artichokes were subjected to two different treatments: a) Dipping (Dip): fresh-cut artichokes were dipped for 1 min into a solution containing citric acid (1%, w/v) and calcium chloride (CaCl2) (10%, w/v) (pH= 0.10). b) Coating (Coat): fresh-cut artichokes were dipped into sodium alginate solution (5%, w/v) to obtain a coating of about 100 μm. The sodium alginate solution was prepared by dissolving sodium alginic acid in distilled water at 100 °C for 2 h. A 1% (w/v) of citric acid solution was added to the above alginic solution (pH = 9.27). The coated fresh-cut samples were immersed into a 10% (w/v) calcium chloride (CaCl2) solution for 1 min (pH = 9.33). Sodium alginic acid and CaCl2 were provided by Sigma-Aldrich Co. Inc. (USA), Citric Acid Anhydrous by Baker (Holland). After dipping or coating treatment, 50 g of cut artichokes were packaged in different bags with a surface area of 396 cm2: a multilayer film obtained by laminating an aluminum foil with a polyethylene film (All-PE, thickness 133 μm), kindly supplied by Goglio (Daverio, Varese, Italy); a biodegradable monolayer film based on a blend of biodegradable polyesters (NVT2, thickness 25 μm) kindly provided by Novamont (Novara, Italy), and an Oriented Polypropylene film (OPP thickness 20 μm) kindly provided by Metalvuoto (Milano, Italy). Bags were hermetically sealed. Samples simply washed in chlorinated water were also packaged in the three different bags, to be used as control (Cntr). All bags were stored at 4 °C for 6 days. To better explain the adopted experimental method, a flow chart of the samples preparation procedure is reported in the following.
2. Experimental 2.1. Raw material ‘Madrigal’ (Nunhems) artichokes were collected in an experimental field of Nunhems in the area of Foggia from plants raised by “seeds” transplanted the preceding summer. ‘Madrigal’ artichokes are a new “seed” propagated cultivar characterized by a pale green color of the external bracts, with a good yield of uniform heads concentrated exclusively in the spring period. After harvesting, the fresh produce was directly transported from the field to the laboratory. 2.2. Artichokes morphological characterization A number of 30 heads, uniform in size and weight, at the optimal stage for processing were selected. Heads were deprived of the floral stalk and the equatorial diameter and the height were measured. Heads were further processed by applying a cut to the top part at 60% and at 70% of its total height for removing the inedible leathery apex of the bracts, and by eliminating the outermost and the hardest bracts (15–20). In order to achieve the optimal degree of tenderness, starting from the subsequent bract, every single bract was subjected to the measure of the cutting force, until reaching the cutting force of 35 N, which was previously set as optimal tenderness threshold value. A penetrometer with a prismatic body (3 mm width and 10 mm length) was used and the force was measured 5 mm below the transversal
2.4. Weight loss The percentage weight loss was determined according to the following Eq. (1): kWLðt Þ ¼
W0 −Wðt Þ d100 W0
ð1Þ
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where: %WL(t) is the percentage weight loss at time t, W0 is the initial sample weight and W(t) is sample weight at time t. A digital precision balance (±0.1 g) (Gibertini Europe, Italy) was used to determine the product weight.
conditioning time, 1 mL of the gas contained in the bags was sampled and injected in the GC-TCD system.
2.5. Microbiological analyses
The results were compared by one-way variance analysis (ANOVA). A Duncan's multiple range test, with the option of homogeneous groups (P b 0.05), was used to determine significance between treatments. STATISTICA 7.1 for Windows (StatSoft, Inc, Tulsa, OK, USA) was used for this purpose.
An aliquot of 10 g of artichokes was removed from each package and homogenized with 90 mL of a sterile saline solution (0.9%) mixed in a Sterilmixer II (International PBI, Milan, Italy) for 2 min. Decimal dilutions of artichokes homogenates were performed, and microbiological counts of total mesophilic and psychrotrophic bacteria, total coliforms, yeast and moulds were determined. The following media and the incubation conditions were used: spread plating onto plate count agar (Oxoid), plates incubated at 30 °C for 48 h for total mesophilic bacteria; pour plating in violet red bile agar (Oxoid), incubated at 37 °C for 24 h for total coliforms; spread plating onto plate count agar (Oxoid) plates incubated at 7 °C for 10 days for psychrotrophs; spread plating onto sabouraud dextrose agar (Oxoid), supplemented with chloramphenycol (0.1 g L− 1) plates incubated at 25 °C for 5 days for yeast and moulds. The analyses were carried out twice.
2.9. Statistical analysis
3. Results and discussion The quality of minimally processed artichokes depends on several quality sub-indices, among which product appearance, weight loss, pH, and microbiological stability are the most important for this specific crop. In fact, due to the rapid decrease in the fresh-cut artichokes quality observed during refrigerated storage (Giménez et al., 2003), the produce respiratory activity does not affect, to a great extent, its degree of acceptability. Therefore, the quality loss kinetic of ready-to-use artichokes was determined by monitoring the above quality sub-indices for about 6 days. Results are presented in the following.
2.6. pH evaluation 3.1. Film barrier properties pH was evaluated twice on the homogenated artichoke by a pHmetre (Crison Instruments, Barcelona, Spain). 2.7. Sensory evaluation A sensorial test was run to determine packed artichokes whole quality as determined by its appearance. A panel of seven judges assessed the sensory characteristics of the investigated fresh-cut produce during the entire observation period, according to the procedure reported in the literature by Giménez et al. (2003). Freshcut produce was used as control (score = 5). The products were presented on coded plastic dishes. The intensity of the evaluated general appearance was indicated on a scale from 1 to 5, where 1– 2 = very poor, 3–4 = fair, and 5 = excellent. The sensory evaluation was used to determine the shelf life of packed produce. Scores below 3 for any of the attributes assessed were considered as an indication of food product unacceptability. During the test sessions, the sample presentation order was randomized.
Carbon dioxide permeation test was run on the package made of the All-PE film used in this investigation. The package was tested in place of the film because aluminum foil can rupture during thermal sealing of the package, reducing its barrier properties. After 28 days no passage of carbon dioxide through the package was detected. Based on this result, it can be assumed that for the investigation period the All-PE film used can be considered as impermeable to low molecular weight compounds. The measured values of Water Vapor Transmission Rate of the investigated films are 760 ± 5.00 g/m2 the number must be put as apex day and 0.61 ± 0.06 g/m2 day, respectively for NVT2 and OPP. It is worth noting that permeability tests were conducted at 23 °C instead of 4 °C (the temperature at which the quality decay tests were conducted). This is because it was not possible to reach temperatures as low as 4 °C with the apparatus used to measure the permeability of the investigated films. Therefore, these values must be considered only for comparative purpose. 3.2. Raw material characterization
2.8. Permeation tests The Water Vapor Transmission Rate of OPP and NVT2 films was determined by means of Permatran (Mocon, Model W 3/31, Neuwied, Germany). Samples with a surface area of 5 cm2 were tested at 23 °C and 85% of relative humidity. A flow rate of 100 mL/min of nitrogen was used. The CO2 permeability of All-PE film was measured using a gas chromatography HP 5890 with a Thermal Conductivity Detector (TCD). Eight bags were conditioned in a CO2 saturated ambient at 23 °C and 0% of relative humidity, according to the following conditions: 3 bags at 5 days; 3 bags at 7 days; 2 bags at 28 days. At the end of the
Before processing, the artichokes were physically characterized in order to assess the optimal preparation of the heads and to evaluate the yield performances of the cultivar, when processed. The ‘Madrigal’ artichoke heads weighed on average 126 g. They showed a globe shape, with height/equatorial diameter ratio of 1.1, and a total number of 82 bracts. The first optimal bract in terms of tenderness (with a cutting resistance less than 35 N) was the 34th and the 28th for the cutting at 70% and 60%, respectively (Table 1). As expected, with the lowest cut it was possible to eliminate 7 leaves less in order to reach the targeted tenderness level. However, no differences were observed between the two cutting heights in processed yield and in total waste production,
Table 1 Effect of cutting point height of head apex on produce performance Height of apex removal
35-N bract (n.)a
Head processed weight (g)
Head waste (g)
Remaining bracts after processing (n.)
Produce yield (kg/kg)
Heads per kg of produce (n.)
60% ht. max 70% ht. max Significanceb
27.7 33.9 ⁎⁎
43.0 43.6 Ns
82.6 84.6 ns
47.2 38.2 ⁎
0.34 0.36 ns
23.3 22.9 ns
a b
Represent position on the receptacle of the first bract that showed a cutting force lower or equal to 35 N (1 = the outermost bract of the head). ns, ⁎, and ⁎⁎: not significant or significant at P b 0.05 and P b 0.01, respectively.
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3.4. Sensory evaluation Fig. 2 shows the fresh-cut artichokes visual quality plotted as a function of the storage time for all the investigated samples. As can be inferred from the above data, Cntr sample has a shelf life ranging from 1 to 2 days, depending on the packaging film. In particular, sample packed in All-PE film and in NVT2 show a shelf life of 1 day, whereas a shelf life of 2 days was measured for Cntr sample packed in OPP film. A slightly higher shelf life was recorded for Dip sample, reaching 3 days in All-PE and NVT2. The above evidence is in agreement with what reported in the literature, where it is showed that dipping in water solution of citric acid and calcium chloride can delay the browning kinetic of several fresh-cut produce (Lee et al., 2003; Martin-Diana et al., 2007; Rico et al., 2007). Coated artichokes show the best results among the investigated samples, because they maintained for more time a good quality level, probably due to the fact that coating, with added anti-browning agents, provides a semi-permeable barrier that reduces water loss and oxidative reaction rate, that play the major role in determining product acceptability (Park, 1999). It is worth noting that after 3 days of storage, all samples lost their typical color, and their consistency slightly changed. Moreover, spots, moulds and general browning appeared. It
Fig. 1. Effect of treatments and packaging films on percentage weight loss of the investigated fresh-cut artichokes.
due to the compensation of the portion eliminated by the lower cut with the higher number of bracts remaining on the receptacle (Table 1). As average from a kilogram of raw material they were obtained 350 g of produce and they were necessary about 23 raw artichokes to obtain 1 kg of processed produce. As average, the industrial yield for the European cultivars ranges between 20 and 22% of the raw material (Lahoz et al., 2004), it is noteworthy that in ‘Madrigal’ it was 35%. 3.3. Weight loss Fig. 1 shows the time course, during the refrigerated storage, of weight loss for all samples investigated in this study. As expected, weight loss increases with time for all samples due to packed produce dehydration. Data shown in Fig. 1 also highlight that produce dehydration kinetic is strongly related to the packaging film water vapor barrier properties. In fact, the highest weight loss values were recorded for samples packed in NVT2 film, which has lower water vapor barrier properties than OPP film. No statistically significant differences between artichokes packed with All-PE and OPP were observed. In fact, both films have good water vapor barrier properties. Regarding the treatments tested in this investigation prior to packaging, it is worth noting that they do not seem to influence, to a great extent, the minimally processed artichoke dehydration kinetic.
Fig. 2. Influence of treatments and packaging films on the general appearance of the investigated fresh-cut artichokes.
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Table 2 Total mesophilic load (log CFU/g) of artichokes samples before and after storage as affected by pre-treatments and packaging films
Table 4 Total psychrotrophic load (log CFU/g) of artichokes samples before and after storage as affected by pre-treatments and packaging films
Pre-treatments
Pre-treatments
Initial count
Final count
Initial count
Packaging films
Control Dipping Coating
5.231
Final count Packaging films
All-PE
NVT2
OPP
6.84a,2 6.81a,3 6.81a,2
6.62a,2 7.33c,4 6.99b,2
7.24b,2 6.16a,2 6.92b,2
Control Dipping Coating
4.211
All-PE
NVT2
OPP
6.10a,2,3 6.04a,2 5.92a,2
6.22a,3 6.24a,2 5.65a,2
5.59a,2 5.94b,2 5.94b,2
Means in the same column with different superscript letters are significantly different (P b 0.05). Means in the rows with different superscript numbers are significantly different (P b 0.05).
Means in the same column with different superscript letters are significantly different (P b 0.05). Means in the rows with different superscript numbers are significantly different (P b 0.05).
was also observed that the dehydrated appearance of samples packed in NVT2 was particularly significant after day 3. The above evidence is in agreement with what reported above, where it has been observed that, regardless the pre-treatment used in this investigation, samples packed in NVT2 film show the highest percentage of weight loss. In summary, results underline that an increase in shelf life was obtained for both treated samples (i.e., Coat and Dip samples), if compared to the control. Shelf life increase ranges from 50 to 200% depending on the pre-treatment and on the packaging film barrier properties. In particular, coating together with packaging in NVT2 film seems to represent the better strategy to preserve the quality of artichokes. In fact, this is the sole sample that obtained the highest score after 2 day storage.
Table 5 Total coliforms (log CFU/g) of artichokes samples before and after storage as affected by pre-treatments and packaging films
3.5. Microbiological analyses The cell loads of the main spoilage microorganisms steadily increase with storage time (data not shown). The recorded cell loads on untreated artichokes are in agreement to what reported by Giménez et al. (2003) on minimally processed ‘Blanca de Tudela’ fresh-cut produce. For the sake of comparison, the initial and final cell loads of the investigated spoilage fungi and bacteria are listed in Tables 2 to 5. It seems that coated artichokes packaged in the NVT2 film maintain a higher microbial stability than other samples. However, even though one-way variance analysis shows some statistically significant differences between the investigated samples, the differences do not exceed one order of magnitude, suggesting that either treatments (i.e. dipping and coating) or polymeric films do not affect, to a great extent, the growth cycle of the monitored microbial groups. Moreover, it is worth noting that the microbial quality of the fresh-cut produce tested in this work can be considered more than acceptable, because the maximum cell load (i.e., that measured after 6 day storage) never exceed the threshold (5 × 107 CFU/g) imposed by French Regulation for fresh-cut vegetables (Ministere de l'Economie des Finances et du Budget, 1988), probably due to good quality of the raw materials (Francis, Thomas, & O'Beirne, 1999). The pH remained fairly constant during the entire observation period in all investigated samples. It ranged between 5.3 and 5.8, suggesting that it could not be considered responsible for artichokes
Table 3 Total yeasts load (log CFU/g) of artichokes samples before and after storage as affected by pre-treatments and packaging films Pre-treatments
Initial count
3.291
Initial count
Final count Packaging films
Control Dipping Coating
3.531
All-PE
NVT2
OPP
4.96a,4 5.35b,4 5.44b,4
4.26b,3 3.11a,2 4.32b,2
3.93a,2 4.06a,3 4.69b,3
Means in the same column with different superscript letters are significantly different (P b 0.05). Means in the rows with different superscript numbers are significantly different (P b 0.05).
quality loss. In fact, the recorded pH values are in agreement with those reported on packaged fresh-cut artichokes by Giménez et al. (2003). 4. Conclusions “Madrigal” artichokes proved to have suitable characteristics for industrial processing in terms of produce yield. The quality decay kinetic of fresh-cut artichokes during refrigerated storage, as affected by both post-harvest treatments and film barrier properties, was addressed. Two treatments, such as dipping in active solution and coating with active sodium alginate, were combined with three different packaging materials. Produce appearance, weight loss, pH, and viable cell load of the main spoilage microorganisms were monitored during storage to determine the artichoke quality loss kinetic. Results indicate that coated fresh-cut Madrigal artichokes packed in NVT2 film guarantee a shelf life of 3 days, which compared to the control sample packed in the same film, corresponds to an increase in the shelf life value of 200%. A shelf life of about 3 days seems to be enough for produce distribution to the local markets. In addition, the developed packaging strategy is characterized by a low environmental impact that could increase its potential industrial application. Acknowledgement This work was financially supported by Ministero dell'Istruzione, dell'Università e della Ricerca Scientifica e Tecnologica (MIUR) by the program “Grandi progetti Strategici (PNR 2005–2007)” — Title: “Qualità distintiva Made in Italy”.
Final count
References
Packaging films
Control Dipping Coating
Pre-treatments
All-PE
NVT2
OPP
6.32a,2 6.34a,3 6.28a,3
6.08b,2 6.68c,3 4.77a,2
6.80c,3 5.10a,2 6.03b,3
Means in the same column with different superscript letters are significantly different (P b 0.05). Means in the rows with different superscript numbers are significantly different (P b 0.05).
Adzet, T., Camarasa, J., & Laguna, C. J. (1987). Hepatoprotective activity of polyphenolic compounds from Cynara scolymus against CCl4 toxicity in isolated rat hepatocytes. Journal of Natural Products, 50, 612−617. Avella, M., De Vlieger, J. J., Errico, M. E., Fischer, S., Vacca, P., & Volpe, M. G. (2005). Biodegradable starch/clay nanocomposite films for food packaging applications. Food Chemistry, 93, 467−474. Bastioli, C. (1997). In L. Aaron, A. L. Brody, & K. S. Marsh (Eds.), The Wiley Encyclopedia of Packaging Technology (pp. pp. 77−83). (2nd ed.). John Wiley & Sons.
M.A. Del Nobile et al. / Innovative Food Science and Emerging Technologies 10 (2009) 128–133 Conti, F., Abbate, G., Alessandrini, A., & Blasi, C. (2005). An Annotated Checklist of the Italian Vascular Flora (pp. pp. 428). (1st ed.). Roma: Palombi Ed. Del Nobile, M. A., Licciardello, F., Scrocco, C., Muratore, G., & Zappa, M. (2007). Design of plastic packages for minimally processed fruits. Journal of Food Engineering, 79, 217−224. Devlieghere, F., Vermeulen, A., & Debevere, J. (2004). Chitosan: Antimicrobial activity, interactions with food components and applicability as a coating on fruit and vegetables. Food Microbiology, 21, 703−714. FAO (2008). FAO Statistics Division. URL. http://faostat.fao.org/site/567/DesktopDefault. aspx?PageID=567 (access date 08 January 2008). Francis, G. A., Thomas, C., & O'Beirne, D. (1999). The microbiological safety of minimally processed vegetables. International Journal of Food Science & Technology, 34, 1−22. Giménez, M., Olarte, C., Sanz, S., Lomas, C., Echàvarri, J. F., & Ayala, F. (2003). Relation between spoilage and microbiological quality in minimally processed artichoke packaged with different films. Food Microbiology, 20, 231−242. Jimenez-Escrig, A., Gragsted, L. O., Daneshvar, B., Pulido, R., & Saura-Calixto, F. (2003). In vitro antioxidant activities of edible artichoke and effect on biomarkers of antioxidants in rats. Journal Agricultural & Food Chemistry, 51, 5540−5545. Koide, S., & Shi, J. (2007). Microbial and quality evaluation of green peppers stored in biodegradable film packaging. Food Contaminants, 18, 1121−1125. Lahoz, I., Malumbres, A., Macua, J. I., Bozal, J. M., Urmentea, I., & Arrondo, M. A. (2004). Agricultural and industrial study of the principal European varieties of artichoke in Navarra. Acta Horticulturae, 660, 531−537. Lee, Y. J., Park, H. J., Lee, C. Y., & Choi, W. Y. (2003). Extending shelf life of minimally processed apples with edible coatings and antibrowning agents. LebensmittelWissenschaft und-Technologie, 36, 323−329. Martin-Diana, A. B., Rico, D., Frias, J. M., Barat, J. M., Henehan, G. T. M., & Barry-Ryan, C. (2007). Calcium for extending the shelf life of fresh whole and minimally processed fruits and vegetables: A review. Trends in Food Science & Technology, 18, 210−218.
133
Muratore, G., Del Nobile, M. A., Buonocore, G. G., Lanza, C. M., & Nicolosi, A. C. (2005). The influence of using biodegradable packaging films on the quality decay kinetic of plum tomato (Pomodorino Datterino). Journal of Food Engineering, 67, 393−399. Ministere de l'Economie des Finances et du Budget (1988). Marché consommation, Produits vegetaux prets a l'emploi dits de la “IVemme Gamme”: Guide de bonnes pratique hygieniques. J. Off. De la Republic Francaise, 1621−1629. Park, H. J. (1999). Development of advances edible coatings for fruits. Trends in Food Science & Technology, 10, 254−260. Perez-Garcia, F., Adzet, T., & Canigueral, S. (2000). Activity of artichokes leaf extract as reactive oxygen species in human leukocytes. Free Radical Research, 33, 661−665. Ragaert, P., Devlieghere, F., & Debevere, J. (2007). Role of microbiological and physiological spoilage mechanisms during storage of minimally processed vegetables. Postharvest Biology & Technology, 44, 185−194. Rico, D., Martín-Diana, A. B., Barat, J. M., & Barry-Ryan, C. (2007). Extending and measuring the quality of fresh-cut fruit and vegetables: A review. Trends in Food Science & Technology, 18, 373−386. Tharanathan, R. N. (2003). Biodegradable films and composite coatings: Past, present and future. Trends in Food Science & Technology, 14, 71−78. Wang, M., Simon, J. E., Aviles, I. F., He, K., Zheng, Q. Y., & Tadmor, Y. (2003). Analysis of antioxidative phenolics compounds in artichoke. Journal Agricultural & Food Chemistry, 51, 601−608. Watada, A. E., & Qi, L. (1999). Quality of fresh-cut produce. Postharvest Biology & Technology, 15, 201−205. Yommi, A., Giletto, C., Horvitz, S., & Lòpez Camelo, A. (2001). Effects of temperature and semi-permeable films on quality of stored artichokes (Cynara scolymus L.). Acta Horticulturae, 553, 619−620.