QUALITY OF MINIMALLY PROCESSED LETTUCE AS INFLUENCED BY PACKAGING AND CHEMICAL TREATMENT

Shredded lettuce was packaged in sealed bags of monooriented polypropylene (OPP) film and also in polyethylene (PE) trays overwrapped with a multilayer polyolefin (RD106) or plasticized polyvinyl chloride (PVC) film; and stored at 4C in a refrigerated case during 8 days. Chemical treatment by dipping in a 0.3% ascorbic acid /0.3% citric acid solution did not significantly affect changes in microbial populations or visual sensory attributes. Type of package was not a significant factor for microorganism populations, but was significant (p<0.001) for changes in gas composition and visual sensory attributes. The modified atmosphere within the packages changed from normal air composition to about 1.5% O₂/12% CO₂ for OPP bags and to about 17–18% O₂/1–2% CO₂ for PVC-PE trays and RD106-PE trays after 8 days of storage. The visual sensory quality of the product was retained better in OPP bags than in the other ones.     

The effects of packaging film and storage temperature on the quality of a dry coleslaw mix packaged in a modified atmosphere

Summary The effects of six packaging treatments on the quality of dry coleslaw packaged in modified atmospheres and stored at 4 and 8 °C for 9 days were determined. The coleslaw was packaged within either oriented polypropylene (OPP) or one of four microperforated OPP films, PA‐120, PA‐160, PA‐190, and PA‐210. It was also stored within punctured OPP (i.e. in air). Packaging within OPP resulted in an atmosphere with very low O₂ (<1%) and extremely high CO₂ (25–35%) levels. These storage conditions had detrimental effects on the quality of coleslaw: loss of firmness, falling pH, high cell permeability and exudate, high surface moisture and poor acceptability of aroma. By contrast, the microperforated films generated less atmosphere modification; in some cases this was insufficiently modified to be technically useful. The relatively high O₂ levels in these microperforated packs resulted in lower appearance and colour scores, increased surface dryness and higher firmness values. Increasing storage temperature from 4 to 8 °C resulted in a reduction in shelf‐life for all film types. While still not optimal, packaging within microperforated films allowed better preservation of quality and reduced cell membrane damage.     

Survival and Growth of Salmonella hadar on Minimally Processed Cabbage as Influenced by Storage Abuse Conditions

Shredded, washed and centrifuged cabbage was packaged in monooriented polypropylene (OPP) bags, inoculated with Salmonella hadar and stored 10 days at 4°C, 12°C and 20°C. Microbiological, appearance, odor and headspace gas analysis were evaluated throughout storage. S. hadar and mesophilic aerobic and psychrotrophic microorganism growth was affected by storage time and temperature. S. hadar counts were lower (p<0.05) at 4°C than at 12°C and 20°C. The score ratings for general appearance, wilting, browning and off-odor showed that all samples were commercially acceptable. Results indicated that S. hadar could survive and proliferate on minimally processed cabbage, thereby posing a potential hazard to consumers.     

自发气调包装对鲜切白菜货架期的影响

为延长鲜切白菜的货架期,本文采用不同透气率和不同面积的气调窗与包装袋相结合进行试验,通过对鲜切白菜包装袋内感官品质、气体成分进行统计和分析,筛选和优化出鲜切白菜最适宜的气调包装。结果表明：自发气调包装可有效改善鲜切白菜贮藏品质,鲜切白菜适宜选用O2和CO2透过速率分别为4×105和1.6×106 cm3/m2?d?atm,透气比为1:4气调窗,所需要气调窗的面积为1~2 cm2/kg,在4 ℃条件下至少可延长货架期4 d;综合计算气调窗和薄膜的透气量可知,适于鲜切白菜包装袋O2和CO2的透过量应分别为1.85×103~2.08×103 和8.59×103~9.51×103 cm3/kg?d?atm,达到鲜切白菜的适宜气体浓度,O2为3.63%~5.10%,CO2为7.77%~8.07%。研制的自发气调包装袋可使鲜切白菜处于适宜的气体状态,可很好地解决包装袋内由于无氧呼吸产生的异味问题,且保留原有的鲜切白菜气味,延长其货架期,为鲜切企业提供有力的技术支持。     

Sensory Characteristics of Fresh-Cut Spinach Preserved by Combined Factors Methodology

Fresh‐cut spinach was treated with citric acid and ascorbic acid solutions and packaged in monooriented polypropylene (OPP) bags or low density polyethylene (LDPE) bags. Sensory attributes, chlorophyll retention, and weight loss were evaluated throughout refrigerated storage. Mathematical models were developed to analyze and predict the effect of the citric acid and ascorbic acid concentrations and storage time on off‐odor development, general appearance, wilting, browning, and color. Sensory attributes of fresh‐cut spinach decreased with storage time. Type of film affected off‐odor development, but did not influence visual sensory attributes. Chemical treatment and type of packaging film did not affect chlorophyll retention. Both types of packaging film controlled weight loss.     

贮藏温度和包装材料对百合保鲜包装品质的影响

采用不同贮藏温度(30℃和5℃)和包装材料(PE、OPP、OPP/PE膜)对百合进行保鲜包装,测定不同贮藏时间下的百合球茎Vc含量、总糖含量、色差、失重率和感官品质变化。结果表明:低温能够显著抑制百合失重,保持其较好的色泽和总糖含量。不同包装材料比较,具有较高透气率的PE、OPP膜保鲜效果较好,OPP/PE膜次之。低温与包装之间有较好的协同作用。     

USE OF FLEXIBLE POLYMER MATERIAL FOR PACKAGING FRESH PEACHES

Fresh peaches (Prunus persica) were overwrapped in trays with 1 of 3 formulations of flexible polyvinyl chloride (PVC) film that differed in gas transmission rate or they were held in nonwrapped trays (controls). The CO₂ transmission rate at 0°C for PVC type III film was 280 mL/m^2. h (1 atmos); that of type II was 4 times greater and that of type I, about 5 times greater. The peaches were stored either 14 days at 0° or 7.5°C, or 7 days each at 0° and 7.5°C plus 2 days at 20°C to simulate retail display. The mean CO₂ levels were 10, 7.2 and 4.7% in packages that were wrapped with PVC III film and held at 7.5°, 0°/7.5° and 0°C, respectively. CO₂ in packages wrapped with PVC I or II was below 3% at each storage temperature. O₂ concentration remained about 4% in all packages. Weight loss was less and fruit was firmer among those packaged in PVC III than among nonwrapped controls at each of the 3 storage temperatures. Storage temperature had no effect on weight loss or of fruit held in PVC III film. External appearance of fruit packaged with the 3 types of film was significantly better than that of the controls. Internal appearance of the peaches was unaffected by any of the treatments. A microatmosphere favorable for fresh peaches can be maintained within packages overwrapped with polymer films that are selectively permeable to respiratory gases.     

Effects of type of packaging material on shelf-life of fresh broccoli by means of changes in weight,colour and texture

Five polymeric films were studied to determine their ability to retain the colour, weight and texture of broccoli (Brassica oleracea L. var. Italica Monterey). The materials were oriented polypropylene (OPP), polyvinyl chloride (PVC) and two different low-density polyethylenes (LDPE), one of which contained a sachet reported to absorb ethylene. The broccoli was packaged and stored at 4 and 10 °C for 4 weeks. The weight, colour, chlorophyll content and texture were monitored during storage as well as O₂ and CO₂ concentrations inside the packages. Packaging prolonged the broccoli shelf-life by up to 14 days. The shelf-life varied depending on the packaging material and quality parameter considered. The atmosphere was modified inside the packages; however, no package provided the recommended atmosphere (O₂ 1–2% and CO₂ 5–10%) for broccoli. Packaging in OPP resulted in the highest CO₂ concentration, 6%, while the lowest O₂ concentration, 9%, was created in the LDPE package without a sachet for ethylene absorption. Storage in LDPE without ethylene absorber resulted in the overall longest shelf-life. Broccoli stored in PVC deteriorated faster than broccoli packaged in the other materials. The influence of packaging material was greater at the higher temperature.     

Volatile compounds of modified atmosphere packaged cut iceberg lettuce: Effect of extremely low O2, season,cultivar and storage time

This study investigates the changes in volatile compounds in minimally processed iceberg lettuce as a function of season, cultivar, packaging and time. In order to achieve this, iceberg lettuce cultivars Platinas, Diamantinas and Morinas were harvested from June to September 2009. Lettuces were minimally processed and stored under three different treatments: two passive modified atmosphere packagings using films of different permeabilities, F1 (OPALEN 65 AF) and F2 (OPP/PE-L 2040 AF), and storage in air. All packages were stored at 5 °C. Gas composition and volatile compounds were assessed at 1, 5, 8 and 11 days of storage in packaged lettuce, whereas in air stored samples volatiles were analyzed only at 1 and 5 days of storage. Twenty one potent odorants were identified by GC–O. Among the months, August presented a notary increase of elemene, β-selinene and 2,3-butanedione, which likely contribute to off-odor of packaged cut lettuce. The content of O₂ and CO₂ was demonstrated to influence the formation of odorants as storage time increased. Higher amount of cis-3-hexenol was related to aerobic conditions found in the modified atmosphere packages and air stored samples after 1 day of storage, whereas levels of odorants such as 2,3-butanedione, elemene and β-selinene were significantly enhanced under anaerobic conditions after 11 days of storage. Film F2 seems to be the most promising because it kept the concentration of elemene and β-selinene lower than film F1. No clear differences were seen between the cultivars Morinas, Diamantinas and Platinas with regard to production of objectionable odorants under anaerobic conditions.     

Modified Atmosphere Packaging of “Napoleon” Cherry: Effect of Packaging Material and Storage Time on Physical,Chemical, and Sensory Quality

Effects of modified atmosphere and polymeric packaging material on the physical (mass loss, color, firmness), chemical (pH, total titratable acidity, total soluble solid, total phenolic content, total anthocyanin content), and sensory quality of “Napoleon” cherry (Prunus avium L. “Napoleon”) were studied. While lightness (L*) remained fairly unchanged, redness (a*), yellowness (b*), and chroma (C*) decreased during a 42-day storage period, resulting in darker fruit. Firmness did not differ significantly from the initial values (P ≤ 0.05) after 42 days of storage at 0°C. pH increased for all treatments over the storage period. In general, total titratable acidity increased during the first 2 weeks, and then decreased afterwards. Packaging significantly reduced mass losses, which were 24.08%, 0.50%, 0.39%, and 0.81% for control (unpackaged), polypropylene tray/biaxially oriented polypropylene film (PP/BOPP), polypropylene tray/cast polypropylene film, and polyvinyl chloride-polyethylene tray/polyethylene terephthalate-polyethylene films, respectively. Modified atmosphere packaging was found beneficial on extending the shelf life of fruit during storage. The shelf life of “Napoleon” cherries was suggested as 28 days for packaged samples and 14 days for unpackaged samples at 0°C. Samples packaged with PP/BOPP under 21% O₂ 79% N₂ preserved their physical, chemical, and sensory quality better than other treatments.     

PROLONGING THE SHELF-LIFE OF FRESH GREEN CHILE PEPPERS THROUGH MODIFIED ATMOSPHERE PACKAGING AND LOW TEMPERATURE STORAGE

The postharvest quality of green chile fruit was compared after storage in 3 types of packages at 2 temperatures (24C and 8C). Package types were corrugated cardboard boxes, pressed cardboard trays overwrapped with VF-71 polyethylene, or low-density polyethylene (LDPE) bags. Fruit packaged in boxes or overwrapped trays had 24.8% and 10.1% weight loss, respectively, after 1 week of storage at 24C. Fruit packaged in polyethylene bags lost 0.3% weight and remained green. After 1 week at 8C, the weight losses were 3.8%, 1.8% and 0% for the boxed, overwrapped and bagged treatments, respectively. Postharvest quality was maintained up to 4 weeks when fruit were packaged in LDPE bags and stored at 8C. In a second study, steady state O₂ and CO₂ levels were determined inside the LDPE packages as fruit weight and temperature were varied. Storage temperatures were 24C, 16C and 8C. At 8C, steady state O₂ levels ranged from 12.0 kPa to 0.9 kPa, and CO₂ levels ranged from 2.0 kPa to 4.6 kPa as fruit weight was increased from 120 to 480 g. At 24C and 16C, fruit packaged in 480 g units had slower ripening rates than fruit packaged in smaller units; however, fruit stored at 8C remained green the longest, regardless of fruit weight.     

Quality of minimally processed red chicory (Cichorium intybus L.) evaluated by anthocyanin content,radical scavenging activity,sensory descriptors and microbial indices

Changes in the quality of minimally processed red chicory (Cichorium intybus L.) were studied during storage in a polyvinyl chloride (PVC) film and in a mono‐oriented polypropylene (OPP) film at 4 °C. The maximum limit of 5 × 10⁷ CFU g^?1 for mesophilic aerobic bacterial count was attained after 4 days using the PVC film and after 4.5 days using the OPP film. The loss of fruity aroma occurred after 3 days in the products stored in PVC but not in those stored in OPP. In spite of microbial growth, no off‐odour was perceived by trained panellists. Storage in PVC slightly decreased the contents of cyanidin 3‐O‐malonyl glucoside, total phenolics and antioxidant activity, whereas these parameters increased upon storage in OPP. When red chicory heads subjected to mild stress in the field were minimally processed, OPP packaging decreased the microbial growth with respect to PVC, but antioxidants were degraded in both conditions.     

Control of Microbial Spoilage on Fresh Poultry using a Combination Potassium Sorbate/Carbon Dioxide Packaging System

The effects of potassium sorbate combined with vacuum or carbon dioxide modified atmosphere packaging on natural poultry spoilage flora were examined. Fresh chicken thighs were dipped into either 2.5% potassium sorbate solution or distilled water, adjusted to pH 6.0 and packaged on trays in Nylon/Plexar/Surlyn bags. Atmospheres of either air, vacuum or 100% C0₂ were created in the packages which were then stored at 10 ± 1°C for 10 days. Changes in aerobic plate counts, lactic acid bacteria and pseudomonads were monitored. The combination of CO₂ packaging and sorbate treatment provided the most effective inhibitory system against the poultry spoilage organisms, especially Pseudomonas species, without creating a selective environment for the growth of lactic acid bacteria and premature souring of the product. The shelf life of the sorbate/CO₂ samples was extended 3 days over the control/air samples at 10°C.     

Effects of packaging type, gas atmosphere and storage temperature on survival and growth of Listeria spp. in shredded dry coleslaw and its components

The survival and growth of Listeria populations inoculated on to dry coleslaw mix and its components were investigated, focusing on effects of storage temperatures and gas atmospheres within packaging films or storage chambers. There were few significant effects of packaging film at 3 °C, but at 8 °C the elevated CO₂/low O₂ atmospheres generated within orientated polypropylene (OPP) packages and used in controlled atmosphere chambers were inhibitory. Although two strains of Listeria monocytogenes had survival characteristics comparable with Listeria innocua, L. monocytogenes ATCC 19114 survived better at 3 °C and also in the elevated CO₂/low O₂ atmospheres within OPP at 8 °C. The effects of product components on the survival of L. innocua were linked to storage temperature. Shredded carrot reduced initial counts and at 8 °C inhibited survival of L. innocua in comparison with shredded cabbage.     

Effects of fibre orientation, myoglobin redox form, and postmortem storage on NIR tissue oximeter measurements of beef longissimus muscle

To determine near-infrared tissue oximeter responses to muscle fibre orientation, display time, and surface colour differences of beef longissimus lumborum steaks, beef loins were cut into steaks either perpendicular or parallel to the muscle fibre orientation. Surface colour differences were created by packaging steaks in vacuum (VAC), 80% O₂ and 20% CO₂ modified atmosphere packaging (HiOx MAP), polyvinyl chloride film overwrap (PVC), and HiOx MAP converted to PVC (HiOx-PVC) after 2 days. Changes in surface colour and subsurface pigments during display (0, 2, 4, 10, and 15 days at 2 °C) were characterized by using a reflectance-spectrophotometer and a near-infrared tissue oximeter, respectively. Fibre orientation, storage, and packaging affected (P < 0.05) colour, total pigment, deoxymyoglobin, and oxymyoglobin content. Tissue oximetry measurements appear to have potential for real-time monitoring of myoglobin redox forms and oxygen status of packaged meat, but fibre orientation needs to be controlled.     

Use of hyperspectral imaging for evaluation of the shelf-life of fresh white button mushrooms (Agaricus bisporus) stored in different packaging films

The shelf life of mushrooms packaged using different polymer top-films (PVC, PET with different levels of perforations) was investigated using hyperspectral imaging (HSI). Packaged mushrooms were stored at 4 ± 0.2 °C for 14 days and weight loss, Hunter L, a, b values, maturity index and in-pack gas composition (% CO₂ and O₂) were also measured. The results obtained showed that the PET film perforated with small holes (1 mm in diameter) was generally superior in terms of maintaining overall mushroom quality. Regression models were built to correlate HSI data with measured quality parameters. Prediction maps were generated from hyperspectral data to show the model performance at pixel level. Results presented in this work show hyperspectral imaging can be used to evaluate the effect of different packaging systems on mushroom quality and that perforated PET packaging film is a viable alternative to the conventional PVC packaging, facilitating an increase in shelf life from 10 to 14 days.Industrial relevanceThe present study demonstrates HSI can be used for rapid evaluation of mushroom quality facilitating non-destructive evaluation of the effect of packaging systems on mushroom shelf-life. In addition, this work suggests an effective packaging solution to extend shelf life of mushrooms during storage. The proposed solution potentially improves the packaging recyclability as the same polymer material (PET) is used for the tray and top film, compared to conventional mushroom packaging where PVC is used for the top film and polypropylene (PP) for the tray.     

Active Packaging of Cardboard to Extend the Shelf Life of Tomatoes

In order to extend the shelf life of fresh tomatoes using biodegradable materials, an active microcorrugated cardboard tray package was tested for use with fresh Cherry tomatoes (Lycopersicon esculentum var. cerasiforme). Active packaging characteristics were achieved by coating the interior surface of the cardboard tray with polylactic acid (PLA; 3% w/v) and, after filling with tomatoes, the tray was wrapped with a low-density polyethylene (LDPE) film of 70 or 20 μm thickness and hermetically heat sealed. Uncoated trays were used as control. The trays of tomatoes were stored at 20?±?0.5 °C and 55?±?2% relative humidity, for 30 days, and the ethylene concentration in the package atmosphere was measured periodically as an indicator of ripeness. The following fruit quality parameters were also studied: weight loss, surface colour, microbial count, firmness, soluble solids and pH. It was demonstrated that the capacity of PLA to adsorb ethylene and water vapour and the thickness of the LDPE film were decisive for controlling the ethylene concentration of the package atmosphere and for preventing condensation of water vapour on the fruit and film. The active packaging configuration and storage conditions used preserved fruit quality for a month, thus extending the useful life of the tomatoes and saving refrigeration costs.     

MICROFLORA CHANGES IN MODIFIED-ATMOSPHERE-PACKAGED BROCCOLI FLORETS STORED AT REFRIGERATED TEMPERATURE

Changes in the microflora of packaged (Resinite VF-71 film) and nonpackaged broccoli florets held at 8C for 7 days were analyzed. Oxygen and carbon dioxide concentrations, aerobic plate, coliform yeast/mold counts, and overall quality were determined. Level of O₂ decreased from 15.58 to 5.15%, while CO₂ increased from 2.88 to 8.22% after 94 h of storage. Within each microorganism group, similar growth trends were observed between the packaged and nonpackaged samples; however, the packaged samples consistently exhibited a statistically significant (p ≤ 0.05) lower microbial count compared with nonpackaged samples throughout the storage period. Packaged and nonpackaged florets retained their green color and no off-odor was detected; however, the nonpackaged florets were found to be less crispy than the packaged samples.     

Colour of hot paprika from the La Vera and Murcia regions packaged in different atmospheres during storage

This study compared the behaviour of hot paprika (Capsicum annuum L.) samples from the district of La Vera and the region of Murcia packaged in five different conditions during storage. The following five different packaging conditions were used in this study: modified atmosphere packaging with three different conditions (100% N₂; 50% N₂ and 50% CO₂; and 100% CO₂), vacuum packaging and traditional packaging (product packaging system without modifying the atmosphere). After the samples were packaged, they were stored for 8 months at room temperature (normal storage conditions). The following parameters were used to indicate the quality of the samples: Aw, ASTA colour, CIE_L*a*b* colour parameters, and the composition of red and yellow compounds. The results indicate that the modified atmosphere packaging and vacuum packaging exerted a protective effect on the paprika quality characteristics regardless of the paprika origin. However, no clear differences were detected between the effect of vacuum packaging and the different modified atmosphere packaging conditions.