Shelf life of Turkish whey cheese (Lor) under modified atmosphere packaging

In this study, the shelf life of Lor cheese stored under different atmosphere compositions was assessed and compared. Lor cheeses were held in four different atmospheres containing: vacuum packaging (VP), 40% CO₂/60% N₂, 60% CO₂/40% N₂ and 70% CO₂/30% N₂ (modified atmosphere packaging). Control cheeses were stored in air. All cheese samples were kept in the refrigerator at 4°C for 45 days and investigated for physicochemical, microbiological and sensory properties. The acidity index value was significantly higher ( P  < 0.05) in the control and vacuum packaged samples than in those stored for the same period under CO₂. Microbiological results showed that modified atmosphere packaging delayed microbial growth compared with air and VP samples. Of the three modified atmospheres, gas mixtures 60% and 70% CO₂ were the most effective for inhibition of growth of micro-organisms. Sensory evaluation (odour and taste) results showed that Lor cheese packaged under modified atmosphere packaging (60% CO₂/40% N₂ and 70% CO₂/30% N₂ ) retained good characteristics for 45 days of storage, while vacuum and control samples were sensorily unacceptable after 10 days of storage.     

Effect of irradiation and modified atmosphere packaging on the microbiological and sensory quality of pork stored at refrigeration temperatures

The effect of combining low-dose irradiation (1.75 kGy) with modified atmosphere packaging (MAP) on the microbiological and sensory quality of pork chops stored at refrigeration temperatures was studied. The microflora of irradiated MAP pork was almost exclusively composed of lactic acid bacteria, predominantly Lactobacillus spp. Modified atmospheres containing either 25 or 50% CO₂, balance N₂, resulted in the best microbial control in irradiated pork held at 4°C, compared to an unirradiated MAP control, and these atmospheres were subsequently used in sensory studies. The atmosphere containing 25% CO₂ 75% N₂ maintained the uncooked colour and odour of irradiated pork chops more effectively than 50% CO₂ 50% N₂. Therefore packaging in a modified atmosphere containing 25% CO₂, balance N₂, followed by irradiation to a dose of 1.75 kGy is recommended to improve the microbiological and sensory quality of pork chops.     

GROWTH/SURVIVAL OF NATURAL FLORA AND LISTERIA MONOCYTOGENES ON REFRIGERATED UNCOOKED PORK AND TURKEY PACKAGED UNDER MODIFIED ATMOSPHERES

Listeria monocytogenes was inoculated onto fresh pork and turkey slices. Inoculated and control samples were packaged under modified atmospheres (100% N₂, and 20%/80% and 40%/60% CO₂O₂) or air in plastic bags of low gas permeability. Samples were stored at 1 and 7C. Samples stored in air showed a similar microbiological pattern to that usually observed in fresh meat stored aerobically. Packaging under modified atmospheres extended the meat shelf-life. Bacterial growth was strongly inhibited at 1C, particularly in samples stored under CO₂/O₂ enriched atmospheres. Temperature and pH were critical factors for L. monocytogenes growth. This pathogen grew only on pork (initial pH 5.3) packaged in air and stored at 7C. No L. monocytogenes growth was observed at 1C in any atmosphere assayed. However, growth on turkey (initial pH 6.0) was marked at 7C in all atmospheres tested, while at 1C, this bacterium grew weakly only on samples stored in air .     

Shelf-life of chicken liver/egg paté in modified atmosphere packages

Shelf-life of paté (salad in Israel) made by blending fried chicken liver and onions with hard-boiled eggs was extended, from 6 days in air to 14 days by Modified Atmosphere Packaging (MAP), using high CO₂/low O₂ mixtures. Aerobic microbial growth, mainly B. subtilis , and lipid oxidation (as TBA values) were largely inhibited, during 14 days, and odour up to 8 days (not tested beyond). the microbial growth inhibition was due to high CO₂ levels. Oxidation was prevented due to microbial inhibition and not due to reduced O₂.     

Quality Changes of Deepwater Pink Shrimp (Parapenaeus longirostris) Packed in Modified Atmosphere

ABSTRACT: The storage of deepwater pink shrimp ( Parapenaeus longirostris ) in modified atmosphere was studied. Two gas mixtures were tested (40% CO₂/30% O₂/30% N₂ and 45% CO₂/5% O₂/50% N₂), combined with sulfites-based pretreatment, in comparison with air storage. The quality of shrimp was evaluated by sensory (black spot presence) and chemical analyses (pH value and nucleotides breakdown products). Generally, both atmospheres preserved the shrimp quality up to 9 d compared with 4 to 7 d of ice storage (only with pretreatment), although it seems that atmosphere containing 45% CO₂/5% O₂/50% N₂ was the most effective.     

EFFECT OF OXYGEN-ENRICHED ATMOSPHERES ON STORAGE QUALITY OF PACKAGED FRESH MEAT

SUMMARY —The extension of fresh meat shelf-life is important from both practical and theoretical points of view. Color is usually used as a measure of fresh meat quality during storage. Beef top-round slices were prepared using sanitary precautions. Meat slices were enclosed in a thermally sealed semi-rigid polyvinyl chloride tray system of special design. Face-to-face meat samples were used to compare the effects of high oxygen with normal air atmospheres. One package from each pair was evacuated and the atmosphere readjusted to approximately 90% oxygen through a septum. Packages were kept at 4 ± 0.5°C and gas chromatographic readings for CO₂, O₂ and N₂ were conducted daily. Spectrophotometric and bacteriological evaluations were made on selected pack ages during storage to determine pigment oxidation and microbial growth. Three experiments each containing six to eight pairs of samples were conducted. The generation of CO₂ was observed in two periods–the first immediately after packaging and lasting for 1–2 days, after which the CO₂ level remained approximately stable up to 8—9 days, when it again started to increase in correspondence with increased bacterial growth. There was more CO₂ produced than O₂ utilized in the stored samples. In the first stage, samples stored in oxygen-enriched atmospheres had higher O₂ uptake than samples stored in air. Microbial growth was similar in both atmospheres. Under conditions of this study, head space enrichment to about 90% oxygen prolonged acceptable meat color when compared with samples stored in an air atmosphere.     

Some effects of modified-atmosphere packaging and vacuum packaging in combination with antioxidants on quality and storage life of chilled potato strips

A modified-atmosphere packaging system for chilled fresh potato strips, which rapidly produced oxygen levels < 3%, was identified. This system enclosed the strips within 25 μ low density polyethylene film heat sealed to a fibre tray lined with Surlyn-PVdC-Surlyn, and the package flushed with an initial atmosphere of 5% O₂, 10% CO₂. An equilibrium-modified atmosphere of 3–4% CO₂, 1–2% O₂ was established after 3 days' storage at 5°C. This modified-atmosphere package, used in combination with dipping of potato strips in a 10% ascorbic acid solution, inhibited enzymatic discoloration for 1 week at 5°C. Vacuum packaging within a Surlyn/PVdC-coated polyester film, with or without dipping in ascorbic acid solution, inhibited discoloration of chilled potato strips stored at 5°C for at least 2 weeks.     

Fruit Quality, Antioxidant Contents and Activity, and Antiproliferative Activity of Strawberry Fruit Stored in Elevated CO2 Atmospheres

ABSTRACT:  The effects of CO₂ in the storage atmosphere on color, firmness, ascorbic acid (AA), anthocyanins, flavonoids, phenolics, total antioxidant activity, and antiproliferative activity of strawberry fruit have been investigated. "Northeaster" and "Earliglow" strawberries were stored in air or in 20% CO₂ (in air) at 3 °C for 20 d. Color changes in Northeaster were delayed more by CO₂ treatment than in Earliglow. Firmness of CO₂-stored fruit increased slightly compared with those stored in air. The increases in total and reduced AA concentrations during air storage were usually prevented by CO₂ storage in both cultivars. Dehydroascorbic acid (DHA) concentrations increased during CO₂ storage. Anthocyanins and flavonoids, and total antioxidant activity of both cultivars were higher in air-stored fruit than in CO₂-stored fruit. The total phenolic concentration was lower in CO₂-stored Earliglow fruit than in air, but storage treatment did not affect that of Northeaster. A 40 mg/mL concentration of Northeaster strawberry extract inhibited about 80% of HepG₂ human liver cancer cell proliferation. CO₂ treatment did not affect the antiproliferative activity of strawberry fruits, but antiproliferative activity was greater at harvest than after storage.     

Shelf Life and Microbial Quality of Fresh-cut Mango Cubes Stored in High CO2 Atmospheres

ABSTRACT: Fresh-cut'Carabao'and'Nam Dokmai'mango cubes were stored in air or in high CO₂ atmospheres (3%, 5%, and 10%) at 5 °C and 13 °C. Freshly sliced'Carabao'mango cubes had a lower respiration rate and total bacterial count and higher L-ascorbic acid content and firmness than'Nam Dokmai'mango cubes. The shelf life of fresh-cut mango, based on browning discoloration and water-soaked appearance, was 6 d at 5 °C and 4 d at 13 °C for'Carabao'and 2 d at 5 °C and less than 1 d at 13 °C for'Nam Dokmai'. High CO₂ atmospheres retarded the development of water-soaked'Carabao'cubes at 5 °C and 13 °C and'Nam Dokmai'cubes at 5 °C. Texture of'Carabao'cubes was enhanced by high CO₂, but ethanol and L-ascorbic acid contents were not affected at 5 °C and 13 °C. Total bacterial count was lower in'Carabao'cubes than in'Nam Dokmai'cubes during storage at both temperatures, and a 10% CO₂ only reduced the bacterial count on'Carabao'and'Nam Dokmai'cubes stored at 13 °C. Bacterial flora in'Nam Dokmai'mango cubes consisted mostly of Gram-negative rods assigned primarily to phytopathogenic bacteria such as Pantoea agglomerans and Burkholderia cepacia . The genera of bacteria isolated from cubes stored in 10% CO₂ were similar to those from cubes on the initial day.     

Chemical and sensory changes in haddock and herring stored under modified atmosphere

The effectiveness of storage in atmospheres with increased proportions of CO₂ to extend the shelf-life of haddock and herring was examined. Using a 40: 30: 30/CO₂: O₂: N₂ atmosphere with haddock no useful extension of shelf-life was achieved at +5°C and only limited extension at 0°C. A more useful extension of shelf-life at 0°C was obtained by storing haddock in a 60: 20: 2O/CO₂: O₂: N₂ atmosphere and with herring in a 60:40/CO₂::N₂: atmosphere. Total volatile bases (TVB) and hypoxanthine values (Hx) correlated with the cooked flavour. There were no significant differences in drip-loss between the modified atmosphere packaging (MAP) stored samples and the controls. Peroxide values (PV) in herring were lower in MAP stored samples. Whole haddock and whole herring were found to have a longer shelf-life when stored in MAP at 0°C than when stored as fillets.     

Microbiological, physicochemical and organoleptic changes in dry-salted olives of Thassos variety stored under different modified atmospheres at 4 and 20 °C

Microbiological, physico-chemical and organoleptic changes were studied in dry-salted olives, cv. Thassos, stored under different atmospheres (100% carbon dioxide and nitrogen, 40% CO₂/30%O₂/30%N₂ and air) at 4 and 20 °C for 180 days. The initial microbial flora comprised of yeasts, no lactic acid bacteria, enterobacteria, pseudomonads or Staphylococcus aureus were detected, as the low water activity/high salt content does not favour their growth. At 4 °C, the population of yeasts declined steadily throughout storage but to a different extent depending on the gaseous atmospheres. At 20 °C, there was an initial decline in yeast counts in all samples followed by a steady increase until the end of the storage period. The CO₂ atmosphere was most effective at keeping the number of yeasts low at both storage temperatures. All gas atmospheres prevented fungal growth at both temperatures apart from the samples stored in air. The pH, a_w and salt content of the olives did not change significantly throughout the storage period. The prevailing yeast species was the salt tolerant Candida famata . The organoleptic characteristics did not differ significantly among differently treated olives. However, increased rancidity and reduced fruit colour was observed in the samples stored at 20 °C.     

Inhibition of Fungal Growth on Wheat and Rye Bread by Modified Atmosphere Packaging and Active Packaging Using Volatile Mustard Essential Oil

ABSTRACT: Wheat and rye bread artificially inoculated with molds were packed in modified atmospheres of 0%, 50%, 75%, or 100% CO₂ balanced with N₂, and 3 levels of residual O₂, 1%, 0.03%, or <0.01%/O₂-absorber, and stored for 30 to 35 d. Modified atmosphere packaging (MAP) was quantitatively more effective for rye bread because fewer mold species grew at elevated CO₂. However, the major rye bread contaminant, Penicillium roqueforti , was the overall most CO₂-resistant mold and only the use of O₂-absorber could prevent growth of this species. On wheat bread, the most CO₂-tolerant mold was Penicillium commune , growing in 99% CO₂ (with high residual O₂), and Aspergillus flavus was the mold species that grew at lowest O₂ in 75% CO₂ treatment. The spoilage yeast/"chalk mold" Endomyces fibuliger was less affected by the different O₂ levels than the true filamentous molds, and none of the tested MAP treatments could prevent growth, but lag-phase was increased with O₂-absorber on wheat bread and decreased with 1% residual O₂ on rye bread. Experiments with volatile mustard oil showed that A. flavus and Eurotium repens were the most mustard oil-resistant species on wheat and rye bread, respectively. A combination strategy with MAP and mustard oil proved most optimal, and total inhibition was achieved with 2 μL mustard oil/rye bread slice and between 2 and 3 μL/wheat bread. Results indicated that the nature and surface area of the product influences effectiveness of active packaging with mustard oil.     

High Oxygen and High Carbon Dioxide Modified Atmospheres for Shelf-life Extension of Minimally Processed Carrots

The impact of high O₂+ high CO₂ modified atmospheres (MA), on the preservation of minimally processed carrots was studied. A combination of 50% O₂+ 30% CO₂ prolonged the shelf life of sliced carrots compared to storage in air by 2 to 3 d. When the carrots received a pre-treatment with a 0.1% citric acid dip and a sodium alginate edible coating prior to packaging, shelf life was extended by 5 to 7 d. Advantages and disadvantages of the proposed MA over previously recommended MA (1% O₂+ 10% CO₂), related to a range of physicochemical and microbiological characteristics of carrots are discussed.     

Modeling Botrytis Cinerea Spores Growth in Carbon Dioxide Enriched Atmospheres

ABSTRACT: This study simulates the conditions in which Botrytis may appear in a modified atmosphere packed horticulture product, such as strawberry, so as to elaborate a predictive model that could allow us to estimate the shelf-life of a contaminated food product in such atmosphere conditions (0 to 40% CO₂). The estimated shelf-lives obtained at 18 °C were 92, 164, and 236 h in storage atmospheres of 0, 10, and 20% CO₂, respectively, very close to observed values; no growth was observed above 30% CO₂. The elaborated predictive model allows us to: (a) control development of this fungi if the food product is maintained in an atmosphere containing more than 20% CO₂ and (b) predict the time taken for potential colonies to become visible (3 mm dia) and, thus, cause immediate rejection by consumers.     

Quality changes during refrigerated storage of MA-packaged pre-rigor fillets of farmed Atlantic cod (Gadus morhua L.) using traditional MAP, CO2 emitter, and vacuum

ABSTRACT:  Quality changes during 3 wk of refrigerated storage (1.3 °C) were studied on pre -rigor filleted farmed Atlantic cod packed in modified atmosphere (MAP, 60% CO₂ and 40% O₂) or vacuum. The packages of MAP contained either a CO₂ emitter and low gas volume to product volume (g/p ratio) of 1.3, or a 3.9 g/p ratio and no emitter. The CO₂ level remained stable or increased in the packages with CO₂ emitter, whereas the CO₂ level in the packages with no CO₂ emitter decreased to 40% after 4 d of refrigerated storage. High levels of oxygen in the gas mixture prevented formation of trimethyl amine (TMA) during storage of the MA-packed fish, whereas the TMA content increased significantly after 10-d storage in vacuum. MA-packed samples had the highest values of 1-penten-3-ol. Sensory scores of sour, sulfur, and pungent odors were significantly higher for vacuum-packed cod compared to the 2 MA-packaging methods measured 14 d after slaughtering. No differences in sensory scores were observed between the 2 methods of MAP, and shelf life of these samples seemed to be 14 to 21 d. Cod samples packaged in vacuum packages had higher pH values compared to ordinary MAP and packages containing a CO₂ emitter. Bacterial growth was inhibited by MAP and resulted at the end of the storage period in dominance of Carnobacterium and some Photobacterium . In MA packages with high O₂ levels the Photobacterium was inhibited. It is concluded that CO₂ emitters are well suited for reduction of transport volume for MA-packaged farmed cod.     

Changes of glucosinolates in mixed fresh-cut broccoli and cauliflower florets in modified atmosphere packaging

ABSTRACT:  Glucosinolates of broccoli and cauliflower florets were assessed to determine the effect of modified-atmosphere packaging on postharvest glucosinolate dynamics in mixed florets of Brassica vegetables. Mixed-packaged broccoli and cauliflower florets stored in food trays sealed with 2 different microperforated biaxial-oriented polypropylene films for up to 7 d at 8 °C were analyzed. Both applied modified atmospheres (1% O₂+ 21% CO₂; 8% O₂+ 14% CO₂) maintained aliphatic glucosinolates in cauliflower florets, whereas in broccoli florets, the aliphatic glucosinolate concentration decreased slightly in each modified atmosphere. In addition, total indole glucosinolate concentration for both broccoli and cauliflower florets was maintained, and even increased in cauliflower florets at 1% O₂+ 21% CO₂ due to rising neoglucobrassicin concentration. Thus, to simultaneously maintain glucosinolates and external appearance as well as to prevent off-odor, a modified atmosphere of 1% O₂+ 21% CO₂ provides a suitable environment for storage of this Brassica floret medley for up to 7 d at 8°C.     

EFFECT OF MODIFIED ATMOSPHERE PACKAGING ON THE QUALITY OF SMOKED CATFISH

Smoked catfish were inoculated with Listeria ivanovii then packaged under 80% CO₂/20% N₂ (M₁) and 40% CO₂/30%O₂/130% N₂ (M₂) and stored at 2 and 8C. Noninoculated samples packaged under air (A) served as controls. Fillets stored under M₂ at 8C showed the fastest growth of L. ivanovii. L. ivanovii counts in samples stored under M₁ at both temperatures decreased significantly over time. Listeria growth was observed in samples stored under air at 2 and 8C after 2 weeks. APC results were similar to that of Listeria The highest TBA values were observed in M₂-stored samples followed by air-stored samples. Lightness ("L" values) increased significantly, whereas "a" (redgreen) and "b" (blue/yellow) values decreased in all atmospheres at both temperatures over time. The combined use of M₁ and 2C improved the quality of smoked catfish by inhibiting microbial growth and minimizing the extent of lipid oxidation.     

INFLUENCE OF MODIFIED ATMOSPHERE PACKAGING ON GROWTH OF CLOSTRIDIUM PERFRINGENS IN COOKED TURKEY

Clostridium perfringens containing samples of sterile ground turkey were studied to assess growth under modified atmosphere conditions. Samples were packaged under various atmospheres (CO₂/O₂/N₂: 75/5/20, 75/10/15, 75/20/5, 25/20/55, 50/20/30), stored at 4, 15 and 28C, and sampled periodically for growth. Diluted samples were plated on Shahidi Ferguson perfringens agar (Difco Laboratories, Detroit, MI) to determine vegetative cell counts. Temperature abuse (cyclic and static) of the turkey product was also investigated. The results showed that the growth of C. perfringens was slowest under 25–50% CO₂/20% O₂/balance N₂ at 15 and 28C. There was no growth at 4C for up to 28 days. Temperature abuse (28C storage) of refrigerated products for 8 h did not permit C. perfringens growth. Use of 25–50% CO₂/20% O₂/balance N₂ may extend the shelf-life of turkey, but in the absence of proper refrigeration, it cannot be relied upon to eliminate the risk of C. perfringens food poisoning .     

Effects of storage atmosphere on Listeria monocytogenes and competing microflora using a surface model system

A solid-surface model system was used to study the effects of gas atmospheres encountered in modified atmosphere packaging of vegetables on the survival and growth of Listeria monocytogenes and competing micro-organisms. The effects of increasing CO₂ levels (from 5% to 20%), 100% N₂ and 3% O₂ were determined. The model system allowed for estimation of the growth of L. monocytogenes alone or in the presence of competing microflora. CO₂ concentrations of 5–10% (with 5% O₂ in N₂) had no inhibitory effect, by comparison with air, on the growth and survival of pure cultures of L. monocytogenes . At 20% CO₂ population densities were reduced up to day 8, but the final population densities reached were not. An atmosphere of 100% N₂ allowed survival of pure cultures of L. monocytogenes , but populations did not significantly change ( P  > 0.05) during storage, whereas a low O₂ (3%, balance N2) atmosphere allowed significant growth ( P  < 0.05) of L. monocytogenes . Growth and inhibitory activities of Enterobacter cloacae and E. agglomerans were inversely related to the concentration of CO₂. By contrast, the growth and anti-listerial activities of Leuconostoc citreum increased with elevated CO₂ concentrations. In the low O₂ atmosphere, L. monocytogenes grew considerably better in the presence of populations from the indigenous microflora of lettuce than when in pure culture. The results indicate that the gas atmospheres present within modified atmosphere packages of minimally processed vegetables may affect the interactions between the pathogen and the natural competitive microflora sufficiently to indirectly enhance L. monocytogenes growth.     

COLOR IMPROVEMENT OF KOSHER BEEF USING SODIUM ASCORBATE AND ERYTHORBATE

The koshering process involves soaking meat in water followed by massive surface salting and rinsing to remove the salt. This process causes undesirable discoloration during storage at 4C, as compared to nonkosher beef (P<0.01). Beef steaks were dipped into sodium ascorbate (SA) or erythorbate (SE) solutions for various time periods. Untreated steaks, from the same cut, served as controls. All samples were packaged into modified atmospheres of 65% O₂ and 35% CO₂. The color of sample was observed periodically during illuminated storage at 4C. The typical red color was maintained at 4C for up to 21 days when the meat was dipped for 1 min in a 2 or 4% SE solution (pH 6.5), packaged in 65% O₂ and 35% CO₂, while the controls showed severe discoloration after 2 to 3 days. The treatment with SE had also a positive effect in reducing initial total microbial counts by 1.5 log CFU/g.