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.     

Microbiological, physicochemical and organoleptic changes of shredded carrots stored under modified storage

The effect of initial head spaces of air, 4.9% CO₂/2.1% O₂/93% N₂ and 5% CO₂/95% N₂ on the microbial flora of shredded carrots was studied at 4 and 10°C. The microbial flora of shredded carrots comprised lactic acid bacteria, pseudomonads and yeasts. Lactic acid bacteria were the predominant organisms in all samples. The pH dropped during the storage of carrots and this was more pronounced at 10°C. The concentration of different organic acids such as lactic, acetic, tartaric, citric and succinic increased in all samples stored under modified atmosphere packaging conditions at both temperatures. The spoilage of carrots stored under 5% CO₂/95% N₂ was delayed, as indicated by the changes in their texture, colour and odour, compared with those samples stored under air or 4.9% CO₂/2.1% O₂/93% N₂.     

Portable Electronic Nose for Detection of Spoiling Alaska Pink Salmon (Oncorhynchus gorbuscha)

ABSTRACT:  The ability of a portable hand-held electronic nose (EN) in detecting spoilage of whole Alaska pink salmon ( Oncorhynchus gorbuscha ) stored at 14 °C and in slush ice (1 °C) was investigated. Fish were sampled daily at 14 °C for up to 3 d, while fish stored in slush ice were sampled at various intervals up to 16 d. Sensory evaluations indicated that fish were rejected at day 3 when stored at 14 °C and at day 12 when stored in slush ice. Aerobic bacteria counts for fish skin at 14 °C ranged from 3.4 log₁₀ colony-forming units (CFU)/cm² (day 0) to 4.8 log₁₀ CFU/cm² (day 3) and for fish stored in slush ice ranged from 3.4 log₁₀ CFU/cm² (day 0) to 5.5 log₁₀ CFU/cm² (day 16). The correct classification rate using forward stepwise general discriminate analysis was 85% and 92% for EN analysis of belly cavity volatiles for fish held at 14 °C and in slush ice, respectively. A predictive model may be developed for spoilage of whole Alaska pink salmon by analyzing belly cavity odors using the EN.     

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.     

Controlled atmosphere storage to decrease physiological disorders in nectarines

'Fantasia', 'Flavortop', and 'Flamekist' nectarines were examined for their response to controlled atmosphere (CA) storage. All three cultivars stored well for up to 6 weeks at 0°C in an atmosphere of 10% O₂+ 10% CO₂, while some but not all the cultivars also stored well in 2% O₂+ 5% CO₂ or 10% O₂+ 5% CO₂. The physiological storage disorders of internal breakdown and reddening were almost completely absent in nectarines kept in 10% O₂+ 10% CO₂. When 'Flamekist' nectarines from two harvests were stored in 10% O₂+ 10% CO₂ atmosphere for 6 or 8 weeks at 0°C, the fruit from the first harvest was of better quality after post-storage ripening. Although this controlled atmosphere prevented internal breakdown and reddening, after extended storage fruit did not develop the increased soluble solids content or extractable juice during post-storage ripening that occurred in non-stored fruit. Therefore, while preventing storage disorders, CA does not reduce the loss of ripening ability occurring during nectarine storage.     

THE EFFECT OF OXYGEN SCAVENGERS ON THE COLOR STABILITY AND SHELF-LIFE OF CO, MASTER PACKAGED PORK

Pork chops were stored with and without O₂ scavengers in a modified atmosphere (50% CO₂/50% N, or 100% CO₂) master pack system at 0C for up to 21 days, At 7-day intervals, the chops were displayed at ca. 4.5C for 96 h. Color (L, a, b, hue and chroma); panelist assessments of color and odor; and drip losses were recorded. Oxygen scavengers reduced O₂ levels, resulting in chops that were generally as red as flesh, but tended to have higher hue angles at 0 h, and towards the end of display (P<0.05). Visually, chops packaged in 50% CO₂/50% N₂ were less acceptable than flesh (P<0.05). There were no odor differences between flesh and packaged chops. Fresh chops had lower drip losses than packaged (P<0.05). An acceptable display life was obtained for pork chops stored for up to 21 days in a modified atmosphere CO₂ master pack containing O₂ scavengers.     

Effect of controlled atmospheres on maintaining quality of persimmon fruit cv. "Rojo Brillante"

ABSTRACT:  Astringent "Rojo Brillante" persimmon fruits were stored in air or in 2 different controlled atmospheres: 10% CO₂+ 90% N₂ (CA1) or 97 % N₂+ air (CA2) for up 50 d at 15 °C. After different periods, the fruit were treated with 95% CO₂ for 24 h at 20 °C in order to remove astringency, and then transferred to 20 °C in air free of CO₂ for 5 d to simulate shelf life. Other fruits were directly transferred to shelf life without being submitted to deastringency treatment. Storage under CA2 allowed storability of persimmon "Rojo Brillante" during 30 d at 15 °C, maintaining commercial firmness. Moreover, CA2 had an effect on removing astringency when fruits were stored for 30 d at 15 °C, or after 20 d following to shelf life. As consequence, deastringency treatment could be avoided when the fruits were previously stored under this controlled atmosphere.     

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.     

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 carbon dioxide on improving the keeping quality of raw milk

Fresh cows' milk samples were treated with CO₂ to give a calculated CO₂ content of 77mM. The treated samples as well as the control were stored at 7° and 20 ± 5°C for three days and analysed periodically. The increase in the total count as well as the counts of psychrotrophic, lactic acid and coliform bacteria during storage at 7°C was found to be inhibited by the addition of CO₂. The treated samples had higher titratable acidity and lower pH values than the controls but satisfied the clot-on-boiling test. The keeping quality of cooled milk can therefore be improved by the addition of CO₂.     

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.     

INFLUENCE OF MODIFIED ATMOSPHERE PACKAGING ON SHELF-LIFE OF CHICKEN CARCASSES UNDER REFRIGERATED STORAGE CONDITIONS

The effect of modified atmosphere packaging (MAP) (70% CO₂/30% N₂; 30% CO₂/70% N₂) on the shelf-life of fresh chicken carcasses stored at 2, 4, 7 and 9C was investigated. The shelf-lives of MAP carcasses (70% CO₂/30%N₂) stored at 2, 4, 7 and 9C were 25, 21, 12 and 8 days, respectively compared with 7 days for air-packaged ones stored at 4C; the shelf-life of MAP carcasses (30% CO₂/70%N₂) stored at the same temperatures were 20, 15, 8 and 8 days, respectively. The inhibitory effect of MAP on the growth of Enterobacteriaceae and on the production of spoilage metabolites, such as free fatty acids and extract release volume, was negligible at higher temperatures (7 and 9C) and more pronounced at lower temperatures (2 and 4C), especially at higher concentrations of CO₂ (70% CO₂/30% N₂). The occurrence and growth of organisms such as Escherichia coli, coliforms , Staphylococcus aureus, Salmonella and Campylobacter in carcasses stored at different temperatures were also documented .     

The Effects of Residual Oxygen on the Storage Life of Retail-Ready Fresh Beef Steaks Masterpackaged Under a CO2 Atmosphere

ABSTRACT:  Retail-packed rump ( Gluteus medius , GM) and striploins ( Longissiumus dorsi, LD) steaks were masterpackaged under carbon dioxide (CO₂) and stored at 1 °C ± 1 °C for 14, 28, 35, and 42 d. A commercial oxygen (O₂) scavenger (ATCO HV1000®, Standa Industrie, Caen, France) was used in the masterpacks to achieve an O₂-free atmosphere. Similar packages without the O₂ scavengers were also prepared. At each storage time, 2 masterpacks of each treatment were opened and the retail trays were placed in a display case at 4 °C ± 2 °C for 1 and 48 h for microbiological and sensorial evaluations. The low growth rate of aerobic psychrotrophic flora on the stored beefsteaks demonstrated the bacteriostatic effect of CO₂ during storage. The maximum level of psychrotrophic aerobic bacteria reached during storage was approximately 10⁶ CFU/g. The steaks stored in masterpacks with scavengers bloomed to the desirable red color associated with freshly cut meat in the display case for all of the storage periods, except in the case of GM steaks, which showed a cycle of transient discoloration. GM and LD steaks were well accepted (65% and 82%, respectively) after 42 d under CO₂ at 1 °C ± 1 °C. The GM and LD steaks stored without the O₂ scavenger showed variable fractions of discoloration that significantly detracted from the appearance of the samples.     

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.     

The extension of the shelf-life of 'pesto' sauce by a combination of modified atmosphere packaging and refrigeration

Summary This study was intended to extend, by optimizing modified atmosphere packaging (MAP), the shelf-life of the Italian vegetable sauce used for spaghetti and known as 'pesto'. A mathematical model was developed in order to predict gas composition inside the polymeric package (CO₂ concentration). Predictions of equilibration time and equilibrium gas composition showed moderately good agreement with experimental data. A useful extension of pesto shelf-life, up to 120 days, was achieved by adopting a target atmosphere containing, at steady-state, 10% CO₂ and 90% N₂ at 5 °C. Microbial growth was inhibited by the CO₂ levels, but was not accompanied by significant changes in odour and colour.     

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.     

Quality changes in fresh-cut Fuji apple as affected by ripeness stage, antibrowning agents, and storage atmosphere

ABSTRACT:  The effect of ripening state, modified atmosphere, and the use of antibrowning agents was investigated in an attempt to determine optimum ripeness and processing conditions for extending the shelf-life of fresh-cut Fuji apple. Apples were classified in 3 groups: mature-green, partially ripe, and ripe; after peeling and slicing, fruits were treated with 1% (w/v) N -acetylcysteine, or 1% (w/v) ascorbic acid (control), and then packed into polypropylene trays with air or a gas mixture (2.5% O₂+ 7% CO₂+ 90.5% N₂) and sealed. Trays containing the apple slices were stored in darkness at 4 °C ± 1 °C and analyzed periodically during 43 d. Changes in atmosphere composition, color, and firmness were examined. Partially ripe apples, based on their lower ethanol production and maintenance of their original color and firmness, were the most suitable to prepare the fresh-cut commodities. A postcutting dip in 1% (w/v) N -acetylcysteine was the most effective treatment to prevent cut surface browning and preserve the initial appearance of Fuji apple slices during more than 1 mo at 4 °C. Low O₂ and elevated CO₂ (2.5% O₂+ 7% CO₂) atmosphere extended the shelf life of apple slices because of a significant inhibition of ethylene production.     

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.     

MODIFIED-ATMOSPHERE PACKAGING OF BONE-IN PORK LOINS

Paired bone-in pork loins (n = 110 pairs) trimmed to 3.2 and 6.4 mm subcutaneous fat were placed five per box in modified-atmosphere packages (MAP) and stored for up to 19 days at 1°C. Using commercial conditions and a single flush of 0.61 1/kg of meat of carbon dioxide (CO₂), the resulting CO₂ concentration was 78.5%, which then decreased to 55.1% (day 3) and 41% (day 19). Oxygen, 3.1% initially, increased to 7.2% (day 3), decreased to 3% (day 15), then increased to 7.1%. Although microbial counts increased from 3 to 19 days, those through 9 days of MAP (331 CFU/cm²) were lower than prior to MAP (653 CFU/cm²). Longer storage increased (P < 0.05) loin weight loss; off-odor; and discoloration of the blade and sirloin lean, subcutaneous fat, and bone surface. Off-odor intensity and microbial levels were acceptable at day 19, thus discoloration was the limiting factor in loin shelf-life and retail chop display color stability.