Postmortem changes in yellow grouper (Epinephelus awoara) fillets stored under vacuum packaging at 0 °C

The freshness of yellow grouper (Epinephelus awoara) stored under vacuum-packing at 0 °C was assessed by physicochemical, sensory and microbiological methods. No significant differences were found in pH and thiobarbituric acid (TBA) values during the storage, while TVB-N, TMA-N, HxR, Hx and K values increased significantly with time. The content of IMP was decreased significantly with the storage time. The texture profile, hardness and chewiness were significantly decreased with the time. L∗ values, the values of chroma and hue were all decreased. However, the increased b∗ values were observed. Furthermore, the significant variations and correlations of sensory attributes were shown with the storage time. A regression analysis for total viable counts yielded a shelf life of 26 days. This suggested that the TMA-N, IMP, HxR, Hx, K value, hardness, chewiness, colour, sensory attributes and microbiological counts may be considered suitable indicators for evaluating yellow grouper fillets spoilage during refrigerated storage.     

Characterisation of the spoilage microbiota in raw salmon (Salmo salar) steaks stored under vacuum or modified atmosphere packaging combining conventional methods and PCR-TTGE

In order to characterise the spoilage related to microbiota of raw salmon, a combination of culture-dependent and -independent methods, including PCR–TTGE, was used to analyse 3 raw salmon batches stored for 3 days at chilled temperature in modified atmosphere packaging (MAP) (50% CO₂/50% N₂) or under vacuum. Sensory evaluation, microbiological enumeration and chemical analysis were performed after 3, 7 and 10 days of storage. At the onset of spoilage, 65 bacterial isolates were picked from the plates. Thus, 13 different genera or species were identified by phenotypic and molecular tests: Serratia spp., Photobacterium phosphoreum, Yersinia intermedia, Hafnia alvei, Buttiauxella gaviniae, Pseudomonas sp., Carnobacterium maltaromaticum, Carnobacterium divergens, Lactococcus piscium, Lactobacillus fuchuensis, Vagococcus carniphilus, Leuconostoc gasicomitatum and Brochothrix thermosphacta. The PCR–TTGE profiles and band identification enabled a shift of the dominant populations during the storage to be visualised for all the batches, probably due to the temperature change and the packaging. At the beginning of storage, Pseudomonas sp. dominated the raw salmon microbiota while in the following days (7 and 10), P. phosphoreum and L. piscium were identified as the main bacterial groups. This study enhances the knowledge of MAP and vacuum-packed raw salmon spoilage microbiota.     

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 packaging atmosphere on the microbial attributes of pearlspot (Etroplus suratensis Bloch) stored at 0-2 degrees C

Effect of packaging atmosphere (air and under different modified atmospheres (MAs), 40% CO2/60% O2, 50%/50% O2, 60% CO2/40% O2, 70% CO2/30% O2 and 40% CO2/30% O2/30% N2) on the microbial and biochemical attributes of fresh pearlspot (Etroplus suratensis Bloch) stored at 0-2 degrees C was investigated. Trimethylamine nitrogen (TMA-N) and thiobarbituric acid (TBA) values remained lower than the proposed acceptability limits throughout the storage period. Results demonstrated that storage of pearlspot under air and MA 40% CO2/30% O(2)/30% N(2) resulted in growth of Enterobacteriaceae, Aeromonas and H(2)S-producing bacteria including Shewanella putrefaciens, while all other packaging atmospheres did not allow multiplication of Enterobacteriaceae and Aeromonas within 3 weeks. Aeromonas spp. identified were Aeromonas hydrophila, Aeromonas veronii biovar sobria and A. veronii biovar veronii. Significant reduction (p<0.01) was noticed in Aeromonas population of pearlspot stored under MA 60% CO2/40% O2 and 70% CO2/30% O2. A delay of growth of Pseudomonas below 5.0log(10)cfug(-1) was observed during the 15th day of storage at 0-2 degrees C under modified atmosphere packaging (MAP) conditions. Growth of faecal streptococci was significantly inhibited in all the packaging atmospheres at 0-2 degrees C during the entire storage period. Survival of coagulase positive Staphylococci (<50cfug(-1)) in low numbers was noticed during storage in all the packaging atmospheres. Clostridium botulinum toxin was not detected. All the packaging atmospheres did not allow multiplication of sulphite-reducing clostridia at 0-2 degrees C during the entire storage period. Packaging in MA 60% CO2/40% O2 resulted in the inhibition of growth of Aeromonas and Enterobacteriaceae, and the slowest growth of psychrotrophic bacteria, H(2)S-producing bacteria, including Shewanella putrefaciens and Pseudomonas and extended microbiological shelf life to 9-10 days. This study confirms the survival of potentially pathogenic A. hydrophila, A. veronii biovar sobria and A. veronii biovar veronii capable of growth at low temperature in pearlspot stored under MA.     

Storage behaviour of minimally processed pumpkin (Cucurbita maxima) under modified atmosphere packaging conditions

 Minimally processed vegetables in fresh, ready-to-cook form are gaining the confidence of both the trader and the consumer. This has led to a need to develop technology for increasing shelf life while maintaining the microbial, nutritional and sensory quality of minimally processed vegetables. This investigation was carried out on pumpkin in minimally processed form, packed in different polymeric film bags of varying permeabilities, creating an active equilibrium modified atmosphere within the package for the extention of storage life. It was observed that minimally processed pumpkin, which has a high respiratory rate at room temperature (155.7 mg CO₂/kg/h) could be stored for a period of 25 days at 5±2  °C under modified atmosphere packaging conditions with a minimum physiological loss in weight of 0.06% and marginally low changes in biochemical constituents, such as vitamin C, total soluble solids, moisture, carotenoids and titrable acidity, enabling the retention of near-fresh quality. The microbial loads of mesophilic aerobes and coliforms, which were log 5.5 and log 4.3 were less than threshold level. There was no growth of yeasts and moulds or mesophilic spore formers at the end of the storage period. Received: 24 January 2000 / Revised version: 4 April 2000     

Microbiological quality of maatjes herring stored in air and under modified atmosphere at 4 and 10 degrees C

Microbiological and sensory changes of maatjes herring stored in air (experiment I) and under modified atmosphere (MAP) (experiments II and III) were evaluated during storage at 4 and 10 degrees C. Microbial (total and psychrotrophic viable bacteria, lactic acid bacteria and Enterobacteriaceae) counts and chemical analyses (chloride content, fat content, dry matter, ash and pH) were performed. A Quality Index Method (QIM) scheme developed for maatjes herring was used for sensory evaluation. The main reasons for sensory rejections at both storage temperatures were a strong rancid taste for herring stored in air (Experiment I) and a sour, bitter, rotten taste and an aftertaste like old flower water for MAP herring (Experiments II and III). A soft texture of freshly produced samples (Experiment II) was noticed. The sensory shelf-life of maatjes herring stored in air (Experiment I) was three days at both 4 and 10 degrees C. The MAP herring in Experiments II and III had a shelf-life of 5 and 6 days, respectively, at both storage temperatures. Rancidity due to oxidation of fat was the main spoilage indicator for air-stored maatjes herring. Autolytic enzymes may affect textural deterioration. The characteristic off-odour and off-taste in the MAP herring (Experiments II and III) were may well be attributable to microbial metabolism. On the day of sensory rejection, total viable counts for herring in all three experiments (Experiments I-III) stored at 4 degrees C did not reach 10(6)cfu/g, which is considered the limit of acceptability for maatjes herring given by the Dutch fishery authorities. It appears that total viable counts have minor significance in the sensory assessment of maatjes herring.     

Antimicrobial activities of spice extracts against pathogenic and spoilage bacteria in modified atmosphere packaged fresh pork and vacuum packaged ham slices stored at 4 °C

The antimicrobial activity of 14 spice extracts against four common meat spoilage and pathogenic bacteria (Listeria monocytogenes, Escherichia coli, Pseudomonas fluorescens and Lactobacillus sake) was screened in cultured media (experiment 1). The results showed that individual extracts of clove, rosemary, cassia bark and liquorice contained strong antimicrobial activity, but the mixture of rosemary and liquorice extracts was the best inhibitor against all four types of microbes. Subsequently, mixed rosemary/liquorice extracts were spray-applied to inoculated fresh pork in modified atmosphere packaging (experiment 2) and to inoculated ham slices in vacuum packaging (experiment 3). The meat samples were stored at 4 °C over a 28-day period and microbial growth was monitored regularly. The L. monocytogenes population on fresh pork by day 28 decreased 2.9, 3.1 and 3.6 logs, the MAB decreased 2.7, 2.9 and 3.1 logs, the Pseudomonas spp. count decreased 1.6, 2.1 and 2.6 logs and the total coliform count decreased 0.6, 0.8 and 1.2 logs, corresponding to 2.5, 5.0 and 10.0 mg/ml of spray, respectively, when compared to control (P < 0.05). The number of L. monocytogenes on ham slices decreased 2.5, 2.6 and 3.0 logs, the MAB plate counts decreased 2.9, 3.0 and 3.2 logs and the LAB counts decreased 2.4, 2.6 and 2.8 logs (P < 0.05), respectively, after 28-days, by the same levels of mixed rosemary/liquorice extract treatments. The results demonstrated strong potential of mixed rosemary and liquorice as a natural preservative in fresh pork and ham products.     

Effect of modified atmosphere packaging and vacuum packaging on the shelf-life of refrigerated chub mackerel (<Emphasis Type="Italic">Scomber japonicus</Emphasis>): biochemical and sensory attributes

The effect of modified atmosphere packaging (MAP 1: 70% CO₂/30% N₂ and MAP 2: 50% CO₂/30% N₂/20% O₂) and vacuum packaging (VP), on the shelf-life of chub mackerel (Scomber japonicus) fillets stored under refrigeration was studied. Quality assessment was based on sensory analysis and biochemical indices determination. Increase in total volatile basic nitrogen (TVBN) and trimethylamine nitrogen (TMAN) followed the order: MAP 1 < MAP 2 < VP < air (control samples). The presence of oxygen into the fish package (air or MAP) resulted in an increase in the 2-thiobarbituric acid (TBA) values in comparison with samples packaged in the absence of oxygen. The most effective MAP used was MAP 1 which contributed to a considerably slower rate of fish spoilage. Based primarily on odour scores it was observed that raw chub mackerel fillets stored in the presence of air remained acceptable up to ca. 11 days, VP and MAP 2 samples up to ca. 15–16 days, while MAP 1 samples up to ca. 20–21 days of storage. On the other hand, flesh texture and flesh colour of all packaged samples received scores above or equal than the acceptability limit up to ca. 13–14 days of storage.     

Evaluation and predictive modeling of shelf life of minced beef stored in high-oxygen modified atmosphere packaging at different temperatures

The aims were: (1) to follow the freshness decay of minced beef stored in high-oxygen modified atmosphere packaging at different temperatures (4.3, 8.1 and 15.5 °C) by applying traditional methods (microbiological counts, color evaluation, thiobarbituric acid assay TBA, headspace gas composition) and e-nose; (2) to model the decay kinetics to obtain information about the maximum shelf life as function of storage conditions. The minced beef, packaged in modified atmosphere was supplied by a manufacturer at the beginning of its commercial life. The study demonstrated the ability of the traditional methods to describe the kinetics of freshness decay. The modeling of the experimental data and the comparison with microbiological or chemical thresholds allowed the setting, for each index, of a stability time above which the meat was no longer acceptable. The quality decay of meat was also evaluated by the headspace fingerprint of the same set of samples by means of a commercial e-nose. A clear discrimination between “fresh” and “old” samples was obtained using PCA and CA, determining at each temperature a specific range of stability time. The mean value of the stability times calculated for each index was 9 days at 4.3 °C (recommended storage temperature), 3–4 days at 8.1 °C (usual temperature in household refrigerators) and 2 days at 15.5 °C (abuse temperature). Resolution of the stability times allowed calculation of mean Q₁₀ values, i.e. the increase in rate for a 10 °C increase in temperature.The results show that the Q₁₀ values from the traditional methods (3.6–4.0 range) overlapped with those estimated with e-nose and color indexes (3.4 and 3.9, respectively).     

Sensory, physical, chemical and microbiological changes in European sea bass (Dicentrarchus labrax) fillets packed under modified atmosphere/air or prepared from whole fish stored in ice

Quality changes and shelf‐life in European sea bass fillets packed under 40% CO₂: 60% N₂ (MAP) and air (AIR) or prepared from the whole ungutted fish stored in ice (ROUND) were compared. Raw and cooked sensory scores, pH, colour, expressible water, malonaldehyde, total viable count, Pseudomonas spp., H₂S‐producing bacteria, Lactobacillus spp., Streptococcus spp., Staphylococcus spp., coliforms and proteolytic counts, were determined until AIR and MAP raw fillet spoilage. Raw ROUND fillets had the best quality and shelf‐life (10 vs. 8 vs. 7 days after slaughtering in ROUND, MAP and AIR, respectively), while the MAP fillets had better sensorial scores, lower pH values and better microbiological counts, but greater lightness values than the corresponding AIR fillets. MAP fillets also had the highest malonaldehyde levels. The higher correlation between Streptococcus spp. and odour scores (r = ?0.971, P < 0.01) compared to the other species could suggest that it is a specific spoilage organism in the MAP condition used.     

Changes in carotenoids and chlorophylls in fresh green asparagus (Asparagus officinalis L) stored under modified atmosphere packaging

Asparagus is a highly perishable product owing to its high respiratory rate, a reason why modified atmosphere packaging (MAP) has been used in order to increase the shelf‐life of fresh asparagus. Carotenoid and chlorophyll pigments are important compounds for the maintenance of both the nutritional and sensory quality of asparagus. In this study, green asparagus spears were stored under refrigeration at 2 °C for 14 days, under MAP at 2 °C for 26–33 days and under MAP at 10 °C for 20 days. Pigment profiles were determined using high‐performance liquid chromatography (HPLC), with three classes of compounds being detected, namely oxygenated carotenoids (xanthophylls), hydrocarbonated carotenoids (carotenes) and chlorophylls. The xanthophylls identified were neoxanthin, violaxanthin, lutein and zeaxanthin. Only β‐carotene was detected in the carotene fraction. In the chlorophyll pigments, three molecules were isolated, chlorophyll b, its epimer chlorophyll b′ and chlorophyll a. Also detected were the first degradation products of chlorophylls, pheophytins b and a respectively. Modified atmosphere packaging at 2 °C was found to be effective in extending the shelf‐life for up to 4 weeks and in preserving the colour of fresh asparagus. Copyright © 2004 Society of Chemical Industry     

Effects of modified atmosphere and vacuum packaging on the growth of spoilage and inoculated pathogenic bacteria on fresh poultry

Fresh chicken breast meats inoculated withYersinia enterocolitica andAeromonas hydrophila were packaged in glass jars either containing different compositions of modified atmospheres (MA) (100% CO₂; 80% CO₂/20% N₂), or in vacuo or containing air, and were stored at 3±1°C and 8±1°C. The changes in gas composition as well asY. enterocolitica, A. hydrophila, total aerobic bacterial, total psychrotrophic, Lactobacilli and Enterobacteriaceae counts were determined after 0,1,3,7,9,11 and 14 days of storage. The results show that while the growth ofY. enterocolitica andA. hydrophila were retarded following MA storage, the pathogens were capable of growth in MA and vacuum storage at both temperatures, for the inoculation levels studied. For total aerobic bacterial counts, there were no differences between the values for chicken breast meats kept in different atmospheres. Being packaged in CO₂ had the greatest inhibitory effect on the growth of psychrotrophic aerobic bacteria during the first 3 days. Lactic acid bacteria levels of samples stored in MA conditions and in vacuo increased rapidly when compared to those levels of samples stored in air. It was also found that the effect of MA storage increased at 3±1°C.     

Chemical quality and sensory attributes of marinated Pacific saury (Cololabis saira) during vacuum-packaged storage at 4 °C

This study was carried out to evaluate the chemical changes and sensory attributes of Pacific saury (Cololabis saira), brined (12% NaCl brine solution) or marinated (12% NaCl + 2% acetic acid; or 12% NaCl + 3% acetic acid solutions) followed by vacuum-packaging and storage at 4 °C for 90 days. The chemical analysis revealed a significant reduction in the pH value, total volatile bases nitrogen (TVBN), and trimethylamine (TMA) contents in marinated versus brined fillets. Lipid oxidation, as indicated by the 2-thiobarbituric acid (TBA) values, was significantly delayed in marinated fillets in comparison with the brined fillets. The growth rate of psychrotrophic bacteria was significantly (P < 0.05) reduced in marinated versus brined fillets. No significant differences were detected for the sensory attributes between the two marinating conditions although the overall acceptability was significantly higher in marinated versus brined fish. Both conditions of the marinating process resulted in an extension of the shelf life of the product to more than 90 days versus only 60 days for the control brined fillets. The study concluded that marination of Pacific saury can delay the undesirable chemical changes, retard lipid oxidation, improve the sensory attributes and extend the shelf life of the product during refrigerated storage.     

Effect of temperature and modified atmosphere packaging on overall quality of fresh-cut bell peppers

The effect of vacuum packaging (VP) and modified atmosphere packaging without vacuum (MAP) on shelf-life of fresh-cut green bell pepper stored at 5°C and 10°C were evaluated. In-package atmosphere, overall quality, percentage of leaked juice, texture, ascorbic acid content, ethanol and acetaldehyde, and microbial growth, were evaluated at different intervals of storage. MAP-fresh-cut peppers presented better visual quality, less leaked juice and higher firmness than those stored under VP. Microbiological and quality analysis revealed a limit of shelf-life of 14 and 21 days, when fresh-cut peppers were stored at 10°C and 5°C, respectively. We conclude that MAP could be used to maintain quality attributes of fresh-cut peppers for up 21 days at 5°C.     

Combined effect of packaging atmosphere and storage temperature on growth of Listeria monocytogenes on ready-to-eat shrimp

Cooked, peeled, and deveined shrimp were inoculated with a 5 strain mixture of Listeria monocytogenes and packaged in air, vacuum, and a 100% carbon dioxide modified atmosphere. The packaged shrimp were then stored at 3, 7, and 12 degrees C for 15 days to monitor the growth of L. monocytogenes and psychrotrophic bacteria. Uninoculated shrimp were also subjected to sensory evaluation by a trained panel to measure odor and appearance over the storage period. Results demonstrated that shrimp packaged in CO(2) and stored at 3 degrees C did not permit growth of L. monocytogenes during the 15-day storage period, while all other packaging/temperature combinations allowed for multiplication of the bacterium. Carbon dioxide packaging also resulted in the slowest growth of psychrotrophic bacteria and resulted in shrimp having acceptable sensory odor and appearance scores at the end of storage. When strict temperature control is difficult, such as during processing, transportation, retail display, or home use, additional antimicrobial hurdles may be necessary to ensure safety.     

Effect of lactate-enhancement, modified atmosphere packaging, and muscle source on the internal cooked colour of beef steaks

Earlier studies on lactate-mediated colour stability in beef did not address the possible influence on cooked colour. Our objective was to examine the effect of lactate-enhancement, muscle source, and modified atmosphere packaging (MAP) on the internal cooked colour of beef steaks. Longissimus lumborum (LL) and Psoas major (PM) muscles from 16 (n = 16) beef carcasses (USDA Select) were randomly assigned to 4 enhancement treatments (non-injected control, distilled water-enhanced control, 1.25% and 2.5% lactate), and fabricated into 2.54-cm steaks. Steaks were individually packaged in either vacuum (VP), high-oxygen MAP (HIOX; 80% O₂ + 20% CO₂), or carbon monoxide MAP (CO; 0.4% CO + 19.6% CO₂ + 80% N₂), and stored for 0, 5, or 9 days at 1 °C. At the end of storage, surface and internal colour (visual and instrumental) was measured on raw steaks. Steaks were cooked to an internal temperature of 71 °C, and internal cooked colour (visual and instrumental) was evaluated. Lactate-enhancement at 2.5% level resulted in darker (P < 0.05) cooked interiors than other treatments. Interior cooked redness decreased (P < 0.05) during storage for steaks in VP and HIOX, whereas it was stable for steaks in CO. Our findings indicated that the beef industry could utilise a combination of lactate-enhancement and CO MAP to minimise premature browning in whole-muscle beef steaks.     

Nisin treatments to control Listeria monocytogenes post-processing contamination on Anthotyros, a traditional Greek whey cheese, stored at 4°C in vacuum packages

Post-processing contamination and growth of Listeria monocytogenes in whey cheeses stored under refrigeration is an important safety concern. This study evaluated commercially available nisin (Nisaplin^®) as a biopreservative to control L. monocytogenes introduced post-processing on Anthotyros, a traditional Greek whey cheese, stored at 4°C in vacuum packages for up to 45 days. The whey used (pH 6.5–6.7) was from Feta cheese manufacture, and it was subjected either to natural acidification (pH 5.3, readjusted to 6.2 with 10% NaOH) prior to heating, or to direct acidification (pH 6.0–6.2) at 80°C with 10% citric acid. Nisin was added either to the whey (100 or 500 IU g⁻¹) prior to heating, or to the cheese (500 IU g⁻¹) prior to packaging, also inoculated with ca. 10⁴ cfu g⁻¹ of L. monocytogenes strain Scott A. In cheese samples without nisin, L. monocytogenes (PALCAM agar) exceeded 7 log cfu g⁻¹ after the first 10 days of storage, irrespective of the whey acidification method. All nisin treatments had an immediate lethal effect (0.7–2.2 log reduction) on L. monocytogenes populations at inoculation (day 0), which was more pronounced with 500 IU g⁻¹ added to the whey. This treatment also suppressed L. monocytogenes growth below the inoculation level for 30 and 45 days in naturally and directly acidified samples, respectively. All other treatments had weak antilisterial effects. Nisin reversed the natural spoilage flora of Anthotyros cheese from Gram-positive to Gram-negative, and this ecological alteration was far more pronounced in the most effective antilisterial treatments.     

Effects of modified atmosphere packaging (MAP) on the microbiological quality and shelf life of ostrich meat

Effects of various concentrations of O₂/CO₂ in modified atmosphere packaging on the microbiological quality and shelf-life of ostrich meat was investigated. Nine–12 months old ostriches were used. The iliofibularis muscle was cut into small cubes that were divided into five groups and then separately packaged under various gas mixes: air and O₂:CO₂:N₂ ratios of 80:20:0, 60:20:20, 60:40:0, and 40:40:20, using 2 different headspace ratios (1:1 and 3:1). The packaged meats were kept at 4 °C for 10 days and were analysed microbiologically, physico-chemically and sensorially. As a result, the meat quality and shelf-life of ostrich meat under various gas compositions were improved; microbial growth was delayed due to high CO₂ usage and shelf-life was increased by 5–7 days. However, an undesired loss of red colour of the ostrich meat may affect consumer acceptance.     

Quality of superchilled vacuum packed Atlantic salmon (Salmo salar) fillets stored at −1.4 and −3.6 °C

The most important factor for increasing shelf life is the product temperature, and since fish is more highly perishable than meat, the temperature is even more important. In the present study, portions of fillets of farmed Atlantic salmon (Salmo salar) were superchilled at two temperature levels, −1.4 and −3.6 °C. Texture, drip loss, liquid loss, cathepsin activities and protein extractability were investigated during storage and compared to ice chilled and frozen references. Drip loss was not a major problem in superchilled salmon. Textural hardness was significantly higher in superchilled salmon fillets stored at −3.6 °C compared to those stored at −1.4 °C, ice chilled and frozen references. Cathepsins B and B + L were not deactivated at the selected storage temperatures. The storage time of vacuum packed salmon fillets can be doubled by superchilled storage at −1.4 °C and −3.6 °C compared to ice chilled storage.