Maintenance of safety and quality of refrigerated ready-to-cook seasoned ground beef product (meatball) by combining gamma irradiation with modified atmosphere packaging

Abstract: Meatballs were prepared by mixing ground beef and spices and inoculated with E. coli O157:H7, L. monocytogenes, and S. enteritidis before packaged in modified atmosphere (3% O₂+ 50% CO₂+ 47% N₂) or aerobic conditions. The packaged samples were irradiated at 0.75, 1.5, and 3 kGy doses and stored at 4 °C for 21 d. Survival of the pathogens, total plate count, lipid oxidation, color change, and sensory quality were analyzed during storage. Irradiation at 3 kGy inactivated all the inoculated (approximately 10⁶ CFU/g) S. enteritidis and L. monocytogenes cells in the samples. The inoculated (approximately 10⁶ CFU/g) E. coli O157:H7 cells were totally inactivated by 1.5 kGy irradiation. D¹⁰‐values for E. coli O157:H7, S. enteritidis, and L. monocytogenes were 0.24, 0.43, and 0.41 kGy in MAP and 0.22, 0.39, and 0.39 kGy in aerobic packages, respectively. Irradiation at 1.5 and 3 kGy resulted in 0.13 and 0.36 mg MDA/kg increase in 2‐thiobarbituric acid‐reactive substances (TBARS) reaching 1.02 and 1.49 MDA/kg, respectively, on day 1. Irradiation also caused significant loss of color and sensory quality in aerobic packages. However, MAP effectively inhibited the irradiation‐induced quality degradations during 21‐d storage. Thus, combining irradiation (3 kGy) and MAP (3% O₂+ 50% CO₂+ 47% N₂) controlled the safety risk due to the potential pathogens and maintained qualities of meatballs during 21‐d refrigerated storage. Practical Application: Combined use of gamma irradiation and modified atmosphere packaging (MAP) can maintain quality and safety of seasoned ground beef (meatball). Seasoned ground beef can be irradiated at 3 kGy and packaged in MAP with 3% O₂+ 50% CO₂+ 47% N₂ gas mixture in a high barrier packaging materials. These treatments can significantly decrease risk due to potential pathogens including E. coli O157:H7, L. monocytogenes, and S. enteritidis in the product. The MAP would reduce the undesirable effects of irradiation on quality, and extend the shelf life of the product for up to 21 d at 3 °C.     

Combined effects of irradiation and modified atmosphere packaging on minimally processed Chinese cabbage (Brassica rapa L.)

Cut Chinese cabbage with air, CO₂ or CO₂/N₂ packaging was irradiated at doses up to 2 kGy and the microbiological and physicochemical qualities were investigated during a refrigerated storage for 3 weeks. Irradiation significantly reduced the microorganisms, and additionally, the modified atmosphere packaging (MAP) enhanced the reduction of the total aerobic and coliform bacteria during storage. Irradiation effectively inhibited the changes of the titratable acidity and pH, while a significant effect was not shown in the texture by irradiation. Antiradical and antioxidant activity, and the phenolic contents were slightly increased by irradiation at 0.5 kGy, while the phenolic contents were reduced by irradiation over 1 kGy. Our results suggest that irradiation at 1 kGy or above can be used to enhance the microbial safety of cut Chinese cabbage without a significant loss in the quality attributes.     

Control of Salmonella enterica Typhimurium in chicken breast meat by irradiation combined with modified atmosphere packaging

Salmonella is one of the leading causes of human foodborne illnesses originating from meat and poultry products. Cross-contamination of Salmonella from raw to cooked products continues to be problematic in the food industry. Therefore, new intervention strategies are needed for meat and poultry products. Vacuum or modified atmosphere packaging (MAP) are common packaging techniques used to extend the shelf life of meat products. Irradiation has been well established as an antibacterial treatment to reduce pathogens on meat and poultry. Combining irradiation with high-CO(2)+CO MAP was investigated in this study for improving the control of Salmonella enterica Typhimurium on chicken breast meat. The radiation sensitivities (D10-values) of this pathogen in chicken breast meat were found to be similar in vacuum and in high-CO(2)+CO MAP (0.55 ± 0.03 kGy and 0.54 ± 0.03 kGy, respectively). Irradiation at 1.5 kGy reduced the Salmonella population by an average of 3 log. Some Salmonella cells survived in both vacuum and high-CO(2) + CO MAP through 6 weeks of refrigerated storage following irradiation. This pathogen also grew in both vacuum and MAP when the product was held at 25°C. This study demonstrated that irradiation is an effective means of reducing Salmonella on meat or poultry, but packaging in either vacuum or MAP had little impact during subsequent refrigerated storage.     

Effect of muscle,ageing time and modified atmosphere packaging conditions on the colour,oxidative and microbiological stability of packed beef

The objective of this study was to evaluate the influence of two different vacuum ageing times (7 and 14 days) and the impact of the modified atmosphere packaging (MAP) configuration (gas/product ratios: 0.5 and 1 and gas composition: 70% O₂ + 30% CO₂ and 40% O₂ + 30% CO₂ + 30% N₂) on the quality of fresh beef during subsequent storage at 4 °C. For this purpose, three separate experiments were performed. For each experiment, two different muscles (Longissimus dorsi and Biceps femoris) were sampled from four double‐muscled Belgian Blue beef carcasses. Next to colour, also the evolution in microbial load, pH, O₂ and CO₂ in the headspace and lipid oxidation at the meat surface were evaluated. A vacuum ageing for 14 days compared with 7 days resulted in a higher initial microbial load on the day of MAP packaging, which resulted finally in a significantly shorter shelf life. This ageing effect was less pronounced on the colour stability and lipid oxidation of the meat samples. No significant influence of the packaging configuration on any of the analysed parameters (colour, microbial load, pH and lipid oxidation at the meat surface) was observed.     

Influence of gamma irradiation on growth and survival of Escherichia coli O157:H7 and quality of cig kofte, a traditional raw meat product

Cig kofte is a traditional Turkish food containing raw ground meat. Samples inoculated with Escherichia coli O157:H7 were irradiated at 0.5–6 kGy with a ⁶⁰Co source and stored at 4 and 25 °C. Total aerobic mesophilic count decreased with increasing irradiation doses, D₁₀ value was 0.83 kGy. Escherichia coli O157:H7 count decreased from 5.1 log₁₀ CFU g^?1 to an undetectable level (<1 log₁₀ CFU g^?1) after 1‐day storage at 4 °C following irradiation at 2 kGy, D₁₀‐value was 0.29 kGy. Irradiation doses up to 2 kGy did not affect sensory quality after 1 day. There was colour loss in samples irradiated at 2 kGy or above and stored for longer periods. Storage of the irradiated products at abused temperature must be avoided for safety assurance. Irradiation at 2 kGy has a great potential for extending the shelf‐life of cig kofte and assuring safety by decreasing the number of E. coli O157:H7 and other bacteria, but further studies with suitable package designs are needed to decrease quality degradation during extended storage.     

Combined effect of chitosan and modified atmosphere packaging for shelf life extension of chicken breast fillets

The combined effect of dipping in a chitosan solution (1 g/100 ml) and packaging under modified atmosphere (MAP, 70% CO₂, 30% N₂) on shelf life extension of refrigerated chicken fillets was investigated. Microbiological (Total Viable Counts, Pseudomonas spp., Lactic Acid Bacteria and Enterobacteriaceae), physicochemical (headspace gas composition, pH, color and Thiobarbituric Acid test) and sensory (odor and taste) parameters were monitored for up to 14 days. TVC were 3.9–4.9 log cfu/g lower on day 6 of storage in treated vs. untreated air-packaged samples with the strongest effect being shown by the combination of chitosan plus MAP. A similar reduction in LAB, Pseudomonads and Enterobacteriaceae was recorded during storage. pH values varied between 5.73 (day 8, for acetic acid treated samples) and 6.28 (day 6, for air-packaged samples). Malondialdehyde (MDA) values ranged between 0.19 and 0.80 mg/kg indicating negligible oxidation of lipids. The color parameter L* decreased with time in the air-packaged samples but remained unaffected in all other treatments. Parameters a* and b* were not significantly affected by the chitosan or the MAP treatments. Based on the microbiological and sensory data, shelf life of air-packaged, chitosan-treated, MAP-treated and chitosan/MAP treated samples was 5, 11, 12 and 14 days, respectively.     

Shelf-Life Extension of Fresh Ready-to-Bake Pizza by the Application of Modified Atmosphere Packaging

Combined effects of modified atmosphere packaging (MAP) and refrigeration (7±1 °C) were studied on shelf-life extension of ready-to-bake pizza. The gas atmospheres in the present study included four variables, namely viz. MAP1, air (control); MAP 2, 100% CO₂; MAP 3, 100% N₂; and MAP 4, 50%CO₂/50%N₂. The effect of MAP variables was observed for moisture content, water activity, pH, titratable acidity, free fatty acids, peroxide value, thiobarbituric acid, tyrosine content, lycopene content and L* a* b* values. The results indicated that MAP with 100% CO₂ significantly inhibited the lipid oxidation, reduced proteolysis and prevented total acidity (less decrease in pH). Also, the MAP (MAP 2) showed preservative effect on colour indices and shelf life higher than other treatments. Sensory analysis showed that the control samples had a limited shelf life of 5 days while a significant increase in shelf life of 15 days (300% increase) was achieved under modified atmospheres for unbaked pizza samples.     

Relation of biogenic amines to microbial and sensory changes of precooked chicken meat stored aerobically and under modified atmosphere packaging at 4 °C

The formation of biogenic amines and their correlation to microflora and sensory characteristics of a precooked chicken meat product stored aerobically and under modified atmosphere packaging (MAP) (30% CO₂, 70% N₂) was studied. Putrescine was the main amine formed both in aerobically and MA-packaged chicken samples. For the rest of the biogenic amines, including tyramine, histamine, and cadaverine, a stepwise increase was recorded throughout the 23-day storage period under the above packaging conditions. Spermidine was found in higher amounts, as compared to spermine in both aerobically and MA-packaged chicken samples at 4 °C. Formation of these amines in precooked chicken stored either aerobically or under a 30% CO₂, 70% N₂ atmosphere followed an inconsistent trend during the entire storage period at 4 °C. Agmatine, β-phenyl-ethylamine, and tryptamine were not detected in precooked chicken. Of the bacterial groups monitored, lactic acid bacteria (LAB) became the dominant bacteria after day 8 of storage under MAP while LAB were the dominant population of natural microflora of precooked chicken stored both aerobically or under MAP, reaching 7.5 and 8.0 log cfu/g, respectively, on day 23 of refrigerated storage. Enterobacteriaceae populations in chicken meat were below the detection limit (<1 log cfu/g) by pour plating throughout the 23-day storage period, irrespective of packaging conditions. Based on sensory data, after ca. 8 days for the precooked chicken meat stored aerobically and after 12 days under MAP (time to reach initial decomposition stage, score of 2) the putrescine and tyramine content of chicken samples were ca. 14–19 and 1.4 mg/kg, values that may be proposed as the limit for spoilage initiation of precooked chicken meat (respective TVC for both aerobically and MA-packaged chicken meat were ca. 6.5 log cfu/g).     

Retail Shelf-Life of Pork Dipped in Organic Acid before Modified Atmosphere or Vacuum Packaging

Modified atmosphere packaging (MAP) is increasingly popular for meat, but raw, chilled pork in vacuum or anoxic environments has a purple color. The retail shelf‐life of pork chops dipped in 500 ppm ascorbic acid, 250 ppm citric acid, or no acid dip and stored at 1 °C before simulated retail display in MAP with gas exchange or air‐permeable packaging after vacuum pouch storage was determined. The 80% N₂:20% CO₂ in MAP was exchanged with 80% O₂:20% CO₂, and chops were removed from vacuum packages and overwrapped with permeable film (VP‐PVC) on the 7th day before simulated retail display at 4 °C. Shelf‐life traits were determined at 1, 7, 8, 10, 12, and 14 d postpackaging. The pH values changed with time, but returned to post‐dipped, prepackaged levels at the end of simulated retail storage. Weight loss of chops increased (P < 0.05) in VP‐PVC compared with MAP. The a* values increased (P < 0.05) and L* and b* values decreased during simulated retail display, with higher L*, a*, and b* color values for chops in MAP than VP‐PVC. Log numbers of psychrotrophic microorganisms were higher (P < 0.05) on VP‐PVC samples than for chops in MAP on days 12 and 14. Psychrotrophic counts on ascorbic acid‐treated samples were decreased compared with citric acid or no dipping on pork during simulated retail display. Pork chops in MAP with gas exchange had lighter and redder color, increased weight retention, decreased psychrotrophic counts, and increased lipid oxidation compared with conventional vacuum and overwrap packaging systems.     

Spoilage and shelf life of sardines (Sardina pilchardus) packed in modified atmosphere

The effect of modified atmosphere packing (MAP) (O₂/CO₂/N₂, 5/35/60 (%) and O₂/CO₂/N₂, 5/70/25 (%)) on the quality of sardine stored in refrigerator was investigated in terms of sensory, chemical and microbiological analysis. Although chemical and microbiological analyses indicated that modified atmosphere packing prolonged the shelf life of sardine compared with that of air packing, sensory analysis showed that the extension of shelf life was (condition: O₂/CO₂/N₂, 5/70/25 (%)) 8 days and in air (condition: O₂/CO₂/ N₂, 5/35/60 (%)) 6 days. The results showed significant differences (p <0.05) between air and MAP storage conditions.     

Effects of low dose gamma irradiation on microbial inactivation and physicochemical properties of fried shrimp (Penaeus vannamei)

Changes in microbiological, physicochemical and sensory properties of shrimp gamma irradiated with ⁶⁰Co at doses of 0, 1, 3, 6, 9 kGy were investigated. Irradiation at 6 kGy eliminated most of the spoilage microorganisms and did not affect sensory quality. The L* value increased as irradiation dose increased, while a* value decreased as irradiation dose increased. Irradiation had no significant effect on the texture of shrimp samples; however, increasing the dose up to 9 kGy significantly increased the amount of volatile compounds, such as, alcohols, ketones, aldehydes, furans, and oxides. According to the total sensory points, the appearance and flavour of the shrimp product was considered as acceptable by sensory evaluation when irradiated at doses of 0–6 kGy. These results showed that gamma irradiation processing (<6 kGy) had the potential to extend the shelf life of fried shrimp.     

Effect of modified atmosphere packaging on the growth of spoilage microorganisms and Listeria monocytogenes on fresh cheese

Queso Fresco has a limited shelf life and has been shown to support the rapid growth of Listeria monocytogenes during refrigerated storage. In addition to improving quality and extending shelf life, modified atmosphere packaging (MAP) has been used to control the growth of pathogenic microorganisms in foods. The objectives of this study were to determine the effects of MAP conditions on the survival and growth of spoilage microorganisms and L. monocytogenes during storage of Queso Fresco manufactured without starter cultures. For L. monocytogenes experiments, cheeses were surface inoculated at ～4 log₁₀ cfu/g before packaging. Inoculated and uninoculated (shelf life experiments) cheeses were placed in 75-µm high-barrier pouches, packaged under 1 of 7 conditions including air, vacuum, or combinations of N₂ and CO₂ [100% N₂ (MAP1), 30% CO₂:70% N₂ (MAP2), 50% CO₂:50% N₂ (MAP3), or 70% CO₂:30% N₂ (MAP4), 100% CO₂ (MAP5)], and stored at 7°C. Samples were removed weekly through 35 d of storage. Listeria monocytogenes counts were determined for inoculated samples. Uninoculated samples were assayed for mesophilic and psychrotolerant counts, lactic acid bacteria, coliforms, and yeast and mold. In general, cheeses packaged under conditions consisting of higher contents of CO₂ had lower pH levels during storage compared with those stored in conditions with lower levels or no CO₂ at all. Similarly, the antimicrobial efficacy of MAP in controlling spoilage microorganisms increased with increasing CO₂ content, whereas conditions consisting of 100% N₂, vacuum, or air were less effective. Mean L. monocytogenes counts remained near inoculation levels for all treatments at d 1 but increased ～2 log₁₀ cfu/g on cheeses packaged in air, vacuum, and 100% N₂ (MAP1) conditions at d 7 and an additional ～1.5 log₁₀ cfu/g at d 14 where they remained through 35 d. In contrast, treatments consisting of 70% CO₂ (MAP4) and 100% CO₂ (MAP5) limited increases in mean L. monocytogenes counts to <1 log₁₀ cfu/g through 14 d and ～1.5 log₁₀ cfu/g by d 21. Mean L. monocytogenes counts increased to levels significantly higher than inoculation (d 0) on cheeses stored in MAP2 and MAP3 on d 21, on d 28 for MAP4, and on d 35 for cheeses stored under MAP5 conditions. Overall, significant treatment × time interactions were observed between air, vacuum, and MAP1 when each was compared with MAP2, MAP3, MAP4, and MAP5. These data demonstrate that packaging fresh cheese under modified atmospheres containing CO₂ may be a promising approach to extend shelf life while limiting L. monocytogenes growth during cold storage.     

Effect of irradiation, active and modified atmosphere packaging, container oxygen barrier and storage conditions on the physicochemical and sensory properties of raw unpeeled almond kernels (Prunus dulcis)

BACKGROUND: The present study investigated the effect of irradiation, active and modified atmosphere packaging, and storage conditions on quality retention of raw, whole, unpeeled almonds. Almond kernels were packaged in barrier and high‐barrier pouches, under N₂ or with an O₂ absorber and stored either under fluorescent lighting or in the dark at 20 °C for 12 months. Quality parameters monitored were peroxide value, hexanal content, colour, fatty acid composition and volatile compounds. Of the sensory attributes colour, texture, odour and taste were evaluated. RESULTS: Peroxide value and hexanal increased with dose of irradiation and storage time. Irradiation resulted in a decrease of polyunsaturated and monounsaturated fatty acids during storage with a parallel increase of saturated fatty acids. Volatile compounds were not affected by irradiation but increased with storage time indicating enhanced lipid oxidation. Colour parameters of samples remained unaffected immediately after irradiation. For samples packaged under a N₂, atmosphere L* and b* values decreased during storage with a parallel increase of value a* resulting to gradual product darkening especially in irradiated samples. CONCLUSION: Non‐irradiated almonds retained acceptable quality for ca. 12 months stored at 20 °C with the O₂ absorber irrespective of lighting conditions and packaging material oxygen barrier. The respective shelf life for samples irradiated at 1.0 kGy was 12 months packaged in PET‐SiOx//LDPE irrespective of lighting conditions and 12 months for samples irradiated at 3 kGy packaged in PET‐SiOx//LDPE stored in the dark. Copyright © 2010 Society of Chemical Industry     

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.     

Combined effects of a natural Allium spp. extract and modified atmospheres packaging on shelf life extension of olive‐based paste

This study aimed to extend the shelf life of non‐thermally stabilised olive‐based paste by adding different concentrations (0.2, 0.5, 1.0 g kg^?1) of a natural Allium spp. extract and/or by using different packaging atmospheres (MAP1, 75% Ar‐23% CO₂‐2% H₂; MAP2, 70% N₂‐30% CO₂) during refrigerated storage. Higher amounts of the natural extract gave the highest level of microbial inhibition, increased hardness, a greater release of aldehydes, esters, and ketones, and a better colour preservation when used with MAP1. The natural extract and MAP, either alone or in combination, produced no sensory defects (except for the control in MAP2), but a greater loss of typical olive flavour. The addition of the natural extract used with an appropriate MAP, can retain the quality attributes and extend shelf life for approximately 14 days longer than the control (without natural extract and MAP), and a better performance is achieved by using greater amounts of natural extract and MAP1.     

Shelf‐life extension of vacuum‐packaged sea bream (Sparus aurata) fillets by combined γ‐irradiation and refrigeration: microbiological,chemical and sensory changes

The combined effect of γ‐irradiation and refrigeration on the shelf‐life of vacuum‐packaged sea bream (Sparus aurata) fillets was studied by monitoring the microbiological, chemical and sensory changes of non‐irradiated and irradiated fish samples using low‐dose irradiation doses of 1 and 3 kGy. Fish species such as sea bream and sea bass are very popular in the Mediterranean countries due to their high quality characteristics, and their preservation is a constant challenge given their extreme perishability. Irradiation (3 kGy) dramatically reduced populations of bacteria, namely, total viable counts (3 vs 7 log cfu g^?1) for the non‐irradiated samples, Pseudomonas spp (<2 vs 7.6 log cfu g^?1), H₂S‐producing bacteria typical of Shewanella putrefaciens (<2 vs 5.9 log cfu g^?1), Enterobacteriaceae (<2 vs 6.0 log cfu g^?1) and lactic acid bacteria (<2 vs 3.5 log cfu g^?1) after 10 days of storage. The effect was more pronounced at the higher dose (3 kGy). Lactic acid bacteria, Enterobacteriaceae and H₂S‐producing bacteria typical of Shewanella putrefaciens showed higher sensitivity to γ‐radiation than did the rest of the microbial species. Of the chemical indicators of spoilage, Trimethylamine (TMA) values of non‐irradiated sea bream increased very slowly, whereas for irradiated samples significantly lower values were obtained reaching a final value of 7.9 and 6.3 mg N per 100 g muscle at 1 and 3 kGy respectively (day 42). Total volatile basic nitrogen (TVB‐N) values increased slowly attaining a value of 67.3 mg N per 100 g for non‐irradiated sea bream during refrigerated storage, whereas for irradiated fish, lower values of 52.8 and 43.1 mg N per 100 g muscle were recorded (day 42). Thiobarbituric acid (TBA) values for irradiated sea bream samples were higher than respective non‐irradiated fish and increased slowly until day 21 of storage, reaching final values of 1.1 (non‐irradiated), 2.0 (1 kGy) and 2.2 mg malonaldehyde kg^?1 muscle (3 kGy), respectively (day 42). Sensory evaluation showed a good correlation with bacterial populations. On the basis of overall acceptability scores (sensory evaluation) a shelf‐life of 28 days (3 kGy) was obtained for vacuum‐packaged sea bream, compared with a shelf‐life of 9–10 days for the non‐irradiated sample. Copyright © 2004 Society of Chemical Industry     

Effects of electron beam irradiation on microbial inactivation and quality of kimchi paste during storage

The effects of electron beam irradiation on microbial inactivation and quality of noninoculated and inoculated (Listeria monocytogenes) kimchi pastes were examined. Kimchi paste samples were irradiated at doses of 2, 4, 6, 8 and 10 kGy and stored for 21 days at 4 °C. Irradiation (10 kGy) reduced the populations of total aerobic bacteria, lactic acid bacteria, and yeast and moulds in the samples by 1.72, 2.24 and 0.86 log CFU g^?1, respectively, compared to the control. In particular, coliforms were not detected at 8 and 10 kGy, and the population of L. monocytogenes in inoculated samples was significantly decreased by 2.67 log CFU g^?1. Electron beam irradiation delayed the changes in O₂ and CO₂ concentrations, pH, acidity and reducing sugar content observed in kimchi paste during storage. These results suggest that electron beam irradiation can be used to improve the microbiological safety and shelf life of kimchi paste.     

Shelf Life and Sensory Characteristics of Baby Spinach Subjected to Electron Beam Irradiation

Abstract: The use of ionizing radiation for the control of foodborne pathogens and extending the shelf life of fresh iceberg lettuce and fresh spinach has recently been approved by the U.S. Food and Drug Administration. The efficacy of electron beam irradiation for controlling foodborne pathogens has been reported. For this experiment, the effectiveness of electron beam irradiation on the microbiological and sensory characteristics of fresh spinach was studied. Total aerobic plate counts were reduced by 2.6 and 3.2 log CFU/g at 0.7 and 1.4 kGy, respectively. Lactic acid bacteria were reduced at both doses of e-beam but grew slowly over the 35 d of the experiment. Yeasts and molds were not reduced in samples exposed to 0.7 kGy whereas 1.4 kGy significantly reduced microbial counts. Gas compositions (O₂ and CO₂) were significantly different than controls. Oxygen levels inside the spinach sample bags decreased over time; however, O₂ levels did not drop below 1% that can induce anaerobic fermentation. CO₂ levels for all treatments increased through day 4; yet 7 d after irradiation, CO₂ level differences were not significant in both control and irradiated samples. Irradiation dose did not affect the basic tastes, aromatics, or mouth feels of fresh spinach, however; hardness attributes decreased as irradiated dose increased and slimy attributes of fresh spinach were higher in control samples compared to irradiated samples.     

Shelf Life Assessment of Modified Atmosphere Packaged Turbot (Psetta maxima) Fillets: Evaluation of Microbial, Physical and Chemical Quality Parameters

Quality and safety of turbot fillets under modified atmosphere packaging (MAP) were assessed by microbial (total viable counts), physical (drip loss, pH, colour CIE Lab) and chemical parameters (total volatile basic nitrogen (TVBN), trimethylamine nitrogen (TMAN), biogenic amine contents). Three different atmospheres (MAP 1, 10/40/50 % O₂/CO₂/N₂; MAP 2, 10/60/30 % O₂/CO₂/N₂; MAP 3, 10/80/10 % O₂/CO₂/N₂) were tested. Packaged turbot fillets were stored at 2?±?1 °C and monitored over 30 days, at intervals of 5 days. Fillets from the control group, packaged with air (AIR), were the first to present signs of degradation reaching rejection threshold values for all evaluated parameters. In MAP fillets, total bacterial count was lower than 10⁶ cfu/g for a longer period. After 10 days of storage, MAP and AIR fillets showed significant differences (p?<?0.05) on the values of TVBN, TMAN and biogenic amines. MAP fillets presented a higher drip loss, and fillets in AIR became more yellowish (upper b* values) while those in MAP looked whitish for an increased period (upper L* values). All microbial, chemical and physical traits revealed the protective effect of the different MAP studied, especially those with a higher percentage of CO₂. MAP application added, at least, 5 days to shelf life of turbot fillets.     

Effects of gamma irradiation on the biogenic amines in pepperoni with different packaging conditions

Combined effects of gamma irradiation and packaging on biogenic amine (BA) formation in pepperoni sausage were investigated during storage. Pepperoni (fermented sausage) was made and packaged with air, vacuum and CO₂/N₂ (25%/75%) gas and then gamma-irradiated at 0, 5, 10 and 20 kGy. The pH was decreased after storage and non-irradiated samples showed a lower pH than irradiated. Lactic acid bacteria (LAB) were not detected after 5 kGy of gamma irradiation, while the LAB in the non-irradiated samples were 4–5 log counts during storage. A total of six different BAs, putrescine, cadaverine, β-phenylethylamine, spermidine, spermine and tyramine, were found in the pepperoni sausage. Detected BAs were statistically low under the irradiation or packaging conditions, except for cadaverine and β-phenylethylamine. Gamma irradiation was effective in reducing putrescine, spermidine, spermine and tyramine. Irradiation effects were not observed on the β-phenylethylamine level, while the CO₂/N₂ packaging caused increasing of the level. Most BAs detected were reduced by gamma irradiation of the pepperoni sausage during storage. However, CO₂/N₂ packaging was an improper condition for BA reduction in the pepperoni sausage.