Microbiological,chemical and sensory assessment of mussels (<Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis>) stored under modified atmosphere packaging

Wild mussels (Mytilus galloprovincialis), were packaged aerobically under vaccum packaging(VP) and modified atmosphere packaging (MAP (50%/50% CO₂/N₂: M1, 80%/20% CO₂/N₂: M2, 65%/35% CO₂/N₂: M3), and stored at 2 ± 1 °C. Quality evaluation was carried out using microbiological, chemical and sensory analyses. Microbiological results revealed that M2 and M3 delayed microbial growth compared to M1. Of the chemical indices determined, the TVB-N and TMA-N values of M2 remained lower than the proposed acceptability limits of 35 mg N/100 g and 8 mg N/100 g, respectively, up to 8 days of storage. All of the MAP and VP mussel samples exceeded these limits after 12 days of storage. All samples retained desirable sensory characteristics during the first 8 days of storage. Based on microbiological and chemical analyses along with sensory evaluation, M2 and M3 gave a longer shelf-life compared with VP and M1. M2 gas mixture was the most effective for mussel preservation.     

Influence of Injection, Packaging, and Storage Conditions on the Quality of Beef and Bison Steaks

The combined effects of injection, packaging (modified atmosphere packaging [MAP] with 70% O₂/ 30% CO₂ and vacuum packaging [VP]), storage temperature (‐1 °C and +4 °C), and storage time on the color, microbial and oxidative stability of beef and bison longissimus lumborum (LL) steaks were investigated. Beef LL steaks in MAP retained their bright red color longer than bison steaks. Bison steaks developed higher 2‐Thiobarbituric acid reactive substances (TBARS) during storage, and this might have influenced the resulting rapid loss of redness from the bloomed meat. Storage at ‐1 °C in MAP provided greater color stability and a longer storage life for both meat species studied. Injection of salt/phosphate had a beneficial effect on the color stability of steaks during retail display; however, this positive effect was more pronounced for bison steaks compared with those of beef. Steaks stored overnight under MAP before retail display maintained the highest a* values for up to 5 d compared with those stored under vacuum. MAP‐OV steaks generally maintained the highest OMB content for up to 5 d during retail display compared with those stored under vacuum. Nevertheless, OMB levels were significantly (P < 0.05) lower in bison steaks compared with those of beef irrespective of packaging treatments. Injected steaks and those stored at ‐1 °C had significantly (P < 0.05) higher OMB levels compared with non‐injected counterparts and those stored at +4 °C, respectively. MAP is an excellent option for short‐term storage due to its positive effects on meat color, but for longer storage, VP may be necessary. Storing meat under vacuum and then placing it under MAP just before retail display might be another option to increase shelf life.     

Effects of high-pressure treatment on the microflora of oysters (Crassostrea gigas) during chilled storage

The microbiological quality of oysters high-pressure (HP)-treated in-shell at 260 MPa for 3 min, or 500 or 800 MPa for 5 min and then stored at 2 °C, were investigated. Microbial counts after HP treatment showed that the bacterial load was reduced after treatment at all pressures to levels below the detection limit. Randomly-selected isolates from the total aerobic viable counts of untreated and HP-treated oysters after 14 days of storage were identified by the API identification system. Bacteria isolated from oysters HP-treated at 260 MPa were Shewanella putrifaciens and Pseudomonas fluorescens. For oysters HP-treated at 500 or 800 MPa, the main bacteria isolated were Pseudomonas spp. Vibrio spp. comprised 44% of the microflora in untreated oysters after storage for 14 days at 2 °C, but no Vibrio were detected in HP-treated oysters. This study confirmed that HP processing can inactivate microorganisms and delay microbial growth in chilled stored oysters.

Industrial relevance

High-pressure (HP) treatment is being increasingly employed for commercial processing of oysters but no studies of the microflora of HP-treated in-shell oysters have been reported. HP treatment significantly changed the microflora of oysters and apparently has good potential for inactivation of Vibrio spp as HP treatment, in combination with adequate chilled storage, can improve the microbiological shelf-life and safety of oysters.     

Lipid and cholesterol oxidation in Chinese-style sausage using vacuum and modified atmosphere packaging

The oxidation of lipid and cholesterol in Chinese-style sausage in vacuum packaging (VP) and modified atmosphere packaging (MAP) stored at 4°C and 15°C, respectively, for 5 months was investigated. The 2-thiobarbitaric acid reactive substance (TBARS) and peroxide value (POV) of sausage were variable with packaging treatments during storage. TBARS and POV in sausage stored at 15°C were significantly greater (p < 0·05) than at 4°C, and the MAP treatment was more stable than the VP treatment. In addition, the polyunsaturated fatty acids (PUFA) in sausage decreased with storage for both treatments. The content of cholesterol decreased significantly after 3 months of storage. 7-β-hydroxycholesterol, 7-ketocholesterol and 22-ketocholesterol were the major cholesterol oxidation products (COPs), but there was no detectable (< 1 μg/100 g) 25-hydroxycholesterol or cholestanetriol with either treatment.     

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.     

Postharvest performance of fresh‐cut ‘Big Top’ nectarine as affected by dipping in chemical preservatives and packaging in modified atmosphere

Fresh‐cut ‘Big Top’ nectarines were dipped in 2% (w/v) ascorbic acid–1% (w/v) calcium lactate and stored at 4 °C for up to 12 days in 10 kPa O₂‐ and 10 kPa CO₂‐modified atmosphere packaging (MAP). The used microperforated plastic film allowed O₂ and CO₂ concentrations to reach steady values from the fifth day in storage onwards. Samples stored in MAP after chemical dipping showed the highest visual quality score, slight browning symptoms, increment in firmness and very low ethanol and acetaldehyde content. The chemical dipping also increased antioxidant capacity, probably due to the effect of ascorbic acid. The results suggested that the control of yeasts was mainly exerted by MAP, whereas only a slight effect was achieved by the chemical dipping. Therefore, MAP plus ascorbic acid/calcium lactate dipping was the best combination to preserve phytochemical content, antioxidant capacity and microbiological safety of fresh‐cut nectarines during storage.     

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).     

Effect of dietary humate on the pH,TBARS and microbiological properties of vacuum‐ and aerobic‐packed breast and drumstick meats of broilers

The current trial determined the influence of dietary humate, including humic, fulvic and ulmic acids and some microminerals on the pH, TBARS and microbiological properties of vacuum‐packed and aerobic‐packed breast fillets and drumsticks of broilers. A total of 240 male broiler chicks (Ross‐308) were randomly allocated into four dietary treatments (H₀, H₁, H₂ and H₃ groups). A basal diet (H₀), basal diet plus 0.1 (H₁), 0.2 (H₂) and 0.3% (H₃) humate (Farmagulator DRY^?, Humate, Farmavet International Inc, Kocaeli 41 400, Turkey) were offered during the experimental feeding period. At the end of the trial all chicks were slaughtered. After standard dissection of carcasses, the breasts and drumsticks were divided into two groups for vacuum packaging or aerobic packaging. Packed breasts and drumsticks were stored at 3 °C for 12 days. The breasts and drumsticks were analyzed for pH, TBARS, total mesophilic, total psychrotrophic, lactic acid bacteria and Enterobacteriacea counts at 0, 2, 4, 6, 8, 10 and 12 days of storage. The feeding of humate decreased pH values of breast fillets and drumstick muscles (p < 0.01), especially at the 0.1% level. The TBARS value decreased (p < 0.01) when compared with the without‐humate group (H₀). Total aerobic mesophilic (p < 0.01), total aerobic psychrotrophic (p < 0.01) and lactic acid bacteria (p < 0.05) counts were lower in the H₃ group than the other groups. The effect of meat type on pH, TBARS, total aerobic mesophilic (p < 0.01) and lactic acid bacteria (p < 0.05) and Enterobacteriacea counts was significant. While the pH and TBARS values of breast fillets were lower than those of drumstick meats, the total mesophilic, total psychrotrophic, lactic acid bacteria and Enterobacteriacea counts of drumstick meats were higher than those of breast fillets. The effect of packaging type on pH (p < 0.01), TBARS (p < 0.01), total aerobic psychrotrophic bacteria (p < 0.01) and Enterobacteriacea counts (p < 0.01) was found statistically significant and the maximum values were determined in the aerobic‐packed samples. In addition, investigated parameters were also affected by storage period. While the total aerobic mesophilic count decreased, the other parameters increased when compared with zero day of storage. Copyright © 2005 Society of Chemical Industry     

Shelf‐Life Extension of Chill‐Stored Beef Longissimus Steaks Packaged under Modified Atmospheres with 50% O2 and 40% CO2

This study was conducted to compare the shelf‐life of beef steaks stored in different packaging conditions: overwrapped (OW) packaging and 2 modified atmosphere packaging systems (MAP): 80% O₂ MAP (80% O₂/20% CO₂) and 50% O₂ MAP (50% O₂/40% CO₂/10% N₂). Steaks were stored at 2 °C for 20 d. Headspace gas composition, microbial counts, color stability, pH, purge loss, and lipid oxidation were monitored. Among the packaging types, 50% O₂ MAP was superior to OW packaging and 80% O₂ MAP in delaying bacterial growth and extending shelf‐life to 20 d. 50% O₂ MAP also gave steaks an acceptable color during storage. No significant differences were observed in color stability of steaks packaged in both 50% O₂ MAP and 80% O₂ MAP. This study reveals 50% O₂ MAP is a realistic alternative to preserve beef steaks efficiently.     

Effect of different high pressure treatments on shucking,biochemical, physical and sensory characteristics of oysters to elaborate a traditional Taiwanese oyster omelette

BACKGROUND: Whole oysters (Crassostrea gigas) were processed using high‐pressure (HP) treatment (150–300 MPa) to determine their shucking and biochemical properties. Subsequently, HP‐treated oysters were cooked at 160 °C for 90 s, as when preparing the oyster omelette dish, to evaluate their physical and sensory characteristics as compared to raw oysters. RESULTS: The treatments of 250 and 300 MPa for 2 min and 0 min, respectively, resulted in 100% release. The pH of HP‐treated oysters increased slightly from 6.50 to 6.82, and the moisture contents of the HP‐treated oysters with or without further cooking were all higher than those of the control. The brightness, yellowness and cutting strength of HP‐treated oysters with further cooking changed insignificantly, while the redness decreased compared to the control. Sensory evaluation showed that oysters treated at 250 and 300 MPa oysters after cooking received higher quality scores than the control. CONCLUSIONS: HP processing at 250 and 300 MPa proved to be a good method for oyster shucking. The HP‐treated oysters cooked in the oyster omelette are acceptable to consumers. Overall, the application of HP as a processing method to improve the quality and acceptability of oysters and their related products would be possible. Copyright © 2009 Society of Chemical Industry     

Effects of High‐Hydrostatic Pressure on Inactivation of Human Norovirus and Physical and Sensory Characteristics of Oysters

The purpose of the study was to determine the effect of high‐hydrostatic pressure (HHP) on inactivation of human norovirus (HuNoV) in oysters and to evaluate organoleptic characteristics of oysters treated at pressure levels required for HuNoV inactivation. Genogroup I.1 (GI.1) or Genogroup II.4 (GII.4) HuNoV was inoculated into oysters and treated at 300 to 600 MPa at 25 and 0 °C for 2 min. After HHP, viral particles were extracted by porcine gastric mucin‐conjugated magnetic beads (PGM‐MBs) and viral RNA was quantified by real‐time RT‐PCR. Lower initial temperature (0 °C) significantly enhanced HHP inactivation of HuNoV compared to ambient temperature (25 °C; P < 0.05). HHP at 350 and 500 MPa at 0 °C could achieve more than 4 log₁₀ reduction of GII.4 and GI.1 HuNoV in oysters, respectively. HHP treatments did not significantly change color or texture of oyster tissue. A 1‐ to 5‐scale hedonic sensory evaluation on appearance, aroma, color, and overall acceptability showed that pressure‐treated oysters received significantly higher quality scores than the untreated control (P < 0.05). Elevated pressure levels at 450 and 500 MPa did not significantly affect scores compared to 300 MPa at 0 °C, indicating increasing pressure level did not affect sensory acceptability of oysters. Oysters treated at 0 °C had slightly lower acceptability than the group treated at room temperature on day 1 (P < 0.05), but after 1 wk storage, no significant difference in sensory attributes and consumer desirability was observed (P > 0.05).     

Effects of packaging method and storage time on the chemical, microbiological, and sensory properties of Turkish pastirma - A dry cured beef product

The effects of packaging method (aerobic packaging (AP), vacuum packaging (VP) or modified atmosphere packaging (MAP)), the form of pastirma (sliced or non-sliced) and storage time (0, 15, 30, 60, 90 or 120 days) on the chemical, microbiological and sensory properties of a Turkish pastirma were investigated. Overall, MAP preserved chemical, microbiological and sensory properties of Turkish pastirma better than AP or VP. Very high correlation coefficients (almost all >0.90) were observed between subjective quality parameters (sensory properties) and objective quality parameters (TBARS, hexanal content, L^*, a^*, and b^*), which suggests that sensory panel was able to determine the quality changes over storage time precisely. Based on the results of this study, MAP should be the preferred choice of packaging in order to preserve overall quality of Turkish pastirma and its implication for pastirma packaging may increase pastirma’s current share in the processed meat product market.     

Effect of High Pressure and 4-Hexylresorcinol on Enzymatic Activity and Darkening in Oysters

ABSTRACT: Oysters treated with and without 4-hexylresorcinol were pressurized (400 MPa/7 °C/10 min) and stored chilled for 21 d, either vacuum-packed or packaged aerobically. The results of visual evaluation of darkening and polyphenoloxidase (PPO) activity levels suggest that during storage, non enzymatic browning occurred 1st, followed by blackening caused by PPO activity. PPO activity did not increase in the vacuum-packed oysters during storage, but pressurization was observed to activate the PPO. Autolytic activity in the oysters increased due to the high-pressure treatment, although higher autolysis levels were recorded in the unpressurized oysters at the end of storage. Inhibition of PPO activity by the 4-hexylresorcinol was observed chiefly in the vacuum-packed batches.     

The combined effect of superchilling and modified atmosphere packaging using CO2 emitter on quality during chilled storage of pre‐rigor salmon fillets (Salmo salar)

BACKGROUND: Pre‐rigor fillets of Atlantic salmon were either superchilled or chilled prior to packaging in air or in modified atmosphere (MAP, 60% CO₂/40% N₂) with a CO₂ emitter, in 5.3 L high‐density polyethylene trays with three to four layers of fillets (3.0–3.7 kg). All samples were stored at 0.1 °C for 28 days. RESULTS: Fillets stored in MAP had significantly lower bacterial growth compared to fillets stored in air, and MAP superchilled bottom fillets had lower bacterial counts compared to the corresponding chilled fillets. Samples superchilled prior to refrigerated storage in air had similar bacterial growth to ordinary chilled samples. Faster fillet softening during storage and higher liquid loss were observed in superchilled MAP samples. CONCLUSION: Combining short‐term superchilling and MAP with a CO₂ emitter prolonged the shelf‐life of pre‐rigor salmon fillets, which can improve sustainability throughout the value chain. The superchilling method needs to be optimized to avoid negative effects on texture and liquid loss. Copyright © 2009 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.     

Effect of Packaging and Basil Essential Oil on the Quality Characteristics of Whey Cheese “Anthotyros”

In this study, we compared the effect of basil essential oil (EO) and various packaging conditions on “Anthotyros,” a Greek whey cheese. This cheese was stored at 4 °C under aerobic (A), vacuum (V), and modified atmosphere (M, 40%/60%; CO₂/N₂,) conditions, without or with (AB, VB, and VM) basil EO added to the cheese samples to a final concentration of 0.4% (v/w). The quality characteristics and the shelf life of both untreated and basil EO-treated cheese were assessed using microbiological, physicochemical, and sensory parameters. Microbiological results revealed that either modified atmosphere/vacuum packaging (MAP/VP) singly or in combination with basil EO delayed microbial growth as compared to the control (A) samples. The sensory and microbiological data showed that the combined use of MAP and VP with added basil EO extended the shelf life of fresh Anthotyros (4 °C) by approximately 10–12 days (treatment MB) and 6 days (treatment VB) as compared to aerobic packaging (A). Under these treatments, whey cheese samples maintained good sensory characteristics. This study has shown that the combined use of either VP or MAP, and basil EO, can extend the shelf life of whey cheese and maintain the freshness and the sensorial characteristics of the product.     

Shelf Life Determination of Sliced Portuguese Traditional Blood Sausage—Morcela de Arroz de Monchique through Microbiological Challenge and Consumer Test

Morcela de Arroz (MA) is a ready‐to‐eat blood and rice cooked sausage produced with pork, blood, rice, and seasonings, stuffed in natural casing and cooked above 90 °C/30 min. It is commercialized whole, not packed, with a restricted shelf life (1 wk/0 to 5 °C). The objective of this work was to establish sliced MA shelf life considering both the behavior of L. monocytogenes through a microbiological challenge test (MCT) and the consumer acceptability of MA stored: vacuum packed (VP), modified atmosphere packed (MAP: 80% CO₂/20% N₂), and aerobic packed (AP). The MCT was conducted inoculating ±3 log CFU/g of L. monocytogenes cell suspension on the MA slices. Packaged samples were stored at 3 ± 1 °C and 7 ± 1 °C until 20 d. At 3 ± 1 °C, L. monocytogenes behavior was not affected by packaging or storage time. At 7 ± 1 °C, the pathogen increased nearly 1 log CFU/g in the first 4 d. L. monocytogenes populations in AP were higher (P < 0.05) than in MAP. The pathogen may grow to hazardous levels in the 1st days if a temperature abuse occurs. Considering the acceptability by the consumers, the shelf life of MA stored at 3 ± 1 °C was 4.4 d for AP, 8.1 d for VP, and 10.4 d for MAP. The sensory shelf life established based on sensory spoilage is shorter than the shelf life to maintain the population of L. monocytogenes in safe levels.     

Antioxidant properties and shelf‐life extension of fresh‐cut tomatoes stored at different temperatures

BACKGROUND: The feasibility of using modified atmosphere packaging (5 kPa O₂ + 5 kPa CO₂) to maintain the antioxidant properties of fresh‐cut tomatoes during shelf‐life was assessed through storage at different temperatures (5, 10, 15 and 20 °C). Health‐related compounds, antioxidant capacity, microbiological counts, physicochemical parameters and in‐package atmosphere of tomato slices were determined. RESULTS: Initial lycopene, vitamin C and phenolic contents and physicochemical parameters of tomato slices were well maintained for 14 days at 5 °C. Lycopene and total phenolic contents were enhanced over time in tomato slices stored at 15 and 20 °C. However, this increase in antioxidant compounds of fresh‐cut tomatoes during storage may be associated with excessive amounts of CO₂ (R² = 0.5679–0.7328) in the packages due to microbial growth. Although keeping tomato slices at temperatures above 10 °C increased their antioxidant content, the shelf‐life of the product was reduced by up 4 days. CONCLUSIONS: A storage temperature of 5 °C is appropriate for maintaining the microbiological shelf‐life of fresh‐cut tomatoes for up to 14 days and also allows the antioxidant properties of tomato slices to be retained over this period, thus reducing wounding stress and deteriorative changes. Copyright © 2008 Society of Chemical Industry     

Microbiological,physical and chemical characteristics of freshwater prawns (Macrobrachium rosenbergii) in modified‐atmosphere packaging

This study evaluated the influence of packaging atmosphere (air versus 50% N₂/50% CO₂) on microbiological (mesophiles, psychrotrophs), physical (gas measurement) and chemical (pH, total volatile basic nitrogen [TVB‐N], NH₃, H₂S and biogenic amines) parameters in freshwater prawns during storage at 0 ± 1 °C for 240 h. To select the most appropriate packaging, 21 batches of each treatment were analysed. Both the packaging permeability and the combination of gases affected the shelf life, but the modified‐atmosphere packaging (MAP) was more efficient than air packaging, increasing the shelf life by 40 h. The parameters of pH and TVB‐N showed no statistical difference between the two atmosphere conditions all along the storage period. The biogenic amine agmatine showed potential for use as a quality indicator due to the increased concentration during storage. In further studies, this amine can be applied as an indicator for public health issue.     

Physicochemical and microbiological changes of “Souvlaki” – A Greek delicacy lamb meat product: Evaluation of shelf-life using microbial,colour and lipid oxidation parameters

Fresh Souvlaki-type lamb meat was packaged under vacuum (VP) and modified atmospheres (MAs) and stored under refrigeration (4 °C) for a period of 13 days. The following gas mixtures were used: M1: 30%/70% (CO₂/N₂) and M2: 70%/30% (CO₂/N₂). Identical samples were aerobically-packaged and used as control samples. Quality evaluation of product stored under the above packaging conditions was conducted using physicochemical and microbiological analyses. Of the chemical parameters determined, pH values of product showed no significant differences for all packaging treatments as a function of storage time. Lipid oxidation of lamb meat was enhanced by aerobic storage and gas mixture M1, whereas VP and gas mixture M2 controlled lipid oxidation to a greater extent. Souvlaki colour stability (as determined by a^∗, b^∗ and L^∗ values) was not negatively affected by either VP or MA conditions during the 13 days of storage. Of the two MAs and VP used, gas mixture M2 and VP were the most effective treatments for the inhibition of total viable counts (TVC), Pseudomonas spp., yeasts and Brochothrix thermosphacta in Souvlaki meat. Lactic acid bacteria (LAB) and Enterobacteriaceae were also found in the microbial flora of Souvlaki and increased during storage under all packaging conditions used. Based on microbiological analysis data and on the proposed a^∗ values, the use of VP and MAP (M2: 70%CO₂/30N₂) extended the shelf-life of “Souvlaki” meat stored at 4 °C by approximately 4–5 days compared to aerobic packaging.