MICROBIAL PROFILE OF SPOILAGE FLORA FROM PORK SAUSAGE STORED UNDER THREE DIFFERENT COOLER CONDITIONS

A microbial examination was made of linked pork sausage stored until off-color development in three cooler arrangements – retail display case, walk-in cooler and walk-in cooler with incandescent illumination (2,200 lumens). Ninety mesophilic and ninety psychrotrophic organisms were isolated from 9 sausage batches held under each cooler condition. Isolates were identified using standard tests for identification of bacteria. The predominate psychrotropic isolate from all three types of cooler conditions was Pseudomonas. The predominate mesophilic isolate from the cooler and the cooler with illumination was Lactobacillus while the predominate mesophilic isolates from the retail display case were Enterobactericeae. High product holding temperatures (12°C) allows the growth of low-temperature mesophiles, such as some Enterobacteriaceae, as well as some mesophilic Pseudomonas, both of which contribute to the unacceptability of pork sausage.     

Determination of Spoilage Microbiota of Pacific White Shrimp During Ambient and Cold Storage Using Next‐Generation Sequencing and Culture‐Dependent Method

This study was conducted to determine the initial and spoilage microbiota of Pacific white shrimp during ambient and cold storage using next‐generation sequencing (NGS) and a culture‐dependent method. The quality changes were also evaluated by sensory analysis and total volatile basic nitrogen (TVB‐N) values. After 1 d of storage, the psychrotrophic bacteria were only 5.97 log CFU/g, accounting for 1.1% of the mesophilic bacteria counts (7.94 log CFU/g). The psychrotrophic bacteria counts exceeded the counts of mesophilic bacteria for shrimp stored at 4 °C after 6 d of storage, indicating that psychrotrophic bacteria became predominant. The NGS was used to identify the bacterial species in samples stored at 25 and 4 °C. The results showed that the dominant microorganisms were Vibrio at 25 °C, and Acinetobacter, Psychrobacter, and Shewanella at 4 °C. By the culture‐dependent method based on 16S rRNA gene and VITEK®2 CompactA system, it showed that the dominant microorganisms were Proteus spp. at 25 °C, and Shewanella putrefaciens, Acinetobacter johnsonii, and Aeromonas sobria at 4 °C. In conclusion, differences in results of microbiota analyzed by culture dependent and independent approaches were observed. The combination of both methodologies may provide more comprehensive information about the dominant spoilage microbiota in Pacific white shrimp during ambient and cold storage.     

Shelf-life of Domiati cheese under modified atmosphere packaging

The present study describes the effects of modified atmosphere packaging (MAP) on shelf-life extension, chemical, microbiological, and sensory properties of Domiati cheese. Five different MAP were studied [10% CO₂/90% N₂ (G1), 15% CO₂/85% N₂ (G2), 25% CO₂/75% N₂ (G3), 100% CO₂ (G4), and 100% N₂ (G5)]. Control samples were packaged in air (CA) and under vacuum. In both groups of cheeses, chemical analysis was significantly affected by MAP during cold storage. Ripening indexes were significantly affected by MAP during cold storage. Microbiological data showed that G4, followed by G5, were the most effective groups inhibiting the growth of total aerobic mesophilic and psychrotrophic bacteria, and yeasts and molds until the end of storage. Sensory evaluation was significantly affected by MAP and storage period, at 45 d CA cheese samples were judged as unacceptable. The best sensory properties were obtained in G5, G4, and G3 treatments, and recorded a relatively higher sensory evaluation scores. The best shelf-life extension was obtained in G5, G4, and G3 treatments.     

Shelf-life of a Greek whey cheese under modified atmosphere packaging

“Anthotryros” cheese was packaged under vacuum (VP) or modified atmosphere (MAP) and stored at 4 or 12 °C. MAP mixtures were 30%/70% CO₂/N₂ (M1) or 70%/30% CO₂/N₂ (M2), while VP was taken as the control sample. Microbiological results showed that M1 and M2 delayed microbial growth compared with VP samples. Of the two modified atmospheres, gas mixture M1 was the most effective for inhibition of growth of mesophilic bacteria. Based primarily on sensory evaluation, the use of both MAP conditions extended the shelf-life of fresh Anthotyros cheese stored at 4 °C by ca. 10 days (M1) or 20 days (M2) compared with VP, and by ca. 2 days (M1) and 4 days (M2) at 12 °C, with cheese maintaining good sensory characteristics.     

Use of carbon monoxide combined with carbon dioxide for modified atmosphere packaging of pre- and postrigor fresh pork sausage to improve shelf life

Fresh pre- and postrigor pork sausage patties were manufactured in the Iowa State University Meat Laboratory and packaged either in modified atmosphere (MAP) with 0.4% carbon monoxide (CO) and 99.6% carbon dioxide (CO2) or on foam trays overwrapped with oxygen-permeable film (OW). Packages were stored at 2 to 40C under fluorescent lights for up to 31 days. Aerobic, anaerobic, and psychrotrophic plate counts, raw and cooked color, purge, and lipid oxidation were measured during storage. Results indicated that both pork sausage products in MAP had lower aerobic and psychrotrophic counts and less lipid oxidation throughout storage (P < 0.05). Raw color of both products in MAP was redder than the OW patties (P < 0.05), but the prerigor pork sausage in MAP benefited more from the CO atmosphere in terms of raw color than the postrigor pork sausage in MAP. Cooked color of the prerigor pork sausage in MAP was significantly redder than cooked color of the postrigor pork sausage. Both pork sausage products in MAP were also lighter (L* value) than the OW patties for raw and cooked color. Therefore, the combination of CO and CO2 in MAP was beneficial in extending the shelf life of pre-and postrigor fresh pork sausage by reducing aerobic and psychrotrophic microbial growth and improving oxidative stability and color, compared to conventional OW packaging. However, increased purge, increased anaerobic growth, and changes in cooking behavior were also observed for the products in MAP during storage (P < 0.05).     

Microbial shelf life determination of vacuum-packaged fresh beef treated with polylactic acid, lactic acid, and nisin solutions.

The effectiveness of polylactic acid, lactic acid, nisin, and combinations of the acids and nisin on extending the shelf-life of raw beef was determined. Fresh beef pieces (5 by 5 by 2.5 cm) were dipped in a solution of 2% low molecular weight polylactic acid (LMW-PLA), 2% lactic acid (LA), 200 IU of nisin per ml, or the combinations of nisin in either 2% LMW-PLA or 2% LA. The samples were then drip-dried, vacuum-packaged, and stored at 4 degrees C for up to 56 days. The beef surface pH values and numbers of psychrotrophic aerobic bacteria, psychrotrophic and mesophilic Enterobacteriaceae, Pseudomonas, and Lactobacillus were determined weekly for 56 days. The average surface pH values of the beef samples treated with 2% LMW-PLA or the combination of 200 IU of nisin per ml and 2% LMW-PLA were significantly reduced to 5.19 and 5.17, respectively, at day 0 (P < or = 0.05), while those decontaminated with 2% LA or 200 IU of nisin per ml in 2% LA solution were significantly decreased from 5.62 to 4.98 and 4.96, respectively. The 2% LMW-PLA, 2% LA, or the combinations of each acid and nisin showed immediate inhibitory effects on psychrotrophic aerobic bacteria (1.94, 2.36, 2.59, and 1.76 log reduction, respectively), psychrotrophic Enterobacteriaceae (1.37, 1.86, 1.77, and 1.35 log reduction, respectively), mesophilic Enterobacteriaceae (1.00, 1.00, 0.82, and 0.68 log reduction, respectively), and Pseudomonas (1.77, 1.57, 1.76, and 1.41 log reduction, respectively) on fresh beef (P < or = 0.05). The reduction was evident up to 56 days as seen by the numbers of Enterobacteriaceae and Pseudomonas (P < or = 0.05). Because there was no interaction between treatments and storage times, the data in each period were combined and presented as effect of treatments on overall microbial counts of fresh beef. It was found that 2% LMW-PLA, 2% LA, and the combinations of each acid and nisin significantly lowered the population of the above organisms compared with the untreated control, water, or nisin alone (P < or = 0.05).     

Sodium lactate addition on the quality and shelf life of refrigerated sliced poultry sausage packaged in air or nitrogen atmosphere

The aim of this study was to determine the effect of sodium lactate addition on shelf-life extension of sliced poultry sausage packaged both in air and nitrogen atmospheres and stored in refrigerated conditions. Basic chemical composition, pH, and malonaldehyde content were assayed and color measurement using the reflection method was carried out. Microbiological examination consisted of determination of total number of aerobic psychrotrophic bacteria and number of lactic acid bacteria. Sensory evaluation of products was performed. Microbiological and sensory quality of sliced poultry meat sausage was dependent on the addition during production of sodium lactate and the composition of gases (air or nitrogen) used in packaging. Slices of poultry sausage with 1% as well as 2% of sodium lactate maintained their initial quality of evaluated sensory attributes longer, irrespective of the applied gases. Sodium lactate inhibited growth of aerobic psychrotrophic bacteria and lactic acid bacteria during refrigerated storage. Sodium lactate also inhibited the formation of malonaldehyde in sliced poultry sausage during refrigerated storage. The effectiveness of this process depended on the concentration of sodium lactate addition. It was concluded that 1% as well as 2% addition of sodium lactate could extend the shelf life of sliced poultry sausage packaged in air atmosphere and stored at 5 to 7 degrees C by 3 or 4 times, respectively. Sliced poultry sausage treated with 2% sodium lactate packed in nitrogen had the longest (35-day) shelf life. This was a sevenfold increase in the shelf life of sliced poultry sausage compared with the control.     

Effects of water extract of Urtica dioica L. and modified atmosphere packaging on the shelf life of ground beef

Effects of lyophilized Urtica dioica L. water extract (LUWE) and modified atmosphere packaging (MAP) on the quality and shelf life of ground beef were investigated. Ground beef was stored as aerobic control, MAP (80%O₂ + 20% CO₂), MAP + 250 ppm LUWE and MAP and 500 ppm LUWE at 2 ± 0.5 °C for 14 days. MAP and LUWE had significant effects on mesophilic, psychrotrophic and lactic acid bacteria and Pseudomonas counts. Depending on the level of LUWE, Pseudomonas and psychrotrophic counts decreased. Treatment with 500 ppm LUWE + MAP showed the lowest TBARS values compared to other groups during storage. 80% O₂-MAP increased TBARS values. Treatment had no significant effect on L* and b* values of the exterior of the ground beef, but had significant effects on the color of interior sections.     

Effect of Combined Natural Antimicrobials on Spoilage Microorganisms and Listeria Innocua in a Whey Cheese “Ricotta”

The effect of nisin alone and in combination with Microgard? on the natural microbial flora of ricotta cheese and in post-process contamination with Listeria innocua was studied. Microbial groups studied were mesophilic, psychrotrophic, proteolytic, lactic acid and coliform bacteria, and total molds and yeasts. Considering the evolution of all microbial groups and failure criteria adopted for mesophilic and coliform bacteria, this product reached the end of its shelf life before 5 days, which is insufficient time for product commercialization. The combined use of nisin and Microgard? proved to be more effective than the individual application on these microbial groups, resulting in a 13 days shelf life extension. Additionally, the combined treatment reduced the growth of L. innocua as a post-process contamination.     

Effects of Soaking with Natural Additives in Combinations with Vacuum or Modified Atmosphere Packaging on Microbial Populations and Shelf Life of Fresh Truffles (Chinese Tuber Indicum)

The objective of this study was to evaluate the relative effects and interactions of combined soaking treatment using citric acid (CTA) and apple polyphenol (APP) at mild heating temperatures for the inactivation of the external and internal microflora (mesophilic aerobic bacteria, mesophilic anaerobic bacteria, and fungi) in Chinese Tuber indicum, as well as to analyze the microbiological and sensory changes under modified atmosphere packaging (MAP)‐ and vacuum atmosphere packaging (VAC)‐packed Chinese T. indicum stored at 4 °C for up to 55 d. Chinese T. indicum was soaked with CTA and APP alone or in combination for 10, 20, and 30 min at 35, 45, and 55 °C. A disinfection method using CTA and APP (3% CTA + 3% APP for 20 min at 45 °C) was obtained. Under this set of combination, the experimental values of microbial counts of mesophilic aerobic bacteria, mesophilic anaerobic bacteria, and fungi were 2.31 ± 0.4 log CFU/g, <1.0 log CFU/g, and <1.0 log CFU/g, respectively. Through the analysis of sensory qualities and microbial populations for MAP‐ or VAC‐packed Chinese T. indicum, the shelf life of soaked truffles was prolonged to 45 or 40 d, respectively. The synergistic effect of CTA and APP may provide valuable insight into the reduction of microorganisms on fresh truffles.     

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     

Effects of post-packaging pasteurization process on microbial,chemical, and sensory qualities of ready-to-eat cured vacuum-packed Turkey breast

Ready-to-eat (RTE) cured vacuum-packed turkey breast was pasteurized (80°C, 5.5 min) and stored at 8°C (like supermarkets refrigerator temperature). After 42 days (current shelf life of this product), in control group (RTE cured vacuum-packed turkey breast), the number of mesophilic, anaerobic, lactic acid bacteria, mold and yeast, coliform, and psychrotrophic increased 5.82, 6.85, 5.85, 4.75, 1.49, and 5.57 log CFU/g, respectively. However, in the pasteurized samples, the number of mesophilic, anaerobic, and lactic acid bacteria increased 1.86, 2.12, and 2.28 log CFU/g, respectively, and mold and yeast, coliform, and psychrotrophic bacteria were under the detection limit. The effects of post-packaging pasteurization on the reduction of total mesophilic, anaerobic and lactic acid bacteria counts on Day 42 of storage was 7.04 ± 0.33, 4.73 ± 0.11, and 5.58 ± 0.11 log CFU/g, respectively. Sensory quality of treated samples was significantly better than the control's (p < .05). Post-packaging pasteurization (PPP) significantly inhibited the reduction in the pH and the increase in TVB-N, TBARS, titratable acidity, and drip loss (p < .05). This study shows the effectiveness of PPP on microbial, chemical, and sensory quality of cured vacuum-packed turkey breast during cold storage.     

Use of natural compounds to improve the microbial stability of Amaranth-based homemade fresh pasta

A study on the use of natural antimicrobial compounds to improve the microbiological stability of refrigerated amaranth-based homemade fresh pasta is presented in this work. In particular, the antimicrobial activity of thymol, lemon extract, chitosan and grapefruit seed extract (GFSE) has been tested against mesophilic and psychrotrophic bacteria, total coliforms, Staphylococcus spp., yeasts and moulds. A sensory analysis on both fresh and cooked pasta was also run. Results suggest that chitosan and GFSE strongly increase the microbial acceptability limit of the investigated spoilage microorganisms, being the former the most effective. Thymol efficiently reduces the growth of mesophilic bacteria, psychrotrophic bacteria and Staphylococcus spp., whereas it does not affect, substantially, the growth cycle of total coliforms. Lemon extract is the less effective in preventing microbial growth. In fact, it is able to delay only total mesophilic and psychrotrophic bacterial evolution. From a sensorial point of view no significant differences were recorded between the control samples and all the types of loaded amaranth-based pasta.     

Microbiological stability and diversity in raw pre-peeled potatoes packed in different atmospheres

Microbial growth on raw pre-peeled potatoes was analysed in relation to different process and storage parameters. Raw peeled potatoes with or without tumbling were packed in vacuum or modified atmosphere (MA) and stored at 4 °C and 15 °C for 7 and 5 days, respectively. Microbial growth was analysed throughout the storage period and growth was observed for mesophilic and psychrotrophic bacteria, lactic acid bacteria, Pseudomonas spp., and coliform bacteria. Growth at 4 °C was significantly lower compared to 15 °C. The number of bacteria was after seven days significantly higher on tumbled potatoes stored at 4 °C than on the untumbled potatoes. The bacterial counts generally exceeded 10⁶ CFU/g on tumbled potatoes after 7 days at 4 °C and 5 days at 15 °C, respectively. The CO₂ content increased during the storage period. A total of 243 isolates were grouped according to ITS-PCR profiles. Of these 47% had similar band profiles and thereby constituted the dominating flora at the end of shelf life. The dominating flora, identified on the basis of sequencing and microbial analysis of a subset of isolates, belonged to Enterobacteriaceae and consisted mainly of Enterobacter spp. and Kluyvera spp.     

THE EFFECT OF PRETREATMENT OF SHREDDED CELERIAC USING SOLUTIONS OF ENZYMATIC BROWNING INHIBITORS ON THE QUALITY OF MINIMALLY PROCESSED PRODUCT

ABSTRACT

The study investigated the effect of soaking celeriac flakes in solutions containing various concentrations of enzymatic browning inhibitors on the quality of stored minimally processed product. Ascorbic acid (0.2–0.5%), 4‐hexylresorcinol (0.003–0.01%), sodium chloride (0.1–0.5%) and sodium lactate (2–3%) were used as browning inhibitors. On the basis of the conducted tests, it was found that among the applied browning inhibitors, only ascorbic acid had an advantageous effect on the quality of stored celeriac flakes. Along with an increase in its concentration in the solution (0.2–0.5%) used for the pretreatment of the flakes, the value of color parameter a* decreased, while the value of parameter b* increased. At the concentration of ascorbic acid in the solution exceeding 0.25%, flake color in the sensory examination was evaluated as desirable. An increase of ascorbic acid concentration in the solution in the range from 0.2 to 0.4% resulted in a decrease in the total mesophilic and psychrophilic bacteria counts, respectively, by 3 and 1 log cfu/g of the stored product.

PRACTICAL APPLICATIONS

Minimal processing of celeriac provides convenience for consumers and many economic benefits for producers. Minimal processing of celeriac can induce disadvantageous changes in tissue, which may lead to darkening of the flakes and deterioration of product sensory attributes. Moreover, shredded raw material constitutes an excellent medium for the development of microorganisms. This article contains information about the effectiveness of enzymatic browning inhibitors for extending the shelf life of celeriac flakes. We show a range of concentrations of inhibitors, which improve the preservation of color, intrinsic taste and microbial quality of minimally processed celeriac.

     

USE OF A CONTROLLED CHLORINE DIOXIDE (CLO2) RELEASE SYSTEM IN COMBINATION WITH MODIFIED ATMOSPHERE PACKAGING (MAP) TO CONTROL THE GROWTH OF PATHOGENS

ABSTRACT

Salmonella Typhimurium and Listeria monocytogenes are major bacterial pathogens associated with poultry products. A controlled released ClO₂ sachet applied with modified atmosphere packaging (MAP) was evaluated for its ability to control the growth of S. Typhimurium and L. monocytogenes on raw chicken breast during refrigerated storage. The fresh chicken samples were inoculated with one or the other of the pathogens at 10⁴ cfu/g, and the packages (with and without ClO₂ sachet) were flushed with ambient air or 30% CO₂/70% N₂ before sealing, and then stored at 4C for up to 21 days. The maximum reduction in MAP plus ClO₂ (compared with MAP alone) was 0.68 log cfu/g for S. Typhimurium and 1.87 log cfu/g for L. monocytogenes. Color and pH changes of the chicken breast were observed at 8 µg/h of ClO₂ during the storage period.

PRACTICAL APPLICATIONS

We think that the results of the study with the combined treatment of chlorine dioxide (ClO₂) and modified atmosphere packaging may enhance the effectiveness of antimicrobials, reduce the amount of agent needed, and decrease the risk of off‐flavors. The applications of the results will be useful for poultry industry to give the significant improvement in shelf life for packaged fresh products.     

Antioxidant and Antimicrobial Activity of Commercial Propolis Extract in Beef Patties

The objective of this study was to evaluate the efficacy of propolis extract (PE) to reduce lipid oxidation and microbial growth on beef patties during refrigerated storage. Beef patties were manufactured by incorporating PE in 4 different treatments: (1) Control (no PE addition); (2) commercial propolis 1 (2% w/w; CP1); (3) commercial propolis 2 (2% w/w; CP2); and (4) noncommercial propolis (2% w/w; NCP). Raw patties were wrapped with polyvinyl chloride and stored at 2 °C for 8 d. Total phenolic content (TPC), free‐radical scavenging activity (FRS), and polyphenolic content of the PE were evaluated using high‐performance liquid chromatography (HPLC). Lipid oxidation (thiobarbituric acid‐reactive substances (TBARS), conjugated dienes (CnDs), metmyoglobin (MetMb%), pH variation, and color (L*, a*, b*, C*, and h*), and microbial growth (mesophilic and psychrotrophic bacteria) of patty samples were measured. NCP treatment demonstrated the highest FRS (64.8% at 100 μg/mL), which correlated with TPC and the presence of polyphenolic compounds. Lipid oxidation (78.54%, TBARS; 45.53%, CnD; 58.57%, MetMb) and microbial mesophilic and psychrotrophic growth (19.75 and 27.03%, respectively) values were reduced by NCP treatment in refrigerated samples after 8 d. These results indicate that PE has great potential as a natural antioxidant and antimicrobial additive to extend the shelf life of beef patties.     

Use of chitosan,honey and pineapple juice as filling liquids for increasing the microbiological shelf life of a fruit‐based salad

The activity of some natural compounds for extending the storage life of fresh‐cut fruits was examined. In particular, the effect of chitosan, honey and pineapple juice used as filling solution on the growth of mesophilic bacteria, psychrotrophic bacteria, lactic acid bacteria and yeasts, in fruit‐based salads stored at 4 °C, 8 °C and 12 °C was investigated. Honey showed the greatest antibacterial effect on mesophilic and psychrotrophic bacteria, with non significant effects on lactic acid bacteria and yeasts. The antimicrobial activity of chitosan affected the growth of all microbial groups considered (mesophilic and psychrotrophic bacteria, lactic acid bacteria and yeast), particularly, in conditions of refrigerated storage. In contrast, no difference in the growth of monitored microorganisms between samples containing pineapple juice and control was detected.     

Modified Atmosphere Packaging and UV-C Radiation on Shelf Life of Rainbow Trout (Oncorhynchus Mykiss)

Effects of modified atmosphere packaging (MAP) in combination to UV-C radiation on rainbow trout fillets were examined. The samples were submitted to two treatments: (T1) aerobic package; (T2) MAP+UV-C radiation (80% CO₂/20% N_2; 106.32mJ/cm²) and were analyzed daily for microbiological (mesophilic and psychrotrophic count) and chemical (biogenic amines) parameters. MAP+UV-C radiation (T2) promoted lag phase formation and lower number of colonies in the stationary phase as well as retarded cadaverine production during storage time. MAP+UV-C radiation retard microbial growth and delay chemical changes enhancing the shelf life of rainbow trout fillets by at least twice.     

Modeling Microbial Spoilage and Quality of Gilthead Seabream Fillets: Combined Effect of Osmotic Pretreatment,Modified Atmosphere Packaging,and Nisin on Shelf Life

ABSTRACT: The objective of the study was the kinetic modeling of the effect of storage temperature on the quality and shelf life of chilled fish, modified atmosphere-packed (MAP), and osmotically pretreated with the addition of nisin as antimicrobial agent. Fresh gilthead seabream (Sparus aurata) fillets were osmotically treated with 50% high dextrose equivalent maltodextrin (DE 47) plus 5% NaCl. Water loss, solid gain, salt content, and water activity were monitored throughout treatment and treatment conditions were selected for the shelf life study. Untreated and osmotically pretreated slices with and without nisin (2 × 10⁴ IU/100 g osmotic solution), packed in air or modified atmosphere (50% CO₂–50% air), and stored at controlled isothermal conditions (0, 5, 10, and 15 °C) were studied. Quality assessment and modeling were based on growth of several microbial indices, total volatile nitrogen, trimethylamine nitrogen, lipid oxidation (TBARS), and sensory scoring. Temperature dependence of quality loss rates was modeled by the Arrhenius equation, validated under dynamic conditions. Pretreated samples showed improved quality stability during subsequent refrigerated storage, in terms of microbial growth, chemical changes, and organoleptic degradation. Osmotic pretreatment with the addition of nisin in combination with MAP was the most effective treatment resulting in significant shelf life extension of gilthead seabream fillets (48 days compared to 10 days for the control at 0 °C).