The use of nisin as a preservative in fish sausage stored at ambient (28 ± 2 °C) and refrigerated (6 ± 2 °C) temperatures

Summary The efficacy of nisin at three different concentrations, 12.5, 25 and 50 ppm, on the keeping quality of fish sausage in synthetic casing at ambient (28 ± 2 °C) and refrigerated (6 ± 2 °C) temperatures was assessed. Gel strength, expressible water content, total volatile base nitrogen, total plate count and aerobic spore counts were affected by the storage temperatures and nisin concentrations used. Fish sausage treated with 50 ppm of nisin was acceptable after storage at ambient temperature for 20–22 days compared with the control, which were acceptable only for 2 days. The keeping quality of the sausages, at refrigerated temperature, varied from 30 days in the control to 150 days in 50‐ppm nisin‐treated samples. The residual nisin decreased slowly in samples stored at refrigerated temperature, whereas, in fish sausages stored at ambient temperature, the decrease was rapid. Nisin at 50‐ppm level showed a significant effect (P ≤ 0.05) on the gel strength and overall acceptability scores both at ambient and refrigerated temperature.     

Evaluation of changes during storage of probiotic dahi at 7°C

Low-fat probiotic dahi (an Indian traditional fermented milk product like yogurt) prepared with lactococci starter and two adjunct probiotic cultures of Lactobacillus acidophilus and Lactobacillus casei was stored at 7°C. The survival of bacterial species was affected during storage of dahi, in which viable counts increased up to 2 days and gradually decreased from 2 days, up to 8 days. The quality of refrigerated dahi was assessed by a panel of trained judges. On storage, pH significantly decreased over storage time, indicating that the dahi samples did not develop much acidity under the storage conditions of the study. However, after 8 days of storage, the samples were disliked by the panel, which reported slight bitterness, which may have been due to proteolysis. Proteolysis increased during storage. More α_s1-casein was degraded than β-casein. On the basis of the results of this study we can conclude that dahi stored up to 8 days may be acceptable to consumers.     

Comparison of quality and shelf life of buffalo meat patties stored at refrigeration temperature

Scientific investigation on the quality changes of processed meat products will boost and sustain the meat production and utilization in buffalo abundant countries. A programme was undertaken to compare the quality of buffalo meat patties made from intensively reared young male, semi extensively reared spent male and female groups and stored at refrigeration temperature (4 ± 1 °C). Buffalo meat patties were evaluated for shelf life attributes by analysing the changes in physicochemical, microbiological and sensory attributes. The overall acceptability of patties was better in spent buffalo group than young male group. Increasing storage time resulted in significantly higher pH, TBARS, total aerobic mesophils, coliforms, Staphylococcus aureus and psychrophilic counts but decreased appearance, flavour, juiciness, tenderness, connective tissue residue and overall acceptability scores of buffalo meat patties. The patties were well acceptable within 20 days in young male group and 25 days in spent buffalo group respectively during refrigerator storage.     

Effect of storage at 0 °C on mantle proteins and functional properties of jumbo squid

Effect of iced storage of jumbo squid mantle with fin on gelling capacity and changes in protein fractions and functional properties of jumbo squid mantle protein during storage at 0 °C were assessed. Most values of texture variables in gels did not significantly change during storage. On average, they were: strength 65.07 ± 4.71 N; elasticity 68.14 ± 5.3%, fracturability 52.97 ± 1.28 N and cohesiveness 36.6 ± 0.1%. Protein solubility increased more than 40%. Whippability increased during storage for 16 days at 0 °C (81–162%), as did foam stability (73–94%). Results suggest that iced squid mantle protein is a suitable ingredient for food products where these functional properties are desirable. Muscle fibres of squid mantle undergo various changes during storage. At 0 °C, they are disrupted, whereas at −20 °C, they aggregate and develop empty spaces in the tissue.     

Quality changes in frozen whole and gutted anchovies during storage at −18°C

Fresh samples of whole and gutted anchovies were blast frozen at −35°C and stored at −18°C. The quality of the samples was examined as organoleptic, microbiological and chemical changes during the storage period. Gutting had no significant effect on the quality of the final product. Sensory quality was good for up to 90 days of storage. No increase in microbial activity was detected, but some oxidative and hydrolytic deterioration of fats were observed. The final product was still edible after 180 days.     

Effect of marinating process on the microbiological quality of Pacific saury (Cololabis saira) during vacuum-packaged storage at 4 °C

This study was carried out to evaluate the microbiological quality of Pacific saury ( Cololabis saira ) treated with marinating solutions containing either 12% NaCl + 2% acetic acid or 12% NaCl + 3% acetic acid, followed by vacuum packaging and storage at 4 °C for 90 days. The fish-to-marinating-solution ratio was 1:1.5. The growth rate of aerobic, halophilic, lactic acid bacteria and Pseudomonas spp. were significantly ( P  < 0.05) reduced in marinated vs. brined (12% NaCl + 0% acetic acid) fillets. Complete inhibition in the growth of both Enterobacteriaceae and Staphylococcus aureus was detected in fillets marinated in 3% and 2% acetic acid by the days 30 and 50 of storage, respectively. Both marinating conditions resulted in shelf life extension of the product to more than 90 vs. 60 days only for the brined fillets. Listeria monocytogenes , Vibrio parahaemolyticus and Salmonella spp. could not be detected in any of the analysed raw or treated samples.     

Microbial flora of technological interest in raw ovine milk during 6°C storage

Changes in the microbial flora of ovine milk of medium hygienic quality (initial mean total plate count 3.3  ×  10⁵ cfu/mL) were studied throughout refrigerated storage at 6°C. Total plate counts after 48 h of refrigerated storage (mean count 4.6  ×  10⁵ cfu/mL) were under the current standards in the European Union (EU) for raw ovine milk to be used for cheesemaking after heat treatment. However, after 96 h, mean total plate counts (1.6  ×  10⁷ cfu/mL) were above the standards. Lactococci were found at levels higher than Pseudomonas spp. in milk freshly drawn (54.5% and 3.5% of total plate count, respectively) and after 96 h at 6°C (47.9% and 33.9% of total plate count, respectively). Lactobacilli, enterococci, coliforms and thermodurics were found at values lower than lactococci and Pseudomonas spp., before and after refrigerated storage ( ≤  0.08% of the total plate count). A significant growth ( P  < 0.001) was detected for mesophiles, Pseudomonas spp. and lactococci after 96 h of refrigeration at 6°C; however, thermodurics, coliforms, lactobacilli and enterococci, showed no significant increase ( P  > 0.05). Presumptive Escherichia coli (β-glucuronidase-positive) underwent a decrease throughout storage at 6°C.     

QUALITATIVE AND QUANTITATIVE CHANGES IN AEROBIC MICROFLORA FROM INTESTINAL CONTENTS OF SOUTH-BALTIC COD DURING STORAGE AT 1-2°C

SUMMARY— The bacterial flora of the intestinal content of cod (Gedus morrhua L) were investigated during a period of 1 year. The quantity of bacteria in recently caught fish was studied during the full period. the quality during only 6 months. 3 groups of fish from the same capture and fishing grounds were analyzed: fresh, and stored at 1–2°C for 5 and 10 days. It was seen that in general gram-positive bacterial flora dominated in recently caught fish, while after 5 and 10 days of storage gram-negative flora our numbered the former. In the intestinal contents of fresh fish the Vibrio species dominated, whereas at storage, Pseudomonas spp. became dominant. In fresh fish, the bacterial flora of stored fish amounted to 3.10% of the total initial quantity after 5 days of storage and 1.5% after 10 days. Also, the gram-positive flora decreased comparatively more rapidly than gram-negative flora. The authors believe that the temperature of 1–27°C may play a part in the decreasing number of flora, as well as some other factors not investigated in the present research.     

Biogenic amines formation in Atlantic herring (Clupea harengus) stored under modified atmosphere packaging using a rapid HPLC method

A rapid high-performance liquid chromatographic (HPLC) method for the determination of nine biogenic amines and trimethylamine (TMA) was developed. A derivatization procedure is reported. It involves dissolving benzoyl chloride in acetonitrile to enhance its reaction with biogenic amines. This was compared with benzoyl chloride dissolved in methanol and with only benzoyl chloride to find the optimal condition for benzoylation of biogenic amines in terms of time and derivatization conditions. A gradient elution system was used for analysis with a mixture of acetonitrile and HPLC grade water and took less than 7 min to complete the analysis. The application of this method to detect biogenic amines in herring stored at 2 ± 2 °C and in modified atmosphere packing (MAP) was investigated. The concentrations of amines in herring held at 2 ± 2 °C increased more rapidly than herring stored in MAP. The level of TMA in herring held at 2 ± 2 °C was higher than herring stored in MAP. No significant differences were found in histamine concentrations between herring stored at 2 ± 2 °C and in MAP during the early stages of storage period but there was a significant difference ( P  < 0.05) after 6 days of storage. Significant differences were found ( P  < 0.05) in concentrations of putrescine (after 6 days) and cadaverine (after 4 days) between herring held at 2 ± 2 °C and in MAP.     

Microbiological, physicochemical and organoleptic changes in dry-salted olives of Thassos variety stored under different modified atmospheres at 4 and 20 °C

Microbiological, physico-chemical and organoleptic changes were studied in dry-salted olives, cv. Thassos, stored under different atmospheres (100% carbon dioxide and nitrogen, 40% CO₂/30%O₂/30%N₂ and air) at 4 and 20 °C for 180 days. The initial microbial flora comprised of yeasts, no lactic acid bacteria, enterobacteria, pseudomonads or Staphylococcus aureus were detected, as the low water activity/high salt content does not favour their growth. At 4 °C, the population of yeasts declined steadily throughout storage but to a different extent depending on the gaseous atmospheres. At 20 °C, there was an initial decline in yeast counts in all samples followed by a steady increase until the end of the storage period. The CO₂ atmosphere was most effective at keeping the number of yeasts low at both storage temperatures. All gas atmospheres prevented fungal growth at both temperatures apart from the samples stored in air. The pH, a_w and salt content of the olives did not change significantly throughout the storage period. The prevailing yeast species was the salt tolerant Candida famata . The organoleptic characteristics did not differ significantly among differently treated olives. However, increased rancidity and reduced fruit colour was observed in the samples stored at 20 °C.     

Effect of packaging and frozen storage temperature on beef pigments

The influence of final freezing and storage temperature on pigment modifications of beef samples wrapped in polyethylene and EVA/SARAN/EVA was analysed. Met-, oxy- and myoglobin relative surface concentrations were determined using reflectance spectrophotometry. Pigment behaviour during storage of beef packaged in both films and oxygenation of vacuum-packaged samples was described by different reaction schemes and modelled to obtain kinetic and equilibrium constants. Comparative studies performed with beef samples (a) refrigerated, (b) frozen to –5°C and stored at this temperature (partial freezing), and (c) frozen to -25°C and stored at -5 and -20°C, indicated that for aerobic storage periods of 90 days, metmyoglobin levels of partially frozen samples upon thawing were comparable to those of frozen samples stored at –20°C. For vacuum-packaged beef, pigment concentrations remained practically constant during frozen storage; partial freezing increased oxygenation capacity of the tissue compared with chilled and frozen conditions.     

QUALITY OF NUGGETS PREPARED FROM FRESH AND SMOKED SPENT LAYER CHICKEN MEAT

Nuggets were prepared from fresh and smoked meats of spent layer chicken of age approximately 18 months, packed in polyethylene bags and stored at -18 ± 2C for 6 months. Thawed nuggets were fried on hot pan coated with refined sunflower oil and product quality was evaluated. Nuggets from smoked chicken had lower (P ± 0.05) moisture and higher fat contents and lower weight loss on frying compared to fresh meat nuggets. Free fatty acid (FFA expressed as percent of oleic acid) increased from 3.6 to 3.9 and 3.2 to 3.7, and thiobarbituric acid (TBA) values (mg malonaldehyde/kg sample) increased from 0.90 to 1.19 and 0.63 to 0.71 for fresh and smoked meat nuggets, respectively, during frozen storage for 6 months. Shrinkage in product diameter on frying ranged from 4.6 to 5.0%. Warner-Bratzler shear values ranged from 0.89 to 1.28 lbs for all products stored frozen up to 6 months. Sensory quality scores for smoked meat nuggets were significantly (P ± 0.05) higher, except for juiciness (P ≥ 0.05), than for fresh meat nuggets. Smoked chicken meat produced better nugget products compared to fresh meat as indicated by lower FFA and TBA values and better sensory quality attributes. Products packed in polyethylene bags can be stored at -18 ≥ 2C for up to 6 months without marked deterioration in product quality.     

PREPARATION AND STORAGE PROPERTIES OF DRUM DRIED WHITE YAM (Dioscorea rotundata Poir) FLAKES

The white yam Dioscorea rotundata Poir was characterized, drum dried to different moisture levels, and stored at temperatures of 21.l °C, 29.4 °C and 37.8 °C for 90 days. Fresh and stored samples were analyzed for changes in color, ascorbic acid and organoleptic qualities. Freshly dried and reconstituted yam flakes were judged highly acceptable compared to conventionally mashed fresh yam and retained acceptability through storage. The taste panel consisted of persons from several West African countries. Changes in the flakes during storage are described.     

MICROBIOLOGICAL, SENSORY AND COLOR CHANGES OF ANCHOVY (ENGRAULIS ENCRASICHOLUS) PATTIES DURING REFRIGERATED STORAGE

In this study, the microbiological, sensory and color changes of anchovy patties during refrigerated storage were investigated. Total viable bacteria and psychrotrophic bacteria counts increased, and sensory scores decreased during the storage period. Total bacteria count exceeded the critical limit of 10⁶   cfu/g on day 5. Yeast–molds, Staphylococcus aureus and Escherichia coli were not detected during the storage period. L*, a* and b* values of anchovy patties were changed from 36.8  ±  1.2, 4.67  ±  1.00, 13.0  ±  2.12 to 35.3  ±  3.8, 4.20  ±  0.89, 14.12  ±  2.76, respectively, on day 5. Up to day 4, anchovy patties were determined as "acceptable," but on day 5, they were no longer acceptable according to the results of microbiological and sensory analysis.

PRACTICAL APPLICATIONS

Anchovy is very suitable for patties because of their flavor and taste. In recent years, the increasing numbers of working women of the population have led to direct consumer's preference to ready-to-eat fish foods. For this purpose, anchovy patties were made, and microbiological, sensory and color changes of anchovy patties during refrigerated storage were investigated. The other discarded fish species can be used for making fish patties. The variety of fish patties can be increased and discarded fish can be evaluated on this way.     

Application of competitive indirect enzyme-linked immunosorbent assay (Ci-ELISA) for monitoring the degree of frozen denaturation of bovine myosin

The denaturation of myosin on freezing and frozen storage was monitored using competitive indirect enzyme-linked immunosorbent assay (Ci-ELISA) formatted with polyclonal antibodies anti-MWM IgG, anti-S-1 IgG and anti-LMM IgG raised against the antigens (Ags) bovine myosin whole molecules (MWMs), heavy meromyosin S-1 (myosin head part, S-1) and light meromyosin (myosin tail part, LMM) respectively. Beef slices and cuts stored at −20 °C or −50 °C lost immune affinity with all antibodies, in particular anti-LMM IgG. Repeated thawing–refreezing treatment caused more myosin denaturation than simple freezing. Myosin from beef stored at −20 °C was denatured more than that stored at −50 °C. The immune affinities between anti-LMM IgG and thawed samples were similar to those from anti-MWM IgG. We were unable to differentiate reliably between fresh and thawed beef using anti-S-1 IgG. Myosin was denatured by freezing, in particular its tail part (LMM).     

Microbiological quality of sous-vide cook chill fish cakes during chilled storage (3 °C)

Fish cakes prepared from emperorbream ( Lethrinus lethrinus ) were vacuum packed (VP), conventionally cook-chilled (CCC) and sous-vide cook-chilled (SVCC) and examined for their microbiological quality and safety during chilled storage (3 °C) for a period of 3, 5 and 16 weeks, respectively, in comparison with conventional pack(CP). The shelf life of CP, VP, CCC and SVCC packs of fish cakes were 2, 2, 4 and 16 weeks, respectively, based on the acceptable break point of the overall sensory scores. The total bacterial counts were 5 log cfu g⁻¹, in CP, VP and CCC packs; and 3 log cfug⁻¹ in SVCC pack on sixteenth week. Total lactic acid bacteria were 2 log cfu g⁻¹ on 2 and 3 weeks in CP and VP, respectively. Staphylococci were detected in all packs on sixteenth week at 2 log cfu g⁻¹. Total bacilli were detected in CP and VP at 3 log cfu g⁻¹ level after 2 weeks. Aeromonads were detected after 1, 2 and 4 weeks in CP, VP and CCC packs at 3 log cfu g⁻¹. Total anaerobic sulphite-reducing clostridia were detected only in CP and CCC packs at 3 MPN counts g⁻¹ level on the final day.     

EFFECT OF SODIUM ALGINATE COATING WITH PRESERVATIVES ON THE QUALITY OF MEAT PATTIES DURING REFRIGERATED (4 ± 1C) STORAGE

Edible coatings are the substances that are used to preserve and enhance food quality. An attempt was made to improve the quality of buffalo meat patties (BMPs) by method of alginate coating involving dipping BMPs during the end of the broiling process in alginate solution with preservatives for 30 s, followed by dipping in calcium chloride solution for 30 s, followed by draining for 30 s. The coated BMPs were kept at refrigeration (4  ±  1C) temperature in a polyethylene bag. They were analyzed for quality changes at regular intervals. Alginate coating significantly ( P ≤  0.05) decreased the overall shear force values, thiobarbituric acid and tyrosine value, total plate count, psychrophilic count, and yeast and mold count. The enterobacteriaceae count could not be detected. The coating at 2% level significantly ( P ≤  0.05) improved the overall appearance and color, juiciness, flavor, texture and overall palatability of the product. During storage, the overall values for shear force, TBA, pH, tyrosine and count for total plate, psychrophilic, yeast and mold, and staphylococcal, increased linearly. The overall sensory scores of the products decreased linearly with storage time.

PRACTICAL APPLICATIONS

Edible coating of meat products provides better protection against oxidative and microbiological deterioration. It can also significantly enhance the sensory qualities of meat products. The freshness of meat products is comparatively prolonged.     

Descriptive Profile Analysis of Cooked, Stored, and Reheated Chicken Patties

A trained panel evaluated off-flavor development in precooked, stored and reheated chicken patties. Factor analysis of intensity scores on 12 sensory attributes yielded three factors. Calculated Factor I scores increased with storage time and predominantly characterized cooked samples stored 2 and 3 days. Factors II and III characterized fresh cooked product and cooked product stored 0 or 1 day. Canonical Discriminant Analysis (CDA) revealed a spatial configuration that classified storage times according to attribute subsets corresponding to Factor scores. The second and third canonical variables classified samples stored 0 and 1 day differently from other stored samples and probably represented flavor characteristics which were important indicators of flavor change occurring within 24 hours of refrigerated storage.     

不同贮藏方式对高压鸡汤品质的影响及货架期预测模型的建立

研究冷藏、微冻和冻藏3 种贮藏方式对高压鸡汤感官品质、pH值、L*（亮度）、b*（黄度）、Y总（浊度）、总挥发性盐基氮（total volatile basic nitrogen,TVB-N）值、硫代巴比妥酸反应物（thiobarbituric acid-reactivesubstance,TBARS）值以及菌落总数（total viable count,TVC）的影响,并建立了高压鸡汤货架期预测动力学模型。结果表明：随着贮藏时间的延长,冷藏、微冻和冻藏鸡汤的感官评分、pH值均呈现逐渐下降趋势,而TVB-N值、TBARS值和TVC的变化趋势则与之相反。其中冷藏因贮藏温度较高较另两种方式变化显著（P＜0.05）。此外,鸡汤的L*、b*和Y总在贮藏期间没有呈现一定的规律性变化。结合一级化学反应动力学方程和Arrhenius方程建立了高压鸡汤TBARS贮藏动力学预测模型,验证结果显示,利用此模型得到的鸡汤货架寿命预测值与实际值相对误差低于10%,说明模型可靠,在此基础上得出－2.5 ℃和－18 ℃贮藏温度条件下高压鸡汤的货架期预测值分别为136 d和258 d,较4 ℃冷藏分别延长了55 d和177 d,可为营养汤品的安全贮藏提供一定的理论指导。与其他2 种方式相比,微冻保藏产品品质好,货架期长,成本低,可能会成为营养汤品未来工业化生产贮存和超市销售存放的较佳途径。     

Walleye Pollock (Theragra chalcogramma): Changes in Quality When Held in Ice, Slush-ice, Refrigerated Seawater, and CO2-Modified Refrigerated Seawater Then Stored as Blocks of Fillets at - 18°C

Walleye pollock were held in ice, slush-ice, refrigerated seawater (RSW) and CO₂-modified RSW (MRSW) for up to 8 days, filleted and stored as blocks of fillets at -18°C. Good quality fillets were obtained from pollock held for 4 days in all systems. Uptake of salt presented a problem for pollock held more than 4 days in RSW at 1°C. Flavor scores remained essentially unchanged during frozen storage but nearly all samples became slightly tougher and slightly drier at 6 months. Freshness at time of freezing did not affect frozen storage characteristics. Protein functionality was generally adversely affected when fish were held in RSW or MRSW.