Microbial and sensory changes during refrigerated storage of desalted cod (Gadus morhua) preserved by combined methods

Water blanching and the use of additives (potassium sorbate and citric acid) combined with different types of packaging (air, vacuum "VP" and modified atmosphere packaging "MAP": 60% CO(2), 30% N(2) and 10% O(2)), were studied as new methods of preservation of chilled desalted cod. Microbial counts and total volatile basic nitrogen (TVB-N) analyses were carried out during a period of 42 days on all samples stored at 4 degrees C. No Aeromonas or sulphite-reducing Clostridium were isolated from any of the analysed samples. The lowest microbial counts of mesophilic, psychrotrophic, Pseudomonas, moulds and yeasts, were found in samples with additives in all kinds of packaging. These samples in VP or MAP maintained an excellent microbial quality throughout the 42 days of storage, with mesophilic and psychrotrophic counts always below 4 log CFU/g. Counts of the four microorganisms above-mentioned in blanched samples packaged with air, exceeded 5 log CFU/g on days 21-28, so it became necessary to use VP or MAP to maintain these microorganisms at an acceptable level for the entire storage period. TVB-N contents were low in samples with additives, regardless of the kind of packaging, as well as in blanched samples packaged in VP and MAP, never reaching 25 mg/100 g. Since there were no significant differences either in microbial growth or in TVB-N between samples in VP and MAP, a sensory analysis was performed only in desalted cod submitted to the two treatments (blanching and additives) combined with VP, both in raw and cooked samples. The results of this analysis showed that the addition of potassium sorbate and citric acid did not alter the typical organoleptic features of desalted cod. The sensory characteristics of both blanched samples and those with additives in VP showed no change during the period of the study.     

Control of Microbial Spoilage on Fresh Poultry using a Combination Potassium Sorbate/Carbon Dioxide Packaging System

The effects of potassium sorbate combined with vacuum or carbon dioxide modified atmosphere packaging on natural poultry spoilage flora were examined. Fresh chicken thighs were dipped into either 2.5% potassium sorbate solution or distilled water, adjusted to pH 6.0 and packaged on trays in Nylon/Plexar/Surlyn bags. Atmospheres of either air, vacuum or 100% C0₂ were created in the packages which were then stored at 10 ± 1°C for 10 days. Changes in aerobic plate counts, lactic acid bacteria and pseudomonads were monitored. The combination of CO₂ packaging and sorbate treatment provided the most effective inhibitory system against the poultry spoilage organisms, especially Pseudomonas species, without creating a selective environment for the growth of lactic acid bacteria and premature souring of the product. The shelf life of the sorbate/CO₂ samples was extended 3 days over the control/air samples at 10°C.     

Influence of different preservation treatments on the volatile fraction of desalted cod

In the present study, desalted cod underwent a water blanching treatment and the incorporation of additives (citric acid and potassium sorbate), combined with different types of packaging (air, vacuum and modified atmosphere), to achieve an improvement of the shelf life of ready-to-use desalted cod. The purpose of this work was to evaluate the effect of these combined methods of preservation on the volatile fraction of desalted cod during 42 days in cold storage. The volatile compounds identified in all samples were those mainly related to fresh odor in whitefish, although with some exceptions. Untreated desalted cod showed a high increase of 3-methyl-1-butanol (described as a microbial spoilage index) during the storage period; a higher increase in air packaging than in vacuum and modified atmosphere packaging. The slow increase of this compound, as well as the evolution of ketones and aldehydes observed for the rest of the samples submitted to treatment, demonstrated the effectiveness of the combined treatments applied. The most efficient treatment was the combination of additives together with modified atmosphere packaging.     

Prediction of the Mould-Free Shelf Life of Muffins

In this article, the effect of commonly used ingredients in muffins (sugar, glycerol, potassium sorbate, acidic agent, salt), with and without ethanol surface spraying and pasteurization on the shelf life, was examined. Citric acid, sodium diacetate, and tartaric acid were used as acidic agents. The investigation was based on a statistical design of experiments. Using simple first order factorial designs, reliable models were constructed revealing the effects of the selected ingredients, and their interactions on the shelf life. The effectiveness of preservation ranked high to low as: (combination of citric acid, potassium sorbate, ethanol, and pasteurization), (combination of citric acid, potassium sorbate, and ethanol), (combination of citric acid and potassium sorbate), (combination of sodium diacetate and potassium sorbate), (combination of tartaric acid and potassium sorbate).     

Storage of Morwong (Nemadactylus macropterus Bloch and Schneider) in Combinations of Polyphosphate, Potassium Sorbate and Carbon Dioxide at 4o C

Combinations of potassium sorbate and polyphosphate, in conjunction with vacuum or modified atmosphere packaging, were assessed for their preservative effects on morwong fillets (pH 6.75) stored at 4°C. Vacuum packaged and/or frozen fillets were used as comparisons for microbiological and taste panel analysis. A combination of potassium sorbate, polyphosphate and 100% CO₂ was the most effective packaging regime. Potassium sorbate on vacuum packaged fish was more effective than a 100% CO₂ atmosphere alone. Polyphosphate had no apparent additional effect on fillets stored under vacuum with or without potassium sorbate.     

INFLUENCE OF VACUUM PACKAGING AND ORGANIC ACID TREATMENT ON THE CHILLED SHELF LIFE OF PEARL SPOT (ETROPLUS SURATENSIS, BLOCH 1790)

The present work was carried out to study the effect of vacuum packaging and organic acids drip treatment, namely, sodium acetate and potassium sorbate (2%), on the quality of pearl spot during chilled storage (1–2C). Changes in pH, drip loss, water-holding capacity, total volatile base nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), total plate counts, instrumental texture properties and sensory characteristics were investigated up to 18 days. Sensory evaluation revealed that the potassium sorbate- and sodium acetate-treated vacuum-packaged samples had good sensory characteristics up to 16 days compared with 7 days in control air packs (CAPs) and control vacuum packs (CVPs). The sensory shelf life followed the following order: CAP  <  CVP  <  sodium acetate-treated vacuum pack  <  potassium sorbate-treated vacuum pack. Chemical analysis demonstrated a significant ( P   <  0.05) reduction in TVB-N, TMA-N and total plate counts, and better textural properties in potassium sorbate- and sodium acetate-treated vacuum-packaged fishes than CAPs and CVPs.

PRACTICAL APPLICATIONS

Limited shelf life is one of the major problems the seafood industry faces today. The study compares the effect of vacuum packaging in combination with preservative chemical treatment on the shelf life of pearl spot. The study indicates that the use of chemical preservative treatments such as sodium acetate and potassium sorbate at 2% level, together with vacuum packaging, helps in extending the shelf life of pearl spot to 16 days compared with 7 days in control air packs and control vacuum packs. Hence, vacuum packaging, together with preservative treatment, is very effective in shelf-life extension compared with vacuum packaging alone.     

Mathematical Modeling of Microbial Growth in Packaged Refrigerated Orange Juice Treated with Chemical Preservatives

ABSTRACT Microbial flora of refrigerated orange juice was analyzed during storage at 10 °C and the effects of the following factors were discussed: 1) the previous washing process of the orange peel, 2) the different levels of the added preservatives (citric acid, ascorbic acid, potassium sorbate, sodium benzoate), 3) the gaseous permeabilities of the packaging film. Gompertz equation was applied to model molds and yeasts growth for the different treatments and packaging conditions. The washing procedure with sodium hypochlorite extend 2–3 d the storage life of the juice (time to reach microbial counts of 10⁶ CFU/ml) in both packaging films. The use of organic acids and potassium sorbate or sodium benzoate (1.66–6.94 mM) led to storage life values > 11 d in polyethylene and > 20 d in the low gaseous permeability film, maintaining good sanitary conditions.     

SHELF-LIFE EXTENSION OF TILAPIA IN CRUSHED ICE WITH ADDITIVES AT −3C

Thirty-six experiments were carried out with potassium sorbate, citric acid and ascorbic acid at 0, 0.1, 0.15 and 0.2% in separate and mixed forms added to water to produce ice for storing tilapia at −3C for 15 days. Every three days chemical indicators trimethylamine and hypoxanthine as well as psychrotrophic bacteria counts were determined.
Fish stored in crushed ice with additives have markedly lower changes in trimethylamine and hypoxanthine with storage compared to iced controls. By linear regression analysis of 36 treatments, the following six treatments were best: 0.2% ascorbic acid, 0.15 or 0.2% citric acid, and 0.1, 0.15 and 0.2% potassium sorbate. These six treatments were not statistically different due to trimethylamine, hypoxanthine content nor due to psychrotrophic bacteria growth during storage. Probably, the treatment with the lowest concentration of citric acid (0.15%) and potassium sorbate (0.1%) should be considered as the best.     

鲜切青笋防腐保鲜工艺的优化及不同包装材料对其品质的影响

为了研究不同防腐剂和不同包装材料对鲜切青笋防腐保鲜的效果,并延长其贮藏时间,通过预试验选择山梨酸钾、纳他霉素、柠檬酸为有效合适的防腐剂,按照L9(34)正交试验制作不同配比的防腐保鲜复合液,以鲜切青笋在贮藏过程中的细菌总数、失重率及硬度为测定指标,最终以综合评分确定最佳复合液配比。结果表明:防腐保鲜液的最佳配比为0.02%纳他霉素+2.0%柠檬酸+0.04%山梨酸钾。以普通塑料薄膜保鲜袋作对照,研究不同规格(0.07 mm、0.08 mm、0.09 mm)透气性的双向拉伸尼龙(BOPA)与低密度聚乙烯(LDPE)复合包装袋对鲜切青笋包装储藏期间的失重率、维生素C的含量、硬度的影响,并选择最佳的包装材料。结果表明:0.07 mm规格的复合材料包装鲜切青笋效果最佳。     

Survival of Anisakis larvae in marinated herring fillets

The survival of Anisakis sp. larvae in herring fillets marinated in brines with different concentrations of salt (NaCl) and acetic acid was examined. Traditional German and Danish procedures for marinating herring fillets require a storage time of at least 5 and 6 weeks, respectively, for all larvae to be killed. Other concentrations of salt and acetic acid were also studied. A reduction of the salt content in the water phase of the fish tissue from 9% (w/w) to 4.3% (w/w), while keeping the concentration of acetic acid constant at 2.6%, increased the survival time of the nematodes from at least 35 days to more than 119 days. Increases in the acetic acid concentration or the addition of potassium sorbate had little or no effect on the viability of the larvae.     

安庆地区5个高产蓝莓品种花青素稳定性研究

目的 考察安庆地区5个高产蓝莓品种（奥尼尔、灿烂、海岸、巴尔德温、密斯蒂）花青素加工稳定性。方法 以花青素保存率为评价指标,分别研究了环境因素（pH、光照、温度）和添加物（金属离子、氧化剂、还原剂、蔗糖、食盐、柠檬酸、山梨酸钾）对5个品种蓝莓花青素稳定性的影响。结果 5个品种蓝莓花青素对pH、光照和高温比较敏感;Zn2+、蔗糖、柠檬酸、山梨酸钾能增强花青素稳定性;花青素与Cu2+、Ca2+共存超过5天,降解速度加快;Fe3+、H2O2、Na?SO?和浓度高于5%的食盐能破坏花青素的稳定性。结论 奥尼尔蓝莓花青素稳定性最弱,巴尔德温中花青素稳定性最强。研究结果能为蓝莓及花青素产品生产提供参考。     

Effects of Vacuum Packaging and Potassium Sorbate on Yield, Yeast and Mold Growth, and Quality of Dry-Cured Hams

Two trials were conducted. In the first trial hams were cured by a standard process and aged 1 month at 24°C. Group I hams were not packaged or treated. Group II hams were vacuum packaged and Group III hams were dipped in a 2.5% potassium sorbate solution and also vacuum packaged. All hams were examined after 1 month and the treated group was dipped in a 5% sorbate solution, vacuum packaged and aged an additional 2 months. Vacuum packaging practically eliminated further weight loss while potassium sorbate reduced but did not eliminate mold growth. In the second trial hams were again cured by a standard process and aged at 24°C until they were officially country hams (18% weight loss). Group I hams were not treated whereas group II hams were dipped in a 10% potassium sorbate solution. All were vacuum packaged. After aging one month they were unpacked, weighed, and examined for molds. No significant weight loss had occurred but mold counts were lower in the dipped group. The dipping procedure was reversed so that group I hams were treated and group II hams were not treated. All hams were again vacuum packaged and held a second month. No additional weight loss was noted. Mold growth, though not eliminated, was minimal, and visual and aroma scores for the cut hams were similar and highly acceptable. Tenderness, flavor, saltiness, and overall satisfaction scores for cooked slices were similar and highly acceptable. In general, mold growth can be greatly reduced by the use of potassium sorbate and weight loss can be controlled by vacuum packaging.     

Effect of Heat Treatment and Selected Antimicrobials on the Shelf-life and Safety of Cooked, Vacuum-Packaged, Refrigerated Pork Chops

The shelf-life of refrigerated (2–4°C) pork chops inoculated with Clostridium sporogenes PA3679 and Staphylococcus aureus Z88 was examined in products sliced from loins cooked to 66°C (150°F), dipped in 5% polyphosphate blend, 2.5% potassium sorbate or 2% acetic acid solutions, vacuum-packaged and stored at 2–4°C. The effect of a second in-the-bag cooking step to 66°C (150°F) after vacuum packaging was also studied. Pork chops not reheated after packaging showed incipient spoilage after 15 days at 2–4°C, depending on surface treatment. The second cooking increased the shelf-life of refrigerated product to more than 60 days and reduced counts of inoculated cultures to undetectable levels. However, on exposure of the chops to simulated mishandling (24–25°C), clostridial growth was detected in all samples except those dipped in polyphosphate or acetic acid solutions.     

Microbiological and Some Physical and Chemical Changes in Vacuum-Packaged Beef Steaks Treated with Combinations of Potassium Sorbate, Phosphate, Sodium Chloride and Sodium acetate

Fresh rib eye steaks were examined for microbiological, lipid oxidation, pH, color and weight changes after immersion in water or in aqueous solutions of a phosphate blend and of a mixture of potassium sorbate, phosphates, sodium chloride and sodium acetate and subsequent vacuum packaging. Keeping characteristics of steaks were monitored during 12-wk storage at 2–4°C. Mesophilic, psychrotrophic, anaerobic and facultative anaerobic bacteria and lactobacilli were strongly inhibited (P<0.05) in steaks treated with the composition that contained potassium sorbate, whereas growth of Enterobacteriaceae was suppressed (P<0.01). Compared with controls, compositions containing phosphates with or without potassium sorbate protected lipids, increased solution uptake and decreased purge in steaks without affecting meat color.     

Effect of chemical preservatives on shelf life of mushroom (Pleurotus ostreatus) cultivated on cassava peels

Short shelf life is a major impediment to the processing and distribution of mushroom. The effect of chemical preservatives on some quality attributes of mushroom during storage was investigated. Mushroom were soaked in four preservatives at two concentrations for 10 mins, packaged, stored at 4 °C for 30 days and analysed at intervals for their microbial population, colour, firmness and weight loss. Sodium benzoate (0.05%, 0.1%) lost its preservative effect on all the micro‐organisms enumerated after 3 days, and samples treated with 0.1% potassium sorbate had the lowest microbial load at the end of the storage period. Change in colour of the potassium sorbate (0.1%)‐treated sample was lower than and significantly different from the citric acid (2%, 4%)‐treated samples. The values of the firmness of the 4% citric acid preserved mushroom were significantly different (P ≤ 0.05) from other samples throughout the storage period. There was a significant negative correlation (r = ?0.807, P < 0.01) between the firmness and weight loss of the preserved mushroom. Potassium sorbate (0.1%) and citric acid (4%) extended the shelf life of mushroom for 24 days.     

Effect of Packaging Film and Vacuum Level on Regular and Sorbate-Cured Bacon

Bacon was produced with either 40 ppm NaNO₂/0.26% potassium sorbate, or 120 ppm NaNO₂. Slices were packaged in either nylon/Surlyn or nylon/Saran/Surlyn pouches and sealed at either a high or intermediate vacuum level. At 0, 10, 21 and 28 days after packaging, residual nitrite, rancidity, pH, residual salt and pigment conversion were measured. Residual nitrite and pH were lower while nitrosopigment conversion was higher in bacon packaged with the high-barrier film. Vacuum level, however, had no effect on any measured characteristic. The sorbate/reduced nitrite cure resulted in lower pigment conversion, lower residual nitrite, and a higher TBA number.     

Effects of Acids on Potassium Sorbate Inhibition of Food-Related Microorganisms in Culture Media

Effects of potassium sorbate in combination with citric, lactic, phosphoric, and hydrochloric acids on the growth of six food-related microorganisms were studied. Trypticase soy broth with 0.1 or 0.2% sorbate adjusted to pH 5.5 with any of the acids was bacteriostatic to Yersinia enterocolitica 0:17. These combinations at pH 5.5 were also bacteriostatic to Salmonello group D, and extended the lag phase of Pseudomonas fluorescens for 24 hr. Combinations of either organic acid with 0.2% sorbate at pH 5.5, reduced the growth rate of Lactobacillus plantarum and an unidentified lactobacillus isolated from frankfurters. Pseudomonas aeruginosa was unaffected by any sorbate-acid combination. Organic acids, specifically citric and lactic, potentiate the antimicrobial action of potassium sorbate.     

Effect of Potassium Sorbate and Vacuum Packaging on the Quality and Microflora of Dry-Cured Intact and Boneless Hams

Intact and boneless hams were dry-cured and aged with and without potassium sorbate or vacuum packaging. Sorbate had no effect on yield but dry sorbate generally improved panel scores in boneless hams. Vacuum packaging eliminated further weight loss, decreased visual appraisal scores in intact hams but had little effect on sensory scores. After 3 months of aging, aerobic and staphylococci counts were as much as 7 logs lower in nonvacuum packaged controls than in either nonvacuum or vacuum packaged sorbate treated intact hams. Counts within all vacuum packaged groups were similar. Yeast and mold counts were lower in sorbate treated than in non-sorbate treated vacuum packaged hams. After aging, coagulasenegative staphylocci were the predominant species.     

Evaluating the effects of zinc chloride as a preservative in cracked table olive packing

This survey studies the influence of different zinc chloride concentrations (0.050, 0.075, and 0.100%, wt/vol) on the shelf life of "Aceituna Alore?a de Málaga" table olives. The Enterobacteriaceae population significantly (P ≤ 0.05) decreased in treatments containing 0.050 and 0.100% ZnCl(2), and those with 0.075% ZnCl(2) had also lower average counts than those observed under the usual packaging conditions (0.12% potassium sorbate). Lactic acid bacteria increased for treatments with 0.050 and 0.075% ZnCl(2), but in the presence of 0.100% they practically disappeared at the end of the shelf life period (～3 months). With respect to yeasts, populations of these microorganisms significantly decreased with the first two concentrations (0.050 and 0.075%) but showed a slight increase in the presence of 0.100% of ZnCl(2), although remaining markedly below populations observed with potassium sorbate packing. The use of this chloride salt also led to products with higher concentrations of sugars in brine because of its selective microbial inhibition. Finally, olives treated with 0.075% ZnCl(2) showed an improved sensory profile.