Spoilage and shelf‐life extension of fresh fish and shellfish

Fresh fish and shellfish are highly perishable products due to their biological composition. Under normal refrigerated storage conditions, the shelf life of these products is limited by enzymatic and microbiological spoilage. However, with increasing consumer demands for fresh products with extended shelf life and increasing energy costs associated with freezing and frozen storage, the fish‐processing industry is actively seeking alternative methods of shelf life preservation and marketability of fresh, refrigerated fish and at the same time economizing on energy costs. Additional methods that could fulfill these objectives include chemical decontamination, low‐dose irradiation, ultra‐high pressure, and modified atmosphere packaging (MAP). This review focuses on the biochemical and microbiological composition of fresh fish/shellfish, the spoilage patterns in these products, factors influencing spoilage, and the combination treatments that can be used in conjunction with refrigeration to extend the shelf life and keeping quality of fresh fish/shellfish. The safety concerns of minimally processed/MAP fish, specifically with respect to the growth of Clostridium botulinum type E, is also addressed.     

Application of antimicrobial ice for extending shelf life of fish

In this study, we investigated whether wild-thyme (Thymus serpyllum) hydrosol had a preserving effect against spoilage of freshwater fish. Sensorial characteristics, chemical freshness indicator contents, and microbial counts (total aerobes, psychrotrophics, Enterobacteriaceae, fecal coliform bacteria, Aeromonas spp., and Pseudomonas spp.) of whole ungutted and gutted Transcaucasian barb (Capoeta capoeta capoeta Guldenstaedt, 1772) stored on ice produced from wild-thyme hydrosol and tap water at 4 degrees C for 20 days were compared. The results did not reveal any significant (P > 0.05) differences in the microbial counts, sensorial characteristics, pH, and total volatile basic nitrogen values between gutted and ungutted groups. Sensory evaluation and microbiological and chemical analyses indicated that the storage of the fish on ice produced from wild-thyme hydrosol had a significant increase in shelf life by at least 15 to 20 days.     

Effects of antioxidants and gamma irradiation on the shelf life of beef patties.

To improve the storage safety of two types of ground beef patty popular in Korea (general beef patties and bulgogi patties), we added various antioxidants (200 ppm; including butylated hydroxyanisole, ascorbyl palmitate, alpha-tocopherol, and beta-carotene) to typical formulations of patties, cooked the patties to 70 degrees C, and irradiated them at a dose of 1.5 or 3 kGy. During 30 d of storage at 5 degrees C, the number of aerobic bacteria and lactic acid bacteria were determined using total aerobic plate count and phenyl ethyl alcohol-sucrose agar, respectively. The concentration of thiobarbituric acid was also determined in each type of patty. No colonies were observed in patties irradiated at 3 kGy regardless of which antioxidant was added. In control patties and patties with butylated hydroxyanisole that were irradiated at a dose of 1.5 kGy, growth of microorganisms appeared to be more rapid than in patties with natural antioxidants. The microbiological safety of nonirradiated patties could not be ensured for a period of 20 d. Lipid oxidation was retarded in both types of patty when an antioxidant was added. Ascorbyl palmitate had the strongest antioxidant effect among the natural antioxidants. However, butylated hydroxyanisole was more effective than ascorbyl palmitate when used in an equal amount.     

Food group symposium shelf life of red meat,fish and poultry

The following are summaries of papers presented at a symposium on ‘The Shelf Life of Red Meat, Fish and Poultry’ organised jointly by the Meat and Sensory Panels of the SCI Food Group. It was held at the Society of Chemical Industry, 14 Belgrave Square, London SWIX 8PS on 23 February 1983. The papers published here are entirely the responsibility of the authors and do not reflect the views of the Editorial Board of the Journal of the Science of Food and Agriculture.     

Impact of irradiation on the safety and quality of poultry and meat products: a review

For more than 100 years research on food irradiation has demonstrated that radiation will make food safer and improve the shelf life of irradiated foods. Using the current food safety technology, we may have reached the point of diminishing returns even though recent figures from the CDC show a significant drop in the number of foodborne illnesses. However, too many people continue to get sick and die from eating contaminated food. New and under utilized technologies such as food irradiation need to be re-examined to achieve new levels of safety for the food supply. Effects of irradiation on the safety and quality of meat and poultry are discussed. Irradiation control of the principle microbial pathogens including viruses, the differences among at-risk sub-populations, factors affecting the diminished rate of improvement in food safety and published D values for irradiating raw meat and poultry are presented. Currently permitted levels of irradiation are probably not sufficient to control pathogenic viruses. Typical gram-negative spoilage organisms are very sensitive to irradiation. Their destruction leads to a significant increase in the acceptable shelf life. In addition, the destruction of these normal spoilage organisms did not provide a competitive growth advantage for irradiation injured food pathogens. Another of the main focuses of this review is a detailed compilation of the effects of most of the food additives that have been proposed to minimize the negative quality effect of irradiation. Most of the antimicrobials and antioxidants used singly or in combination produced an increased lethality of irradiation and a decrease in oxidation by-products. Combinations of dosage, temperature, dietary and direct additives, storage temperature and packaging atmosphere can produce meats that the average consumer will find indistinguishable from non-irradiated meats. A discussion of the production of unique radiological by-products is also included.     

The improvement of color and shelf life of ham by gamma irradiation.

This study was undertaken to determine if gamma irradiation can circumvent the need for sodium nitrite to obtain and maintain the desired color of pork loin ham. A dose of 5 kGy was observed to be as effective as the use of 200 ppm of sodium nitrite to provide and maintain the desired color of the product for 30 days. Peroxidation of the product was reduced with addition of sodium nitrite but increased with irradiation. However, organoleptic quality of the irradiated ham without added sodium nitrite was acceptable.     

Incidence of Salmonella in fish and seafood

Field laboratories of the U.S. Food and Drug Administration collected and tested 11,312 import and 768 domestic seafood samples over a 9-year period (1990 to 1998) for the presence of Salmonella. The overall incidence of Salmonella was 7.2% for import and 1.3% for domestic seafood. Nearly 10% of import and 2.8% of domestic raw seafood were positive for Salmonella. The overall incidence of Salmonella in ready-to-eat seafood and shellfish eaten raw was 0.47% for domestic--one shucked oyster and one shark cartilage powder. The incidence in the 2,734 ready-to-eat import seafood was 2.6%--cooked shrimp, shellfish or fish paste, smoked fish, salted/dried fish, and caviar. The incidence in import shellfish consumed raw was 1% in oyster, 3.4% in clams, and 0% in mussels. The incidence in raw, import fish was 12.2%. Distribution of Salmonella in seafood on a regional basis indicated the incidence to be highest in central Pacific and Africa and lowest in Europe/Russia and North America (12% versus 1.6%). Data on a country basis indicated Vietnam to have the highest (30%) and Republic of Korea the lowest (0.7%). While the most frequent serotypes in import seafood were Salmonella Weltevreden (1st), Salmonella Senftenberg (2nd), Salmonella Lexington, and Salmonella Paratyphi-B (3rd, equal numbers for each serotype), the top 20 list included Salmonella enteritidis (5th), Salmonella Newport (6th), Salmonella Thompson (7th), Salmonella typhimurium (12th), and Salmonella anatum (13th), commonly involved in foodborne illness in the United States. Because the incidence in the present study is based on only a small fraction of the seafood imported into the United States, efforts should be directed toward implementation of hazard analysis and critical control points to reduce the incidence of Salmonella in seafood without relying on testing for Salmonella.     

Application of a systematic experimental procedure to develop a microbial model for rapid fish shelf life predictions

A systematic experimental procedure for fish shelf-life modelling was used to develop a model for predicting the quality of fish in the chill chain. For this, the growth of the naturally occurring bacteria pseudomonads, Shewanella putrefaciens, Enterobacteriaceae, lactic acid bacteria and yeasts, on gilt-head seabream (Sparus aurata), was studied at temperatures from 0 to 15°C. The results from the microbiological, organoleptical and chemical analysis conducted on naturally contaminated fish as well as on inoculated sterile fish blocks identified pseudomonads as a good spoilage index. Growth of pseudomonads was modelled as a function of storage temperature and correlated to organoleptical shelf life. To reduce the time required for the enumeration of the initial pseudomonads number, which is crucial information for shelf life prediction, a conductance assay was established. Compared with the conventional microbiological tests, this method gave results in one-fourth of the time.     

通过综合质量控制手段延长低温肉制品的货架期

延长低温肉制品的货架期是一个系统的工程,它要求从原辅料选择、生产加工过程质量控制、工艺技术选择等各环节入手,采取综合保鲜技术,达到延长货架期的目的,为消费者提供具有较长保质期、安全性高的肉制品。     

On the effectiveness of EDTA in prolonging the shelf life of fresh fish

Summary The purpose of this investigation was to ascertain whether EDTA might be useful in prolonging the keeping quality of fresh fish. The criteria of quality used were: the total bacterial count, the content of volatile basic nitrogen and trimethylamine, the degree of dephosphorylation of the nucleotides, the level of the hypoxanthine, and the organoleptic properties. The material consisted of rainbow trout (Salmo irideus) and Baltic herring (Clupea harengus var. membranus).The results showed that EDTA had a markedly favorable effect on the keeping quality of fish. Although the effect on the total bacterial count was only slight, a chemical and organoleptical comparison with control material revealed that spoilage in the EDTA-treated samples was definitely slower. In the case of fillets of rainbow trout, judged by the organoleptical method, the controls became unacceptable after storage for 18–20 days at +4°C, whereas after the same storage time the EDTA-treated samples were still free of off-odors and had a fair taste. Similarly, the values of volatile basic nitrogen, trimethylamine, and hypoxanthine increased at a slower rate, and the dephosphorylation of nucleotides proceeded less rapidly in the EDTA-treated fillets than in the controls. In the case of fillets of Baltic herring, sensory evaluation brought out the positive effect of the EDTA treatment. A corresponding difference was noted in the volatile basic nitrogen and trimethylamine values, and a slight difference in the hypoxanthine values. In this fish, the dephosphorylation of the nucleotides was rapid, and between the samples subjected to EDTA treatment and the control material there appeared only a small difference. With regard to the round Baltic herring, again, the differences between the two categories were less conspicuous; the chief difference was noted in the volatile basic nitrogen, but in the sensory evaluation the difference was not fully consistent.

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Zusammenfassung Das Ziel dieser Untersuchung war aufzufinden, ob EDTA (die Äthylen-diamin-Tetraessigsäure) zur Verlängerung der Haltbarkeit von frischem Fisch nützlich wäre. Die verwendeten Qualitätskriterien waren die gesamte Bakterienzahl, die Gehalte an flüchtigem basischem Stickstoff und Trimethylamin, der Grad der Dephosphorylierung der Nucleotide, die Menge des Hypoxanthins, und die organoleptischen Eigenschaften. Das Material bestand aus Regenbogenforelle (Salmo irideus) und Ostseehering (Clupea harengus var. membranus).Die Resultate zeigten, daß EDTA einen beachtlich günstigen Einfluß auf die Haltbarkeit der Fische ausübte. Obgleich der Einfluß auf die gesamte Bakterienzahl nur geringfügig war, zeigte der chemische und organoleptische Vergleich mit Kontrollproben, daß das Verderben bei den mit EDTA behandelten Proben deutlich langsamer verlief. Bei der Regenbogenforelle waren die Kontrollen nach Aufbewahrung von 18–20 Tagen bei 4°C, nicht mehr akzeptabel, aber die mit EDTA behandelten Proben waren nach derselben Zeit noch frei von Fehlgeruch und hatten einen annehmbaren Geschmack. Gleicherweise zeigten die Werte von flüchtigem basischem Stickstoff, Trimethylamin und Hypoxanthin eine langsamere Steigerung, und die Dephosphorylierung der Nucleotide war langsamer bei Behandlung mit EDTA als bei den Kontrollen. Im Falle der Filets von Ostseehering stellte sich die positiveWirkung der EDTA-Behandlung bei der organoleptischen Beurteilung heraus. Ein entsprechender Unterschied wurde in den Werten von flüchtigem basischem Stickstoff und Trimethylamin festgestellt, und eine kleinere Wirkung in den Werten von Hypoxanthin. Bei diesem Fisch war die Dephosphorylierung der Nucleotide schnell, und zwischen den mit EDTA behandelten und den Kontrollproben bestand hier nur ein kleiner Unterschied. Beim runden (ungereinigten) Ostseehering wieder waren die Unterschiede zwischen behandelten und Kontrollfischen weniger bedeutend; der hauptsächlichste Unterschied wurde im flüchtigen basischen Stickstoff wahrgenommen, bei der organoleptischen Beurteilung aber war der Unterschied nicht völlig eindeutig.

     

梅菜防腐保鲜工艺条件的研究

以惠州梅菜为研究材料,研究了梅菜防腐保鲜的工艺条件,结果发现,梅菜含盐量高低对梅菜的耐储存性有极为重要的影响,含盐量为12%-15%、8%-10%和5%-6%的梅菜在不添加防腐剂时分别可保持90、60、20d左右不变质:浓度为0.1%的山梨酸钾对梅菜防腐保鲜效果优于0.1%的苯甲酸钠;低浓度(0.01%)高效防霉剂的防腐作用不大;山梨酸钾与苯甲酸钠等浓度(均为0.05%)混合使用时,对梅菜的防腐保鲜效果较佳;采用蒸汽杀菌与防腐剂配合使用,或者在脱盐过程中加消毒剂(ClO2)处理,这两种方法都可延长保质期。     

Functional and bioactive properties of fish protein hydolysates and peptides: A comprehensive review

Global fish processing industries dispose of fish wastes that account for more than 60% of processed fish biomass. In lieu of environmental pollution and disposal problems, these wastes are used to produce fish silage, fishmeal and sauce. They are also utilized for the production of value added products such as proteins, hydrolysates, bioactive peptides, collagen and gelatin. Research on the production of fish protein hydroysates (FPHs) presently focuses on maximizing the industrial potential of fish wastes. Since bioactive peptides containing amino acids hold properties of great interest, this paper reviews current research on the functional and bioactive properties of FPHs with an additional focus on gaps between fish and other hydrolysates, as well as current and future trends for the productive utilization of FPHs.     

泡菜货架期研究

研究了泡菜自然发酵的工艺及其货架期,结果表明,泡菜自然发酵的最佳条件为:6%的加盐量,发酵温度20℃,加入0.05?Cl2,发酵8~10 d。采用真空包装加冷藏后的泡菜保质期可达1年以上,加入0.05%的防腐剂可以延长保质期和改善产品质量。     

Suitability of Dukat strawberries for studying effects on shelf life of irradiation combined with cold storage

Summary A new Dukat variety of strawberries was used to study the effect of irradiation combined with cold storage on their shelf life and chemical composition. Strawberries, with or without stems, were irradiated with a dose of 2.5 or 3.0 kGy within 6–10 or 20–24 h after harvesting. Results of the sensory evaluation showed that the minimum storage time for the fruits could be extended by a minimum of 9 days. If the time between harvest and irradiation was shorter, better results for storage experiments were obtained. Fruits with stems were more suitable for cold storage after irradiation than those without stems. Irradiation of strawberries did not change the titratable acidity and content of the reducing sugars. Colour intensity and ascorbic acid levels decreased in proportion to the absorbed dose and storage time.

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Die Eignung von Erdbeeren der Sorte Dukat durch Bestrahlung die Lagerstabilität bei der Kaltlagerung zu verlängern

Zusammenfassung Bei der neuen Erdbeersorte Dukat wurde der Einfluß der Bestrahlung zusammen mit der Kaltlagerung auf ihre Lagerstabilität und chemische Zusammensetzung untersucht. Die Erdbeeren mit oder ohne Stiele wurden mit 2,5 und 3,0 kGy Bestrahlungsdosen innerhalb 6–10 bzw. 20–24 h nach der Ernte bestrahlt. Die sensorischen Ergebnisse haben gezeigt, daß die Lagerstabilität der Früchte um mindestens 9 Tage verlängert werden kann. Wenn die Zeit zwischen Ernte und Bestrahlung kürzer war konnten bessere Ergebnisse erzielt werden. Die Früchte mit Stiel waren zur Kaltlagerung nach der Bestrahlung besser geeignet als die ohne Stiele. Die Bestrahlung von Erdbeeren beeinflußte nicht die Titrationsacidität und den Gehalt an reduzierenden Zuckern. Die Intensität der Farbe und der Ascorbinsäuregehalt verminderten sich im Verhältnis zur Bestrahlungsdose und Lagerungszeit.

     

Suitability of Dukat strawberries for studying effects on shelf life of irradiation combined with cold storage

A new Dukat variety of strawberries was used to study the effect of irradiation combined with cold storage on their shelf life and chemical composition. Strawberries, with or without stems, were irradiated with a dose of 2.5 or 3.0 kGy within 6-10 or 20-24 h after harvesting. Results of the sensory evaluation showed that the minimum storage time for the fruits could be extended by a minimum of 9 days. If the time between harvest and irradiation was shorter, better results for storage experiments were obtained. Fruits with stems were more suitable for cold storage after irradiation than those without stems. Irradiation of strawberries did not change the titratable acidity and content of the reducing sugars. Colour intensity and ascorbic acid levels decreased in proportion to the absorbed dose and storage time.     

添加CO2延长酸奶保质期对其物理性质的影响

为了把CO2添加到酸奶中延长保质期,对添加不同浓度CO2的酸奶物理性质进行了研究.将空白样及添加浓度分别为5.11,18.58,24.09,30.08 mmol/L的酸奶在4℃贮藏15 d检测每组样品CO2溶解量、pH值、酸度、感官及质构性质.结果表明,在酸奶中通入CO2气体环境温度为18℃到4℃之间,CO2溶解量由2.7 mmol/L增加到38.5 mmol/L.添加CO2的酸奶在第15天pH值为4.02,酸度为102°T;空白样pH值已降至4.00,酸度增至105°T;感官性质没有明显不同.CO2使酸奶粘稠度增加但浓度在30.08 mmol/L时质构性质较差.因此,CO2添加量以不超过24.09 mmol/L浓度为最适宜.     

动力学模型预测泡椒鱼皮产品货架寿命

以泡椒鱼皮产品为研究对象,考察泡椒鱼皮在不同贮藏温度(5℃、25℃、35℃)条件下,产品脆度、泡椒风味、总体可接受性与pH、菌落总数随贮藏时间的变化规律,并利用皮尔逊(Pearson)相关系数分析得到影响产品品质的关键因子.通过分析关键因子在不同条件下的变化,建立该关键因子与贮藏时间、贮藏温度之间的动力学模型和Arrhenius方程.实验表明:一级化学反应动力学模型和Arrhenius方程对细菌总数的变化具有较高的拟合精度(R2＞0.9).预测模型中菌落总数变化的Ea为9.8829kJ/mol,ka0=2.2038,得到泡椒鱼皮细菌总数变化的Arrhenius方程为:ka=2.2038×e9.8829RT.     

Application of shelf life decision system (SLDS) to marine cultured fish quality

Growth of natural microflora of marine cultured, air-packed, sea bass (Dichentrachus labrax) was studied at isothermal conditions in the 0-15 degrees C range and kinetically modelled using the four-parameter Logistic equation. Sensory shelf life was correlated to pseudomonad population and sensory acceptability was correlated to a pseudomonad level, Ns, of 10(7). The variability of their initial population was quantitatively shown and a conductance-based rapid method specific to sea bass pseudomonad enumeration was established as a practical means of N0 determination, required in shelf life predictions. Kinetic models, shelf life correlations and N0 data were incorporated into the shelf life decision system (SLDS) shown to be an effective tool for marine cultured sea bass chill chain management leading to optimization of quality of the fish at consumer's end.