Antioxidant Properties of Chitosan Coatings on Frozen Atlantic Salmon Fillet Portions

Atlantic salmon contain omega-3 fatty acids, which play important roles in promoting human health but are highly susceptible to oxidation. Chitosan has been shown to have antioxidant properties which could be beneficial in extending the shelf life of Atlantic salmon; however, the effects of chitosan molecular size on oxidation of salmon fillets have not been reported. The primary objective of this study was to evaluate the effects of chitosan coatings on lipid oxidation of Atlantic salmon fillet portions during 5 months frozen storage. The effects of chitosan molecular weight (high molecular weight, low molecular weight, and enzymatically degraded chitosan), concentration (0.5 and 1.0%), and the addition of 1% ascorbic acid to the chitosan coating were evaluated. Chitosan molecular weight significantly affected oxidation as evaluated by propanal levels and changes in L* values of the fillet portions. The chitosan treatment with added ascorbic acid resulted in the lowest propanal levels during 5 months of frozen storage. Manipulation of chitosan molecular weight and incorporation of natural antioxidants into chitosan coatings can provide an effective method of reducing lipid oxidation during extended frozen storage of seafood products.     

Quality of Atlantic Cod Frozen in Cell Alive System,Air-Blast,and Cold Storage Freezers

ABSTRACT

Gutted Atlantic cod, packed in cartons, were frozen immediately after killing in a magnetic field (cell alive system). The results were compared with traditional air-blast freezing or by putting the cartons directly in a cold storage room (without forced convection of air). After frozen storage, external and fillet properties were compared. In spite of differences in freezing rates, only minor differences were found among treatments. The mechanism for the freezing of fish in the magnetic field, under the current conditions, appeared to be similar to that of traditional freezing methods.     

Effects of Chilled Storage,Freezing Rates,and Frozen Storage Temperature on Lipid Oxidation in Meat Blocks from Cultured Bluefin Tuna Thunnus thynnus

ABSTRACT

The effects of a short chilled storage period before freezing, frozen storage temperature, and freezing rate on lipid oxidation of bluefin tuna (Thunnus thynnus) meat during frozen storage were investigated. After 12-months storage, all samples had increased in peroxide value though they were less at the lower temperatures (?45 and ?60°C). Peroxide values in all samples stored at ?20°C increased after 3 months storage, particularly those processed and stored 51 h after harvest. The lowest increase in peroxide value occurred in the samples frozen rapidly 3 h after harvest. Vitamin E levels decreased faster during frozen storage at ?20°C. There were no apparent differences in levels of triacylglycerides nor in n-3 fatty acid levels between treatments, storage periods, and storage temperatures. After 12-months storage, headspace oxidative volatiles were highest in samples stored at ?20°C and lowest in those stored at ?60°C. Lipid oxidation in tuna meat stored at ?45°C is similar to that at ?60°C, and rapid freezing rather than slow freezing should be used.     

不同被膜对冷冻牡蛎质量的影响及优化

以提高冷冻牡蛎质量为目的，采用自行设计的冷冻装置，分别以魔芋葡甘聚糖被膜液、壳聚糖被膜液及葡甘聚糖和壳聚糖被膜液各为50％的复合液被膜牡蛎进行冷冻试验。采用正交实验，分析了不同方式处理对冷冻牡蛎质量的影响。结果表明，采用被膜液进行被膜可明显降低冷冻牡蛎VBN值和不合格率，提高冷冻牡蛎质量。在被膜液浓度相同状况下，魔芋葡甘聚糖被膜液被膜的效果最好。此外，还对牡蛎葡甘聚糖涂膜液被膜的状态参数进行了优化。     

Postmortem Changes in the Adductor Muscle of Scallop (Chlamys tehuelchus) in Chilled and Frozen Storage

Abstract

The effects of freezing and frozen storage on the biochemical properties of scallop adductor muscles stored at 2-4EC were investigated. Glycogen content fell 40% in the first 12 hr of chilled storage and decreased slowly thereafter. ATP content increased for a short time after death and then decreased slowly. Glycogen and ATP degradation was accompanied by a decrease in both pH and 260/250 absorbance ratio of scallop muscle extracts. A significant increase (p < 0.05) in the hypoxanthine (Hx) content was also observed in chilled stored adductor muscles. Adductor muscles showed a significant decrease (p < 0.05) in the 260/250 absorbance ratio of extracts and an increase in the Hx level after freezing. An increase in Hx content was observed during frozen storage of adductor muscles frozen immediately after processing. Expressible juice increased with freezing and frozen storage of the muscles. The results shown in this paper indicate a rapid loss of quality in scallop adductor muscles during storage at 2-4. Freezing and frozen storage enhanced the quality deterioration of the muscles.     

The Effects of On-Board Handling and Frozen Storage on Gaping in Hoki (Macruronus novaezelandiae)

Abstract

Hoki were trawl-caughl under commercial conditions and subjected to one of five treatments before heading and gutting and freezing to ?35°C. Fish were either processed within 1 hour of capture, held at ambient temperatures or in ice until rigor was established or held at ambient temperatures or in ice until rigor was resolved. Fish from each treatment were then stored at ?20°C for periods of up to 56 weeks and tested for gaping, pH and other related physical and sensory properties. Fish frozen post-rigor showed the most gaping and fish frozen pre-rigor had less than those frozen in rigor. The temperature of storage before freezing had little effect on gaping other than extending the time taken to proceed through rigor. Extended time in frozen storage resulted in decreased water-holding capacity but had little effect on gaping. Gaping was not related to pH levels and did not affect the texfural properties of the cooked fish.     

The Effectiveness of Official Methods to Measure the Real Glazing Percentage in Frozen Seafood: An Analysis with Frozen Pacific White Shrimp (L. vannamei)

The aim of this study was to evaluate the effectiveness of official methods to quantify the real glazing percentage in frozen Pacific white shrimp (Litopenaeus vannamei) with different glazing percentages. Samples of frozen peeled shrimp were glazed with cold water (0 ± 1°C) at glazing levels of 15, 30, 40, 50, and 60%. The glazing percentage was quantified based on Brazilian methodologies (INMETRO and MAPA) and International methodologies (CODEX, AOAC, and NIST). The official methods were inefficient in quantifying the real glazing percentage, especially with regard to the samples containing higher glazing percentages (> 30%). As an alternative, changes were done to improve the glazing measurement method (mix of the best parameters from all methodologies), which best describes the reliable value of the glazing percentage of frozen shrimp samples and confirms that this methodology can be an alternative used by inspectors after collaborative study for validation. In this sense, a critical review and possible changes in the official methodologies may be suggested in order to improve them for use to combat economic fraud in the seafood frozen products.     

Quality of Filleted Atlantic Mackerel (Scomber Scombrus) During Chilled and Frozen Storage: Changes in Lipids,Vitamin D,Proteins, and Small Metabolites,including Biogenic Amines

Quality changes of vacuum-packed Atlantic mackerel (Scomber scombrus) fillets during 12 months’ frozen storage at ?27°C and 9 days’ chilled storage at +4°C were evaluated. Freezing at ?27°C preserved the long chain n-3 polyunsaturated fatty acids (LC n-3 PUFAs), both in light and dark muscle, vitamin D, and the low molecular weight metabolites (LMW) (studied by high resolution nuclear magnetic resonance spectroscopy, HR NMR). Protein oxidation took place, especially between 1 and 7 months, decreasing water holding capacity and protein extractability. During chilled storage, no lipid or protein oxidation was observed, but lipolysis increased, and several LMW metabolites relevant for sensory and nutritional quality degraded into non-favorable compounds. The content of biogenic amines was high at day 9 (e.g., 18 mg histamine/100 g), jeopardizing safety. Preservation of mackerel fillets by freezing at ?27°C is thus a better option compared to prolonged chilled storage at +4°C; the quality was well preserved for 12 months’ frozen storage.     

Preservation Methods for Retaining N-3 Polyunsaturated Fatty Acids in Alaska Coho Salmon (Oncorhynchus kisutch) Products

Abstract

Coho salmon (Oncorhynchus kisutch) fillets were processed using five different methods (smoking, canning, freezing, acidifying, and salting) to evaluate the effect of preservation choice on the quality of polyunsaturated fatty acids (PUFA). Salmon preserved by smoking, canning, or freezing retained higher values of total fatty acids, including n-3 PUFAs such as eicosapentaenoic acid and docosahexaenoic acid. Salting and acidifying (pickling) treatments resulted in a significant decrease in PUFAs. The results of this study are intended to provide direction for handling and storage of salmon to retain the maximum levels of high-value n-3 PUFAs.     

Maintenance ration, protein synthesis capacity, plasma insulin and growth of Atlantic salmon (Salmo salar L.) with genetically different trypsin isozymes

Growth was found to be associated with the changes of trypsin activity in the pyloric caecal tissues and the level of plasma insulin in Atlantic salmon (Salmo salar L.). A decrease in trypsin activity accompanied by an increase in plasma insulin was detected one month before an enhanced growth was observed. There were significant relationships between weight specific consumption rate, plasma insulin levels and fish growth. The correlation of weight specific consumption rate was higher with growth rate (R²=0.7, p<0.0001) than with plasma insulin concentration (R²=0.4, p<0.0001).When the comparison was made between Atlantic salmon carrying and lacking the trypsin variant TRP-2*92, the fish with the variant had lower maintenance ration (p<0.05), higher capacity for protein synthesis in the white muscle (p<0.02), and a greater ability to utilize the feed at a restricted ration than the fish without the variant. In Atlantic salmon lacking the variant, both plasma insulin concentrations and growth rates were significantly lower (p<0.05) in the fish fed 0.5% bw day^–1 than those fed 1% bw day^–1. Whilst the growth rates of TRP-2*92 salmon fed the different rations became similar one month after similar levels of plasma insulin were observed between them. The TRP-2*92 salmon may be defined as a high protein growth efficiency fish with low protein turnover rate.Genetic variation in trypsin isozyme pattern affects feed utilization, plasma insulin levels and growth in Atlantic salmon.     

Textural Changes During Iced Storage of Salmon (Salmo salar) and Cod (Gadus morhua)

Abstract

Textural properties, protein solubility, water holding capacity and activity of collagenolytic enzymes of salmon (Salmo salar) and cod (Gadus morhua) fillets were measured during iced storage. Breaking strength and hardness of fillets were reduced during iced storage. Elasticity of cod fillets was reduced, while cohesiveness of salmon increased during storage. Salmon was softer and less elastic than cod. During storage, total amount of extracted proteins was reduced for cod, and increased followed by a reduction for salmon. The fraction of salt soluble proteins increased during storage, and values for cod were higher than those for salmon. The activity of collagenolytic enzymes was higher in cod than salmon during the whole storage period.     

Live Chilling and Carbon Dioxide Sedation at Slaughter of Farmed Atlantic Salmon: A Description of a Number of Commercial Case Studies

ABSTRACT

Eleven commercial processing lines for the slaughter of Atlantic salmon were evaluated to investigate the efficiency of the refrigerated seawater live chilling method with respect to stunning fish and reducing body temperature. The method is commonly used in the Norwegian salmon industry to both stun and chill fish before killing. Carbon dioxide gas was added to the live chilling tanks, or in some cases, to a subsequent carbon dioxide stunning tank. Criteria used for evaluation were water quality parameters (dissolved oxygen, carbon dioxide, pH, temperature, total ammonium, ammonia, alkalinity, color, total organic carbon, and ferric ion), fish behavior, white muscle pH, and body and core temperatures. At two processing plants, fillet quality (Roche color, texture, ultimate pH, and water content) was also determined. The results are discussed in terms of fish acclimation temperatures, water quality, welfare, handling stress, chilling efficiency, pre-live chilling factors, refrigerated seawater live chilling process parameters, and fillet quality. Even though the live chilling method can be used to minimize fish handling stress during slaughter and may serve as an efficient chilling method, it was found in most cases that under commercial conditions when large biomasses were slaughtered, both handling stress and chilling efficiency were less than optimal. However, no adverse effects on the fillet texture and color were observed as a result of fish processing.     

Effects of Freezing and Frozen Storage on Protein Functionality and Texture of Some Cephalopod Muscles

The aim of this study was to investigate the effects of freezing and frozen storage on protein functionality and texture of squid (Loligo vulgaris), octopus (Octopus vulgaris), and cuttlefish (Sepia officinalis) muscles. Squid, octopus, and cuttlefish samples were cut into pieces of 4 × 4 cm. These pieces were packed in polyethylene bags. The bags were frozen in a blast freezer at ?45°C until the thermal center reached ?18°C. Frozen samples were stored in a deep freezer at ?18°C for 30 days. After freezing and during frozen storage, total soluble protein and water holding capacity decreased and total free amino acid and cooking loss increased in all cephalopod muscles. According to instrumental texture analysis results, freezing and frozen storage affected textural characteristics of squid and cuttlefish but not of octopus. Sensory hardness and chewiness values of all cephalopods increased after freezing, but elasticity values did not change. There were no significant differences between storage days in hardness values of squid and octopus. However, significant differences in hardness values of cuttlefish were observed between the 1st day of storage and the last day.     

Egg production in the salmon louse [Lepeophtheirus salmonis (Krøyer)] in relation to origin and water temperature

Egg strings of salmon lice, Lepeophtheirus salmonis (Krøyer 1837), collected from farmed and wild Atlantic salmon had similar length and number of eggs string^?1. Egg production was investigated at water temperatures from 7.1 °C to 12.2 °C. A regression model indicated that at low temperatures egg strings were longer and had more eggs. Mean length of single eggs was significantly smaller and the percentage of non‐viable eggs in the strings was higher at 7.1 °C than at 12.2 °C. Adult females survived for up to 191 days at 7.2 °C, and during this period 11 pairs of egg strings were produced.     

Effect of growth hormone on muscle protein synthesis in rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar)

This paper reports on the effect of administration of mammalian growth hormone (GH) on muscle protein synthesis as measured in white muscle using the phenylalanine flooding technique. The effect of exogenous GH was compared with that of insulin and prolactin, and with endogenous GH.The rate of protein synthesis in white muscle of rainbow trout 6 h after the injection of bovine GH or bovine insulin was twice (2.6 and 2.9% d^–1) that of the control saline-injected fish (1.2% d^–1). A metabolic effect of GH, as observed with insulin, is suspected.The rates of change in body weight and body length and the fractional rate of protein synthesis in muscle of rainbow trout were enhanced by mammalian GH administration. The effect of GH on muscle RNA/protein ratios was not significant. An opposite effect of antibodies against salmon GH (Lebailet al. 1989) on growth rate and muscle protein synthesis rate was found in rainbow trout. It is suggested that the effects of exogenous and endogenous GH on capacity and efficiency of muscle protein synthesis were similar.The long-term effects of mammalian GH on presmolt Atlantic salmon was also tested. The same trends were found with ovine prolactin supplementation in Atlantic salmon but not as high as those observed with ovine GH.     

The Effect of Whey Protein Isolate Coating Enriched with Thyme Essential Oils on Trout Quality at Refrigerated Storage (4 ± 2°C)

ABSTRACT

The present study evaluated the effect of whey protein isolate (WPI) coating enriched with thyme essential oil (EO; 3, 5, and 7%, v/v) on whole trout chemical and microbial quality during refrigerated storage at 4 ± 2°C. As a result of this study, the addition of thyme essential oil to WPI coatings enhanced quality significantly better than that of the control and WPI coating without thyme essential oil during refrigerated storage, and this effect increased with an increase in the thyme EO concentration in WPI coating.     

Setting Ability of Threadfin Bream (Nemipterus japonicus) Meat as Affected by Freezing and Frozen Storage with Special Reference to Transglutaminase Enzyme Activity and Rheological Properties

The effect of freezing and frozen storage of threadfin bream fish (Nemipterus japonicus) meat on the setting and gel-forming ability has been evaluated. The dynamic viscoelastic properties of fish meat during setting and thermal gelation process were evaluated using Controlled Stress Rheometer under oscillatory mode. A sharp decrease in setting ability was recorded immediately after freezing as revealed by storage modulus (G?) values. The transglutaminase (TGase) enzyme activity of fish meat decreased from the initial value of 81.09 to 51.46 U/g meat/min at the end of 200 days of frozen storage. A decrease in setting ability of fish meat beyond 160 days of frozen storage is probably related to lower TGase enzyme activity. The gel-forming ability was related to setting ability during the frozen storage period. Although the protein solubility showed a decreasing trend during 200 days of frozen storage, the decrease was not significant. The effect of freezing and frozen storage on calcium-activated adenosine triphosphatase (Ca²⁺-ATPase) enzyme activity of fish mince was significant (P < 0.05). A reduction in protein solubility and Ca²⁺-ATPase enzyme activity is an indication of aggregation/denaturation of myofibrillar proteins.     

大西洋鲑、三倍体虹鳟和金鳟的肌肉营养成分与品质特性

为了解大西洋鲑(Salmo salar)、三倍体虹鳟(Oncorhynchus mykiss)、金鳟(Oncorhynchus mykiss)3种鱼肌肉营养成分和品质特性,利用生化分析、物性分析方法分析3种鱼肌肉的营养成分、氨基酸和脂肪酸组成、肉色、系水力和质构特性。结果表明,大西洋鲑、三倍体虹鳟、金鳟肌肉的水分质量分数分别为62.91%、67.15%、73.02%,粗蛋白质量分数分别为22.39%、21.03%、22.11%,粗脂肪质量分数分别为14.64%、17.16%、5.11%。3种鱼肌肉的滴水损失、黄色值(b~*)、羟脯氨酸含量、内聚性均显著不差异(P0.05)。3种鱼肌肉的硬度和咀嚼性由低到高依次为大西洋鲑、三倍体虹鳟、金鳟,而pH值的结果则与之相反(P0.05)。大西洋鲑和三倍体虹鳟肌肉的灰分、解冻损失、蒸煮损失、回复性、弹性和红色值(a~*)差异不显著(P0.05),但灰分、蒸煮损失、回复性均小于金鳟肌肉的对应指标(P0.05),弹性和红色值(a~*)则均大于金鳟肌肉的对应指标(P0.05)。大西洋鲑、三倍体虹鳟、金鳟肌肉中必需氨基酸含量占氨基酸总量分别为42.28%、41.84%、41.63%(质量分数),必需氨基酸/非必需氨基酸(EAA/NEAA)比值分别为73.25%、71.94%、71.32%,均符合联合国粮农组织/世界卫生组织(FAO/WHO)对优质蛋白质的评价标准;3种鱼肌肉中均检测到22种脂肪酸,组成丰富,其中不饱和脂肪酸含量较高。综上所述,3种鱼的肌肉都是符合人体营养需求的优质水产品,其中大西洋鲑和三倍体虹鳟肉质接近,且都优于金鳟的肉质。     

Preservation of Tilapia (Oreochromis aureus) Fillet by Isochoric (Constant Volume) Freezing

ABSTRACT

The aim of this work was to evaluate the effects of isochoric freezing on the quality of tilapia fillet. Isochoric freezing was compared to chilling, super-chilling, and freezing. Isochoric freezing showed muscle color alterations similar to the other preservation methods. All preservation methods resulted in softer fillets, with the isochoric frozen fillet having the most similar texture to that of the fresh sample. Thiobarbituric acid reactive substances (TBARS) for isochoric samples were similar to those of fresh samples. However, there was a 53%, 55%, and 34% increase in TBARS for chilled, super-chilled, and frozen samples, respectively. Total volatile basic nitrogen (TVB-N) content was 1.4 times higher for isochoric samples than for fresh samples. For chilled, super-chilled, and frozen samples, TVB-N content was 3.0, 1.9, and 1.3, respectively, times higher than for fresh samples. Microstructural analysis indicated that isochoric samples showed less cell damage compared to those using other methods. Subfreezing temperatures in conjunction with no ice formation during isochoric freezing contributed to improved quality of tilapia fillet. This study may find application in the commercial preservation of fish to increase shelf life and allow for expanded distribution of raw fish. This study might also be a potential solution to “food desert” areas, where residents have low access to fresh healthy foods.     

Muscle Quality and Proteolytic Enzymes of Farmed Atlantic Cod (Gadus morhua) During Storage: Effects of Pre-Slaughter Handling and Increased Storage Temperature

ABSTRACT

In the present experiment, the characteristics of minimally handled, directly slaughtered farmed Atlantic cod were compared to cod subjected to 2 h preslaughter handling stress. The results strongly indicate that increasing the storage temperature from 0 to 5°C had a larger negative impact on the quality characteristics than the handling stress applied. Further, there may be interaction effects between handling, storage temperature, and storage time.