Quality Of Fish Fillets Research Articles

Effects of Edible Coatings on the Moisture Content and Lipid Oxidation of Pink Salmon (Oncorhynchus gorbuscha) Fillets during Three Months of Frozen Storage

The effects of a variety of edible coatings, cooked arrowtooth flounder coating (AFC), hydrolysed arrowtooth flounder protein (AFH), acid solubilized arrowtooth flounder protein (AFP), soy protein (SP), whey protein (WP) and non-coated fillets as control (NC) on the biochemical and physical changes in pink salmon fillets stored at - 30o C were evaluated in this study. The AFC and AFH coatings significantly reduced the relative moisture loss (RML) of the fillets, while the thiobarbituric reactive substance (TBARS) assays for AFH and SP were significantly lower than in treatments. The AFP significantly increased coating yield as well as the moisture content of cooked fillets. This study demonstrated the efficacy of arrowtooth flounder protein coatings as a means of maintaining fish fillet quality.

Vitamin B6 supplementation increases the docosahexaenoic acid concentration of muscle lipids of rainbow trout (Oncorhynchus mykiss)

Fish fillet quality is influenced by feed quality. In particular, vitamin B6 availability improves growth rate and nutritional value, because it is related to protein and lipid metabolism. The present study investigates the effect of increasing amounts of vitamin B6 on growth, fatty acid composition and lipid peroxidation of muscle tissue of rainbow trout (Oncorhynchus mykiss). Quadruplicate groups of trout of a mean initial weight of 110 g were fed commercial diets supplemented with four different quantities of vitamin B6 (0, 10, 25 and 50 mg kg−1 diet). Over the experimental period, there were no significant differences in weight gain and feed intake, while vitamin B6 concentration of muscle was affected by dietary intake, even though its increase was not proportional to the concentrations in the feed. The fatty acid composition of muscle lipid showed differences between the four groups. The percentage of long-chain unsaturated fatty acids, in particular docosahexaenoic acid, increased significantly in vitamin B6-supplemented groups. However, despite the increased fatty acid unsaturation index, lipid peroxidation parameters such as vitamin E content, malondialdehyde production, glutathione reductase and glutathione peroxidase activities did not show significant differences, meaning that the higher level of long-chain unsaturated fatty acid did not increase the muscle susceptibility to oxidative stress.

Grilling of sardine fillets. Effects of frozen and thawed modality on their protein quality

Sequential freezing, thawing and cooking may affect the protein quality of fish fillets. Fillets of fresh raw sardine (R) were stored frozen, thawed at 4°C in a refrigerator (RR) or in a microwave oven (MR), and subsequently grilled (G). Proximate and amino acid compositions, solubility in sodium dodecylsulphate+ β-mercaptoethanol, –SH group content and amino acid chemical score were determined. Freezing–thawing increased ( p<0.05) (in wet matter basis) fat and decreased protein content in RR samples and ash content in RR and MR samples. Grilling produced a drip-loss phenomenon that causes loss of moisture that was more prominent after thawing (RG and MG samples). Thawing in refrigerator decreased the protein solubility, but grilling reversed that effect increasing and decreasing it in RG and MG samples, respectively. Every step of all processes caused a decrease in –SH group, cyst(e)ine and methionine giving rise to the lowest chemical score in RG and MG samples. The cholesterolemic index given by the arginine/lysine ratio and the smallest changes in the protein quality suggest that consuming grilled fresh raw sardine fillets is better than consuming refrigerator or microwave thawed–grilled sardine fillets.

The effect of dietary vitamin E and C level on market-size turbot (Scophthalmus maximus ) fillet quality

Fish fillet quality has been shown to be influenced by the level of antioxidants in preslaughter diet. Thus, an experiment was conducted to study the effect of different levels of vitamin E and C on the fillet quality of market-size reared turbot (Scophthalmus maximus). Turbot of a mean initial weight of 347 ± 20 g were divided into four groups and fed commercial turbot diets (60% protein, 12% fat), supplemented with α-tocopheryl acetate (mg kg−1) and ascorbyl-2 monophosphate (mg kg−1) at the following dietary levels: 500/100, 1000/100, 100/1000, 100/100 respectively. Over a dietary supplementation period of 15 weeks, fish were fed to satiation and reached a final mean weight of 916 ± 29 g. α-Tocopherol levels increased significantly (P < 0.001) in tissue (i.e. muscle, liver, heart and kidney) of fish fed diets containing elevated levels of α-tocopheryl acetate. In ice storage, fillets of these fish exhibited significantly lower (P < 0.001) levels of lipid oxidation, and showed significantly less (P < 0.001) colour deterioration (higher hue angle and lower chroma). Elevated dietary α-tocopheryl acetate levels had a negative effect (P ≤ 0.001) on the concentration of ascorbic acid in muscle tissue. An increase in dietary vitamin C did not have any detectable effect on fillet quality. Prolonged feeding times had a negative effect on lipid oxidation (P < 0.001) and colour deterioration (P < 0.01). These results suggest that increased dietary α-tocopheryl acetate could prevent colour deterioration and lipid oxidation of turbot fillets in retail storage on ice.

Fillet shelf-life of Atlantic halibut Hippoglossus hippoglossus L. fed elevated levels of α -tocopheryl acetate

Fish fillet quality may be influenced by the antioxidant level in preslaughter diet. Thus, the effects of dietary α-tocopheryl acetate supplementation and feeding time on the flesh quality of farmed Atlantic halibut Hippoglossus hippoglossus L. were investigated. Halibut of mean initial weight of 312 ± 12.3 g were divided into two groups and fed commercial diets, supplemented with different levels of α-tocopheryl acetate at the dietary inclusion levels of 189 and 613 mg kg−1 diet. Fish were sampled after 6,9,12 and 24 weeks. Over the experimental period, they reached a final mean weight of 1320 ± 108.4 g. Tissue α-tocopherol of fillet and liver was significantly affected by the levels of α-tocopheryl acetate given with the diets (P < 0.001). In storage on ice, fillets of fish fed the diets high in α-tocopheryl acetate exhibited significantly lower (P < 0.001) levels of lipid oxidation. The colour of fillets in all groups deteriorated slightly, but diet did not affect this process. Halibut fed the supplemented diets for longer periods were better protected against lipid oxidation (P < 0.001) and colour deterioration (P < 0.01) than those fed for shorter periods. However, after 9 days of storage, lipid oxidation levels were still extremely low [< 0.6 µg malondialdehyde (MDA) g−1 fillet], even in fillets of fish fed the low α-tocopheryl acetate diet for a short period preslaughter. Different slaughtering methods tested at the end of the trial showed that percussive stunning can delay the onset of rigor mortis by 8–12 h compared with bleeding of the fish. These results suggest that halibut fillets have enhanced shelf-life stability even at low doses of dietary α-tocopheryl acetate, and that other factors in the antioxidant defence mechanisms of the species might play a major role in the prevention of lipid oxidation.

低線量照射と食品防腐剤の併用による鮮魚の鮮度保持効果

低線量照射と食品防腐剤の併用による鮮魚の鮮度保持効果