The connective tissues of fish

Summary. 'Gaping'is a phenomenon in which slits or holes appear between the muscle blocks, so that in a bad case the fillet falls to pieces and cannot be processed or sold. the gaping in whole fish frozen in rigor mortis, thawed and filleted was shown to be related to the biological condition of the fish, strong healthy fish gaping a great deal, while spent or starving fish did not gape at all. It is postulated that when fish are frozen in rigor mortis the ice growing in the connective tissue weakens it, so that it may break under the rigor mortis contraction. the contraction of spent or starving fish appears to be too weak to break the connective tissue. No gaping was shown by similar fish frozen before rigor mortis. the practical importance of the findings is discussed.     

不同温度条件下鱼油氧化的动态变化

鱼油是水产饲料重要的脂肪源,但由于其富含多不饱和脂肪酸而极易氧化。系统研究了不同氧化温度下,鱼油过氧化值(POV)、酸值(AV)、碘值(IV)、羰基值(CV)和硫代巴比妥酸反应物(TBARS)随氧化时间的变化规律。结果表明:在各氧化温度下,鱼油的POV、AV、CV和TBARS均随氧化时间的延长而显著升高(P<0.05);IV随氧化时间的延长而显著降低(P<0.05)。在各氧化温度下,鱼油的POV和AV随氧化时间的延长均呈二次曲线变化;IV和CV随氧化时间的延长均呈线性变化;而TBARS随氧化时间的延长呈幂回归变化。     

Seasonal evaluation of nutritional benefits of two fish species in the eastern Mediterranean Sea

Fish are a good nutritional source of proteins, essential fatty acids and minerals. Societies with high fish intake have lower rates of acute myocardial infarctions and atherosclerosis, better cognitive functions, and better neural and visual development in foetuses. In the present work, we evaluated seasonal variation in proximate composition of two commercial fish species, the rabbitfish Siganus rivulatus, an algaevore, and the white sea bream Diplodus sargus, a carnivore from the eastern Mediterranean. Fifteen fish were collected on the second weekend of each of 8 months covering the four seasons. Results show that the nutritive value of a species of fish varies throughout the year. Furthermore, rabbitfish tissue generally contains more lipids than white sea bream, and fillet yield from rabbitfish is greater than from sea bream. As both fish are sold at a similar price in Lebanese markets, results suggest that rabbitfish offers better value for the price than does white sea bream.     

Behaviour of connective tissue in fish surimi on fractionation by sieving

The surimis prepared from the three fish species, red barracuda Sphyraena pinguis, yellow sea bream Dentex tumifrons, and spotted shark Mustelus manazo, were fractionated by sieving through a 30-mesh stainless steel sieve. Chemical analyses revealed significant differences in the collagen content among the residual fraction on the sieve (fraction A), the passed fraction (fraction C), and the original surimi before sieving (fraction B): the fractions A and B showed values 10–20 and 5–10 times higher than those of the fraction C, respectively, for all the species examined. Histological observation indicated the richness of the thick connective tissues derived from myocommata in fractions A and B, while thick connective tissue was hardly observed in fraction C. These results suggested that the present fractionation method may have an effect of reducing the collagen content to about 10–20% of the original value, and that a large part of collagen in fish surimi exists in the relatively thick connective tissue, probably derived from myocommata.     

The connective tissues of fish. II. Gaping in commercial species of frozen fish in relation to rigor mortis

Summary. Fish of different species frozen whole, thawed and filleted gape according to the time after death at which they were frozen. Those frozen immediately after death gaped least, a marked increase accompanying the onset of rigor mortis. Thereafter, there was a steady increase in gaping as the fish were held for longer periods in melting ice prior to freezing. the cause of this second type of gaping is unknown.
There was a marked difference between species, haddock showing the most gaping and catfish and skate none at all. the three species of flat fish gaped less than the four round fish (apart from catfish) species, which fact may relate to the shape of the fish, especially as the roundest-bodied of the flat fish, halibut, gaped the most of the group.
The site of gaping was identified histologically, and different degrees of gaping are illustrated by means of photographs.     

Marine and farmed fish in the Polish market: Comparison of the nutritional value

The proximate composition and fatty acids profiles of the muscle tissues of nine fish species that are popular on the Polish market were examined. The nine studied fish species were: Baltic fish (cod, herring, salmon), fish farmed in Poland (carp, trout), oceanic fish imported from China (walleye pollock, sole), and farmed fish imported from Vietnam and China (sutchi catfish, tilapia). The lowest lipid content (below 0.1%) was noted in the muscle tissues of Baltic cod and walleye pollock caught in the Pacific. The muscle tissue of walleye pollock also had the lowest protein content (12.2 ± 2.0%). The highest lipid content was noted in the muscle tissues of Baltic salmon (13.1 ± 2.4%). The highest percentage content of eicosapentaenoic (C20:5 n − 3 – EPA) and docosahexaenoic (C22:6 n − 3 – DHA) acids (over 40%) was noted in the fat extracted from the oceanic fish and Baltic cod. However, due to the low fat content, the concentrations of EPA + DHA in these fish species and in imported farmed fish expressed in mg/100 g of muscle tissues are the lowest and range on average from 24.8 ± 5.7 mg/100 g (sutchi catfish) to 207.4 ± 125.4 mg/100 g (sole). This is why the consumption of these fish species has no significant meaning for coronary heart disease prevention. Consumers with symptoms of cardiovascular diseases should include the following fish species, which have high concentrations of EPA + DHA: Baltic salmon (3807.2 ± 666.3 mg/100 g); Polish farmed trout (1804.0 ± 279.2 mg/100 g); and Baltic herring (940.9 ± 306.6 mg/100 g) in their diets. However, the consumption of Baltic salmon must be limited on account of the levels of persistent organic pollutants found in it.     

带鳞田鱼丸的研制

为了开发青田田鱼加工新产品,结合田鱼鱼鳞柔软可食的特点,进行了带鳞田鱼丸的研制。利用感官评定法、凝胶特性分析、正交实验等方法确定鱼丸的最适生产工艺。结果显示:田鱼糜与杂鱼糜的最适质量比为4:1;正交实验得出最佳鱼丸制作配方为:田鱼糜55%,淀粉15%,色素0.03%,水15%;田鱼鳞片的最佳预处理方式为0.5%醋酸浸泡30min,最适添加量为鱼丸质量的2%~3%。利用本工艺制作的鱼丸,颜色鲜艳,口感爽滑,丰富了市场鱼丸的品种。