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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of applied ichthyology 12 (1996), S. 0 
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The muscle tissue of coregonid ‘lavarello’ (Coregonus forma hybrida) from Lake Bolsena (Central Italy), ‘bondella’ (C. macrophthalmus) from Lake Maggiore (Northern Italy) and ‘bondelle’ (C. macrophthalmus) from Lake Neuchǎtel (Switzerland), sampled during the whitefishes' growth season, were analysed to evaluate the fat content and the fatty acid composition. In fact, the lipid profile of the muscle is strongly subjected to environmental influence and, as a consequence, its use as a parameter allowing ‘identification of origin’ of the fish products may be possible. ω3 HUFA (highly unsaturated fatty acids = C 20:5 + C 22:5 + C 22:6) content of fish from Lake Bolsena was lower than in coregonid from Lake Maggiore, while the saturated fraction (SFA) was higher. Fish from Lake Neuchǎtel showed a lower ω3 HUFA proportion than in the two other lakes. These data demonstrate that significant differences in fatty acid composition occur in similar fish species living in different lakes. Further studies are required to identify the role of each environmental variable, with special attention to temperature and food range.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The Lake Maggiore bondella Coregonus macrophthalmus use perivisceral adipose tissue for gonadal development (with particular evidence in females), and muscle fat as an energy source. Females use mainly saturated fatty acids (SFA) for energy purposes, while males use monounsaturates (MUFA) also. During vitellogenesis, females can also mobilize fatty acid precursors of gonadal highly unsaturated fatty acids of the ω3 family from muscle tissue, but in both sexes specific retention of docosahexaenoic acid (DHA=22: 6ω3) in muscle is evident. Landlocked shad, unlike several freshwater fishes, can utilize the liver as well as body cavity and muscle as a fat reserve depot. The perivisceral fat stored during the feeding period appears to be utilized mainly for winter energy maintenance requirements. Lipid reserves from liver and muscle are also mobilized to meet the requirements resulting from gonadal development. In particular, females seem to use liver reserves, especially 18: 1ω9, more than males, to meet the demands of ovogenesis. In the muscle, SFA are used mainly for energy purposes. During gonadal development, specific muscular and hepatic ω3 highly unsaturated fatty acids (ω3 HUFA=20: 5 + 22: 5 + 22: 6) and ω6 HUFA (20: 4+22: 4+22: 5) retention is evident in both sexes, while fatty acid precursors of ω3 and ω6 HUFA are mobilized, especially from muscle tissue.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Twenty-two samples of commercial fish meals from Norway, Chile and Peru were analysed for cholesterol and oxysterols using gas chromatography. Cholesterol content ranged from 25.2 to 64.8 g kg−1 total lipids. Detectable levels of the oxysterols 7β-hydroxycholesterol and 7-ketocholesterol were found and their identity was confirmed by gas chromatography-mass spectrometry. Samples of fish meal exhibited wide variability in oxysterols content, 7β-hydroxycholesterol ranging from 3.9 to 105.6 mg kg−1 total lipids (0.4–9.4 mg kg−1 dry matter) and 7-ketocholesterol from 2.0 to 56.2 mg kg−1 total lipids (0.2–5.0 mg kg−1 dry matter). The formation of 7β-hydroxycholesterol and 7-ketocholesterol in one sample of Norse LT94 fish meal stored at room temperature was also studied. Oxysterol content increased during the first 42 days of storage by about 350% and then decreased with further storage. The low amount of oxysterols measured indicates a limited degree of cholesterol oxidation in commercially available fish meals.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture nutrition 2 (1996), S. 0 
    ISSN: 1365-2095
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effect of heat treatment during fish meal processing on amino acid racemization was studied. The hydrolysis-induced racemization rate (R) and the d-isomer content in the sample before hydrolysis (I) were differentiated by means of deuterium labelling and gas chromatography-mass spectrometry (GC-MS) analysis in selected ion monitoring mode. A preliminary experiment on laboratory-made herring meals cooked at 125°C for different time intervals showed aspartic acid (Asp) as the only amino acid with significant racemization before hydrolysis. Aspartic acid racemization rate appeared to be a nearly linear function of the duration of thermal treatment (R2= 0.93; P 〈 0.01). Analyses were carried out on several samples of commercial fish meals from different origin. Low-temperature-dried fish meals had a d-Asp content, expressed as I= 100 [d-isomer concentration before hydrolysis / (d- +l-isomer concentration before hydrolysis)], at less than 1%, while the d-isomer content of high-temperature dried fish meals exceeded 2%. Differences between the two commercial categories were statistically significant (P 〈 0.001). Further studies are required in order to evaluate the effects of d-Asp in protein of fish feeds and the role of the raw material and processing parameters in inducing amino acid racemization in protein of fish meals.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 32 (2001), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Aspartic acid racemization and oxysterol content have been evaluated as indicators of fish meal and aquafeed nutritional value in a series of studies reviewed in the present paper. Kinetic studies and assessment of the d-aspartic acid content of commercial fish meals and fish feeds supported the use of the extent of racemization of this amino acid as a reliable indicator of the thermal history of fish meal. Preliminary results suggest that d-aspartic acid could be a useful indicator of the protein nutritional value for fish, expressed by nitrogen retention or in vivo digestibility. However, species-related differences seem to occur. Therefore, further studies are needed to evaluate the reliability of d-aspartic acid content as an indicator of protein nutritional value affected by processing conditions. With regard to lipid quality, two major oxysterols, namely 7β-hydroxycholesterol and 7-ketocholesterol, have been identified and quantified in commercial fish meals. The measured levels were very low compared with the values reported in the literature for fish products, probably because of antioxidant addition during fish meal processing. An effect of storage time on cholesterol oxidation was also demonstrated in a laboratory-scale experiment. Research needs for the future include a deeper understanding of the chemical reactions affecting the nutritional quality of aquafeeds, development of innovative and reliable chemical methods for raw material and feed quality assessment, and identification of critical control points in the manufacturing process to try to maintain the original nutritional value of raw materials.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Fillet yield and chemical composition were evaluated in small, medium and large (about 150, 350 and 700 g, respectively) size classes of sunshine bass (Morone chrysops♀ × Morone saxatilis♂) fed high-energy diets. Fish size had a major effect on the fillet yield, which was significantly higher (38.8 vs. 33.4–34.6%) in fish belonging to the medium-size class. The lipid contents of both whole and skinned fillets were higher than those reported in the literature, ranging from 7.8 to 10.6% in whole fillets and from 5.9 to 7.6% in skinned fillets, thereby allowing classification of sunshine bass fed high-energy diets as a medium-fat fish. A significant effect of fish size on lipid content was found only for whole fillets, therefore indicating that dietary energy excess in larger fish is mainly stored as subdermal fat. The dietary fatty acid profile was found to be the major determinant of edible muscle lipid composition in all size-classes considered. The cholesterol content of muscle tissue ranged from 23 to 29 mg/100 g tissue.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A 12-week feeding trial was undertaken to evaluate the effects of partial replacement of marine raw materials in the diet with soybean meal and beef tallow on growth and product quality of European eel (Anguilla anguilla). Based on growth, feed efficiency and chemical composition, soybean meal was found to be an unsuitable ingredient for eel diets as a substitute for fishmeal (25% on a protein basis), probably because of the low digestibility of its carbohydrate content. However, beef tallow can be used to replace 50% of fish oil without reduction in growth, provided that digestible carbohydrates are present in the diet. No major effects of protein and lipid sources in the diet were found on fillet chemical composition. Sensory analysis revealed no significant differences between fish fed the control and the experimental diets, with the exception of salty taste which was significantly higher in fish fed combined soybean meal and beef tallow compared with fish fed the control diet.
    Type of Medium: Electronic Resource
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