Two apple skin extracts (ASE) prepared from "Northern Spy" cultivar were examined for their antioxidant properties to inhibit lipid oxidation in aqueous eicosapentaenoic acid (EPA) emulsions and bulk fish oil. The ASE were effective in reducing the oxidation induced by heat, UV light and peroxyl radical, when the extent of oxidation of the emulsions and bulk oil was measured by using the ferric thiocyanate test, the thiobarbituric acid reactive substances assay and Rancimat. On the basis of total phenolic concentration of extracts, removal of sugars and organic acids (ASE 2) from crude ethanol extract of apple skins (ASE 1) enhanced the antioxidant properties in both the emulsion and bulk fish oil systems. The average induction times of accelerated oxidation at 50 to 80 degrees C of fish oil incorporated with ASE 2 (400 microg/mL) was similar to that of alpha-tocopherol (400 microg/mL) and butylated hydroxytoluene (200 microg/mL).

The present study was conducted to investigate the effects of dietary conjugated linoleic acid (CLA)-and conjugated docosahexaenoic acid (CDHA)-supplemented diets on the growth and body lipid composition of tilapia Oreochromis niloticus . Four dietary treatments of linoleic acid (LA), CLA, docosahexaenoic acid (DHA) and CDHA were tested in this experiment over a feeding period of 9 weeks. The initial average body weight and length of fish were 4.53 ± 0.96 g and 5.18 ± 0.34 cm, respectively, and temperature was maintained at 25 ± 1 ∞ C. Two replicate groups and two control groups of fish were applied among the four dietary treatments and each group consisted of 20 juvenile fish. Growth rate, feed efficiency and tissue lipid contents were not significantly affected ( P < 0.05) by CLA compared to the LA control group. A higher level of hepatosomatic index and lower growth rate were obtained from the CDHA dietary group. CLA and CDHA isomers were detected mainly in non-polar lipids of muscle, liver and brain. Lower values of mono-unsaturated fatty acids and 18:2n-6 levels were found in the CLA dietary fish group and there was no effect on the 20:4n-6 level in muscle, liver and brain. Conversely, higher levels of total mono-unsaturated fatty acids were found in liver and the 20:5n-3, 22:5n-3 level of the muscle polar fraction in the CDHA dietary fish group. These results indicate that 5% of CLA in diet does not influence the growth and feed efficiency of juvenile tilapia and that CLA was observed to be incorporated into muscle, liver and brain. Lower growth and higher liver lipid contents were observed in the CDHA-supplemented dietary fish group.

The antioxidant properties of two apple dihydrochalcones, namely phloretin and phloridzin, were evaluated and compared with those of α-tocopherol and butylated hydroxytoluene (BHT). The effects were studied in an oil-in-water emulsion system containing methyl linolenate (ML), methyl eicosapentaenoate (MEPA), and methyl docosahexaenoate (MDHA) in which oxidation was initiated by the peroxyl radical generator 2,2-azobis(2-amidinopropane) dihydrochloride (AAPH) and in fish oil where oxidation was initiated thermally. In the emulsion system, phloretin (1 and 5 mM) completely inhibited the oxidation of ML tested as evidenced by the thiobarbituric acid reactive substances (TBARS) assay. Under the same conditions, phloridzin was less effective than phloretin, but still more effective than α-tocopherol. Both phloretin and phloridzin molecules had a marginal inhibitory effect against oxidation of fish oil induced by heating at 70 °C for 3 hours, when compared to BHT. These results indicate that phloretin and phloridzin have the potential to suppress lipid oxidation in polyunsaturated fatty acid (PUFA) containing foods.

No abstract

This study investigated the effect of conjugated linolenic acid (CLNA) on the growth and lipid composition of fingerling rainbow trout Oncorhynchus mykiss. Thirty individuals in each tank with three dietary treatments and duplicate groups were subjected to three dietary levels (0:4, 2:2, 4:0) of CLNA and linolenic acid (LNA) at 16∞C in the laboratory for a period of 9 weeks. Punicic acid (cis-9, trans-11, cis-13-18:3) and linseed oil were used as sources of CLNA and LNA, respectively. The hepatosomatic index and body lipid content of the 2% CLNA dietary treatment increased significantly (P < 0.05) with respect to the control (LNA treatment). But the specific growth rate and percent gain did not improve significantly. After 6 weeks' observation, the 4% CLNA dietary treatment exhibited higher mortality and liver weight but lower weight gains (1.1-1.9 g). No significant differences were observed in the results of the feed efficiency and moisture as well as the protein content of the whole body among the treatments. Incorporation of CLNA into fish tissues was at a distinctly higher level in neutral lipids than in polar lipids. Increased levels of 22:6n-3 were found in the 4% CLNA treatment but decreased levels were found in the 2% CLNA treatment in both neutral and polar fractions. In the CLNA treatments, saturated fatty acid was relatively unaffected, the level of 18:1 was increased and the level of 18:2n-6 was decreased. These results indicate that the lower level (2%) of CLNA had no significant effect on the growth and the higher level (4%) of CLNA caused higher mortality as well as attenuating the growth of the fish. Dietary CLNA accumulated in a greater amount in the neutral lipids and modulated the fatty acid composition in the whole body of rainbow trout fingerlings.