No abstract

The antioxidant properties of phosphoHpids (PL) in a refined salmon oil model system were measured by deteP mining changes in the 2-thiobarbituric acid number and decreases in the ratio of docosahexaenoic acid (DHA)I palmitic acid (22:6/16:0) of a fish oil system incubated at 180°C for up to 3 h. The more phosphatidylcholine (PC) added to the oil system, the higher the oxidative stability obtained. The order of effectiveness of commercial phospholipids in inhibiting oxidation and the loss of polyunsaturated fatty acids was as follows: sphingomyelin (SPH) = lysophosphatidylcholine (LPC) = phosphatidylcholine (PC) = phosphatidylethanol~mine (PE) > phosphatidylserine (PS) > phosphatidyHnositol (PI) > phosphatidylglycerol (PG) > control s n|mon oil. Nitrogen contaJnlng PL, including PE, PC, LPC and SPH, were equally effective in exerting greater antioxidant properties than PS, PG and PI. The inverse relationship observed between the oxidation index (C22:6/C16:0) and color intensity for treatments following 2 h of heating suggests that Maillard-type reaction products may have contributed to the oxidative stability of PL-supplemented fish oils.

The cytotoxicity of cholesterol and a mixture of beta-sitosterol/campesterol (50%/40%) and their oxides was examined in a cultured-derived macrophage cell line, C57BL/6. Cell numbers, lactate dehydrogenase (LDH) leakage, protein content, lipid uptake, and mitochondria dehydrogenase activity were determined after exposure of cell mononlayers to sterols and sterol oxides at a concentration of 200 microg/mL for up to 120 h. Results indicate that the oxides of cholesterol, beta-sitosterol, and campesterol exhibited similar patterns of toxicity as indicated by LDH leakage, cell viability, and mitochondria dehydrogenase activity. Greatest cell damage was associated with treatments containing 5 alpha,6 alpha-epoxide or cholesterol oxides, followed by beta-sitosterol/campesterol oxides, cholesterol, and beta-sitosterol. The oxides of beta-sitosterol/campesterol caused less LDH leakage and less of an effect on protein content. Results of this study demonstrate that phytosterols contained in vegetable oils, when subjected to frying conditions, do oxidize and may cause cellular damage in an in vitro cell line similar to cholesterol oxides, although less severe.

Physical, chemical and sensory properties of cooked surimi seafood gels (crab analog) fortified with omega-3 fatty acids (FA) were monitored during chilled storage. Three sources of stabilized omega-3 FA (fish oil concentrate, menhaden oil, and a purified marine oil) were each incorporated into gels to an omega-3 FA content of 1.5% or 2.5%, wt/wt. Omega-3 FA stability, development of off-flavors, and changes in color and texture were monitored during chilled storage for two months. Gels with fish oil concentrate developed fishy flavor and aroma within 30 days and were eliminated from the study. Gels containing menhaden oil and purified marine oil exhibited little change in sensory properties or oxidation products throughout two months of storage. Relative polyene index values (ratio of polyunsaturated to saturated fatty acids) indicated that the omega-3 FA were stable at both levels of addition. Omega-3 fortified gels were whiter than control gels and gel texture was modify when adding menhaden and purified oil but not significantly affected by level of omega-3 addition. KEYWORDS omega-3, surimi, lipid stability, chilled storage .

The stability of unsaturated fatty acids to oxidation was monitored by following gas chromatographic (GC) analyses of headspaee volatiles in comparison to changes in polyunsaturated fatty acids (PUFA) and increases in malonaldehyde v/a the 2-thiobarbituric (TBA) assay. Pure standards of linoleic acid (Lo) and n~ fatty acids [eicosapentaenoic (EPA) and docosahexaenoic acid (DHA)] were added to headspace vials, equilibrated in air for 10 mln, followed by heating at 80°C in teflon~apped vials for different time intervals. Headspace analysis showed inc~mses in acetaldehyde, propenal, and propanal, corresponding to the oxidation of n-3 fatty acids, whereas hexanal production corresponded to losses of linoleic acid. The analysis of pro panal by GC-headspace after only five minutes of heating appeared to be the most effective method of monitoring the oxidation of n-3 fatty acids, as indicated by correlations between TBA values and loss of PUFA. The oxidation of I~ EPA and DHA appeared to be a function of the number of double bonds. Correlations between PUFA depletion, TBA values and volatile formation indicate that under the prescribed conditions of this experiment, GCheadspace analysis of propanal and pentane/hexanal is an excellent method for following the oxidation of selected n-3 fatty acids and linoleic acid.