Influence of storage and microwave heating on stability of soya spread lipids with linseed content
We have chosen to experiment with soya spreads containing linseeds, which enrich the spreads with essential fatty acids and valuable related substances. The soya spreads with linseeds represent an ideal combination for nutritionally valuable foods with health benefits. In this work we examined the influence of microwave heating and storage on stability of linseed oil and soya spread lipids. Industrially produced soya spreads (S1) with addition of 5, 7 and 10 % linseeds and linseed oil were stored without a protective atmosphere in refrigerator at 5 °C. The lipids of commercial soya spreads (S2) enriched with 2, 5 and 10 % ground linseeds and soya spread lipids (S2) without linseeds were microwave-heated. The data obtained from experiments have shown that the storing of linseed oil for 30 days in refrigerator has caused excess of the maximum acceptable peroxide value (Food Codex of SR). Microwave-heated lipids from commercial soya spreads (S2) enriched with 2 % ground linseeds have the best result of stability and protective factor, compared with lipids from 5 and 10 % linseeds enriching soya spreads (S2). After the 5, 10 and 20 min of microwave heating, the lipids of soya spread (S2) enriched with 2 % ground linseeds have the protective factor 1.02, 1.15 and 1.43 respectively, compared with lipids from soya spread (S2) without linseeds. The microwave heating for 5 min has been accompanied by a decreasing of hydroperoxides and by formation of secondary oxidation products.