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The influence of heat treatment on the activity of lipo-and hydrophilic components of oat grain

Zadernowski, R., Nowak-Polakowska, H., Rashed, A.A.
Journal of food processing and preservation 1999 v.23 no.3 pp. 177-191
oats, lipids, heat treatment, antioxidants, phenolic compounds, extrusion, phenolic acids, purification, triacylglycerol lipase
Lipids in oat grains are protected against oxidation by various chemical compounds with antioxidant properties. Biologically active compounds such as tocopherols, L-ascorbic acid, thiol, phenolic amino acids and phenol compounds feature such properties. Phenolic compounds inhibit lipase activity, protect lipids against oxidation and, as a consequence, protect plant cells against the destructive activity of free radicals. The disadvantage of natural antioxidants is their low resistance to high temperatures since heating over 80C destroys their antioxidant properties. Operation such as drying blanching, roasting or extrusion destroy the protective system of plant lipids. The paper is an attempt to explain to what degree extrusion conditions influence activity of natural antioxidants. Oat flour possessing the largest amount of lipids and biologically active compounds compared to other cereal flour was used in the model system. It has been found that oat phenolic compounds are a mixture of free phenolic acids, esters and phenolic acid glycosides as well as flavonols and polyphenols. It has been established that alcoholic extracts produced from oat groat and flour had strong antioxidant properties, whereas the extracts from extruded substances did not reveal such properties. During extrusion, about 50% degradation of phenolic compounds was observed. Phenolic compounds were the main group of organic compounds enabling enzyme activity and playing an antioxidant role.