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The inhibition effects of the brown pigments produced by reaction of glyoxal with glycine or ethyl amine and by self-condensation of diacetyl onl -ascorbic acid oxidation catalized by bivalent copper were studied. The relative inhibition constants of the pigments were 150 and 110 for the glyoxal-glycine pigments, 70 for the glyoxal-ethylamine pigment and 20 ml/g · min for the diacetyl pigment. More polar pigments had better antioxidative activity in solutions ofl -scorbic acid, while less polar pigments were more effective in protecting lipids against autoxidation.

Summary Carbonyl derivatives produced by lipid oxidation, e. g. aldehydes and hydroxyketones, can react with free amino groups with formation of various coloured condensation products. The reaction is rather slow at room temperature, but it is accelerated by moderate increase of temperature so that it may be finished within one hour. The main products formed in the beginning of the reaction have the composition corresponding to imines. In presence of excess amine groups, these products probably predominate even after longer reaction times. In the case of media where aldehydes are present in excess, and, particularly, in acid media, compounds containing two or even more aldehydee radicals for each amino group are formed by further aldolization of primary reaction products. In the case of hydroxy ketones, no reactions analogous to aldolization take place, on the contrary, one hydroxyketo group can bind two amino derivatives.

Summary Tocopherols are easily oxidized by ferric salts and other oxidizing agents present in food products, the major reaction products being toco red and toto spiro dimer and trimer. Toco red reacts either with the e-amino group of lysine bound in protein with formation of insoluble products or may form chloroform-soluble amino derivatives via Strecker degradation. These latter products of purple colour which are chloroform-soluble are easily polymerized, especially at high temperatures or during longer beating times. Brown polymers remain liposoluble at least partially. The dimer is partially decolourized by reaction with protein, probably because it is not able to attack amino acids via Strecker degradation. As the condensation reaction is relatively rapid, quinoid derivatives of tocopherols are probably almost completely transformed into brown nitrogenous condensation products under the conditions of processing and storage of food.