Oxidation of soybean lipids catalyzed by lipoxidase was prevented by heat treatment of soybean meats, which were then ground to give a full‐fat soy flour free of rancid odor and flavors. Our previous studies showed that lipids in cracked, dehulled, soybeans rapidly oxidized after the lipoxidase system was activated by increasing moisture content to 20%. A series of experiments are reported in which various heat treatments were evaluated for effectiveness of lipoxidase deactivation. Dry heat to 212 F, steaming, or both, deactivated lipoxidase to give flours that had low values of peroxide, conjugated diene and free fatty acid and had good flavors after 2 years’ storage. Wet heat alone was also an effective treatment, whereas wet heat preceded by dry heat at 180 F gave poor flavor stability after 2 years. Gas liquid chromatography studies gave evidence that the rapid formation of volatiles in full‐fat soy flours was catalyzed by an enzyme system. A 10 member taste panel was able to detect significant flavor and odor differences between oxidized and nonoxidized samples.

Soybean flour and various derivatives, with different natural, interacting primary antioxidants and synergists can stabilize lipids in formulated foods. Soybean flour has been shown to be a basic source of such antioxidant compounds as isoflavone glycosides and their derivatives, phospholipids, tocopherols, amino acids and peptides. There may be some antioxidant impact from aromatic amines and sulfhydryl compounds. Successful efforts have been made to concentrate the antioxidant activity in soy flour by aqueous extraction and by extraction with various organic solvents. Residual antioxidant activity has been reported in food systems containing soy protein concentrates, isolates and textured vegetable protein. Soy protein hydrolyzates have antioxidant activity which is associated with free amino acids and lower molecular weight peptides.

Whole millet adjusted to 15% moisture was gradually heated to 97°C over 12 min by passing through a steam-jacketed paddle conveyer to inactive lipid enzymes. Both processed and unprocessed millet were milled to 50% and 80% extraction flours. The 80% flour contained germ fractions, which resulted in much higher protein, lipid, thiamine, riboflavin, niacin, iron, zinc, available lysine, and protein efficiency ratios than the 50% flour. After 49°C storage, peroxide and fat acidity values were lower and flavor scores higher for processed than for unprocessed millet flours. No differences between processed and unprocessed flours were found in birefringence, water absorption and solubility, viscoamylograph values, or in their use in several traditional foods.

Full-fat soy flours prepared by the extrusion process were shown to have good nutritive value, flavor, and stability. A flour cooked to a nitrogen solubility index (NSII of 30 stored well, but the addition of tertiary butyl hydroguinone was necessary to prevent rancidity in flours cooked to 19 and 11 NSI values. The 30 NSI flour was more yellow than a commercial flour cooked to the same degree by a different process. When soy flours were compared in bread to 3 and 6% nonfat dry milk on an equivalent protein, fat, and reducing sugar basis, baking properties were similar. At 15 and 20% levels of soy flour, loaf volume decreased less with the extruded products than with nonextrusion-processed soy flour.

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