BIOCHEMICAL ASPECTS OF LIPID-DERIVED FLAVORS IN LEGUMES

Lipoxygenase-mediated conversion of polyunsaturated fatty acids to aldehydes and alcohols is a major contributor to the off-flavors in legume protein products. Numerous volatile compounds produced by action of either purified pea or soybean lipoxygenases on linoleic acid and linolenic acids include 2-n-pentylfuran and 3-cis-hexenal, both of which reportedly contribute to the green-beany flavor of soybeans. Higher alka-2, 4-dienals, described as tasting oxidized, cardboardlike, oily, and painty, have also been generated by enzymic oxidations. A novel 5-substituted-2-furaldehyde from linolenic acid decomposition is released from bitter tasting soy phospholipids. Nonvolatile oxygenated fatty acids are also generated in model systems with soybean lipoxygenase and linoleic acid or its hydroperoxide in the presence of electron donors. Similar fatty acids can also arise from action of cysteine-Fe3+on linoleic acid hydroperoxides, are found on bitter-tasting soy phosphatidylcholines (SPC), and are produced by soy lipoxygenases acting on purified SPC substrates. Development of off-flavors can be controlled by inactivation of lipoxygenase with heat, acid, alcohol, or antioxidants. © 1979, American Chemical Society. All rights reserved.