Cereal Chem 49:586 -
597. | VIEW
Lipoxygenase and Peroxidase Activities of Soybeans as Related to the Flavor Profile During Maturation.
J. J. Rackis, D. H. Honig, D. J. Sessa, and H. A. Moser. Copyright 1972 by the American Association of Cereal Chemists, Inc.
Hawkeye and Amsoy soybeans were picked at 15 intervals from 24 to about 66 days after flowering. During maturation, percentage of dry matter increased from 16 to 92 and total dry matter from 5 to 243 mg. per bean. Flavor intensities of each picking were determined by a taste panel. Lipoxygenase activity of beans of similar fresh weight, picked on the same day, was measured by the oxygen uptake method. Beany and bitter were the two predominant flavors in maturing soybeans. Most tasters used the terms green-beany, beany, and raw beany to describe the "beaniness" of soybeans. Grassy was an infrequent response. Beany and bitter flavor responses were recorded as flavor intensity values (FIV) based on a scale of 1 for weak, 2 for moderate, and 3 for strong. FIV with respect to beany varied from 2.0 to 2.7 during maturation, with the average being 2.4; no significant trends were noted. The average FIV for bitter for the two varieties increased threefold from about 0.54 in immature soybeans to 1.9 at maturity. Lipoxygenase activity at pH 6.8 varied from a low of 12 microliters O2 per min. per mg. dry matter in the early stages to 35 at 34 days after flowering, then down to 23 at 45 days, up to 43 at about 1 week before maturity, and then slowly increased to about 32 microliters O2 uptake at maturity; 02 uptake values of 11 to 23 microliters were recorded for lipoxygenase activity at pH 9.0. The FIV for beany did not correlate with changes in lipoxygenase activity; however, a correlation (r = 0.73) exists between lipoxygenase activity and the increase in FIV for bitter flavor as beans mature. An active peroxidase capable of utilizing linolenic hydroperoxide was also present. Peroxidase activity remained relatively constant throughout most of the maturation period, except for a large decrease at maturity.