Bitterness of soy extracts containing isoflavones and saponins

Chemical profiles of isoflavones and saponins in defatted soy flakes, soy protein isolate, and soy germ extracts were determined. The isoflavone and saponin concentration and distribution in the soy extracts were different. Recognition thresholds for bitterness were lower for extracts of defatted soy flake and soy protein isolate than for soy germ extract in water. Bitterness thresholds were higher in milk; bitterness was detected in the soy flake extract at lower concentrations of isoflavone and saponins than in isolate or germ extracts. Soy protein isolate extracts were less astringent and had less off-flavor than the soy flake and soy germ extracts in water at same total isoflavone concentration. The distribution of isoflavone and saponin forms compared with threshold and descriptive analysis suggested that the p-malonyl-glucoside isoflavone and the 2,3-dihydro-2,5dihydroxy-6-methyl-4H-pyran-4-one (DDMP)-saponins maybe the components responsible for flavor differences in soy matrices.