Soyasaponin composition complexities in soyfoods relating nutraceutical properties and undesirable taste characteristics

Abstract

Soyasaponin is classified to group A saponin (gr.A) and DDMP-saponin (DDMPs) by its aglycone structure. DDMPs includes DDMP and its derivatives; group B saponin (gr.B) and group E saponin (gr.E). Gr.A is reported as a major cause of undesirable taste in soybean whilst gr.B can promote health benefits. Soyasaponin composition in various soyfoods were evaluated by Liquid Chromatography-Photodiode-Array-Mass-Mass spectrometry to reveal and clarify polymorphism of soyasaponin relating nutraceutical properties and taste characteristics. The different chemical structure of gr.A could interpret different taste characteristics. Minor soyasaponin compounds of gr.A such partially-deacetylated gr.A compositions in soyfood were newly revealed along with fully-acetylated and null-acetylated gr.A compositions. The major gr.A in raw and thermal soyfoods were fully-acetylated gr.A, averaged 125.77 and 32.1 μmol/100 g DB respectively whilst it was 22.06 μmol/100 g DB in fermented soyfoods. The ratio of fully-acetylated and de-acetylated gr.A (including partially- and null-acetylated gr.A) of raw, thermal and fermented soyfoods were 10.61, 2.28 and 0.34, respectively. DDMP was major compound in raw sample, averaged 481.3 μmol/100 g DB while gr.B was the major in thermal and fermented samples, averaged 228.4 and 532.1 μmol/100 g DB. The ratios of gr.B and DDMP were 0.1, 0.7 and 1 for raw, thermal and fermented soyfoods, respectively. The result shown process could degrade both fully-acetylated to de-acetylated gr.A and DDMP to gr.B saponins. Thus, food process could reduce undesirable and promote nutraceutical properties especially fermented soyfoods could be recommended to consume as functional foods. However, nutraceutical properties of soyasapogenol still be scant thus it should be evaluated together with the taste characteristics of partially-deacetylated gr.A.