Functional properties of protein ingredients prepared from high-sucrose/low-stachyose soybeans

High-sucrose/low-stachyose (HS/LS) soybeans were used to prepare ethanol-washed soy protein concentrate (EWSPC), soy protein isolate (SPI), and a new low-fiber soy protein concentrate (LFSPC) in which the protein was extracted with alkali to remove fiber and the protein extract was neutralized and freeze-dried. LFSPC prepared from HS/LS soybeans contained significantly higher ratios of P-conglycinin to glycinin (1:1.32) than did EWSPC (1:1.75) or SPI (1:1.69), which may have affected functional properties. The LFSPC were also high in soluble sugars (14.7%) and low in fiber (0.3%) compared with traditional EWSPC (2.9 and 3.4%, respectively) and SPI (1.8 and 0.3%, respectively). For both normal and HS/LS soybean varieties, the LFSPC, especially when extracted at pH 7.5 as opposed to pH 8.5, had higher denaturation enthalpies than did EWSPC and SPI, indicating less denaturation had occurred. Water solubilities, surface hydrophobicities, and emulsification properties were highest for the LFSPC and lowest for EWSPC. The LFSPC also had good foaming properties and low viscosities. These desirable functional properties of the LFSPC make them unique among alternative soy protein ingredients and highly suitable for industrial applications as food additives and ingredients.