Processing Influences on Composition and Quality Attributes of Soymilk and its Powder

Soymilk is the aqueous extract of whole soybeans, resembling dairy milk in physical appearance and composition. The basic steps of its preparation include selection of soybeans, soaking in water, wet grinding, separation of soymilk from fiber (okara), cooking to inactivate lipoxygenase and trypsin inhibitors, formulation and fortification, and packaging. The properly processed soymilk and its derivatives offer many neutraceutical and health benefits. The type of processing and ensuing processing conditions such as high or low temperatures, short or prolonged temperature and cooking time, ultra high temperature, spray-drying parameters, processing treatment combinations with alkali or other chemicals etc. affect the properties of soymilk. The present article focuses on various processing aspects like soaking, blanching, heat treatments, chemical and enzyme treatments, fermentation, homogenization, filtration, spray-drying etc., and their effects on the composition, anti-nutrients, physico-chemical properties, sensory attributes, microbial load, and shelf-life of liquid and powdered soymilk. The applications of some novel techniques such as high-pressure processing, pulsed electric field, ultra high-pressure homogenization, ultrasound, and membrane separations on soymilk processing are also discussed.