Book Description

This body of research focuses on three major areas related to soy protein ingredients. The first area is the use of genetically modified high-sucrose/low-stachyose soybeans (HS/LS) in a new simplified procedure to prepare soy protein concentrate; secondly, fractionating soy protein into ingredients enriched in either glycinin or [Beta]-conglycinin; and lastly, processing effects on soy protein isolate functionality. Soy protein fractionation was significantly improved by increasing protein yields and reducing processing costs. In the three-step or Wu fractionation procedure, significant advances were made by identifying the optimum SO2 concentration to be 5 mM, the optimum NaCl concentration to be 250 mM, and the optimum dilution factor to be 1-fold. Furthermore, this procedure was modified by using mM amounts of CaCl2 at pH 6.4 improving both yield and purity of the [Beta]-conglycinin-rich fraction. A new two-step fractionation procedure was developed based on the differential calcium reactivity of glycinin and [Beta]-conglycinin. The use of 5 mM SO2 in combination with 5 mM CaCl2 in this fractionation procedure yielded improved purities in the glycinin-rich (85.2%) and [Beta]-conglycinin-rich (80.9%) fractions. This procedure yielded fractions with improved solids, protein, and isofiavone yields. In addition, the ingredients produced by this method had unique and improved functional properties. Phytic acid was proposed as playing an important role in fractionating soybean storage proteins because of its ability to complex with calcium ions and soy protein. HS/LS soybeans were used to produce a new soy protein concentrate that was low in fiber, high in isoflavones and soluble sugars, and had unique functional properties, which were, in most cases, similar to or better than those found in traditional soy protein isolates. HS/LS soybeans were identified as good starting material for fractionating soy protein. In the Wu fractionation procedure, HS/LS soybeans yielded high amounts of the individual storage proteins with 100% electrophoretical purity. The functionality of soy protein isolate was affected by extraction temperatures and method of preservation. Spray-dried soy protein isolates (SPI) were more soluble, hydrophobic, and formed more stable emulsions than did freeze-dried SPIs. The drying method, however, did not affect denaturation enthalpy of SPI.