Soybeans are an important source of protein and oil. On average, over one-third of the soybean mass is protein and about 20% is oil. One of the most common type of soy product for food applications sold in the Western marketplace is soymilk. Soymilk is the pasteurized extract of soaked ground soybeans, and soy protein isolates are purified fractions containing >90% protein (db). Soy protein isolate is extensively used as a food ingredient in many fabricated foods such as comminuted meat products. The recent increase in soy protein products consumption is the result of advances in achieving improved taste and recognition of health benefits. The U.S. Food and Drug Administration approved a health claim that soy protein positively impacts cardiovascular health in humans.

Novel technologies for producing and processing soy products are of great interest to the food industry. New technologies must assure food safety while maintaining nutritional, functional, and sensory characteristics that consumers demand. Thermal processing of soymilk leads to off-flavors, changes in color and reduced nutritional content. High-pressure processing (HPP) is a potential alternative for processing soymilk without exposure to elevated heat. Pressure treatment does not affect color and nutrients, and inactivates microorganisms. In the first study, our objective was to determine the impact of high-pressure processing conditions (i.e., pressure level, pressure hold time and temperature) and storage atmosphere (aerobic and anaerobic) on microbiological reduction and protein stability during refrigerated storage. We hypothesized that higher pressures, longer dwell time, and higher temperature (75yC) would yield greater microbial reduction immediately and over refrigerated anaerobic storage.

Commercial production of soy protein isolates traditionally uses defatted soybean meal that had the oil extracted with hexane. A new screw-pressing process using CO₂ as a displacement fluid and known as gas-supported screw pressing (GSSP) or Hyplex® offers an environmentally friendly way to produce soybean meal with little heat denaturation. Other traditional screw-pressing processes involve frictional heat that denatures protein decreasing protein solubility. High solubility, however, is required to obtain maximum soy protein isolate yields.

A simplified procedure to fractionate soy protein into glycinin- or β-conglycinin-rich fractions was developed by Deak and Johnson (2005, 2007). The Deak and Johnson method yields fractionated soy protein isolates with similar functional properties to commercial soy protein products. Surimi, also known as imitation crab meat, requires fillers and/or extenders to meet consumer demand. Soy protein isolate produced from hexane-extracted soybean meal is a common functional ingredient used in surimi processing. The objective of the second study was to determine the effects of fractionated GSSP soy protein isolates and moisture content on the physical properties of surimi produced from Alaskan pollock. We hypothesized that fractionated GSSP soy protein ingredients can be used effectively to extend surimi and the surimi can be further extended by adding water to above the normal level used in industry.

The research reported in this thesis strives to provide groundwork for future efforts to develop novel processes and techniques for producing and processing soy products for the food industry.