Functional properties of extruded‐expelled soybean flours from value‐enhanced soybeans

Abstract

The functional properties (protein solubility, emulsification characteristics, foaming characteristics, water-and fatbinding capacities) of extruded-expelled (EE) soy flours originating from six varieties of value-enhanced soybeans (high-sucrose, high-cysteine, low-linolenic, low-saturated FA, high-oleic, and lipoxygenase-null) and two commodity soybeans were determined. The soy flours varied in protein dispersibility index (PDI) and residual oil (RO), with PDI values ranging from 32 to 50% and RO values ranging from 7.0 to 11.7%. Protein solubility was reduced at pH values near the isoelectric region and was higher at both low and high pH. There were no significant differences for water-holding capacity, fat-binding capacity, emulsification activity, or emulsification stability. Only the high-oleic soy flour had significantly lower emulsification capacity. In general, the PDI and RO values of EE soy flours originating from value-enhanced and commodity soybeans had the greatest influence on protein functionality. The genetic modifications largely did not affect functional properties.Soybeans are traditionally processed by solvent extraction using hexane. Today's solvent extraction plants require a large capital investment and the use of a hazardous and environmentally regulated solvent. One alternative to solvent extraction is the extruded-expelled (EE) method. This technology results in soybean meal containing approximately 6-11% oil depending on the processing conditions used (1). EE processing is gaining in popularity due to reduced capital investment, ease of running EE equipment, and the ability to process identity-preserved (IP) soybeans.IP soybeans cannot be combined with any commodity-type soybean or any other IP soybean. Separation must be provided at every step of processing. In order to maintain IP, the equipment used for the transporting, processing, and storing of these soybeans must be thoroughly cleaned and inspected between uses. Documentation stating that the IP soybeans have been handled properly must follow each step of processing.IP soybeans that offer marketing opportunities include soybeans that are organically produced, certifiable non-genetically modified, and specialty soybeans that are genetically enhanced for specific end-uses (i.e., soybeans with altered FA composition, increased sucrose content, altered protein composition). Although the acreage of IP soybeans is growing, the acreage is not now nearly as large as that of commodity-type soybeans. For this reason, many large soybean processors (processing over 1000 tons/day of soybeans) find it financially difficult, logistically challenging, and inefficient to process IP soybeans.Functional properties have been defined by Kinsella (2) as "any physicochemical property which affects the processing and behavior of protein in food systems, as judged by the quality attributes of the final product." Functional properties or characteristics have been identified as being extremely important to examine before a new protein is used in a food or ...

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