Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 21, 2003
Publication Date: July 1, 2003
Citation: MOHAMED, A., XU, J. EFFECT OF IONIC STRENGTH AND PH ON THE THERMAL AND RHEOLOGICAL PROPERTIES OF SOY PROTEIN-AMYLOPECTIN BLEND. FOOD CHEMISTRY. 2003.v. 83(2). p. 227-236 Interpretive Summary: Soybean meal is an important source of high nutritional value and quantity protein. The United States is one of the major producers of soybeans. The production and consumption of soybeans for many years had been confined to south Asia, which explains the many traditional soy foods developed in China, Japan, and other south Asian countries. In the past few years, varietal development and production of soybeans in the U.S has increased sharply. Soy oil was considered the first product of interest, but more recently soy proteins have become the most important component of soybeans. Many American companies have started developing protein based soybean products. This work will help soy protein producers to develop better ways to isolate soy protein and thus increase its uses. Products development groups in the food industry can use the information included here.
Technical Abstract: The effect of amylopectin (AP), moisture content, pH, and buffer molarity on the thermal properties of milled defatted soy flour (MDF) and Soy Protein Isolate (SPI) were studied by Differential Scanning Calorimetry (DSC), and the rheological properties of effect of AP on MDF were also investigated. Native soy protein, which is found in the MDF sample showed higher stability at alkaline pH as indicated by higher onset and peak temperature when compared to SPI. The effect of manufacturing isolation process on soy proteins is apparent on the differences between MDF and SPI thermal properties and SDS-PAGE profiles. The onset temperature and deltaH values of the 7S showed significant difference between MDF and SPI at 20% moisture content, 0.3 M and pH 4. The 11S of the MDF and SPI showed that the peak temperature and deltaH to be significant difference at the same buffer amount and pH mentioned earlier. The 30% moisture content generated significant differences between the MDF and SPI at all experimental conditions i.e., pH and molarity. The increase in the moisture content to 40% produced similar changes as 30%. The 11S of the SPI sample displayed deltaH values higher than MDF, which may indicate aggregation as a result of manufacturing process. Amylopectin suspension had strong viscoelastic solid properties and the properties were stable during heating or cooling between 25 deg C and 55 deg C. MDF also displayed viscoelastic solid properties, but not as strong as those of AP. The viscoelastic properties of MDF suspensions were not stable and damaged during heating and cooling process. Blending MDF and AP exhibited similar properties as MDF alone, but reversible during heating/cooling process indicating the networks were not damaged. The strong gel properties of AP in the blend were marginalized.