30A-10 |
Effect of high-pressure homogenization on soy protein concentrate emulsions |
R. ROESCH, Food Science and Technology, University of Georgia, Athens, GA 30602 and M. Corredig. Justification Soy protein concentrate (SPC), a low-cost ingredient containing about 70% protein and 20% polysaccharide, derives from a conventional alcohol wash process of hexane extracted soy flakes. In spite of its low solubility, SPC has been widely utilized as an ingredient in foods; for this reason, a better understanding of the functional properties of SPC is needed. Objective The objective of this work was to study the properties of SPC after high-pressure homogenization with 20% oil. Methods The SPC was dispersed in a 50 mM Sodium phosphate buffer, pH 7.5. Emulsions were made using 20% (w/w) soybean oil and 4%, 6% (w/w) SPC. The samples were pre-homogenized with a hand-held homogenizer (Polytron PT 1200, Kinematica) and passed through a valve homogenizer (Emulsiflex C5, Avestin) at 12,000 psi. Particle size distribution was determined by integrated light scattering (Mastersizer X, Malvern Instruments). The viscoelastic properties were studied using a controlled stress Rheometer (RS 5000, Rheometric), measuring the frequency dependence of storage (G’) and loss (G”) moduli. In addition, microstructural studies were carried out using a confocal microscope (MRC 600 Bio-Rad) and Scanning Electron Microscope (Leo 982, Leo). Results Emulsions containing 20% oil and 4, 6% SPC revealed a linear viscoelastic range for stress values up to 100 Pa. The little dependence of G’ and G” during frequency sweep measurements demonstrated the gel-like properties of the SPC emulsions. Aggregation was clearly shown by changes in particle size distribution of the emulsions. Changes in viscoelastic properties following homogenization at 12,000 psi seemed to be caused by separation of the oil phase as indicated by microstructural observations. Significance Soy protein concentrate can be successfully employed as a functional ingredient in oil-in-water emulsions when homogenized at high pressure. Such systems were characterized by a solid-like behavior in spite of the low SPC concentration used.
Session 30A, Food Chemistry: Lipids
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