A novel three-way interaction among starch, protein, and free -fatty acid: Functionality and mechanism elucidation
Abstract
A model system composed of sorghum starch, whey protein, and FFA (palmitic, oleic, and linoleic acids) was used to investigate the three-way interaction among starch, protein, and lipid. A RVA cooling stage viscosity peak was produced when starch, protein, and FFA were altogether in the system, while no cooling viscosity peaks was formed when only protein or FFA alone was in the system with starch. The height of the RVA cooling stage viscosity peak was affected by the structure of FFA and component interaction sequence, and a certain amount of FFA and protein was required to produce the RVA cooling stage viscosity peak. Both salt addition and lowering the pH of the system decreased, and eventually eliminated the RVA cooling stage viscosity peak. A true three-way interaction among starch, protein, and FFA was established, and the mechanism was subsequently investigated. The starch-FFA complexation was reduced by the presence of whey protein in the system, but the V-type crystalline order of starch-FFA complexes was increased as shown by the pronounced peaks in x-ray diffraction patterns. The ordered starch-FFA complex paralleled the formation of the RVA cooling stage viscosity peak. Starch-FFA and whey protein-FFA complexes were the two secondary structural elements in the three-component system, and a novel high molecular weight three-way complex (∼10 6-107 dal) composed of starch, protein, and FFA was also produced during the three-way interaction. The three-way complex was water-soluble, sensitive to 2-mercaptoethanol (2-ME) treatment, and could be precipitated by 0.1–1 M NaCl. Whey protein existed in the three-way complex as huge aggregates formed by disulfide bond linkages, and starch-FFA complexes were also present in the three-way complex. The electrostatic force contributed from the negative charges of whey protein and FFA was the major force involved in the formation of the three-way complex during the three-way interaction. This three-way complex is indicated to be the structural basis of the three-way interaction as shown by its parallelism to RVA cooling stage viscosity peak formation and the well-formed V-type starch-FFA complexes. Results from lysozyme (pI = 10.7) and other nonionic amylose-complexing agents supported the above hypothesis. A model was proposed based on the above experimental results.
Degree
Ph.D.
Advisors
Hamaker, Purdue University.
Subject Area
Food science
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