INVESTIGATION OF PHYSICOCHEMICAL PROPERTIES OF WHEY PROTEIN MICRO-PARTICLES PRODUCED USING TWOSTEP EMULSIFICATION METHOD AND THEIR USE IN KEFIR
Project no. 21646 · Status: Kapanmış · 2020
Summary
Proteins have both structural and functional properties in the human body. Therefore, proteins are important in human nutrition. Food proteins have functional properties such as increasing satiety and supporting muscle and bone development. Due to these properties, proteins have special importance in the nutrition of the elderly, obese, and sportsmen. In the nutrition of such groups, protein-enriched foods are used. However, the processing of protein-enriched foods is challenging because the proteins undergo structural changes which may cause unwanted results such as increased viscosity, turbidity, or gelation. One of the methods to prevent these unwanted outcomes is the controlled denaturation of the proteins. In this project, whey protein isolate (WPI) micro-particles were produced by using twostep emulsification method, the behavior of these particles in the dispersion was investigated, and the particles were used as functional components in kefir. The behaviour of WPI particles in the presence of NaCl, MgCl2, and AlCl3 salts was investigated and it was determined that the particles behave in accordance with the Schulze-Hardy rule, which was derived from the DLVO theory. In addition, specific ion effects were observed in systems with divalent and trivalent ions. WPI particles behaved like colloidal particles in the presence of salt ions. To see the effect of heat treatment, the heat stability of WPI particles was investigated in different media containing protein and polysaccharides. In systems containing gum Arabic, WPI particles became heat stable. The mechanism behind this is thought to be the steric interaction between protein particles and gum Arabic. By using WPI particles in foam systems, the surface-active properties were examined and it was determined that particles with high electrostatic charges increased the foam stability. This behaviour is different from the behaviour of native proteins and this situation is another indication of the colloidal nature of WPI particles. WPI particles, whose physical and chemical properties were determined, were used to increase the protein content in kefir and to retard the serum separation. Two types of WPI particles with different protein contents were used in kefir. Dense WPI particles could double the protein amount in kefir without changing the physicochemical and sensory properties of the plain one. Soft WPI particles, with low protein content, delayed serum separation. WPI particles with different microstructures provided a good example of a structure-function relationship. Kefir samples were also analyzed for biogenic amine content that could pose a risk; however, the total biogenic amine content was found within the safe limits. During the storage of kefir samples, it was found that biogenic amines were both formed and degraded. With this study, WPI particles, produced by using a flexible method called two-step emulsification, were investigated in terms of their physical and chemical properties and used in kefir for the first time. The possible use areas of these particles could be protein-enriched foods, controlled release systems, and encapsulation applications. Keywords: biogenic amine, colloidal stability, critical coagulation concentration, dextran, foam stability, functional food, gum Arabic, hardness, heat stability, multivalent ion, protein particle, soft particle, tyramine