Evaluation of the viscosity profile during simulated conditions of thermal processing
The understanding about milk protein interactions provides better cost / benefit to food industry by using each type of protein within the desired characteristics in final product. Denaturation and interaction of different proteins occur in different way and intensity when pH value varies accordingly to the medium in which they are located. This study aimed to verify the influence of whey protein/casein interaction in the evolution of viscosity at different pH (6.0, 6.5 and 7.0) values using the Rapid Viscosity Analyzer (RVA) (model 45000, Perten Instruments, Sweden) as thermal processing simulator. Samples of commercial whey protein concentrate (WPC) and milk protein concentrate (MPC) were analyzed. Thermal denaturation and level of protein interaction were measured by RVA. Further, fat, protein, ash, lactose, pH, protein concentration and moisture were performed according to procedures described by the Association of Analytical Communities (AOAC, 2005). The solid-liquid concentration of the dispersion measured in the RVA was 0.3 gg-1 dry weight in water. Viscosity was as low as possible in low pH and high MPC / WPC level. At pH 7.0 and 100% whey protein concentrate results in higher final viscosity. At pH 6.0 and 100% milk protein concentrate results in lower final viscosity. High viscosity can be related with favoured κ-CN-whey protein complex formation at high pGH (Anema, 2008). Further, increased viscosity in treatments with high proportion of WPC can be explained by the difference in size of aggregates formed between whey proteins and/or κ-CN-whey proteins and by the higher degree of denaturation at higher pH values.
Anema, S.G. On heating milk κ-casein from the casein micelles can precede interactions with the denatured whey proteins. Journal of Dairy Research, 75, p. 415–421, 2008.
AOAC International. Official Methods of Analysis of AOAC International. USA, 2005.
Keywords: protein denaturation, pH, RVA