Viscosity Measurement of Solutions Composed by Whey Protein Using a Rapid Viscosity Analyser (RVA)
The evaluation of the viscosity performance of protein solutions used as ingredients in food is essential for this application in the food production. The Rapid ViscoTM Analyzer (RVATM) is a rotational viscometer capable of continuously measuring the viscosity of a sample under controlled temperature conditions (Booth & Bason, 2007). Using a RVA, the current study aimed to evaluate the viscosity of solutions prepared from whey protein concentrates (WPCs) produced from milk whey samples initially subjected to thermal treatment 72ºC for 15 s (PT72) or microfiltration (0.8 μm - MF0.8 or 1.4 μm - MF1.4). Each treatment was ultrafiltered and subjected to vacuum evaporation using a rotary evaporator and dried in a spray dryer. The resulting WPCs were evaluated for their content of fat, total solids, moisture, ashes, and total protein. Furthermore, water activity (Aw) of each WPC was measured. The solutions prepared from the WPCs were also evaluated for their viscosity. Data analysis was performed using Statistical Analysis System version 9.2 software (SAS Institute Inc., 2006). The WPCs presented composition compatible with the international standards, with a significant difference (p<0.05) for fat concentration . Viscographic profiles indicated that WPCs produced from microfiltered whey had higher viscosities than those subjected to heat treatment. In addition, 10 min. was determined to be the optimal length of time for heat treatment in order to maximise WPCs viscosity. The WPC solutions obtained from pasteurized whey showed lower viscosities than solutions obtained from microfiltration whey. This result demonstrates the importance of technological choices on the behavior of the WPC and further, WPC can be design for different food applications. Finally, a rapid viscosity analyzer was demonstrated to be an appropriate tool to study the application of whey proteins in food systems.
Keywords: milk protein, microfiltration, RVA