Abstract
The rheological properties of soup of tarhana enriched with whey concentrate (WC) at different concentrations (0.0, 6.25, 12.5 and 25.0%) were studied in the temperature ranges of 30, 40, 50, 60, 70 and 80C. Tarhana soup with or without WC behaved as shear thinning. The power law model was determined to be adequate (R2 = 0.900-0.999) to fit the flow curves of tarhana soup with or without WC. Temperature dependency of rheological parameters followed the Arrhenius model (R2 = 0.791-0.965). The mathematical models, power law and exponential functions were developed to determine the apparent viscosity (consistency index, k) of tarhana soup as a function of temperature and added WC. The effectiveness of developed combined models was judged by several statistical parameters In general; exponential function fitted better the effect of WC concentration and combined effect of temperature and added WC than power law function did.
PRACTICAL APPLICATIONS
Tarhana is a traditional fermented food made of mainly a mixture of cereal and yoghurt. Tarhana or tarhana-like products have been enriched or replaced with cereal and cereal by-products; however, no attempts have appeared so far to enrich tarhana with whey protein sources. It was reported that the practical nutritional importance of tarhana is the improvement of the basic cereal protein diet by adding whey protein. Viscosity is among the most important functional properties of whey proteins; however, there is no published data informing the rheological properties of tarhana soup enriched with different concentrations of whey concentrate (WC). In this respect, the rheological properties were studied as a function of WC concentration; also, temperature and relationship models defining the combined effect of concentration and temperature on the consistency index were further developed. In addition, the performance of these developed models was judged by several statistical parameters.