Abstract
Rheological properties of salep beverage samples were evaluated in relation to four processing variables: aspartame concentration, 2-6 g/100 mL; lemon fiber concentration, 0.5-2.5 g/100 mL; cooking time, 5-25 min and serving temperature 25-65C. The power law model fitted the shear stress-shear rate data. Salep beverage samples exhibited a shear-thinning behavior. A second-order composite design was used to investigate the effects of the four processing variables on the consistency index (k) and sensory score (Ss) of the samples to find the optimum levels of these processing variables. The aspartame and lemon fiber concentration had the most significant increasing effect on the consistency index and Ss, while serving temperature had a decreasing effect on these values. Based on Ss, optimum conditions were determined as aspartame concentration = 6.0 g/100 mL, lemon fiber concentration = 2.1 g/100 mL, cooking time = 11.6 min and serving temperature = 26C.
PRACTICAL APPLICATIONS
The rheological properties of salep beverages with added dietary fiber and sweetener have not been well documented. The majority of reported experimental data on the rheological properties have focused solely on the effects of two processing factors, namely concentration and temperature on the rheological properties of salep, but no one has considered the simultaneous effects of sweetener, dietary fiber concentrations, temperature and cooking time on the rheological and the related sensory properties of salep beverage. In addition, no study has appeared to study optimum levels of these processing variables maximizing or minimizing the rheological and sensory score values. Therefore, the results of this study would be useful for engineering applications in the processing of salep beverages under related processing conditions as well as for process design, quality control and sensory properties of salep beverage.