Optimizing the formulation of a natural soft drink based on biophysical properties using mixture design methodology

Abstract

Physical stability during storage is one of the main factors which affect drink quality and has undeniable effect on its marketing success. Whey protein drink sweetened with Iranian date syrup (DS), stabilized with soluble fraction of Persian gum (SFPG), fortified with caffeine and vitamin C was produced. Mixture design method was used to evaluate and optimize the combined effects of SFPG, DS and whey protein concentrate (WPC) as the main variable components on the biophysical properties of the drink. Serum separation, zeta-potential, microstructure and rheological characteristics were studied. SFPG showed the highest effect on the flow behavior index (n) and consistency coefficient (k) value of the drink. The minimum apparent viscosity belonged to the samples without SFPG and DS. The lowest serum separation occurred at maximum concentration of SFPG. Generally zeta-potential increased in the presence of SFPG significantly (P < 0.05). Considering the results optimum values of SFPG, DS and WPC in the mixture design were predicted to be 1.5, 6.5 and 12%, respectively. Consistency coefficient, flow behavior index, apparent viscosity, serum separation, and zeta potential values of the optimized sample were 0.085 (Pa sn), 0.7, 68.54 (Pa s), 3.9% and − 33 (mV), respectively.