Numerical optimization of probiotic Ayran production based on whey containing transglutaminase and gel.

The purpose of this study was to optimize the functional properties of probiotic Ayran. Two-level fractional factorial design with four center points was used to investigate the effect of five independent variables including, reconstructed whey protein (70-90% of milk), salt (0.5-1 g/100 g), gel (0-30 g/100 g), transglutaminase enzyme (0-14 unit/100 g) and storage time (1-21 days). The viability of La-5 and other physicochemical properties such as pH, acidity, viscosity, sedimentation, and color were modeled and then optimized using desirability function method. Results showed that reconstructed whey protein and gel significantly affected the viability of La-5 and other physicochemical properties (< 0.05). The viability of La-5 and viscosity decreased by increasing of whey protein percentage from 70 to 90. Maximum La-5 count was observed in samples with a minimum level of whey protein and maximum level of gel. Milk replacement with whey protein up to 90% caused to decrease acidity and viscosity significantly but sedimentation increased (< 0.05). Optimum condition for production of functional Ayran determined as follow: gel concentration: 25.7%, reconstructed whey protein: 70%, salt: 0.58% and transglutaminase enzyme: 5 unit/100 mL.