OPTIMIZATION OF NON-FAT GREEK YOGURT BASED ON TEXTURAL PROPERTIES

Milk fat plays an important role in the texture of yogurt. Thus, producing fat-free yogurt is a challenge for the food industry. Partial whey syneresis by centrifugation and/or adding casein protein (Cas) and transglutaminase enzyme (TgE) can be useful to obtain a desirable textured non-fat Greek yogurt. We investigated and modeled the effect of yogurt composition and process parameters on the texture properties obtained by texture profile analysis (TPA).The experiment followed the Box Behnken (DBB) design with three factors: centrifuge rotational speed (CRS) (3000, 4250 and 5500 rpm), Cas (3.4, 4.9 and 6.4% w/v) and TgE (0, 1 and 2 U/g protein) concentrations, totaling 13 treatments with 5 repetitions of the central point. A complete second-order model performed the selection of the best model to explain the effect of factors on textural properties. It was evaluated the lack of fit, the regression coefficients, and the determination coefficients. The desirability function was selected for the optimization of responses (hardness and cohesiveness of yogurt were put up at a maximum level, although adhesiveness and gumminess were put up at minimum level). The Cas, TgE and CRS significantly affected the texture properties of yogurt (p <0.05), except for springiness. The values of hardness, cohesiveness, gumminess and adhesiveness ranged between 0.023 – 0.157 N, 0.015 – 2.042, 0.001 – 0.275N and -0,0015 – -0,0003J, respectively. We model the weight of the factors on the hardness, cohesiveness, gumminess, and adhesiveness of non-fat yogurt (R2>99%, p<0.05). The results suggested that the addition of TgE showed less effect on texture properties. The optimized values of each factor, Cas, TgE, and CRS were, respectively, 6.4%, 1.52 U/g protein and 5500 rpm with overall desirability (D) of 0.9704. Under these conditions, it is possible to prepare non-fat Greek yogurt with the desired textural characteristics.