PHYSICOCHEMICAL AND FLOW PROPERTIES OF LOW-FAT YOGURT FORTIFIED WITH CALCIUM AND FIBER

Abstract

This study analyzed the influence of added calcium and fiber on the physicochemical and flow properties of low-fat yogurt. Yogurt was prepared from standardized milk, in which fat content was controlled during formulation to get 1, 2 or 3% w/w; 50 or 100 mg of calcium; and 0.5 or 1 g of fiber into 100 mL of yogurt. The factorial design included 24 samples and 3 control formulations; properties of yogurt were determined through 4 weeks of storage at 4 ± 1C. Syneresis and consistency were the most affected properties. Addition of calcium did not have effects on the physicochemical properties of yogurt (P > 0.05), except on acidity, while the amount and type of added fiber increased pH values and syneresis. Yogurt samples exhibited a non-Newtonian behavior of pseudoplastic type, well fitted by the power law equation, in which the consistency coefficient decreased as a function of the storage time. PRACTICAL APPLICATIONS Food process operations, such as pipe handling, pumping, mixing, heat transfer applications and even some mass transfer processes require the knowledge of flow properties, not only for the plain yogurt, but also for yogurt modified in its composition. On the other hand, those physicochemical properties are needed for process manufacturing and quality control to know the effect of formulation variations. All these properties, rheological and physicochemical, and their evolution through the storage will help the consumer and manufacturer to know the stability and shelf life of different yogurt formulations.