EFFECT OF ADDITION OF STARCH AND AGAR-AGAR ON RHEOLOGICAL BEHAVIOUR OF YOGURT

Abstract

The purpose of this work is to study the effect of addition of starch and agar-agar on the rheological behaviour of different types of yogurts. The most common technique used for rheological liquids is Viscometers, measuring shear strength, described by the coefficient of viscosity.  For this study, the yogurt samples were obtained in the laboratory using the cultures starter DIPROX YBA 986. The effect of addition of starch and agar-agar in yoghurt was investigated by a rotational viscometer, Brookfield viscometer (Brookfield Engineering Inc, Model RV – DV I Prime) with RV spindles. The Brookfield viscometer DV I Prime with disk spindles represents an easy and cheap method for rheological characterization of non-Newtonian fluids, in this case of yoghurt. The cluster analysis was performed using Unsrambler X version 10.1 (CAMO Process As, Oslo, Norway, 2005), all the rheological and physicochemical parameters were weighetd and normalized for performing the cluster analysis. In the case of yogurt samples obtained in the laboratory, the addition of starch and agar-agar increases the viscosity, proportional to the doses added. The results of cluster analysis shows that the samples with agar added are in the same group, while the sample with 12.04 g starch is much appropiate to the samples with agar-agar then with the sample with 10.61 g starch.