The study of addition of green tea extract on some physicochemical and sensory properties of probiotic set yogurt

Probiotic yogurt contains some potentially healthful effects on human body. In this study, supplementation of probiotic stirred yogurt by different percentages of green tea extract and measurement of survival rate of lactobacillus casei also some physicochemical(pH, acidity(dornic), dry matter%, fat%, synersis% , total phenol %, and sensory properties(flavor, color, texture and acceptability) were studied during storage in refrigerator. Four treatments were made with different percentages of green tea extract as follows: T1, T2, T3 and T4, which involved (0, 2, 4 and 6%) of green tea extract respectively. T1 as a control sample and also concentration of lactobacillus casei for all treatments was regulated about 108 cfu/ml. Three replications were determined for each sample and all experiments were done during (1,7 and 14) days of storage. The highest content of acidity was attributed to T4, the highest value for dry matter was attributed to T1. Fat % of all treatments was constant during storage and total phenol for T4 was the highest content. The measurement of survival rate of all treatments showed that T4 had highest value. Synersis% of T4 was highest value. Sensory evaluations were carried out according to hedonic,s test and all sensorial scores decreased by adding tea extract. Totally addition of green tea extract had negatively effects on synersis content according to microbial, physicochemical and sensory evaluations, the best treatments was T2 among other treatments and had more similarity to T1 as a control sample.