The effect of green leaf tea extract on probiotic bacterial viabily in watermelon juice

There are several methods to improve the viability of probiotic bacteria in fruit juices such as the use of antioxidant compounds. In this study, effect of green tea extract ( 1.5, 2.5 and 3.5%) as an antioxidant was examined against the survivability of Lactobacillus acidophilus (PTCC 1643), physico-chemical, antioxidant (DPPH radical scavenging) and organoleptic properties of watermelon juice, during 21 days of storage at 4 °C. The pH of samples decreased during 14 days of storage and then increased during the next 7 days. The same results were observed for acidity of samples. Antioxidant activity of all samples containing green tea extract was significantly (P<0.05) higher than control sample and decreased significantly (P<0.05) during storage time. According to our results, the viability of probiotic bacteria increased significantly (P<0.05) by increasing the concentration of green tea and a direct relation was observed between antioxidant activity and viability of probiotic bacteria. In conclusion, by considering all physicochemical, organoleptic properties and survivability of probiotic bacteria, the sample containing 2.5% green tea was recognized as the best treatment.