A study of Iranian traditional dairy beverage (Richal Shiri) and investigation into some properties of its isolated lactic acid bacteria

Abstract

Richal is a traditional fermented dairy beverage that has a long history in the Iranian encyclopedia. This beverage contains whole milk, natural starter, herbs and salt. It can be produced in three different forms, Shiri (from milk), Masti (from yogurt), and Dooghi (from drinking yogurt). The present study was an investigation into the characteristic features of the lactic acid bacteria isolated from Richal Shiri. After preparing the traditional fermented beverage was investigated and several tests such as determining lactic acid and pH were performed on it. Next, lactic acid bacteria and yeasts were isolated from the traditional fermented beverage sample and cultured in different media such as fermented whole or skim milk, at different times temperatures and test cultures. Some strains had anti-bacterial activity against sporogenous microflora S. typhimurium G-38, B. subtilis 17-89, В. Thuringensis 69-6. Eleven Lactic acid bacteria strains were isolated; ten of them were Gram-positive, cocci, and one of them was Gram-positive, Bacillus. Ten strains were catalase-negative and one was catalase positive; the lactic acid bacteria had antibacterial activity by the determination which measuring zone diameters of bacterial growth inhibition. The functions of strains were different but the differences were not significant (p≥0.3). Between the 3 groups, however, B. subtilis 17-89 had the best function. According to the results, Richal Shiri has some lactic acid bacteria strains with anti-bacterial activity and the ability to ferment milk as a starter culture. The isolated fermented milk, according to its properties, may introduce a new functional food product for development in the food industry. These bacteria will be used in future investigations.