Survival of probiotics in soyoghurt plus mulberry (c.v. Chiang Mai 60) leaf extract during refrigerated storage and their ability to tolerate gastrointestinal transit

This study aimed to examine the influence of mulberry leaf extract (MLE) on viability of Lactobacillus casei 01 and Lactobacillus acidophilus LA5 in soyoghurt during refrigerated storage (4 °C) for 30 days. Changes of physiochemical characteristics and sensory attributes of probiotic-soyoghurts supplemented with MLE were investigated. The findings revealed increased antioxidative effects of probiotic-soyoghurts and minimized probiotic cell loss over prolonged storage upon supplementation with MLE, while increased levels of acidity and syneresis were observed. On sensory attributes, all samples showed similar scores for all sensory attributes regardless MLE or probiotic strains. However, overall likeability slightly reduced in the products after 30 days of storage. Based on the study under in vitro gastrointestinal conditions, comparing between soyoghurts with and without MLE addition, both probiotics showed no significant difference in their survivals of tolerance to gastric and bile fluids. Soyoghurt containing L. casei 01 and MLE demonstrated the greatest antioxidative properties and highest level of probiotic survivors throughout refrigerated storage. This study contributes to the future development and applications of the mulberry leaf extract as a potential ingredient in novel probiotic foods with enhanced consumer health benefits.