Lactic acid bacteria, acidity, pH and vitamin C in yogurt from skim milk, whole milk and soybean juice powder fermented with pineapple

Abstract Yogurt is a type of fermented product diversified by lactic acid bacteria. In this research, yogurt was made by using three types of raw materials: skim milk, whole milk, and soybean juice powder with the addition of pineapple juice. The addition of pineapple juice is expected to increase the quality of probiotics produced, improve the taste of yogurt, and explore the potential of pineapple juice as a substitute inngredient in yogurt production due to its bioactive components, which offer additional health benefits. This study aimed to analyze the differences in lactic acid bacteria (LAB), acidity, and pH in yogurt with the addition of pineapple juice. The research employed an experimental design with treatments involving various concentrations of pineapple juice (9%, 12%, and 15%). Data were analyzed using a two-way ANOVA, followed by a DMRT test if significant differences observed. The results showed that the type of raw material and the concentration of pineapple juice had a significant effect on the total lactic acid bacteria, acidity, pH, and vitamin C content in yogurt. The findings revealed that the total LAB, acidity, and vitamin C increased with the addition of pineapple juice, while the pH decreased. The highest number of lactic acid bacteria was observed in yogurt made with skim milk and 15% pineapple juice, with a value of 9,556 log cfu/ml and the pH value was 4,06 which met Indonesian National Standards (SNI). However, the acidity value was 2,90% exceeding the standards set by the SNI.