Chemical Characteristics and Viability of Starter Cultures of Freeze–Dried Sweet Potato Extract–Supplemented Synbiotic Yogurt

¹ Department of Agricultural Product Technology, Faculty of Agriculture, University of Veteran Bangun Nusantara Sukoharjo, Jl. Letjend Sujono Humardani no. 1, Sukoharjo 57521, Central Java, Indonesia
² Department of Food Science and Technology, Faculty of Agriculture and Animal Science, University of Muhammadiyah Malang, Jl Raya Tlogomas No. 246, Malang 65144, East Java, Indonesia
³ Department of Environmental Science, University of Latvia, Raina Blvd.19, Riga LV-1050, Latvia

^* Corresponding author: intanniken@gmail.com

Abstract

The research aimed to determine the sucrose concentration as a cryoprotectant to obtain the chemical properties and the viability of Lactic Acid Bacteria (LAB) and Lactobasillus plantarum in the synbiotic yogurt. It adopted a one–factor Completely Randomized Design (CRD) by including sucrose in concentrations from 0 %, 2.5 %, 5 % to 7.5 %, three replications. The results showed various sucrose concentrations significantly affected the yields of the purple sweet potato extract– supplemented synbiotic yogurt, reduction–sugar level, the total of LAB, and the total of L. plantarum before and after the freeze–drying process, no significant impact on the moisture content and total quantity of LAB. The best treatment of the synbiotic yogurt was induced through the addition of sucrose with a concentration of 5 % as a cryoprotectant. The treatment signified the following characteristics: 14.797 % of yields, 7.51 % of water content, 14.59 % of reduction–sugar level, 1.98 × 109 CFU mL–1 of total LAB before the freeze–drying and 9.28 × 108 CFU mL–1 after the freeze–drying, 8.23 × 108 CFU mL–1 of total L. plantarum before the freeze–drying and 6.81 × 108 CFU mL–1 after the freeze–drying.