Production and quality evaluation of soy milk yoghurt

Abstract

Background: Yoghurt is a fermented dairy product basically produced from cow's milk. In Nigeria, cow’s milk is imported and relatively expensive. Soy milk is inexpensive and available and could be alternative to cow's milk in yoghurt production.
Objective: This study evaluated nutrient composition and sensory characteristics of soy milk yoghurt.
Methods: Soy milk (4.6litres) of 12.5% total solid was produced from 500g of soybean seed using standard method and divided into 3 portions (C1, C2 and C3) of 1000ml each. Liquid cow’s milk was made by mixing 125g of full cream powdered milk with1litreof distilled water; and designated B. The C1, C2, C3 and B, were separately pasteurized (85^o C, 15 mins), homogenized, cooled to 40 – 44^o C and inoculated with 0.44% of 50:50% mixture of Lactobacillus bulgaricus and Streptococcus thermophillus. Sucrose (1.95g), carboxyl methyl cellulose (CMC) (0.96g) and strawberry (2.5ml) and commercial cow's milk flavour (0.10g) were added to samples C1, C2 and C3 while lactose and calcium citrate were added only to C2 and C3 at different concentrations. These were fermented (7h), cooled (44^o C) gradually to set. The yoghurts were analyzed for nutrient composition, microbial and sensory quality.
Results: Soy milk yoghurt which had no CMC was relatively higher in carbohydrate (50.01%) than others which had 2.85% to 4.84% carbohydrate. The sensory attributes of the formulated samples were affected by ingredients, but they compared favourably with the cow's milk yoghurt.
Conclusion: The produced soy milk yoghurts had nutrient and sensory quality characteristics similar to cow's milk yoghurt and could be substitute cow's milk yoghurt.

Keywords: Production quality evaluation, soy milk yoghurt.