Physicochemical and sensory characteristics of Roselle fortified yoghurts stored in refrigerator

Background: Cow’s milk yoghurt is nutritionally rich in protein and micronutrients but has poor keeping quality and is devoid of most bioactive constituents present in plants. Phenolic bioactive constituents could enhance shelf life of yoghurt and promote health of consumers. Objective: The study evaluated the effects of roselle calyx on the physicochemical and sensory properties of yoghurts stored in a refrigerator at 40C. Methods: Ten (10), 20 and 40 grams of ground roselle calyx, were separately boiled in 100ml distilled water for 20mins, cooled and juice extracted overnight (14hours) before filtering through muslin cloth. Each filtrate was boiled (10 mins), cooled and made up to 1litre with distilled water; mixed with 125g full cream powdered cow’s milk and used to produce yoghurts coded B, C and D. A control full cream powdered milk with no roselle was also produced and coded A. The yoghurts were pasteurized (85OC for 15 mins), fermented (44OC for 7hours), cooled to set and analysed for quality characteristics during10 days refrigerated storage. Results: Moisture content of yoghurts increased from 96.11% in yoghurt D to 98.83% in A and was significantly (p < 0.05) higher in A than in the roselle-treated samples. Roselle addition above 1% significantly (p < 0.05) improved the phenol content and viscosity (cp) but decreased syneresis of the yoghurt samples proportionally. Flavour and texture of the yoghurts were also improved. However, the control was most acceptable. Conclusion: Roselle addition improved quality of plain cow’s milk yoghurt and is recommended for its bioactive polyphenols.Key words: Quality characteristics, roselle-fortified, yoghurt, storag

Production and quality evaluation of soy milk yoghurt

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 (85o C, 15 mins), homogenized, cooled to 40 – 44o 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 (44o 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