This research was carried out to evaluate the appropriate levels of substitution of powdered cow milk with soy milk and cornstarch needed to produce yoghurt, evaluating its quality and potential for acceptance. Powdered cow milk was substituted with soymilk and cornstarch up to 30% to produce yogurt and market sample yogurt was used as control. Each composite blend milk samples was homogenized, pasteurized at 75°C for 5 min, cooled and inoculated with a mixed freeze-dried starter culture containing strains of Streptococcus thermophilus and Lactobacillus bulgaricus at 45°C, fermented for 6 h and cooled to 4˚C. The proximate, chemical, microbial, functional and sensory evaluation of the composite yogurt samples was determined. The yogurt samples were coded ACS-1 to ACS-13 where ACS-13 represent control. The result of the proximate analysis showed that moisture content ranged from 82.04 – 88.71%, protein ranged 2.05 – 6.48%, fat ranged from 2.14 – 3.62%, carbohydrate ranged from 4.30 – 9.91% and ash content ranged from 0.53 – 1.48%. The pH ranged from 3.73 – 4.82. For microbial evaluation, the total viable bacteria count ranged from 1.90x107 – 11.60x107, total coliform count ranged from 0.50x107 – 3.90x107. For chemical and functional evaluation, the total solids ranged from 11.28 – 16.96%, titratable acidity ranged from 0.30 – 1.80%, syneresis ranged from 0.00 – 28.33%, water absorption capacity ranged from 0.00 – 75.53% and apparent viscosity ranged from 1337- 4863 cP. For sensory evaluation, yogurt produced with 100% powdered milk (ACS-1) was the most preferred while yogurt sample produced with 50% powdered milk, 30% cornstarch and 20% soy milk (ACS-10) was the least preferred among other yogurt samples. This study revealed the mix ratios of powdered cow milk, soy milk and cornstarch that were acceptable in accordance with yogurt standard and the extent the quality of yogurt was generally accepted with the use of processing adjuncts (soymilk and cornstarch).
Occurrence of aflatoxin M1 in commercial powdered milk in Bangkok, Thailand