EVALUATION OF PHYSICO-CHEMICAL AND MICROBIOLOGICAL PROPERTIES OF STIRRED YOGHURT STABILIZED WITH SWEET POTATO (IPOMOEA BATATAS) STARCH

The physicochemical and microbiological qualities of stirred yoghurts stabilized with sweet potato starch were investigated. The yoghurt was prepared from whole milk powder and other essential ingredients. The product obtained after fermentation was divided into five equal portions and subsequently stabilized by the addition of sweet potato starch at the levels of 10%, 15%, 20%, 25% and 30% to produce different samples of yoghurt. The various samples of yoghurt produced were analysed for their physicochemical and microbiological qualities using standard methods. The physicochemical characteristics of the samples showed the pH of 4.30, 4.28, 4.36, 4.42 and 4.48, dry matter content of 17.74%, 21.26%, 22.76%, 23.10% and 24.38%, titrable acidity of 0.60%, 0.66%, 0.72%, 0.78% and 0.86%, lactose content of 3.86%, 3.92%, 3.98%, 4.18%, and 4.26%, total soluble solids content of 0.08%, 0.09%, 0.16%, 0.18% and 0.26% and viscosity of 334Cp, 356Cp, 368Cp, 374Cp and 386Cp respectively. The microbial count of the yoghurt samples revealed that the total viable count ranged between 0.9 x 102cfu/ml and 1.7 x 102cfu/ml. The coliform and fungal count were nil which is an indication of the microbial safety of all the samples