A Comparison of Some Properties of Vat-Heated and Dry Skim Milk Powder Fortified Set Yoghurts

Some properties, namely; viscosity, flavour, acidity, texture, aroma and palatability of cultured yoghurt made from milk previously heated to 90OC for 30 minutes in a Vat were studied and the results compared to those of yoghurt fortified by addition of dry skim milk powder. The results showed no significant difference (P < 0.05) between the two types of yoghurt regarding viscosity, and syneresis during the first 4 days, after which the yoghurt fortified with dry skim milk powder, tended to whey off, becoming grainy in texture, declining in viscosity and developing high acidity (2.0 to 2.5 % LA). A t-test analysis (p < 0.05) indicated that the two kinds of yoghurt were similar on average. Panellists however, found the fortified yoghurt harsher and inferior in flavour. Sensory evaluation indicated that on average, the unfortified sample of yoghurt made from milk preheated to 90O C for 30 minutes was superior. Besides, the cost of adding extra solids to the fortified yoghurt made it 4.5% more expensive which was discouraging to the ordinary consumers. The Journal of Food Technology in Africa Volume 7 No.1, 2002, pp. 21-23