A comparison of vat-heated and skim milk powder fortified yoghurts

Some properties, namely; viscosity, flavor, acidity, texture, aroma and palatability of cultural yoghurt made from milk previously heated to 90°C 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 significance 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 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. Panelists however, found the fortified yoghurt harsher and inferior in flavor. Sensory evaluation indicated that on average, the unfortified sample of yoghurt made from milk preheated to 90ÚC 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.