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A Comparison of Some Properties of Vat-Heated and Dry Skim Milk Powder Fortified Set Yoghurts
P.G. Bille and E.L. Keya
Abstract
Some properties, namely; viscosity, flavour, acidity, texture, aroma and
palatability of cultured 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 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 90°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.
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