Abstract:
Rheological properties of yoghurt are known to be influenced by several factors
during processing including the milk composition, additives, the type of culture
(ropy or non ropy), heat treatment and mechanical processes it undergoes after
fermentation. The objective of this study was to determine the most appropriate
levels of modified starch that could be added in the yoghurt without noticeably
altering the keeping quality and consumer acceptability of the yoghurt. A stirred
type of yoghurt was developed using modified corn starch as a stabiliser to variably
replace skimmed milk powder (partially or in totally) while maintaining the same
quality and consumer acceptability on the yoghurt product. Different formulations
were made and their quality characteristics studied using the 3% skimmed milk
powder sample as the control. The results showed that the modified corn starch
addition did not affect the gelation process, texture, fermentation time and the
desired pH end point. Two sample formulations were identified as the most
comparable to the control in terms of viscosity, taste, mouth-feel and general
acceptability. These were the 0.5% modified corn starch alone and 0.5% modified
corn starch with 1% skimmed milk powder. These reduced the cost of production
per litre by 22% and 13% respectively. The samples were stable for three
consecutive weeks in all the desirable yoghurt quality parameters tested including
consumer acceptability. In conclusion, the application of modified starch at the
level of 0.4% was found to have the most significant reduction in cost of
production while having the least effect on the keeping quality and consumer
acceptability of the yoghurt.
