EFFECTS OF SUBSTITUTING SKIMMED MILK POWDER WITH MODIFIED STARCH IN YOGHURT PRODUCTION

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.