COMPREHENSIVE ANALYSIS AND QUALITY IMPROVEMENT OF “KOTMALE” SET YOGURT

Abstract

Yogurt is a popular dairy product made from concentrated milk fermentation. There are several types of yogurts, such as set, stirred, drinking, frozen, concentrated and flavoured yogurt. Among them the set type yogurt is very popular and common. Quality of a yogurt basically determine according to the flavour, aroma, viscosity, consistency, appearance, freedom from whey separation and long shelf life. The research was carried out to analyze the quality variation of the set yogurt over the period of one month to diagnose the quality defects of the existing “Kotmale” yogurt and to improve the quality and shelf life of the yogurt. Quality variation was measured by using chemical, microbiological and organoleptic tests. Under chemical tests, pH was measured by using pH meter and acidity was measured by titration method. Coliform, Yeast and Mould counts were counted by using pour plate count technique and organoleptic properties of color, smell and taste were tested everyday over the period of one month. According to the results obtained from the above microbiological, chemical and organoleptic tests; high acidity, high sour taste and presence of yeast and mould were the predominant quality defects that were significant in the existing set yogurt. Therefore to eliminate the above quality defects, a new yogurt culture was selected with low post acidification and developed a improved yogurt with existing formulae. In third day after manufacturing, nine point hedonic scale sensory analysis was carried out to check the consumer preference. There were more consumer preference in texture and taste for improved yogurt but high overall acceptability for existing “kotmale” set yogurt. Chemical and microbiological tests were carried out to the improved set yogurt in 3rd, 14th, 22nd and 28 days after manufacturing. pH of the improved yogurt varied from 4.85 to 4.35 and acidity was varied from 0.79 to 0.99 over the period of 28 days. Coliform and Yeast and Mould counts of the improved yogurt were also conformed to the microbiological limits specified by the Sri Lanka Standard Institute. In 28* day after manufacturing another nine point hedonic scale sensory analysis was conducted to check the keeping quality of the r improved yogurt. According to the analyzed sensory data there were more consumer preference on texture, sourness and overall acceptability to the improved yogurt over the other meritet sample o f set yogurt and existing “Kotmale” set yogurt.