Physico-chemical and microbiological quality of some consumer preferred plain set yoghurts sold in matara municipal area of Sri Lanka

Abstract

As yoghurt is a very popular food item, assessment of quality of commercialized yoghurt during storage in refrigerators is needed. Lack of data on quality parameters of different brands of yoghurt in Sri Lanka poses a risk on consumer safety. This study assessed the changes of physico chemical and microbiological parameters during the shelf life of some plain set yoghurts sold in Matara municipal area of Sri Lanka. Five different brands of plain set yoghurt with highest consumer preference were selected for the present study. From each brand, fifteen samples were collected and kept under refrigerated condition (4 C) for the analysis. Those samples were analyzed for the physico-chemical properties (syneresis effect, pH, titratable acidity, total protein content, calcium concentration) and microbial composition (total plate count, total yeast and mould count) by using three replicates of each sample at 4, 7, 14, 21 and 28 days intervals from the production date and the results were compared with local and international standards. All microbiological parameters and total protein content of all the five yoghurt brands were not within the permissible range for local and international standards. Only the titratable acidity was in the permissible range of local standards. Except calcium concentration, all the other physico-chemical parameters and microbiological parameters of collected yoghurt samples were changed with the storage time. Furthermore, this study revealed that physicochemical and microbial parameters are varied also among different brands of set yoghurt. The results of the study suggest to introduce to quality standard for set yoghurts and producers should motivate to follow standards.