Assessment of Physicochemical and Microbiological Parameters of Plain Set Yoghurt Sold in Colombo, Sri Lanka

Yoghurt is a popular fermented dairy product. The assessment of quality factors of yoghurt is essential to ensure thata safe product is supplied to the consumer. This study aimed to investigate the quality characteristics of marketed, highdemand plain set yoghurts during refrigerated storage in Colombo, Sri Lanka. Four yoghurt brands were selectedbased on a preliminary survey and examined for physicochemical and microbiological attributes. Standard tests fromSLS standard SLS: 824:1989 were adopted to analyze yoghurts on days 4, 7, 14, 21, and 28 of their refrigerated storage.The findings were compared against the control which had the SLS standard. The results revealed that themicrobiological parameters; total aerobic count, and lactic acid bacterial count were within acceptable limits for alltested yoghurt brands. However, yeast and mold counts were higher than the control. Coliforms were not detected inall tested brands. A decrease in moisture content and pH were observed during storage. A rise in titratable acidity was observed in the samples compared to the control (P<0.05). The syneresis effect of yoghurts showed a non-significant increase during the storage period (P<0.05). The protein and fat content of all yoghurt samples varied from the values labeled on the yoghurt. The findings of the present study revealed that the quality characteristics of yoghurt such as the yeast and mold count, moisture content, pH, total titratable acidity, syneresis, fat and protein content are affected by storage conditions. Therefore, manufacturers should focus more on producing yoghurts with physicochemical and microbiological quality and maintaining quality during storage until they are consumed.