Development of Set Type Yoghurt Using Juice of Local Watermelon Varieties of Sri Lanka

Abstract

The objective of the current study was to develop a set-type yoghurt incorporating the juice of three watermelon varieties including ‘Thilini’, ‘Kinaree C28’ and ‘Rocky 475’ which are most commonly grown in the dry zone of Sri Lanka. “Initially, to identify the best watermelon variety for set-yoghurt production, the yoghurts were made separately using each watermelon variety at 25% (v/v) juice concentration. Next, to determine the appropriate inclusion level, batches of yoghurt were made using the selected best watermelon variety at the four concentration levels of 15% (T1), 20% (T2), 25% (T3) and 30% (T4) (v/v). A batch of yoghurt made without watermelon was used as the authenticated control. Sensory evaluations were performed by 30 untrained panelists. Microbiological and physiochemical properties of the watermelon juice incorporated setyoghurts were analyzed during the storage period of 21 days at 4 ̊C. Incorporation of ‘Rocky 475’ variety at 20% level resulted the best sensory attributes for colour, taste, texture and aroma. Both fat and protein content of the yoghurts were gradually decreased with the increased levels of watermelon juice. Highest syneresis was observed in the T4 yoghurts which contained the highest level of watermelon juice and the lowest syneresis was observed in the control. In all treatments, total plate count and yeast and mold counts were within the acceptable level during the storage period. This study results revealed that by using up to 20% (v/v) of the juice extracted from the ‘Rocky 475’ watermelon variety, the organoleptic properties of setyoghurt could enhance while ensuring microbiological safety