Production and Quality Evaluation of Yogurt and Watermelon Juice Blends

The study investigated the effect of incorporation of watermelon juice in yogurt on the quality of the blends. Yogurt and watermelon (Citrullus lanatus) juice were produced. The watermelon juice was used to substitute 0, 10, 20, 30, 40, and 50% of yogurt. The chemical composition, antioxidant activity, physicochemical, and sensory properties of the blends were determined using standard procedures. The pH of the yogurt and watermelon juice were 4.57 and 5.78, respectively and varied from 5.18 -6.04 for the blends. The moisture, protein, ash, fat and carbohydrate contents decreased with increase in the amount of watermelon juice in the blends. The vitamin C, calcium, zinc and magnesium contents increased while the phosphorus and potassium contents decreased with increased level of watermelon juice in the blends. The phenols and carotenoids contents increased while the flavonoids content decreased with increase in the level of watermelon juice in the blends. The antioxidant activity using DPPH assay varied with the samples where yogurt had higher radical scavenging activity than the watermelon juice. The radical scavenging activities and the ferric reducing antioxidant property (FRAP) values also increased with the level of watermelon juice in the blends. The FRAP values for yogurt and watermelon juice were 1.22 and 1.58mg/ml, respectively and increased to a range of 1.29 -3.70 mg/ml for the blends. The yogurt had higher scores than the watermelon juice for all the sensory attributes evaluated. The scores for the sensory attributes decreased with increase in the level of watermelon juice in the blends. However, the scores for the blend containing 10 % watermelon juice for all the attributes were not significantly different (p>0.05) from those of the yogurt. Therefore, it is concluded that watermelon juice could be used to substitute 10% yogurt without adversely affecting the qualities of the blends.