Effect of different levels of Watermelon (Citrullus lanatus) seeds powder on Chemical and sensory properties of set Yoghurt during storage

Abstract

This study was conducted at the Department of Dairy Science and Technology, College of Animal Production Science and Technology, Sudan University of Science and Technology during May 2017 to evaluate the effect of adding different levels of Watermelon (Citrullus lanatus) seeds powder on physicochemical and sensory properties of set Yoghurt during storage. Ten liters of fresh cow’s milk were purchased from dairy farm, College of Animal Production Science and Technology. Water melon seeds were purchased from popular market of Omdurman, and then they were milled. The milk was heated at 90-95oC for 5min and then cooled to 45ºC; Therefore divided into four equal portions. Four treatments were carried out. The first treatment is yoghurt with no additive (a control); in the second, third and fourth treatments 5%, 7% and 10% of watermelon seeds powder were added and mixed with cow’s milk respectively. Three % of starter cultures were added to each treatment, then packed in plastic cups (200ml capacity) in triplicates for each treatment and incubated at 45°C until coagulation occurred. Yoghurt samples were cooled and stored in a refrigerator (4°C) for 10 days. Chemical composition and sensory evaluation were carried out for the yoghurt samples in all treatments at intervals of 1, 5 and 10 days. The results indicated that watermelon seeds powder and storage period had highly significant effect (P<0.01) on chemical composition (protein, fat, titratable acidity, total solid, ash). The sensory characteristics of the yoghurt samples found to be affected significantly (P<0.01) by the watermelon seeds powder on color, flavor and taste; however the texture and overall acceptability were not affected significantly (P>0.05). Storage period had no significant (P>0.05) effect on sensory characteristics of the yoghurt samples. The best sensory evaluation was for the control followed by yoghurt with 5% of watermelon seeds powder samples. According to the sensory evaluation of yoghurt samples it would be concluded that watermelon seeds can be added up to 5% into milk for preparation of yoghurt