Effect of fortifying camel’s milk with different levels of skim milk powder on the physicochemical, microbiological and sensory characteristics of yoghurt

Abstract

The present study was carried out in the milk processing unit at college of animal production, Sudan University of science and technology during month of January 2012. The effect of adding different levels of skim milk powder(0,5,7%) and storage period on the quality of yoghurt was examined in this study. fresh camel milk was purchased from Alaas farm at Khartoum North. Nine litres of raw camels milk were divided into three portions . The first treatment was used as control.To the other two treatments 5 and 7% of skim milk powder was added, then the milk in each treatment was heated in a water bath at 85°C for 30 min. milk samples were cooled to approximately 43°C, and inoculated with commercial yoghurt culture ( 2 %) and packed into plastic cups (200g capacity) in triplicates. The plastic containers were incubated at 43°C for 3 hrs then the incubation temperature decreased to 33°C until coagulation occurred (16 hours), thereafter samples from different treatments were stored at 4°C for 0, 5and 10 days.yoghurt Samples were taken for chemical, microbiological and sensory analysis. The results indicated that yoghurt treated with 7% skim milk powder had the highest viscosity value (p≤0.01) during storage period.The results showed that the control yoghurt had the highest pH value (p≤0.01) during storage period when compared with other treatments. Statistical analysis pointed out that there were no significant differences in chemical composition of the yoghurt from different treatments during storage. vii The results demonstrated that yoghurt treated with 7% skim milk powder was significantly higher (p≤0.05) in total bacterial count (7.70×106 cfu/ml than the control yoghurt (5.29×106) cfu/ml. No significant differenceswere observed in lactic acid bacterial count. Coliforms and E.coli bacteria were not detected in tested samples The results indicated that yoghurt treated with 7% skim milk powder had the highest (p≤0.01) flavour. Also there was significant difference (p≤0.05) in overall acceptability in tested treatments. Yoghurt made with 7% skim milk powder had the highest scores.