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.
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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.
