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Page No. : 37-42

ABSTRACT

Study was conducted to assess the effect of pasteurization and one week refrigeration (4±1oC) storage of pasteurized milk on the microbial quality of milk by evaluating the total viable count (TVC), coliform count (CC), Escherichia coli count (ECC), psychrotrophic count (PC), faecal streptococcal count (FSC) and yeast and mould count (YMC). Pasteurization was effective in reducing the microbial population of raw milk. There was highly significant (p<0.01) reduction in the counts of TVC, CC, PC, FSC and YMC and a significant (p<0.05) reduction in Escherichia coli count. The mean reduction in TVC, CC, PC and FSC in pasteurized milk with that of raw milk before pasteurization was at the level of 0.94, 2.12, 1.40 and 1.51 log10 cfu/ml. Statistical analyses also revealed highly significant (p<0.01) increase in mean TVC, CC, FSC, PC and YMC of pasteurized milk when stored under refrigeration for one week (eighth day). The increase in TVC, CC, PC, FSC and YMC between zero day and 8th day was 2.1, 1.2, 2.2, 1.3 and 1.4 log10 cfu/ml, respectively. However E. coli count did not show much variation. Sensory analysis showed a reduction in the score of colour and appearance, odour and body on storage. Overall, the milk samples were graded fair on eighth day. A significant (p<0.05) reduction in pH value and positive to clot on boiling test (from 2 batches) was noticed on the 8th day.

Keywords: Keeping quality; microbial count, milk, pasteurization; sensory analyses