Microbial and chemical changes in refrigerated pasteurised milk processed in the Santa Fe area (Argentina)
1993
Reinheimer, J.A. | Suarez, V.B. | Haye, M.A. (Instituto de Lactologia Industrial, Facultad de Ingenieria Quinica, UNL, Santa Fe (Argentina))
The change in the total count, acidity, tyrosine equivalent, free fatty acid levels, heat stability and organoleptic characteristics of 70 samples of pasteurised (HTST) whole milk stored at 7 and 12 deg C were studied. In addition, the shelf life and the nature of microbial agents involved in spoilage of the milk were determine. At 7 deg C, milk was mainly affected by post-pasteurisation contamination (especially Pseudomonas), with a low incidence of thermoduric psychrotrophic microflora. The major flavour defects were associated with microbial proteolytic processes. At 12 deg C, there was a higher incidence of thermoduric microflora at spoilage. The flavour was affected mainly by acid development and proteolytic activity. The thermal stability test was shown to be a possible alternative to organoleptic evaluation for determining the shelf life of pasteurised milk.
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