SOURING DYNAMICS OF THE MILK SAMPLES WITH DIFFERENT FAT CONTENT

An influence of butterfat content on the souring dynamics has been evaluated for some commercial samples of drinking cow milk using the standard Turner’s degree as an index of milk souring. No additional measurement of milk fat content was made, and density and other parameters were determined, being taken as indicated in milk packaging or described in the standards. It has been found that some buffering capacity of milk can be related to the butterfat content and the souring dynamics of high-fat milk is slower than that of low-fat milk. This effect can be caused by absorption of lactic acid and/or other acidic products formed by the souring processes on the butterfat globules, which is facilitated by close structural affinity between the butterfat and lactic acid molecules. Even though the difference in the milk samples souring rate is not very significant, it can be influential within last days of the low- and high-fat milk validity term. No effect of the butterfat content on the final milk acidity value has been revealed – the samples with various acidity values exhibit various souring rates only.