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The Effect of Sample Aging on the Accuracy of An Infrared-Analysis of Basic Milk-Composition

HANUS O, GENCUROVA V, GABRIEL B
Veterinarni Medicina 37, 1992, 149-160

The effect of a decrease [and/or fermentation] in the lactose content during milk storage under different conditions was investigated on the accuracy of the results obtained on a Milko-Scan apparatus to contribute to the present knowledge of this problem. The results were in agreement with some results cited in the literature. These wavelengths are used for infrared spectrophotometry on the above apparatus: for fat 3.48-mu-m, for proteins 6.46-mu-m and for lactose 9.60-mu-m. Bulk milk samples used for the tests were untreated or treated with potassium dichromate, bronopol sodium azide and Milkofix at the temperatures of storage in darkness 20-degrees-C and 4-degrees-C. The differences against the reference values [measured on the first day] were determined and evaluated in milk composition and characteristics as arising during milk storage. These differences were used in form of either cumulative means of differences [Figs. 1 to 5] or individual differences [Fig. 8]. In the first part significant correlation coefficients [P < 0.001] were calculated for the relationship between the variations of lactose content and the fat and protein contents: r = -0.59 and/or -0.73 [Figs. 6 and 7]. This suggests that the decrease in the lactose content by 0.10 % recorded by the infrared analysis and caused by lactose decomposition is accompanied by a ,,seeming increase in the fat and protein content by about 0.04 %. In the second part the correlation coefficients for the fat and protein contents r = -0.96 and -0.96 [P < 0.001


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