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Determination of Glucose, Galactose, and Lactose in their Mixtures

Division of Dairy Research Laboratories, Bureau of Dairy Industry, Agricultural Research Administration, U. S. Department of Agriculture

ABSTRACT

A method for determining the amount of glucose, galactose, and lactose in hydrolyzed lactose sirups has been outlined.

The procedure was to determine the sum of the two hexoses by means of a modified Barfoed solution, and the amount of glucose and lactose by following the directions of Shaffer and Somogyi before and after fermentation with washed bakers' yeast.

Four samples of hydrolyzed lactose sirups were analyzed by this procedure and the results and steps in the calculations are described.

Sirup No. 1, which attained a maximum temperature of only 143° C. at the expiration of 35 minutes, still contained 8.6 per cent lactose; whereas sirup No. 3, which was heated for 65 minutes, and 15 minutes of this time the temperature was 143-147° C, showed no lactose. There was, however, a loss of 2.37 per cent in sugar content, which was converted into by-products. The reducing values of these by-products were of negligible amounts.

The maximum error for the complete analysis should not exceed 7 per cent.