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Journal of Dairy Science Vol. 49 No. 2 127-132
© 1966 by American Dairy Science Association ®
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Kinetic Reactions of Alpha and Beta Lactose. I. Mutarotation1

G. Haase and T. A. Nickerson

Department of Food Science and Technology, University of California, Davis

ABSTRACT

Kinetic studies were made of mutarotation of alpha- and beta-lactose by a polarimetric method. Rate constants were determined in the temperature range of 0.5 to 55 C. A complete statistical analysis of the data was made with a computer technique, and interpretation was based on a statistical test of the significance.

The specific optical rotation of an equilibrium solution was dependent upon concentration and temperature. Concentration significantly affected the equilibrium rotation, causing a decrease of 0.01688 degree with each 1 g/100 ml increase in concentration. The following expression was found to hold at equilibrium:
Figure 1
where c is gram anhydrous lactose/100 ml solution, and t is degrees centigrade.

It was shown that the mutarotation of lactose is a first-order reaction: The velocity constants calculated from the experimental data did not vary significantly from the postulation of the first-order rate law. Further evidence supporting this conclusion is that the velocity constant is independent of reaction time and the concentration of the reactant.

The same studies where undertaken in a salt solution simulating natural whey in salt composition. The salt solution catalyzes the reaction about twofold, but does not alter the mechanism.

FOOTNOTES

1 This work was supported by funds granted by the Dairyman 's Cooperative Creamery Association, Tulare, California.






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Copyright © 1966 by the American Dairy Science Association ®.