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Studies on the thermostability of lactase (Streptococcus thermophilus) in milk and sweet whey

Published online by Cambridge University Press:  01 June 2009

Norman A. Greenberg ,
Teresa Wilder  and
Raymond R. Mahoney
Norman A. Greenberg
Affiliation:
Department of Food Science and Nutrition, Massachusetts Agricultural Experiment Station, University of Massachusetts, Amherst, MA 01003, USA
Teresa Wilder
Affiliation:
Department of Food Science and Nutrition, Massachusetts Agricultural Experiment Station, University of Massachusetts, Amherst, MA 01003, USA
Raymond R. Mahoney
Affiliation:
Department of Food Science and Nutrition, Massachusetts Agricultural Experiment Station, University of Massachusetts, Amherst, MA 01003, USA
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Summary

The stability of lactase from Streptococcus thermophilus at 55 °C increased 7-fold, 2-fold and 1·5-fold in the presence of lactose, galactose and glucose respectively; maltose had no effect. Total stability over an 8 h period was more than 10-fold better in milk and sweet whey than in lactose solution, owing to the stabilizing influence of the milk proteins and the milk salts. Ovalbumin and reduced glutathione provided some extra stability but were not as effective as the milk components. In the absence of lactose the enzyme was less stable in milk and was not protected at all by sweet whey constituents. None of the milk protein fractions was as effective in the absence of lactose as when it was present. Enhanced thermostability of the enzyme in milk and sweet whey is due to contributions by all major milk components, but binding of lactose to the enzyme is the major factor controlling the extent of stabilization by other components.

Type
Original Articles
Information
Journal of Dairy Research , Volume 52 , Issue 3 , August 1985 , pp. 439 - 449
Copyright
Copyright © Proprietors of Journal of Dairy Research 1985

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References

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