Section 2
Chapter 1,003

The destruction of enzymes and bacteria during the spray-drying of milk and whey. I. The thermoresistance of some enzymes and bacteria in milk and whey with various total solids contents

Daemen, A.L.H.

Netherlands Milk and Dairy Journal 35(2): 133-144


ISSN/ISBN: 0028-209X
Accession: 001002796

Thermoresistance of 3 enzymes (alkaline phosphatase, chymosin and alpha -amylase) and of 2 bacteria (Serratia marcescens and Staphylococcus C 131) was estimated in milk and whey, in conc. milk and whey, in milk and whey powder, and in moistened milk and whey powder. An increase in TS content generally corresponded to an increase in thermoresistance (increased D and z values). Results obtained with chymosin and Staphylococcus C 131 were treated according to the theory of the absolute reaction rates, relating the equilibrium constant to the change in free enthalpy. Change of free enthalpy was approx. 100 kJ/mol, a value characteristic of protein denaturation. An increase in TS content corresponded to a decrease in the changes in enthalpy and entropy of activation. In the temp. traject studied, temp. had practically no effect on these quantities.

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