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Heat stability of milk: the mechanism of stabilization by formaldehyde

Published online by Cambridge University Press:  01 June 2009

Harjinder Singh  and
Patrick F. Fox
Harjinder Singh
Affiliation:
Department of Dairy and Food Chemistry, University College, Cork, Irish Republic
Patrick F. Fox
Affiliation:
Department of Dairy and Food Chemistry, University College, Cork, Irish Republic
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Summary

The increase produced by formaldehyde (HCHO) in the heat stability of milk did not occur when milk was treated with HCHO at temperatures up to 60°C followed by dialysis at 5°C. However, the minimum in the heat coagulation time (HCT)–pH curve was irreversibly removed if the milk was preheated at 80–C for 10 min in the presence of 5 mM-HCHO. Although this treatment blocked the ε-amino groups of lysyl residues, the stabilizing mechanism is considered to be due to the cross linking action of HCHO which reduced the level of non-sedimentable, κ-casein-rich protein dissociated from the micelles on heating. The specific crosslinking agent, dimethyl suberimidate, modified the HCT-pH profile of milk in a manner similar to preheating at 80°C for 10 min with 5 mM-HCHO, supporting the crosslinking hypothesis. The results of this study appear to lend some support to the proposal of Kudo (1980) that the minimum in the HCT-pH curve of milk is due to the dissociation of κ-casein from the micelles on heating at high temperatures at pH values greater than 6η7.

Type
Original Articles
Information
Journal of Dairy Research , Volume 52 , Issue 1 , February 1985 , pp. 65 - 76
Copyright
Copyright © Proprietors of Journal of Dairy Research 1985

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