Heat stability of milk: the mechanism of stabilization by formaldehyde

TLDR: In this article, it was shown that 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.

Abstract: 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 e-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