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Heat stability of milk: influence of modifying sulphydryl-disulphide interactions on the heat coagulation time–pH profile

Published online by Cambridge University Press:  01 June 2009

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

Addition of reducing agents such as 2-mercaptoethanol (2-ME), dithio-threitol and Na sulphite to milk markedly reduced its heat stability at pH values below 7·1. 2-ME reversibly destabilized milk or serum protein-free casein micelle dispersions and promoted the release of κ-casein-rich protein from the micelles. Reduction of either casein micelles or β-lactoglobulin (β-lg) with 2-ME and subsequent blocking of the newly formed –SH groups with N-ethylmaleimide irreversibly reduced the maximum to minimum ratio in the heat stability profile. 2-ME disrupted κ-casein/β-lg complexes and stripped κ-casein from the micelles on heating. The milk or caseinate systems were thus destabilized. Addition of KBrO4 or iodosobenzoate to milk at 5 HIM eliminated the minimum but destabilized milk in the region of the maximum. However, KIO3 at 5 mm had a strong stabilizing effect throughout the pH range 6·5–7·3.

Type
Original Articles
Information
Journal of Dairy Research , Volume 54 , Issue 3 , August 1987 , pp. 347 - 359
Copyright
Copyright © Proprietors of Journal of Dairy Research 1987

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