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k‐Casein Heterogeneity and Mild Heating Effects on Susceptibility to Chymosin Action
Author(s) -
HAQUE ZAHUR U.,
KHALIFA MAHAMMED Y.
Publication year - 1992
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1365-2621.1992.tb05422.x
Subject(s) - chymosin , chemistry , casein , biochemistry
Bovine SH‐k‐casein (k‐C‐pool) was fractionated into five components based on carbohydrate and sialic acid contents (k‐C‐P 1 < k‐C‐P 2 < k‐C‐P 3 < k‐C‐P 4 < k‐C‐P 5 ) by ion‐exchange chromatography (DEAE‐cellulose). Chymosin susceptibility observed by monitoring changes in optical density during enzyme action, varied among the components. This was a reflection of the difference in self‐association of the proteins in aqueous dispersion as determined by hydrophobic interaction chromatograph. There was an inverse relationship between surface hydrophobicity of the protein polymers (k‐C‐P 2 >k‐C‐P 3 >k‐C‐P 4 > k‐C‐P 5 > k‐C‐P 4 > k‐C‐pool) and their susceptibility to chymosin at 37°C, pH 6.8 (k‐C‐pool >k‐C‐P 1 >k‐C‐P 5 > k‐C‐P 4 > k‐C‐P 3 > k‐C‐P 2 ). Mild heating decreased susceptibility and affected flocculation of all except the highly glycosilated components k‐C‐P 4 and k‐C‐P 5 reflecting amphipathicity imparted thermostability.