Heat stability of milk: influence of modification of lysine and arginine on the heat stability-pH profile

Abstract

SUMMARYSeveral dicarbonyl compounds (glyoxal, substituted glyoxals, diacetyl and 1, 2-cyclohexadione) had a marked stabilizing effect on the heat stability of milk, especially in the presence of urea. These reagents are believed to modify arginine more or less specifically suggesting an important role for arginine residues in heat stability. In contrast, modification of lysine residiles with dansyl chloride, acetic anhydride or cyanoborohydride had little effect on maximum heat stability although it did alter the HCT-pH profile. Since diacetyl is a natural constituent of fermented milks and cheese, it may be acceptable as an additive to increase the heat stability of ṃilk.

Heat stability of milk: the mechanism of stabilization by formaldehyde

“…From these results it appears that preheating milk to 80 °C with 5 mM-HCHO irreversibly modified lysyl residues and that this may stabilize the milk protein to heat via an increase in net negative charge. On the other hand, it has been shown by Shalabi & Fox (19826) that modification of lysyl residues by more specific reagents, e.g. dansyl chloride, decreases the maximum heat stability of milk.…”

“…Dicarbonyl compounds, such as diacetyl, 1,2-cyclohexanedione, glyoxal and substituted glyoxals, markedly stabilize milk to heat, especially in the presence of urea (Shalabi & Fox, 19826). The diketones, diacetyl and 1,2-cyclohexanedione, which are specific for arginine residues, at least at low temperatures, stabilize milk only in the region of maximum stability while dialdehydes, such as glyoxal and substituted glyoxals which are less specific for arginine, stabilize milk throughout the pH range 6 -4-7-4 (Shalabi & Fox, 19826). Modification of lysyl residues with specific reagents, e.g.…”

“…Modification of lysyl residues with specific reagents, e.g. dansyl chloride, acetic anhydride or cyanoborohydride, has little effect on maximum heat stability although these alter the HCT-pH profile (Shalabi & Fox, 19826). Holt et al (1978) have suggested that the increase in the heat stability of milk produced by addition of aldehydes is probably due to modification of the e-amino group of lysine or to crosslinking of polypeptide chains involving lysyl residues.…”

Influence of added lyophilized butter serum on the heat stability of unconcentrated and concentrated bovine milk

“…Additives that have been studied are the sodium or potassium salts of phosphoric, citric or carbonic acid (Sweetsur and Muir 1980; Augustin and Clarke 1990; Van Mil and De Koning 1992), phenolic compounds (O’Connell et al . 1998; O’Connell and Fox 1999a; 1999b), diketones (Shalabi and Fox 1982a; 1982b), cationic detergents (Shalabi and Fox 1982c), oxidizing agents (Singh and Fox 1987) or individual amino acids (Rajput et al . 1984).…”

Mammals, Milk, Molecules, and Micelles

“…The study of heat stability was attractive because, in addition to being commercially important, it is fundamentally interesting and challenging but because few laboratories have been involved, progress is slow and simple equipment is sufficient (progress depends more on ideas than on equipment). Aspects investigated included variability, correlation with compositional factors, interspecies (bovine, ovine, caprine, equine, porcine, and human milk) comparison, each of which has a distinctive HCT-pH profile (Fox & Hoynes 1975, 1976, effect of various additives (phosphates, polyvalent organic acids and their salts, amides, including urea, and carbonyls, including sugars and polyphenols) on heat stability (Shalabi & Fox 1982;Tan-Kinita & Fox 1996;O'Connell & Fox 1999, 2001bO'Sullivan et al 2002) and the mechanism of the maximum-minimum in the HCT-pH profile (Fox 1981, Mohammed & Fox 1987, Singh & Fox 1987, O'Connell & Fox 2001a. I published 60 research papers on the heat stability of milk and reviewed the literature three times (Fox & Morrissey 1977, Fox 1982.…”