Effect of K‐Casein Deglycosylation on the Acid Coagulability of Milk

Abstract

The relationship between the content of N-acetylneuraminic acid residues of micellar -casein and acid coagulability of milk was investigated. At 30 °C, partial deglycosylation of micellar -casein does not significantly affect the content of micellar proteins, micellar surface charge, and micellar solvation. Casein micelles modified by the release of part of the N-acetylneuraminic acid residues showed a shorter acid gelation time, a higher rate of gel strengthening, and a higher final firmness. This enhancement in the gelation ability of the neuraminidase-treated casein micelles of milk should appear as the result of increase in number of hydrophobic sites on the surface of casein micelle due to enzymatic deglycosylation of micellar -casein.

Modifications of structures and functions of caseins: a scientific and technological challenge

“…Difference in the rennin-gel structure for deglycosylated casein was also observed with the observation of larger cluster and pores in comparison with native casein. With the same objective, Cases et al (2003) deglycosylated also casein micelles by neuraminidase and studied the physico-chemical properties and their ability to form acid gel. They indicated that partial deglycosylation (∼85%) did not significantly affect neither the partition of molecules of casein between aqueous and micellar phases nor their charge and hydration.…”

Post-translational Modifications of Caseins

“…Cases et al (2003) found that partial deglycosylation with neuraminidase had little effect on micellar surface charge and solvation but caused a decrease in acid gelation time, a higher rate of gel firming, and a higher final firmness. Because this step does not involve k-casein cleavage, a lesser or different effect might be expected.…”

Enzymatic modification of dairy product texture

“…Due to the fact that glycosylation only occurs in the hydrophilic C-terminus of k-casein, treatment of milk with soluble or immobilized neuraminidase is efficient in removing virtually all NANA from milk (Mehaia and Cheryan, 1983;Mehaia, 1987;Cases et al, 2003). Treatment of milk with neuraminidase had only a small, but significant, effect on its heat stability (Robitaille and Ayers, 1995).…”