Plasmin activity in UHT milk: relationship between proteolysis, age gelation, and bitterness

TY - JOUR

T1 - Plasmin activity in UHT milk

T2 - relationship between proteolysis, age gelation, and bitterness

AU - Rauh, Valentin

AU - Johansen, Lene B.

AU - Ipsen, Richard

AU - Paulsson, Marie

AU - Larsen, Lotte Bach

AU - Hammershøj, Marianne

PY - 2014/7/16

Y1 - 2014/7/16

N2 - Plasmin, the major indigenous protease in milk, is linked to quality defects in dairy products. The specificity of plasmin on caseins has previously been studied using purified caseins and in the indigenous peptide profile of milk. We investigated the specificity and proteolytic pathway of plasmin in directly heated UHT milk (>150 °C for <0.2 s) during 14 weeks of storage at 20 °C in relation to age gelation and bitter peptides. Sixty-six peptides from αS- and β-caseins could be attributed to plasmin activity during the storage period, of which 23 were potentially bitter. Plasmin exhibited the highest affinity for the hydrophilic regions in the caseins that most probably were exposed to the serum phase and the least affinity for hydrophobic or phosphorylated regions. The proteolytic pattern observed suggests that plasmin destabilizes the casein micelle by hydrolyzing casein-casein and casein-calcium phosphate interaction sites, which may subsequently cause age gelation in UHT milk.

AB - Plasmin, the major indigenous protease in milk, is linked to quality defects in dairy products. The specificity of plasmin on caseins has previously been studied using purified caseins and in the indigenous peptide profile of milk. We investigated the specificity and proteolytic pathway of plasmin in directly heated UHT milk (>150 °C for <0.2 s) during 14 weeks of storage at 20 °C in relation to age gelation and bitter peptides. Sixty-six peptides from αS- and β-caseins could be attributed to plasmin activity during the storage period, of which 23 were potentially bitter. Plasmin exhibited the highest affinity for the hydrophilic regions in the caseins that most probably were exposed to the serum phase and the least affinity for hydrophobic or phosphorylated regions. The proteolytic pattern observed suggests that plasmin destabilizes the casein micelle by hydrolyzing casein-casein and casein-calcium phosphate interaction sites, which may subsequently cause age gelation in UHT milk.

U2 - 10.1021/jf502088u

DO - 10.1021/jf502088u

M3 - Journal article

C2 - 24964203

SN - 0021-8561

VL - 62

SP - 6852

EP - 6860

JO - Journal of Agricultural and Food Chemistry

JF - Journal of Agricultural and Food Chemistry

IS - 28

ER -