Interplay between residual protease activity in commercial lactases and the subsequent digestibility of β-casein in a model system

TY - JOUR

T1 - Interplay between residual protease activity in commercial lactases and the subsequent digestibility of β-casein in a model system

AU - Zhao, Di

AU - Le, Thao T.

AU - Larsen, Lotte Bach

AU - Nian, Yingqun

AU - Wang, Cong

AU - Li, Chunbao

AU - Zhou, Guanghong

PY - 2019/8

Y1 - 2019/8

N2 - One of the conventional ways to produce lactose-hydrolyzed (LH) milk is via the addition of commercial lactases into heat-treated milk in which lactose is hydrolyzed throughout storage. This post-hydrolysis method can induce proteolysis in milk proteins due to protease impurities remaining in commercial lactase preparations. In this work, the interplay between lactose hydrolysis, proteolysis, and glycation was studied in a model system of purified β-casein (β-CN), lactose, and lactases using peptidomic methods. With a lactase presence, the proteolysis of β-CN was found to be increased during storage. The protease side-activities mainly acted on the hydrophobic C-terminus of β-CN at Ala, Pro, Ile, Phe, Leu, Lys, Gln, and Tyr positions, resulting in the formation of peptides, some of which were N-terminal glycated or potentially bitter. The proteolysis in β-CN incubated with a lactase was shown to act as a kind of "pre-digestion", thus increasing the subsequent in vitro digestibility of β-CN and drastically changing the peptide profiles of the in vitro digests. This model study provides a better understanding of how the residual proteases in commercial lactase preparations affect the quality and nutritional aspects of β-CN itself and could be related to its behavior in LH milk.

AB - One of the conventional ways to produce lactose-hydrolyzed (LH) milk is via the addition of commercial lactases into heat-treated milk in which lactose is hydrolyzed throughout storage. This post-hydrolysis method can induce proteolysis in milk proteins due to protease impurities remaining in commercial lactase preparations. In this work, the interplay between lactose hydrolysis, proteolysis, and glycation was studied in a model system of purified β-casein (β-CN), lactose, and lactases using peptidomic methods. With a lactase presence, the proteolysis of β-CN was found to be increased during storage. The protease side-activities mainly acted on the hydrophobic C-terminus of β-CN at Ala, Pro, Ile, Phe, Leu, Lys, Gln, and Tyr positions, resulting in the formation of peptides, some of which were N-terminal glycated or potentially bitter. The proteolysis in β-CN incubated with a lactase was shown to act as a kind of "pre-digestion", thus increasing the subsequent in vitro digestibility of β-CN and drastically changing the peptide profiles of the in vitro digests. This model study provides a better understanding of how the residual proteases in commercial lactase preparations affect the quality and nutritional aspects of β-CN itself and could be related to its behavior in LH milk.

KW - Digestibility

KW - Lactose-hydrolyzed milk

KW - N-terminal glycated peptides

KW - Proteolysis

KW - β-casein

UR - https://www.scopus.com/pages/publications/85070692619

U2 - 10.3390/molecules24162876

DO - 10.3390/molecules24162876

M3 - Journal article

C2 - 31398828

AN - SCOPUS:85070692619

SN - 1420-3049

VL - 24

JO - Molecules

JF - Molecules

IS - 16

M1 - 2876

ER -