title: Chemical and proteolysis-derived changes during long-term storage of lactose-hydrolyzed ultrahigh-temperature (UHT) milk.
abstract: Proteolytic activity in milk may release bitter-tasting peptides and generate free amino terminals that react with carbohydrates, which initiate Maillard reaction. Ultrahigh temperature (UHT) heat treatment inactivates the majority of proteolytic enzymes in milk. In lactose-hydrolyzed milk a β-galactosidase preparation is applied to the milk after heat treatment, which has proteolytic side activities that may induce quality deterioration of long-term-stored milk. In the present study proteolysis, glycation, and volatile compound formation were investigated in conventional (100% lactose), filtered (60% lactose), and lactose-hydrolyzed (<1% lactose) UHT milk using reverse phase high-pressure liquid chromatography-mass spectrometry, proton nuclear magnetic resonance, and gas chromatography-mass spectrometry. Proteolysis was observed in all milk types. However, the degree of proteolysis was significantly higher in the lactose-hydrolyzed milk compared to the conventional and filtered milk. The proteins most prone to proteolysis were β-CN and αs1-CN, which were clearly hydrolyzed after approximately 90 days of storage in the lactose-hydrolyzed milk.
authors.affiliation: Department of Food Science, Aarhus University , Kirstinebjergvej 10, DK-5792 Aarslev, Denmark.
authors.forename: Therese
authors.initials: T
authors.lastname: Jansson
authors.forename: Hanne B
authors.initials: HB
authors.lastname: Jensen
authors.forename: Ulrik K
authors.initials: UK
authors.lastname: Sundekilde
authors.forename: Morten R
authors.initials: MR
authors.lastname: Clausen
authors.forename: Nina
authors.initials: N
authors.lastname: Eggers
authors.forename: Lotte B
authors.initials: LB
authors.lastname: Larsen
authors.forename: Colin
authors.initials: C
authors.lastname: Ray
authors.forename: Henrik J
authors.initials: HJ
authors.lastname: Andersen
authors.forename: Hanne C
authors.initials: HC
authors.lastname: Bertram
mesh_terms: D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D005511:Food Handling; D061353:Food Storage; D006358:Hot Temperature; D006868:Hydrolysis; D007785:Lactose / Q000737:chemistry*; D008892:Milk / Q000737:chemistry*; D059748:Proteolysis; D001616:beta-Galactosidase / Q000737:chemistry
chemical_list: D001616:beta-Galactosidase; D007785:Lactose
keywords: Maillard reaction; heat treatment; lactose hydrolysis; lactose-free milk; proteolysis