Destabilization of UHT milk by protease AprX from Pseudomonas fluorescens and plasmin. (15th October 2018)

• Record Type: Journal Article
• Authors: Zhang, Chunyue; Bijl, Etske; Hettinga, Kasper
• Is Part Of: Food chemistry. Volume 263(2018)
• Page Start: 127
• Page End: 134
• Publication Date: 2018-10-15
• Subjects: UHT milk -- AprX -- Plasmin -- Gelation -- Destabilization -- Hydrolysis -- Shelf life; Food -- Analysis -- Periodicals; Food -- Composition -- Periodicals; 664
• DOI: 10.1016/j.foodchem.2018.04.128
• Languages: English
• ISSNs: 0308-8146

Abstract

Highlights: Enzymatic destabilization of ultra-high temperature treated milk by the protease AprX and plasmin were directly compared. Same pattern and level of hydrolysis were found in the gelled samples by specific proteases. AprX induced more solid and compact gels than plasmin by specifically hydrolyzing κ-casein. Lower degree of hydrolysis was needed for the gelation of AprX-containing samples. Knowledge on the differences in enzyme characteristics can be used to develop diagnostic tests. Abstract: Destabilization of UHT milk during its shelf life is mainly promoted by the residual proteolytic activity attributed to the psychrotrophic bacterial proteases and native milk proteases. In this study, we built skim UHT milk-based model systems to which either the major bacterial protease (AprX from Pseudomonas fluorescens ), or the major native milk protease (plasmin) was added, to allow a direct comparison between the destabilization of skim UHT milk by both categories of enzymes. The physical and chemical properties were studied during 6 weeks. Our results showed AprX induced compact gels when almost all the κ-casein was hydrolyzed and the degree of hydrolysis (DH) exceeded 1.3%. Plasmin induced soft gels when around 60% of both β- and αs1 -casein were hydrolyzed and the DH reached 2.1%. The knowledge gained from this study may be used for developing diagnostic tests for determining the protease responsible for UHT milk destabilisation.