Plasmin Activity in UHT Milk: Relationship between Proteolysis, Age Gelation, and Bitterness

Rauh, Valentin; Johansen, Lene Buhelt; Ipsen, Richard; Paulsson, Marie; Larsen, Lotte Bach; Hammershøj, Marianne

doi:10.1021/jf502088u

Cited by 70 publications

(42 citation statements)

References 52 publications

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“…There have been numerous studies examining the relationship between plasmin hydrolysis and the age gelation of milk (Aroonkamonsri, Aroonkamonsri, & Kakuda, ; Datta & Deeth, ; Harwalkar, , ; Nieuwenhuijse & van Boekel, ; Rauh et al., ; Rauh et al., ). There are some studies that state that it is not unequivocally proven that plasmin causes age gelation (Bastian & Brown, ; Datta & Deeth, ; Manji & Kakuda, ; Manji et al., ; McMahon, ).…”

Section: Age Gelationmentioning

confidence: 99%

Age Gelation, Sedimentation, and Creaming in UHT Milk: A Review

Anema

2018

Comp Rev Food Sci Food Safe

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Demand for ultra‐high‐temperature (UHT) milk and milk protein‐based beverages is growing. UHT milk is microbiologically stable. However, on storage, a number of chemical and physical changes occur and these can reduce the quality of the milk. These changes can be sufficiently undesirable so as to limit acceptance or shelf life of the milk. The most severe changes in UHT milk during storage are age gelation, with an irreversible three‐dimensional protein network forming throughout, excessive sedimentation with a compact layer of protein‐enriched material forming rapidly at the bottom of the pack, and creaming with excessive fat accumulating at the top. For age gelation, it is known that at least two mechanisms can lead to gelation during storage. One mechanism involves proteolytic degradation of the proteins through heat‐stable indigenous or exogenous enzymes, destabilizing milk and ultimately forming a gel. The other mechanism is referred to as a physico‐chemical mechanism. Several factors are known to affect the physico‐chemical age gelation, such as milk/protein concentration, heat load during processing (direct compared with indirect UHT processes), and milk composition. Similar factors to age gelation are known to affect sedimentation. There are relatively few studies on the creaming of UHT milk during storage, suggesting that this defect is less common or less detrimental compared with gelation and sedimentation. This review focuses on the current state of knowledge of age gelation, sedimentation, and creaming of UHT milks during storage, providing a critical evaluation of the available literature and, based on this, mechanisms for age gelation and sedimentation are proposed.

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Section: Age Gelationmentioning

confidence: 99%

Age Gelation, Sedimentation, and Creaming in UHT Milk: A Review

Anema

2018

Comp Rev Food Sci Food Safe

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“…The gelation of UHT milk derives from the formation of complexes between the κ-casein and β-lactoglobulin that are denatured as a result of the heat treatment. Gelation is triggered by enzymatic processes of protein degradation (Rauh et al , 2014; Datta and Deeth, 2001). The proteolysis during storage of UHT milk seems to be a consequence of the interaction between the plasminogen-plasmin system (endogenous protease of the milk) with proteases of bacterial origin.…”

Section: Introductionmentioning

confidence: 99%

Characterisation of the thermostable protease AprX in strains of Pseudomonas fluorescens and impact on the shelf-life of dairy products: preliminary results

et al. 2016

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Bacterial proteases are involved in food spoilage and shelf-life reduction. Among the bacterial proteases, a predominant role in spoilage of dairy products seems to be played by the thermostable metallo-protease AprX, which is produced by various strains of Pseudomonas fluorescens. Differences in AprX enzyme activity among different strains were highlighted, but the most proteolytic strains were not identified. In this study, the presence of the aprX gene was evaluated in 69 strains isolated from food matrices and 18 reference strains belonging to the P. fluorescens group, which had been previously typed by the multi locus sequence typing method. Subsequently, a subset of reference strains was inoculated in ultra-high temperature milk, and the expression of the aprX gene was evaluated at 22 and 6°C. On the same milk samples, the proteolytic activity was then evaluated through Azocasein and trinitrobenzenesulfonic acid solution assays. Finally, to assess the applicability of the former assay directly on dairy products the proteolityc activity was tested on industrial ricotta samples using the Azocasein assay. These results demonstrate the spread of aprX gene in most strains tested and the applicability of Azocasein assay to monitor the proteolytic activity in dairy products.

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“…These peptidomics studies revealed that differences in starting materials, production techniques, and storage time resulted in major differences in the peptide profile. For example, peptidomic analysis of lactose-hydrolyzed ultra-high temperature heat-treated milk indicated that residual proteases in the lactase preparation caused protein degradation that resulted in bitter flavor development with storage time [19–21]. Peptidomics can also be used to monitor inter-individual variation among cows [22] and as a marker for their health status—we demonstrated that peptide profiles differed in milk from healthy and mastitic quarters (teats) within the same cow [23].…”

Section: Introductionmentioning

confidence: 99%

Milk Peptidomics to Identify Functional Peptides and for Quality Control of Dairy Products

Dallas

Nielsen

2018

Methods in Molecular Biology

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Human milk and dairy products are important parts of human nutrition. In addition to supplying nutrients, milk proteins contain fragments—peptides—with important biological functions that are released during processing or digestion. Besides their potential functional relevance, peptides released during processing can be used as markers of ripening stage or product deterioration. Hence, identification and quantification of peptides in milk can be used to assay potential health benefits or product quality. This chapter describes how to extract, identify, and analyze peptides within breast milk, dairy products, and dairy digestive samples. We describe how to analyze extracted peptides with liquid chromatography-mass spectrometry, to use software to identify peptides based on database searching, and to extract peak areas for relative quantification of each peptide. We describe methods for data analysis, including predicting which enzymes are responsible for protein cleavage, identifying the site specificity of protein breakdown, mapping identified peptides to known bioactive peptides, and applying models to predict novel functional peptides.

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Plasmin Activity in UHT Milk: Relationship between Proteolysis, Age Gelation, and Bitterness

Cited by 70 publications

References 52 publications

Age Gelation, Sedimentation, and Creaming in UHT Milk: A Review

Age Gelation, Sedimentation, and Creaming in UHT Milk: A Review

Characterisation of the thermostable protease AprX in strains of Pseudomonas fluorescens and impact on the shelf-life of dairy products: preliminary results

Milk Peptidomics to Identify Functional Peptides and for Quality Control of Dairy Products

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