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Open AccessArticle

Investigation of Age Gelation in UHT Milk

1
Commonwealth Scientific and Industrial Research Organisation (CSIRO), Agriculture and Food, Werribee, VIC 3030, Australia
2
Department of Economic Development, Jobs, Transport and Resources, AgriBio Centre, Bundoora, VIC 3083, Australia
3
Genedata AG, 4053 Basel, Switzerland
*
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Beverages 2018, 4(4), 95; https://doi.org/10.3390/beverages4040095
Received: 23 October 2018 / Revised: 16 November 2018 / Accepted: 20 November 2018 / Published: 24 November 2018
(This article belongs to the Special Issue Omics and Beverages)
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Abstract

Milk samples with twelve combinations of κ- and β-casein (CN) and β-lactoglobulin (β-Lg) variants were obtained to investigate the effect of protein variant on the mechanism/s of age gelation in ultra-high temperature (UHT) skim milk. Only milk groups with κ-CN/β-CN/β-Lg combinations AB/A1A2/AB and AB/A2A2/AB suffered from the expected age gelation over nine months storage, although this could not be attributed to the milk protein genetic variants. Top-down proteomics revealed three general trends across the twelve milk groups: (1) the abundance of intact native proteins decreases over storage time; (2) lactosylated proteoforms appear immediately post-UHT treatment; and (3) protein degradation products accumulate over storage time. Of the 151 identified degradation products, 106 (70.2%) arose from β-CN, 33 (21.9%) from αs1-CN, 4 (2.7%) from β-Lg, 4 (2.7%) from α-La, 3 (2%) from κ-CN and 1 (0.7%) from αs2-CN. There was a positive correlation between milk viscosity and 47 short peptides and four intact proteoforms, while 20 longer polypeptides and 21 intact proteoforms were negatively correlated. Age gelation was associated with specific patterns of proteolytic degradation and also with the absence of the families Bacillaceae, Aerococcaceae, Planococcaceae, Staphylococcaceae and Enterobacteriaceae, present in all the non-gelling milk groups pre-UHT. View Full-Text
Keywords: age gelation; casein; milk; top-down proteomics; MS/MS; protein sequencing; ultra-high temperature milk age gelation; casein; milk; top-down proteomics; MS/MS; protein sequencing; ultra-high temperature milk
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Raynes, J.K.; Vincent, D.; Zawadzki, J.L.; Savin, K.; Mertens, D.; Logan, A.; Williams, R.P. Investigation of Age Gelation in UHT Milk. Beverages 2018, 4, 95.

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