Synthesis of Lactose Phosphate and its Conjugation with Whey Proteins

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dc.contributor.advisor Hemar, Y en
dc.contributor.advisor Miskelly, G en
dc.contributor.author Julmohammad, Norliza en
dc.date.accessioned 2017-05-08T02:18:58Z en
dc.date.issued 2017 en
dc.identifier.uri http://hdl.handle.net/2292/32802 en
dc.description.abstract The aim of this study was to investigate the conjugation of whey proteins (WPs) with lactose phosphate (LP) and to compare the functional properties of these conjugates with either non-conjugated whey protein or whey protein conjugates using lactose. Lactose-6’-phosphate (Lact-6’P) was prepared chemically via two chemical pathways, either using unprotected lactose or with protected lactose via a pertrimethylsilyated derivative. The most successful production of Lact-6’P was via a mono-deprotected pertrimethylsilyated derivative of lactose. This compound reacted with diphenylphosphoryl chloride by hydrogenation before hydrolyzed to remove trimethylsilyl protecting groups. Purification and neutralisation, followed by lyophilisation, produced the pure dipotassium salt of Lact-6’P. This material gave LP ions at m/z = 421+ when analysed using High Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS) and had one triplet peak pattern around 4 ppm in the 31P NMR spectrum. Mixed regiosomers of unprotected LP were prepared by reaction of lactose with sodium hexametaphosphate at pH 5.5, 80°C for 5 days. Products from the latter preparation were purified by anion exchange chromatography monitored by p-hydroxybenzoic acid hydrazide (PAHBAH) analysis. This LP preparation contained Lact-6P and Lact-6’P, and other regioisomers. The regioisomeric mixture of protected LP (LP 1) and the 6’ regiospecific LP (LP 2) were conjugated to whey proteins using incubation time varying from 0 to 10 days, at 40°C and at water activity Aw = 0.79. SDS-PAGE analysis, visible browning, absorbance at 294 nm and 420 nm, OPA assay and mass spectrometry were employed to monitor the extent of conjugation. An incubation time of 3 days was selected as the standard conjugation time based on conjugation rates and the degree of Maillard browning. Mass spectrometric analysis of the modified whey proteins at 3 days indicated a maximum of 3 LP moieties were conjugated to α-Lac, in comparison to 8 lactose moieties for α-Lac-Lactose. Meanwhile, 5 LP moieties conjugated to β-Lg-LP in contrast to 10 lactose moieties. Functional studies using the conjugated LP-whey proteins showed that they possessed improved protein heat stability, better emulsifying properties, and also had good solubility compared to non-conjugated and lactose-conjugated whey proteins. Thus, a new approach of LP conjugation to whey proteins has shown to be a useful method for altering the functional properties of proteins. en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA99264921213202091 en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. Previously published items are made available in accordance with the copyright policy of the publisher. en
dc.rights.uri https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm en
dc.title Synthesis of Lactose Phosphate and its Conjugation with Whey Proteins en
dc.type Thesis en
thesis.degree.discipline Food Science en
thesis.degree.grantor The University of Auckland en
thesis.degree.level Doctoral en
thesis.degree.name PhD en
dc.rights.holder Copyright: The author en
dc.rights.accessrights http://purl.org/eprint/accessRights/OpenAccess en
pubs.elements-id 624583 en
pubs.record-created-at-source-date 2017-05-08 en


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