Journal Articles

Permanent URI for this collectionhttps://mro.massey.ac.nz/handle/10179/7915

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Author: search.filters.author.Ye, Aiqian

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    Tuning heat-­‐induced colloidal aggregation of whey proteins, sodium caseinate and gum arabic: effect of protein composition, preheating and gum arabic level
    (ELSEVIER SCI LTD, 2014) Loveday, SM; Ye, Aiqian; Anema, Skelte G; Singh, Harjinder
    Heating can drive the colloidal complexation of negatively-­‐charged proteins and polysaccharides by strengthening hydrophobic interactions and denaturing proteins, thereby exposing reactive sites for covalent and noncovalent bonding. We have previously shown that stable colloidal aggregates comprising whey protein, sodium caseinate and gum arabic can be produced by careful selection of heat treatment, pH and protein type. Here we tested how the size, composition, charge and morphology of colloidal aggregates are affected by the amounts of whey protein, sodium caseinate and gum arabic, as well as the thermal history of the proteins. Increasing amounts of whey protein resulted in larger particles, which were more prone to precipitate. Preheating whey protein slightly enhanced aggregation, and this effect was mitigated when sodium caseinate was present during preheating (chaperone effect). Increasing amounts of gum arabic produced larger particles with less charge, but the gum arabic effect was statistically confounded with ionic strength. We believe that both covalent (disulphide) and noncovalent interactions among protein molecules are required to overcome electrostatic repulsion at pH 7 and form stable aggregates.
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    In vitro gastric digestion of heat-induced aggregates of β-lg
    (Elsevier Inc., 2012) Loveday, SM; Singh, Harjinder; Ye, Aiqian; Peram, Malleswara R.
    An in vitro gastric digestion of heat-induced aggregates of β-lactoglobulin (β-lg) in simulated gastric fluid was investigated using sodium dodecyl sulfate-PAGE under nonreducing and reducing conditions, native-PAGE, 2-dimensional electrophoresis, and size exclusion chromatography. Heating at 90ºC significantly increased the digestibility of β-lg, with a high initial digestion rate followed by a relatively constant rate of digestion at a high enzyme:substrate (E:S) ratio of 3:1. At a low E:S ratio (1:6), the rate of digestion of β-lg was slower, and intermediate and low molecular weight species could be seen. The high molecular weight nonnative aggregates (pentamers, tetramers, trimers, etc.) were digested relatively rapidly, whereas some of the nonnative dimers were resistant to digestion and others were digested rapidly. The intermediate molecular weight species (21 to 23 kDa) were digested slowly. These results indicated that the digestibility of nonnative β-lg aggregates varied significantly depending on the E:S ratio and the types of aggregate. Further investigation is necessary to identify and characterize slowly digested dimers and intermediate molecular weight species.