Abstract/Summary

Whey protein is a functional ingredient used in sports nutrition and in the prevention of sarcopenia in older adults. Non-compliance of whey protein fortified beverages in clinical settings can be due to negative sensory attributes, such as a drying sensation. The mechanism of whey protein derived mouthdrying is yet to be fully defined, with a focus on low pH beverages in the literature. This study aimed to: investigate the effect of thermal denaturation on the build up of drying elicited by neutral pH whey protein concentrate (WPC); determine potential mechanisms; and mitigate drying. This research investigated the sensory properties of four WPC aqueous samples heated for varying lengths of time using two sensory techniques; quantitative descriptive analysis and sequential profiling. Heating time was found to correlate with higher drying, mouthcoating and chalky intensities, with an increase over repeated consumption and a high persistence of sensation seen for all samples. Heated samples had a larger particle size, which could contribute to the increase in drying observed. The physical build-up of WPC in the mouth was measured using an in vivo retention method, which found the most heated sample had the highest retention up to 60 s after the sample had been swallowed. Accessible thiol concentration was seen to increase with heating time, which could lead to interactions with the mucosa, and consequently a higher oral retention. Interactions of WPC with mucin were observed using particle size analysis and spectroscopic analysis; however, interactions were not observed for individual whey proteins, indicating that the complex mix of WPC contributes to the interactions. Polysaccharides were used in an attempt to mitigate drying by blocking mucoadhesive interactions and lubricating the mouth. Although the mitigation of drying was unsuccessful, a reduction in other mouthfeel attributes was observed suggests this is an area requiring further research. The thesis concludes that both particle size and protein structure are implicated in whey protein derived mouthdrying, supporting the proposal of a mucoadhesive mechanism.