Abstract/Summary

Oral Nutritional Supplements (ONS) are nutritional status enhancing beverages prescribed to older adults at risk of under-nutrition. They contain energy, protein, vitamins and minerals, however the low consumption of ONS on elderly care wards can prevent patients from receiving their health benefits. The predominant cause for beverage wastage has been reported to result from patients disliking the taste, improvement of which is predicted to encourage greater consumption. This PhD study investigated the key sensory attributes of ONS, aiming to understand and reduce the negative characteristics to improve ONS products to enable increased consumption by older patients. Eight ultra high temperature (UHT) processed dairy-based ONS and non-ONS products were investigated for unpalatable attributes. The sensory characteristics were assessed with a trained panel by both quantitative descriptive analysis (QDA) and sequential profiling, as well as directly with older adults through a novel use of a taxonomic free sorting (TFS) technique. The results from TFS were directly relatable to QDA, even though the participants were untrained, and the sorting data was combined with liking data to yield a preference map generated entirely from target consumer data. Mouthfeel attributes such as viscosity that had been described in TFS, were investigated by just noticeable difference (JND) testing. There were found to be no significant age-effects for the perception of thickness and mouth coating. Interestingly, older adults were more sensitive to perceived mouth drying than younger adults; a critical attribute found to build to the greatest extent in ONS during repeated consumption. Sequential profiling with a trained panel assessed a range of ONS dairy protein ingredients to find potential sources of mouth drying. Although whey protein concentrate (WPC) was found to be the most drying ingredient, all protein powders elicited some drying which highlighted the need to understand masiGng techniques and potential mechanisms. Sweetness, viscosity, lipid enhancement and lipid type were not found to mask drying in protein enriched milks. However, in a novel application of fluorescence microscopy, the mucoadhesive properties of casein and ~-lactoglobulin were assessed which led to the conclusion that these milk proteins adhere directly to the mucous layer of oral epithelial tissue. The presence of this interaction may be crucial for determining the mechanism behind mouth drying sensations as found in ONS. Through a wide range of techniques this study highlighted mouth drying as a key detectable attribute of ONS. Although masking methods were not able to reduce the drying sensation, the breakthrough of mucoadhesion between dairy proteins and the oral mucosa suggests this attribute could be further investigated and reduced to improve ONS consumption by older patients.