Sensory perceptions of oral nutritional supplements by older adults

Oral Nutritional Supplements (ONS) combined with dietary counselling are effective in alleviating undernutrition in older adults. However, ONS are often associated with negative sensory profiles and poor adherence. This thesis evaluated the sensory perception and liking of ONS in older adults seeking to improve adherence. Different sensory methods were used to test their appropriateness for older adults, thus advancing sensory methodology for this cohort. Chapter 2 measured the effectiveness of the Check-all-that-apply (CATA) method to investigate differences in perception of ONS between younger and older adults over successive sips of a high and low viscosity ONS. Effects of ONS consumption on thirst and appetite were also studied. Significantly lower levels of hunger and thirst were observed for older than younger adults. Hunger declined with ONS consumption volume and thirst increased in both cohorts. Differences in texture perception with age were noted, with younger adults selecting watery significantly more than older adults for low viscosity ONS and thick and viscous more for high viscosity ONS. The study justified the CATA method for use with older adults. The findings enhanced our understanding of how older adults experience ONS and drivers of ‘liking’. Few studies examine ONS within different older adult cohorts. Hence, Chapter 3 investigated the effects of older age, dentures, and medications on sensory perception, liking, and intake of high and low viscosity ONS. 75+ year olds had lower appetite than 65–74 year olds after both ONS. Denture wearing influenced mouthfeel and medications effected flavour perception of high viscosity ONS. Liking did not change across sips for any cohort, but sensory perception changed with increasing sips. Avoiding perceptions of watery/runny mouthfeel but maintaining creaminess may improve ONS acceptance. Chapter 4 investigated the differences in dynamic texture perception between older and younger adults across texturally modified ONS. Limited research has used Temporal Dominance of Sensations (TDS) to evaluate dynamic texture of beverages with older adults. Therefore, Chapter 4 measured the effectiveness of this method in evaluating dynamic texture perception of ONS in older adults. Older adults indicated less dominances based on less attributes, waited longer to select their first attribute, and for each selection generally. However, TDS curves with distinct peaks were generated by both cohorts, with similarities in texture attributes. The low viscosity ONS were perceived similarly by the two cohorts. Older adults perceived the high viscosity ONS sweeter, smoother, and creamier than younger adults who more often selected aftertaste, mouthcoating, and thick. Older adults liked high viscosity ONS more than younger adults. This chapter justifies TDS for dynamic evaluations of ONS with older adults. Chapter 2 showed that thirst increases with ONS consumption. This combined with older adults’ tendency for diminished thirst may contribute to reduced ONS adherence. Hence, Chapter 5 investigated how the viscosity, protein content and type, and sweetness of ONS impact thirst, mouth-drying, pleasantness to consume water, and taste in mouth after ONS consumption. The effects of age, dentures, medications, gender, and salivary flow were also measured. Most of the study cohort were suffering from diminished thirst and had low salivary flow. Each ONS was hypertonic which may contribute to increased thirst. Protein type and content, viscosity, and sweetness did not impact thirst, mouth-drying, taste in mouth, or pleasantness to consume water. However, the visual analogue scales (VAS) may have lacked the sensitivity to describe changes across the ONS. Non-denture wearers and those taking no medications had higher thirst after sweetened ONS compared to denture wearers and those taking medications. This enhanced understanding of how older adults experience ONS.