Redesigning nutritional supplements for older adults: a flavour chemistry and nutrition approach

Lester, Sophie (2021) Redesigning nutritional supplements for older adults: a flavour chemistry and nutrition approach. PhD thesis, University of Nottingham.

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Within the increasing older population, there is a burden of undernutrition. The prescription of oral nutritional supplements (ONS) for those who are undernourished, or at risk of undernutrition, can help improve nutritional status, but the patient must consume an adequate quantity of ONS to gain the clinical benefits.

This research first reviewed the literature to identify factors that influence adherence to ONS. Good palatability is crucial for adequate intake of ONS, but palatability challenges stem from both the product (undesirable sensory properties) and the consumer (age-related sensory changes). The contribution made by aroma compounds to the palatability of ONS was recognised as a comparatively underresearched area. Therefore, this work aimed to fill the evidence gap by investigating the role of intrinsic flavour quality (with emphasis on aroma) and age-related changes in oronasal physiology and sensory abilities on sensory perception and palatability of ONS.

The characterisation of aroma-active compounds in a commonly prescribed ONS was a fundamental stage in the research. Esters (sweet, fruity) and diacetyl (sweet, buttery) were found to make a large contribution to the perceived flavour of the studied ONS. Sulfurous aroma compounds, likely stemming from the heat-treatment of protein ingredients, were also found to contribute to the perceived flavour of ONS. An orthonasal hedonic evaluation established that sulfurous aroma compounds are primarily unpleasant, whereas the fruity ester aroma (isoamyl acetate) and diacetyl are primarily pleasant. However, sulfurous aromas were rated more pleasantly by older adults who also had impairments in their ability to detect aromas at threshold concentrations.

When aromas were combined in a mixture within a real-food matrix (a flavoured dairy beverage), sulfurous aroma compounds were shown to negatively impact consumer acceptance (for consumers aged 18 – 79 years). However, these sulfurous flavours were less objectionable for older adults. This is a novel finding because it suggests that olfactory impairments may benefit older consumers who need to consume protein-rich foods containing off-flavours. Furthermore, the addition of diacetyl increased the acceptability of the sulfurous flavours, demonstrating partial masking abilities of this compound.

Older adults are also known to experience age-related changes in their oral and nasal physiology, such as reduced salivary flow rates which may influence the way flavours are released in the mouth. Therefore, the next stage of the research investigated differences in the temporal consumption experience (comprising in-mouth aroma release, sensory perception and subjective appetite) of a clinically relevant portion of ONS for groups differing in saliva flow rate, in which repeated measurements were made between sips. This study demonstrated that a lower saliva flow rate is associated with significantly more intense in-mouth aroma release (p=0.015), significantly higher aftertaste intensity (p<0.001), and greater increase in mouth drying over sips (p=0.02), compared to a medium- and high- saliva flow rate. These findings occurred concurrently with relatively lower hunger sensations in the low- and medium-flow rate groups.

This research adds to the growing body of evidence on how best to optimise food and beverage palatability for older consumers. Many older patients who are prescribed ONS are likely to experience reduced salivary flow rates and olfactory impairments. The unique sensory experience of these individuals should be considered in both product development and clinical practice to optimise palatability, hence maximising nutritional intake from ONS and other nutritional foods and beverages whilst minimising wastage.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Fisk, Ian
Taylor, Moira
Keywords: Nutritional supplements, Older adults
Subjects: R Medicine > RM Therapeutics. Pharmacology
Faculties/Schools: UK Campuses > Faculty of Science > School of Biosciences
Item ID: 65900
Depositing User: Lester, Sophie
Date Deposited: 31 Dec 2021 04:40
Last Modified: 31 Dec 2021 04:40

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