Identification of aroma compounds in a commonly prescribed oral nutritional supplement and associated changes in olfactory abilities with human ageing.

Undernutrition is prevalent in the older adult population. Oral nutritional supplements (ONS) are a clinically effective nutritional intervention, however, patient acceptance of ONS can be limited by their palatability. While sensory attributes such as sweetness and mouthfeel have been investigated, the contribution made by aroma to the perceived flavour of ONS has not been studied. Firstly, this research aimed to identify the aroma active compounds within a commonly prescribed ONS using estimated odour activity values (OAV) and gas chromatography olfactometry mass spectrometry (GC-O-MS). Secondly, age related differences in olfactory detection were explored. Eight aroma active compounds were identified within the ONS, including diacetyl (sweet), isoamyl acetate (banana), dimethyl trisulfide (sulfur) and methanethiol (sulfur). When compared with younger adults (n = 24, 18-44 years), older adults (n = 24, 62-80 years) had higher detection thresholds for all aroma compounds and this was significant for isoamyl acetate (sweet, fruity) and methanethiol (sulfur) (p = 0.01 and p = 0.03, respectively). Thus, a decline in olfactory sensitivity was present in the older subjects included in the study, and this reduced detection sensitivity was aroma specific. Thus, older adults' flavour perception of ONS likely depends on the combined effect of product factors (the aroma profile) along with age related consumer factors (the degree of impairment in perception). This is a fundamental study which will aid future research into how the aroma profile, and associated age related impairments in perception, shape the global perception of ONS for nutritionally at risk older individuals.