Human Sensitivity to and Qualitative Perception of Non-esterified Fatty Acids.

摘要

Structural features of fatty acids determine their health effects. Features, primarily alkyl chain length and degree of saturation, result in different affinities for receptors, diffusion across membranes, and solubility. Whether these properties also influence the oral detection of non-esterified fatty acids (NEFA) is not established and was the focus of this work. Two studies were conducted on sensitivity. The first demonstrated that humans are more sensitive to short than to long chain fatty acids. The second study tested degree of saturation, and revealed humans are more sensitive to polyunsaturated than monounsaturated fatty acids. Evidence from these studies supports a taste mechanism as other sensory properties were controlled. Finally, a set of studies was conducted on the sensory qualities of various NEFA. First, NEFA were tested for taste intensity over a range of ecologically-relevant concentrations. These NEFA were then tested with other prototypical, iso-intense tastants representing sweet, sour, salty, bitter, and umami sensations. Participants were screened for their ability to detect a linoleic acid solution. They then sorted the samples based on their qualitative similarity. Next, participants sequentially combined groups based on similarity until only two groups remained. Dissimilarity matrices were computed for each participant and bootstrapping was used to generate multidimensional scaling maps with kernel density for each sample. Plots indicated perceptual overlap between the medium and long chain fatty acids and bitter compounds. As this overlap could reflect a similar hedonic impression, a lack of discriminating lexicon, or actual similarity, the sorting procedure was repeated in a second trial using only medium and long chain fatty acids, blanks, and bitter stimuli. Results indicate that the sensations of the medium and long chain fatty acids are unique from the blank and bitter stimuli, and from each other. Together, these studies demonstrate the structural properties of NEFA define their taste thresholds, intensity and qualities. Whether taste responses are predictive of post? ingestive effects of fat ingestion warrants further study.