Focus of taste genetics will be on bitterness because it has been the most extensively studied taste modality
PTC & PROP are members of the thioureas; do not occur naturally in foods Often used interchangeably because of common association of being markers for bitterness perception; PROP is generally used for threshold detection in studies because PTC has a slight smell when used in solutions… TAS2R38 gene has been identified as the gene for PTC sensitivity; three functional single nucleotide polymorphisms within this gene have been found to explain up to 85% of the observed variance in PTC taste sensitivity; some research does show that TAS2r38 polymorphisms aren’t sufficient enough to explain PROP bitterness perception at suprathreshold concentrations suggesting that other genetic or environmental mechanisms might also play a role in PROP taste perception
N-C=s group= Thiocyanate moiety Nontasters- Some people cannot taste this chemical at all Tasters- perceive this chemical to be bitter Being a taster has been shown to correlate with a greater general taste acuity, having heightened responses to sweet & salty stimuli and show increased sensitivity to olfactory cues & viscous substances such as fats and food thickeners
T2Rs are a family of G protein-coupled taste receptors located at the surface of taste cells as well as palate and epiglottis; Polymorphisms of the genes that code for these receptors are what may explain the variability in taste perception These vegetables usually tend to be nutritionally significant (i.e. spinach, endives and many cruciferous vegetables like broccoli, cabbage, cauliflower, and kale just to name a few) Secondary compounds in these veggies include phytochemicals such as polyphenols, methylxanthines, isoflavones and sulfamides which might protect against certain illnesses
do not occur naturally in foods but the variability in response to their taste correlates with taste sensitivity to other bitter substances present in foods
Sweetness- different strains of mice used to detect differences in sweet taste perception of saccaharin, to the point where direct evidence for the role of Tas1r3 in saccharin preference came from studies with mice Umami- studies using rats and Chinese hamster ovary cells helped identify genes associated with umami Sour-coexpression of ion channels associated with this modality were first observed in rats Salty- identification of epithelial sodium channels in rodents may have a role in perception of NaCl Research in all these areas are still in their infancy, and though animal research has helped identify possible genes and ion channels, exact mechanisms for these modalities are still unclear. Could be due to fact that bitterness perception and its genetic basis were discovered over 75 years ago through a series of individual responses
Relationship between food acceptance and bitterness perception are still being defined
Examines the relationship between genetic variation and food acceptance by
Subjects tasted room temperature solutions, expectorated and rinsed to ensure that the threshold is roughly halfway between chance and perfect performance Magnitude Estimation with two or more sense modalities create a common scale of sensory magnitude (if a person assigns the same number to two different sensory events, it would mean they have the same sensory magnitude
1. stimuli were randomized within each block and a tone series always followed a taste series
using principal component analysis with varimax rotation… Factor analysis with principal component solution can be used to reduce a large set of variables into a few underlying dimensions which can be treated as independent variables. These new dimensions account for the most of the variance of the original set of variables. Forming the food categories was necessary because of the large number of food items. Principal component analysis was based on the use frequencies and same categories were applied to desired use and liking scores as the factor solutions for these ratings were almost identical with those from use frequencies. These factor solutions could explain % of the variation of sweet foods Cronbach's alpha measures how well a set of items (or variables) measures a single dimensional construct; a value of 0.70 or higher is generally considered exceptable
The authors felt Ceiling factors are limits that are established not by the intensity of the phenomenon but the measuring instrument; this can inhibit expression of sensory intensity. For example labeled scales have ceilings that force supertasters to give erroneously low ratings
People who taste PROP as exceptionally bitter and have a high density of fungiform papillae have a different oral sensory world from those who taste less PROP bitterness relative to density of fungiform papillae
Relationship will produce a difference in preference for sweet, fat, or bitter foods and beverages
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Zhao L, Tepper BJ. Perception and acceptance of selected high-intensity sweeteners and blends in model soft drinks by propylthiouracil (PROP) non-tasters and super-tasters. Food Quality and Preference. 2007;18(3):531-40.