Abstract/Summary

Fat is perceived through three modalities; mouthfeel, odour and, as discovered more recently, through a taste cue in the mouth where free fatty acids are the stimuli generating this sensation. Although associations between fatty acid sensitivity, fat intake and preference have been studied in model systems, little work has related this to fat perception within real foods. In addition, the mechanisms causing differences in individual oral fat taste perception remain unclear. This thesis investigates how fat is perceived in the mouth using a real food model, relates this to food consumption and preference, and explores the potential mechanisms causing individual oral fat perception via genotypes of the fatty acid translocase CD36 and salivary lipase activity. A real food model using milk and cream was developed at different fat levels. All samples were assessed for perceived fattiness using intensity rating and a discrimination test. We found that odour significantly enhanced fat perception and mouthfeel was an important indicator of perceived fattiness. More interestingly, participants could distinguish fat levels based on "taste" alone. The relationship between individual fatty acid sensitivity, oral fat perception in the milk/cream model, food consumption and preference was investigated. We found that individual preference for foods rich in fats varied and this was positivity correlated with fat consumption. Moreover, oral fat "taste" perception influenced individual preference for foods rich in fat. Individuals had different sensitivities to oleic acid and this impacted on their ability to distinguish fat levels in the real food model. However, no association between the sensitivity to oleic acid and fat consumption was found in this study. With the aim of understanding potential mechanisms underpinning individual oral fat perception; the role of salivary lipase and CD36 genotypes were examined. Fatty acid generation in the mouth was investigated using almonds and levels of oleic acid quantified from expectorated almond sample varied between individuals. Subjects with a greater propensity to generate oleic acid in mouth were found to rate fat intensity higher in the real food model. This indicated that salivary lipase could release free fatty acid from dietary fat and influence oral fat perception. In addition, our results suggested that CD36 genotypes were not only was associated with fat intake and hedonic response to foods rich in fats, but also influenced detection threshold for oleic acid and oral fat perception. Moreover, the influence of CD36 genotypes on oral fat perception differed between subjects with high salivary lipase activity and those with low lipase activity. In conclusion, our work confirms that fat can be perceived through taste and adds new knowledge as to how individual preference to high fat foods varies and can be explained by oral fat perception. Individuals had different sensitivities to fatty acid which could influence their ability to distinguish fat levels. CD36 genotypes and salivary lipase activity played an important role in individual oral fat perception.