Scientists have confirmed the existence of three lipolytic enzymes (lipases) in the salivary glands of the human tongue, bringing an end to many years of dispute. According to the study, these enzymes are located right beside the taste buds – a finding supported by taste tests. This provides further evidence that humans can perceive the taste of fat. The research team has published its findings in the Journal of Lipid Research.
Scientists from Technische Universität München (TUM) and the German Institute of Human Nutrition (DIFE) have made a major breakthrough in the search for the human ability to taste fat. By carrying out molecular and sensory tests, they were able to discover lipases that break down lipids in food – a prerequisite for the recognition of fat by sensory cells in the tongue. The GPR120 receptor plays an important role in this process.
Humans can perceive five basic tastes. There are, for example, taste receptors for two of the essential nutrients for humans: carbohydrates (sweet) and proteins (umami). It is a subject of debate, however, whether humans can also taste the macronutrient with the highest energy content – fat.
Enzymes release fatty acids
Up to now, many scientists have assumed that our partiality for fat is mainly based on the senses of smell and touch, with the appeal lying in the aroma compounds dissolved in the fat and the texture of fatty foods. Earlier studies have indicated, however, that the sense of taste could also play a role in the perception of fat.
The problem was that no-one had discovered a lipase in saliva that could explain how fatty acids are released from the food we eat. But this latest study has made that breakthrough. It shows that contrary to earlier assumptions, a specific type of salivary gland produces lipases. These are able to free fatty acids from dietary fats, at which point they can be recognized by the GPR120 receptor.
Perception of fat varies by individual
“We also found that the test participants perceived the fat taste less strongly if they tasted the fatty foods together with an inhibitor serving to decrease the lipase activity,” explains Prof. Thomas Hofmann of the TUM Chair of Food Chemistry and Molecular Sensory Science. In addition, the taste tests showed that people have different degrees of response to fats. “The test participants’ reactions varied as a direct function of the lipase activity in their saliva,” adds Hofmann.
These observations suggest that dietary fat is broken down into free fatty acids, which activate a receptor and create the typical taste of fat. Nevertheless, further research is required before we can say for sure that this perception of fat truly points to the existence of a sixth “fat” taste.
Voigt N, Stein J, Galindo MM, Dunkel A, Raguse JD, Meyerhof W, Hofmann T, Behrens M: The role of lipolysis in human orosensory fat perception, DOI: 10.1194/jlr.M046029
Technische Universität München
Chair of Food Chemistry and Molecular Sensory Science