Although only five basic tastes are widely recognised in humans, evidence appears to be mounting for fat to be added to the list. Previously, fat perception was thought to be the mouth’s ability to sense the creamy texture of foods, but researchers over the past few years have begun to suggest that fat could have distinct taste properties of its own.
This latest research review, led by Russell Keast of Deakin University’s Sensory Science Group in Australia, suggests that “with the exception of an independent perception, there is consistent emerging evidence that fat is the sixth taste primary”.
According to the paper, fat must meet specific criteria to be accepted as a taste, including having a distinct class of stimuli (for fat, this refers to the breakdown products of fats and fatty acids), the presence of receptors to change the chemical code of the stimuli to electrical signal, neurotransmission of the signal to processing areas of the brain, physiological effects after activation of taste bud cells and, most controversially, perceptual independence from other taste qualities.
On this last point, the study’s authors wrote that the taste of fat may be less well-defined than the sweetness of sugar or the saltiness of sodium chloride, for example. And some researchers have suggested that the taste component of fat may only be perceptible when associated with aroma or chemesthesis – sensations that are separate from taste and smell, like burn from chilli or coolness from menthol.
Fat detection through taste ‘makes sense’
“As the taste system has evolved to detect the nutrients or toxins in foods prior to ingestion, it makes sense that fats, an essential energy-dense macronutrient required in limited amounts for energy and nutritional needs, would be detected through taste, as other macronutrients namely carbohydrates and proteins are detected through the tastes of sweet and umami,” they wrote.
Indeed, researchers have proposed taste receptors and pathways for fatty acid perception, and the review authors added that fat taste sensitivity may also have implications for food consumption and likelihood of obesity – some people may be less sensitive to fatty tastes, making it more likely that they will overconsume fatty foods.
Geneva-based firm Natural Taste Consulting has already spotted the potential of this research for cutting the fat content of foods, with an ingredient intended to stimulate fat taste receptors to mimic the taste and aroma of fat.
However, despite the growing evidence, the researchers behind this latest review concluded that it was still too early to confirm the existence of a distinct fat taste.
“The next 5 to 10 years should reveal, conclusively, whether fat can be classified as the sixth taste, but no matter what, there appears to be a functional significance to oral chemosensing of fats,” they wrote.
“Review: Is fat the sixth taste primary? Evidence and implications”
Authors: Russell SJ Keast and Andrew Costanzo