Humans are thought to be able to taste five qualities but technological advances combined with sophisticated research means we can now test for more subtle tastes we haven’t known about. In a paper we published this week, we show there’s now enough evidence to consider fat a taste quality.
Taste acts as the gatekeeper of ingestion – if a potential food is deemed suitable for consumption it may be swallowed, if not rejected. To guide this decision, we have five taste qualities: sweet, sour, salty, bitter and umami. Sweet, salty and umami are all appetitive and signal the food contains essential nutrient, while excessive sour and bitter signal aversion and potential harm.
When It All Started
Over the past few years, considerable attention has been given to fat as an additional taste. But a series of criteria had to be satisfied before fat could be considered as one.
First, scientists had to show there was a class of stimuli – in this instance, fats or its breakdown products (fatty acids) – that activate receptors on taste cells specific to that stimuli. That is, we had to find taste cells that were there to only recognise fat.
Then, we must find evidence for a signal that’s sent from the taste cell to taste-processing regions of the brain. And when the signal is decoded as a perception, it must be independent of all the other tastes. In other words, it can’t just be a combination of sweet and salt or other possible taste combinations.
The first evidence of a fat taste was published by US researchers in 1997, who found rats had a taste response to fatty acids. In 2001, another US scientist published two papers showing similar receptors may occur in humans.
