It has been known for some time that animals can taste sweet, salty, sour and bitter foods, but whether they can taste alkaline food has remained unclear until now, researchers suggest.

According to a new study, fruit flies can sense alkaline substances – those with a pH greater than seven – through a newly identified taste receptor.

Scientists say that although the research was conducted in the fruit fly Drosophila melanogaster – commonly used for studying taste – it could provide a basis for future studies on alkaline taste in other animals.

When it comes to choosing what to eat, taste influences the decision-making process of animals as it allows them to sample their food before consuming it.

Food sources contain many acids and bases, and pH measures a substance’s acidity or alkalinity.

Therefore, pH sensation enables the animal to select healthy food and reject potentially harmful options.

pH, the scale of how acidic or basic (alkaline) a substance is, plays an essential role for living organisms.

This is because many biological processes, such as breaking down food and enzymatic reactions, need the level of pH to be just right.

Yali Zhang, principal investigator at the Monell Chemical Senses Centre, in America, said: “Detecting the alkaline pH of food is an advantageous adaptation that helps animals avoid consuming toxic substances.”

He added: “Our work has settled the argument about whether there is a taste for alkaline things. There definitely is.”

While researchers are familiar with sour taste, which is associated with acids and allows us to sense the acidic end of the pH scale, little is known about how animals perceive bases on the opposite end of the pH spectrum.

Detecting both acids and bases, which are commonly present in food sources, is important as they can significantly impact the nutritional properties of what animals consume.

The researchers found that when given a choice between neutral food (pH 7) and alkaline food (pH 12, for example), wild-type flies predominantly choose neutral food.

The authors discovered a gene called alkaliphile (alka), which is responsible for detecting alkaline substances.

Overall the team established that alka is a new taste receptor dedicated to sensing the alkaline pH of food.

In the future they hope to explore whether there are comparable high-pH detectors in mammals.