“Starchy” Could be the Next Official Taste

13 Sep 2016 --- We know about salty, sweet, sour, bitter and even the most recent taste category umami, but what about a sixth possible taste - “starchy”? Moving away from the idea of five primary tastes was part of the basis of research carried out by associate professor Juyun Lim of Oregon State University.

She and her team set about researching the possibility of a sixth taste based on complex carbohydrates as many different people can recognize the familiar taste of carbs, whether it’s rice-like, pasta-esque or reminiscent of bread.

FoodIngredientsFirst has been sent a copy of the report.

“The primary function of taste is to identify substances that provide energy and/or electrolyte balance, while avoiding ingestion of toxic substances. Taste can also serve a metabolic function by preparing the body to assimilate ingested nutrients more effectively. Currently, there are five recognized taste categories in humans: sweet, sour, salty, bitter, and umami. Each taste quality is mediated by distinct transduction pathways expressed in subsets of taste receptor cells,” it says.

A total of 22 subjects aged between 18 and 45 years of age (mean = 25) were recruited from the Oregon State University campus and surrounding areas to take part in the research. 

They were given a range of different carbohydrate solutions and were able to detect in solutions that contained long or shorter carbohydrate chains a specific starch-like taste they referred to as “starchy”. 

The participants could still detect this floury flavor even when they were given a compound that blocks the receptors on the tongue for identifying sweet tastes. Professor Lim suggests that this shows people can sense carbohydrates before they have been completely broken down into sugar molecules. They stopped sensing the taste of starch when given solutions containing only long-chain carbohydrates and this suggests the flavor comes about from the shorter chains. 

The most recent taste to be recognized was umami which people can taste through receptors specific to glutamate, widely present in savory foods like meat broths and fermented products and commonly added to some food in the form of monosodium glutamate (MSG). Umami has its own receptors and scientists consider it to be a distinct taste. 

As of yet, there is no findings of specific carbohydrate receptors on the tongue however it makes sense that we should taste such a major component of our diet. 

“It is widely accepted that humans can taste mono- and disaccharides as sweet substances, but they cannot taste longer chain oligo- and polysaccharides. From the evolutionary standpoint, the ability to taste starch or its oligomeric hydrolysis products would be highly adaptive, given their nutritional value. Here, we report that humans can taste glucose oligomer preparations (average degree of polymerization 7 and 14) without any other sensorial cues. The same human subjects could not taste the corresponding glucose polymer preparation (average degree of polymerization 44),” says the report. 

“When the sweet taste receptor was blocked by lactisole, a known sweet inhibitor, subjects could not detect sweet substances (glucose, maltose, and sucralose), but they could still detect the glucose oligomers.This suggests that glucose oligomer detection is independent of the hT1R2/ hT1R3 sweet taste receptor. Human subjects described the taste of glucose oligomers as “starchy,” while they describe sugars as “sweet.”

Before any new flavor or taste becomes officials it must adhere to strict criteria including that it needs to be recognizable, have its own set of tongue receptors and trigger a useful physiological response. As no tongue receptors have been discovered as of yet, “starchy” has some way to go before it could become the sixth taste, however Lim’s research does show some evidence that the flavor is recognizable. 

Among other tastes that are also being investigated are the flavor of carbonated beverages and the metallic taste people detect from blood. Kokumi is also a full-bodied flavor described as “hearty” and there is some evidence that people can taste the fatty acids that made up fats and receptors have been found for kokumi. 

by Gaynor Selby