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American researchers uncover sixth taste responsible for carbohydrate cravings

Researchers from the Department of Food Science and Technology at the Oregon State University have found that carbohydrate-rich foods may elicit a unique taste that makes carb cravings hard to resist.
The study findings, published in the online journal Chemical Senses, revisit the common knowledge that our tongues can only register a small number of primary tastes.
The research of Juyun Lim and colleagues show that, in addition to salty, sweet, sour, and bitter, humans can also specifically taste a “starchy” flavour from the complex carbohydrates.
When we consume complex carbohydrates, like whole grain bread, oatmeal or brown rice, enzymes in our saliva break starch down into shorter chains and simple sugars.
Until now, food scientists have assumed that we detect starch by tasting solely the sweet molecules known as monosaccharides and disaccharides.
This study challenged these assumptions by testing whether humans can directly taste the longer chain oligo- and polysaccharides, also referred to as glucose oligomers, in complex carbohydrates.
To do so, the researchers ran an experiment where they gave a range of different carbohydrate solutions to volunteers with a compound called lactisole that inhibits the hT1R2/hT1R3 receptors on the tongue for detecting sweet tastes like glucose, maltose or sucralose.
It turned out that the participants were able to detect a starch-like taste corresponding to the glucose oligomers from long or shorter carbohydrate chains in these solutions.
The subjects, of different ethnicity, described the distinct taste of glucose oligomers as “rice-like” for Asians or “bread-like” for Caucasians.
This suggests that we can taste starch as a flavour in its own right and that we can sense carbohydrates before they have been completely broken down into sugar molecules.
Before any new flavours can be enshrined as primary tastes, they must meet a list of criteria. Tastes need to be recognisable, have their own set of tongue receptors, and trigger some kind of useful physiological response.
And starch doesn’t tick all of the boxes from the list of criteria. The researchers are yet to identify specific starch receptors on the tongue.
For Lim, these results may explain why people detect and are drawn to complex carbs as a “valuable” energy source. “Sugar tastes great in the short term, but if you’re offered chocolate and bread, you might eat a small amount of the chocolate, but you’d choose the bread in larger amounts, or as a daily staple,” Lim told the New Scientist.
As the latest diabetes research has suggested, having large amounts of complex carbohydrate has negative effects for people with diabetes or at risk of it. For this reason, a low-carbohydrate diet will often be a more appropriate choice.

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