Thaumatin, a protein derived from the fruit of an African tropical plant, is the sweetener of choice when it comes to "diet" beverages and gummy and jelly candies boasting natural ingredients. Thaumatin also masks bitterness and helps enhance flavor.
Researchers have found a way to make thaumatin even sweeter. Only humans and primates taste sweetness from thaumatin. Researchers have analyzed its structure with X-rays to determine which parts of the protein make it taste sweet to us. From these studies they found that the basic amino acids in thaumatin play a crucial role in eliciting "sweetness", implying that substituting acidic amino acids with basic ones could make it sweeter.
In this study, they replaced aspartic acid with asparagine, making thaumatin 1.7 times sweeter than before. This also confirms the complex interaction between thaumatin and the sweetness receptor of the tongue, which was discovered in the early 2000s after long speculation by scientists. Sweetness is detected when positively charged molecules on the protein come in the vicinity of negatively charged molecules on the sweetness receptor.