Researchers at Kyoto University believe they have done so by substituting acidic amino acids in thaumatin, a natural sugar substitute, with basic ones.
Thaumatin, a protein derived from the fruit of Thaumatococcus daniellii Benth, an African tropical plant, is the sweetener of choice when it comes to diet beverages and gummy and jelly candies boasting natural ingredients.
"Making natural sweeteners stronger could be a huge plus to the food industry, especially as there are concerns regarding the consumption of low-calorie sugar substitutes to prevent lifestyle-related diseases," says lead author Tetsuya Masuda, whose work was published in Scientific Reports.
Professor Masuda and colleagues analysed the structure of thaumatin with X-rays to determine which parts of the protein made it taste sweet, finding that the basic amino acids in it played a crucial role in eliciting "sweetness", implying that substituting acidic amino acids with basic ones could make it sweeter.
They found that thaumatin became 1.7 times sweeter than before when aspartic acid was replaced with asparagine. The findings also confirmed the complex interaction between thaumatin and the sweetness receptor of the tongue.
In the early 2000s, after years of speculation, it was found that sweetness could be detected when positively charged molecules on the protein come in the vicinity of negatively charged molecules on the sweetness receptor.
"For a long time the mechanism in which we taste sweetness from thaumatin was a mystery, and for that reason it took very long to sweeten it up," said Prof. Masuda.
"Now that we've taken steps in the right direction, I'm excited about developing applications for a stronger form of thaumatin.”
Source: Scientific Reports
"A Hypersweet Protein: Removal of the Specific Negative Charge at Asp21 Enhances Thaumatin Sweetness"
Authors: Masuda, T. et al.