The neutron diffraction pattern Teixeira obtained from one of the thaumatin crystals. Inset: the crystal structure of thaumatin, where red is the protein itself and the little spheres are water molecules that are always found bound to the structure.
Credit: Susana Teixeira/Keele University
SYDNEY: A substance 100,000 times sweeter than sugar, which is calorie free and better for diabetics, could be mimicked to create healthier and tastier food.
Biophysicist Susana Teixeira from Keele University in Staffordshire presented her research on the super sweet protein thaumatin at ANSTO's recent Food & Neutrons conference in Sydney.
Thaumatin is a naturally occurring protein found in the African Serendipity Berry and is 100,000 times sweeter than sucrose (table sugar). It is already used commercially as a flavour enhancer and modifier and to mask the taste of some medicines.
Calorie free, no insulin response
The protein is expensive and difficult to mass produce, but understanding what underlies the sweetness in the structure of thaumatin will lead to tailor-made, cheaper proteins that could be used in food and pharmaceuticals.
"[Thaumatin] is a lot sweeter than sugar but it's virtually calorie free and doesn't trigger an insulin response," Teixeira said. "If you can identify what makes thaumatin so sweet you have what you need to design sweet proteins that not only keep any sweet tooth happy but are healthier."
Teixeria has already determined that the sweetness of thaumatin is related to the specific charges across a large surface area over which thaumatin can bind to the principle human taste receptor.
Charges over a large surface area
"Sweetness is tremendously complex. In the case of thaumatin the structural basis for sweetness is not just one obvious shape characteristic, it is buried under a network of charges, hydrogen atoms and interactions with water molecules," she said.
While scientists have looked at the structure of thaumatin using x-rays and other techniques, Teixeira, an instrument scientist at the neutron research facilities of the Institut Laue Langevin, France, has for the first time used the novel method of investigating food by firing a beam of neutrons at thaumatin crystals.
Neutrons are neutral particles found in the core of atoms, and are used in experiments to understand the structure of everything from HIV molecules to superconductors. Using neutrons to better understand food is a new field but is ideal to pin down sub-nanoscale detail in molecules, says Teixeira.
Sub-nanoscale detail of structure
"We still have a long way to go to fully understand such a vital thing as taste, but neutrons will play an important role in research in this area," she says.
Food scientist and chemist Peter Lillford, from the University of York and a flagship fellow at CSIRO Food and Nutritional Science, says the research is "a nice idea and a hot topic for the food industry."
"Nature makes wonderful proteins that do almost anything - for example antifreeze found in fish — and we've got to understand how these things work," he says.
"You might think there's no point in changing grandma's recipe, but the more people do in terms of understanding the mechanisms [of molecules], the more you realize we have to change our recipes because of health concerns," he says.
Stop blaming cane sugar!
As someone who is made ill by consuming products sweetened with substances other than cane sugar or honey I really do wonder how much more illness this new product and other being researched will create.
I do not know whether my illness is caused by the direct passage from the manufactured substances to my digestive system or the preservatives, colourings and flavourings needed to replace cane sugar. I only know I eat far more in each serve (often uncontrolably) and feel ill during and after consumption. With cane sugar based products I find it easy to limit my intake and am not ill after eating them.