Scientists have developed a new, simple way to cook rice that could cut the number of calories absorbed by the body by more than half, potentially reducing obesity rates.
"Because obesity is a growing health problem, especially in many developing countries, we wanted to find food-based solutions," said team leader Sudhair A James from the College of Chemical Sciences, Colombo, Sri Lanka.
"We discovered that increasing rice resistant starch (RS) concentrations was a novel way to approach the problem," he said.
By using a specific heating and cooking regimen, the team concluded that "if the best rice variety is processed, it might reduce the calories by about 50-60 per cent."
Starch is a component of rice and can be digestible or indigestible. Unlike digestible types of starch, RS is not broken down in the small intestine, where carbohydrates normally are metabolised into glucose and other simple sugars and absorbed into the bloodstream.
Thus, the researchers reasoned that if they could transform digestible starch into RS, then that could lower the number of usable calories of the rice.
"After your body converts carbohydrates into glucose, any leftover fuel gets converted into a polysaccharide carbohydrate called glycogen," James said.
"Your liver and muscles store glycogen for energy and quickly turn it back into glucose as needed. The issue is that the excess glucose that doesn't get converted to glycogen ends up turning into fat, which can lead to excessive weight or obesity," James said.
The team experimented with 38 kinds of rice from Sri Lanka, developing a new way of cooking rice that increased the RS content. In this method, they added a teaspoon of coconut oil to boiling water.
Then, they added half a cup of rice. They simmered this for 40 minutes, but one could boil it for 20-25 minutes instead, the researchers noted.
Then, researchers refrigerated it for 12 hours. This procedure increased the RS by 10 times for traditional, non-fortified rice.
James explained that the oil enters the starch granules during cooking, changing its architecture so that it becomes resistant to the action of digestive enzymes. This means that fewer calories ultimately get absorbed into the body.
"The cooling is essential because amylose, the soluble part of the starch, leaves the granules during gelatinisation," said James.
"Cooling for 12 hours will lead to formation of hydrogen bonds between the amylose molecules outside the rice grains which also turns it into a resistant starch," he said.
Reheating the rice for consumption, he noted, does not affect the RS levels.
The study was presented at the 249th National Meeting & Exposition of the American Chemical Society (ACS) in Denver.
