They tested eight different ways of cooking rice on 38 different types of the grain found in Sri Lanka, and they discovered that by adding a fat such as coconut oil before cooking, and then immediately cooling the rice,
they could change the starch composition of the end result so that it contained more resistant starch.
The oil works by interacting with the starch molecules and changing its architecture. "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,"
explained James in a press release. And
he notes that heating the rice back up afterwards doesn't change the resistant starch levels.
So far the duo has only measured the specific chemical outcomes in the variety of rice that initially had the worst starch content, but they found that they were able to
reduce the amount of digestible starch 15 fold. This was also associated with a 10 to 15 percent reduction in calorie content.