New Rice Cooking Method Reduces Calories and Aims to Tackle Obesity
DENVER, March 23, 2015 – Scientists have developed a new and simple way to cook rice that could reduce the number of calories absorbed by the body by more than half, potentially curbing obesity rates, which is especially crucial in countries where rice is a staple food.
The presentation took place at the 249th National Meeting & Exposition of the American Chemical Society (ACS), the world’s largest scientific society. The meeting featured around 11,000 reports on new advances in science and other topics and will continue until Thursday.
The number of overweight or obese individuals has been steadily rising as lifestyles change and people become more sedentary, leading to dietary shifts with larger portion sizes and increased food options. Along with consuming more fats and sugars, people tend to opt for carb-rich starchy foods like rice, which contains approximately 240 calories per cup.
“As obesity is a growing health problem, especially in many developing countries, we wanted to find food-based solutions,” says team leader Sudhair A. James, who is from the College of Chemical Sciences, Colombo, Western Province, Sri Lanka. “We discovered that increasing the concentration of resistant starch (RS) in rice was a novel way to address the issue.” By using a specific heating and cooking regime, the scientists concluded that “processing the best variety of rice could reduce calories by about 50-60 percent.”
James explains that starch can be digestible or indigestible. Rice contains both types of starch. Unlike digestible starch types, RS is not broken down in the small intestine, where carbohydrates are typically metabolized into glucose and other simple sugars and absorbed into the bloodstream. Therefore, researchers argued that if they could transform digestible starch into RS, it could reduce the number of usable calories in rice.
Rice is loaded with starch (1.6 ounces per cup), says James. “After your body converts carbohydrates into glucose, any leftover fuel is turned into a polysaccharide carbohydrate called glycogen,” he explains. “Your liver and muscles store glycogen for energy and quickly convert it back into glucose as needed. The issue is that excess glucose that doesn’t get converted into glycogen turns into fat, which can lead to being overweight or obese.”
The team experimented with 38 varieties of rice from Sri Lanka, developing a new rice cooking method 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 and boiled it for 40 minutes, but it was also possible to boil it for 20-25 minutes, the researchers noted. Next, they refrigerated it for 12 hours. This procedure increased the RS content 10 times compared to traditional, non-fortified rice.
How can such a simple cooking change result in a lower-calorie food? James explains that the oil enters the starch granules during cooking, altering their architecture to become resistant to the action of digestive enzymes. This means fewer calories end up being absorbed by the body. “Cooling is essential because amylose, the soluble part of starch, leaves the granules during gelatinization,” James explains. “Cooling the rice for 12 hours will lead to hydrogen bonds forming between the amylose molecules outside the rice grains, which also turns it into resistant starch.” Reheating the rice for consumption, he notes, does not affect RS levels.
He says the next step will involve conducting studies with human subjects to determine which rice varieties are most suitable for the calorie-reduction process. The team will also explore whether other oils besides coconut have a similar effect.
James acknowledges funding from the College of Chemical Sciences, Institute of Industrial Technology, Sri Lanka, and other sources.
The American Chemical Society is a nonprofit organization founded by the U.S. Congress. With over 158,000 members, ACS is the world’s largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals, and scientific conferences. Its main offices are located in Washington, D.C., and Columbus, Ohio.