Changing how rice is cooked could cut calories

By Nathan Gray contact

- Last updated on GMT

A new method for cooking rice that could slash calories by increasing levels of resistant starch may have applications for food companies using rice.
A new method for cooking rice that could slash calories by increasing levels of resistant starch may have applications for food companies using rice.

Related tags: Resistant starch, Rice, Starch

A novel cooking and cooling process for rice could help slash the number of calories absorbed by the body by more than half by increasing levels of resistant starch, say researchers.

The relatively simple cooking method could help families and food manufacturers increase resistant starch (RS) in staple food products – meaning that less of the rice is digested and fewer calories are absorbed.

Led by Sudhair A. James from the College of Chemical Sciences in Colombo, Sri Lanka, the team behind the discovery noted that in addition to consuming more fats and sugars, many people may choose to fill up on starchy carbohydrates like rice, which has about 240 calories per cup.

As a result the team experimented with 38 kinds of rice to develop a new way of cooking rice that increased resistant starch content.

"Because obesity is a growing health problem, especially in many developing countries, we wanted to find food-based solutions,"​ said James. "We discovered that increasing rice resistant starch (RS) concentrations was a novel way to approach the problem."

By using a specific heating and cooking regimen, the scientists increased the levels of RS by ‘at least’ ten-fold – meaning that there are less digestible calories in the rice. Indeed, the team concluded that "if the best rice variety is processed, it might reduce the calories by about 50-60%."

Results from the investigation will be presented at the 249th National Meeting & Exposition of the American Chemical Society (ACS).

Reduced resistant starch

The team experimented with 38 kinds of rice from Sri Lanka, developing a new way of cooking rice that increased the RS content.  The initial RS concentrations ranged from 0.30 to 4.65%, with traditional rice varieties found to contain significantly higher RS concentrations than old and improved varieties.

In this method, they added a teaspoon of coconut oil to boiling water before adding a half a cup of rice.

They simmered this for 40 minutes, although it could be boiled for 20-25 minutes instead, the researchers noted. The team then refrigerated the rice for 12 hours.

This novel method procedure increased the RS by 10 times for traditional, non-fortified rice, said the team.

“The increase in RS content could be attributed to the increase in RS3 and RS5 types, suggesting potential to increase these types of RS in rice,”​ wrote the authors.

Novel cooking method

James explained that the simple cooking method can make a big difference because 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, he commented.

"The cooling is essential because amylose, the soluble part of the starch, leaves the granules during gelatinization,"​ James said. "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."

Reheating the rice for consumption after this cooking method does not affect the RS levels, he confirmed.

James suggested that the next step will be to complete studies with human subjects to learn which varieties of rice might be best suited to the calorie-reduction process. The team also will assess whether other oils besides coconut have the effect.

Source: to be presented at the American Chemical Society
“Rice (Oryza sativa L.) resistant starch and novel processing methods to increase resistant starch concentration”
Authors: Sudhair A. James, et al

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4 comments

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Mrs.

Posted by Martha white,

So, is it clear that re-heating the cooked and cooled rice is OK? ( the benefits will not be destroyed)

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Prebiotic benefits

Posted by Howard Cash,

The process of cooking and subsequent cooling of starches as described induces retrogradation which produces prebiotic fiber. Like all prebiotics it will be digested in the colon by the resident bacteria and, depending on the make-up of your gut microbiome, may induce some gas and irritating substances in addition to SCFAs (short chain fatty acids) like propionate, acetate and butyrate which are good for you and are used as energy by the colonocytes and the rest of the body. So these prebiotics are used for energy but not through the conversion of starch to glucose like starch digested in the small intestine. People using any of the probiotic bacteria which are active in the colon usually get the benefits without the gas, acid or bloating otherwise sometimes seen with increased fiber intake. Incidentally many restaurants cook their rice in large batches, spread it on sheet pans and refrigerate until needed for reheating maybe unintentionally creating a healthier meal.

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We should avoid using the term resistant starch

Posted by S Dhital,

RS is a physiological concept, i.e. it is defined as the fraction of starch that enters the large intestine. It is not a precise physical entity. Enzyme susceptibilities of starches are measurement- and method-dependent and are highly variable for different in vitro conditions and between individual human subjects. The likelihood that all non-modified starches can be completely digested by amylases given sufficient time, enzyme activity and optimal environmental conditions demonstrates that true physiologically resistant starch depends on both digestion rate and gastrointestinal passage rate, which cannot be estimated from in vitro digestion data. The current classification of starch as a combination of RDS, SDS, and RS from a single enzyme digestion experiment should be replaced with single kinetic parameter derived from kinetic analysis of digestion profiles.

http://www.tandfonline.com/doi/abs/10.1080/10408398.2014.922043#.VRJdPfmUf0c

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