Speaking at the World Grains Summit in San Francisco last month, CSIRO's David Topping emphasized the importance for human health of starches that are not digested easily in the small intestine.
According to Topping, there is an increasing focus on the digestive capacity of the large bowel, with emerging evidence that this is an important factor for human health.
Most starches are digested and absorbed into the body through the small intestine, but some resist digestion and pass through to the large intestine where they act like dietary fiber and improve digestive health. This type of starch is called resistant starch (RS).
And tapping into opportunities gleaned from the growing trend for health and wellness foods, resistant starches fit squarely into the low-glycemic food trends, as well as health product positions such as prebiotic fiber benefits and a healthy digestive system.
Resistant starch occurs naturally in some foods such as unripe bananas and cooked and cooled potatoes.
"Slowing amylolysis gives a lower glycemic index, while limiting total small intestine starch digestion allows a fraction to escape into the large bowel. This undigested starch (RS) is metabolized to short chain fatty acids (SCFA) by the colonic bacteria. SCFA promote bowel function and have the potential to lower risk of large bowel disease," said Topping.
"Most current starchy foods have high GI and a high throughput screen has shown that many also have low RS."
CSIRO (Commonwealth Scientific and Industrial Research Organisation) is developing a range of high RS/low GI cereal cultivars for incorporation into popular foods, he said.
One of these- BARLEYmax- is a high RS, low GI, high beta-glucan barley that claims to have good processing characteristics.
The agency is also currently developing new wheat cultivars using advanced breeding technologies to modify starch synthesis to lower GI and raise RS.
"Modifying the food supply to give greater choice at the point of sale is an effective means of risk reduction for important diet-related diseases such as constipation, diabetes, colo-rectal cancer and coronary heart disease," said Topping.
"High fiber foods promote laxation and US fiber intakes are substantially below those needed for regularity. Whereas the average fiber intake in Australia is 27g per person - compared to the recommended 30g- in the US it is only 15g per person."
Common sources of fiber include cereals, fruits and vegetables. However, fiber intake may also be improved by increasing the fiber content of foods, although this has tended to present food and beverage manufacturers with two major obstacles. These are a low digestive tolerance and the challenges associated with processing foods fortified with fiber, which can affect the solubility, viscosity, stability and taste of foods.