Scientists in the US are attempting to find a cost-effective and environmentally friendly means of separating rice's starch and protein, increasingly important ingredients in health-conscious food manufacturing.
Indeed rice starch - with its tiny granule size, neutral taste, and soft mouthfeel - can now be found in a wide range of foodstuffs, for example ice cream and yoghurt. It is also used as an alternative to fat in reduced-fat foods and a thickener in soups and sauces.
The global trend towards healthier food manufacturing follows prolific litigation brought by consumers in the United States. As a result, many global food manufacturers have already voluntarily agreed to reduce the level of ingredients such as saturated fats across their product lines.
Global food giant Kraft, for instance, has already introduced a universal Sensible Solution healthy labelling policy, which alerts consumers about some of its healthier, more nutritious products and has also pledged to review and remove products that fail to meet dietary standards.
This trend has heightened the marketability of rice starch. However a cost-effective and environmentally friendly process for accessing rice starch, by breaking down milled rice into its starch and protein fractions, has been elusive. The processes used to separate and extract bound-up rice fractions can alter the nutritional qualities of starch and protein, and for nearly 60 years, the processing of this starch has relied on the action of a corrosive alkali, sodium hydroxide, to slowly dissolve rice protein and release the starch.
But this procedure, and the copious amounts of salt waste it generates, could soon be replaced with a more benign and efficient separation method developed by USDA's Agricultural Research Service (ARS) food technologist Harmeet Guraya. He believes his approach could help rebuild the rice starch and protein production industries in the United States, which now imports about $40 million worth of rice starch each year.
Guraya's approach relies on very high pressure, supplied by a special homogeniser known as a microfluidiser, to physically split apart the starch-protein agglomerates. A single pass through this piece of equipment yields many small, individual particles of starch and protein homogeneously dispersed in a watery matrix. The starch and protein components can then be separated by traditional density-based separation processes.
"The protein from our processing has higher integrity and functionality," he said. "It hasn't been degraded with pH adjustments and washings."
The technology, which could be in commercial use by next year, could therefore increase the bottom line for US rice farmers and millers, who have historically lost out on valuable rice derivatives because of a lack of cost-effective processing.
Long-, medium-, and short-grain rices contain varying ratios of the two starch components, amylose and amylopectin. Amylopectin is found in highest concentrations in short-grain, also called sticky or waxy rice. Amylose is highest in long-grain rice-enabling these grains to be separate and fluffy when cooked.
These rice starches have different applications in industry. For instance, starch from waxy rice exhibits high freeze-thaw stability.
"Because this starch holds water well, a food product - say Buffalo wings -won't lose valuable moisture or juices when it's frozen and then thawed," said Guraya.
Rice protein is also valued for its easy digestibility. Baby foods and formula and special dietary goods rely on a steady stream of this protein, since some children and adults are sensitive to the proteins in other grains.
Guraya, who's been developing his rice starch separation process for about four years, established a cooperative research and development agreement with Sage V Foods, a rice-based products company, in 1999. Sage V Foods produces rice-based ingredients that are sold to major food companies.
An important part of their collaboration has been trying out a scaled-up version of Guraya's technology. "Being able to produce rice starch in the lab is not enough," he said. "We have to show that it can be done in a large-scale, continuous process."