...From the pages of Agricultural Research magazine
Going With the Grain
Rice starch and protein are
found in a wide range of
products, including frozen
foods, sauces, soups,
baked goods, baby food,
health bars, and
ARS scientist finds a more
natural way to separate rice's valuable starch and protein.
It's the creamy component in some ice creams and yogurts, a satisfying
alternative to fat in reduced-fat foods, and a thickener that adds a
smooth finish to soups and sauces. While many consumers aren't able
to detect it, rice starchwith its tiny granule size, neutral taste,
and soft mouthfeelcan be found in a wide range of foodstuffs.
This list also includes more unexpected consumables, like frozen foods,
meat products, andthanks to rice starch's hypoallergenic natureeven
pharmaceuticals and cosmetics.
But a cost-effective and environmentally friendly process for accessing
rice starchby breaking down milled rice into its starch and protein
fractionshas been elusive. For nearly 60 years, the processing
of this starch has hardly changed, relying always on the action of a
corrosive alkali, sodium hydroxide, to slowly dissolve rice protein
and release the starch.
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 food technologist Harmeet Guraya. Guraya, who works at
ARS's Southern Regional Research Center in New Orleans, Louisiana, 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.
The technologyperhaps in commercial use by next yearcould also increase the bottom line for U.S. rice farmers and millers, who have historically lost out on valuable rice derivatives because of a lack of cost-effective processing.
Whether it's long-grain, sticky, or a specialty type like aromatic,
rice is fast becoming a popular grain. And its componentsstarch,
protein, and branare equally desirable.
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 riceenabling
these grains to be separate and fluffy when cooked.
Each possessing its own unique chemistry, these rice starches have
different applications in industry. "With cosmetics and tableting,
the kind of starch used is not necessarily important," explains
Guraya, "but with foods, starch type does matter."
For instance, starch from waxy rice exhibits high freeze-thaw stability.
"Because this starch holds water well, a food productsay
Buffalo wingswon't lose valuable moisture or juices when it's
frozen and then thawed," says Guraya.
Rice protein is 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.
And the bran, which sits just under rice's outer hull, is getting increasing
acclaim for biologically active compounds that may act as powerful,
cell-protecting antioxidants. High in dietary fiber, too, bran can impart
a hearty flavor to breads and other baked goods.
Despite its potential, says Guraya, "most of the rice bran produced
in the United States is a byproduct of milling and is used for animal
feed or simply discarded."
While it seems a treasure trove of nutritional, food, and sensory possibilities, a grain of rice doesn't easily give away its valued parts. Processes that separate and extract bound-up rice fractions can alter the nutritional qualities of starch and protein and are often not cost effective.
Without a Grain of Salt
Milled rice contains agglomerates, or clumps, of starch and protein.
Typically, rice is steeped in sodium hydroxide for several hours to
dissolve the protein and let the starch molecules break free. But that
degrades the protein, leaving it bitter-tasting and unfit for human
consumption. Salts and other potentially harmful waste products are
Guraya's approach instead relies on very high pressure, supplied by
a special homogenizer known as a microfluidizer, 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.
And Guraya's technology preserves valuable rice protein. "The
protein from our processing hashigher integrity and functionality,"
he says. "It hasn't been degraded with pH adjustments and washings."
Guraya, who's been developing his rice starch separation process for
about 4 years, established a cooperative research and development agreement
with Sage V Foods, a rice-based products company, in 1999. Based in
Los Angeles, with facilities in Freeport, Texas, Sage V Foods produces
rice-based ingredients that are sold to major U.S. 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 says. "We have to show that
it can be done in a large-scale, continuous process."
A complete production line was set up in March 2004, and thousands
of pounds of rice starch were generated. The samples, from different
kinds of rice, are currently being analyzed by Sage V Foods.
"So far, the results from our tests are very encouraging,"
says Pete Vegas, president of Sage V Foods. "While there's still
some uncertainty about the costs related to the process, we're very
Guraya continues to offer technical advice to Sage V Foods, but he's
moved on to another project that's an ideal complement to his rice starch
technology. "It's a method for extracting protein from rice bran,"
he says, "and could ultimately make use of bran's other fractionsoil
and starchwhich are currently being underused."By Erin
K. Peabody, Agricultural Research Service Information Staff.
This research is part of Quality and Utilization of Agricultural
Products, an ARS National Program (#306) described on the World Wide
Web at www.nps.ars.usda.gov.
Harmeet Guraya is
with the USDA-ARS Food
Processing and Sensory Quality Research Laboratory, 1100 Robert
E. Lee Blvd., New Orleans, LA 70124-4305; phone (504) 286-4258, fax
"Going With the Grain" was published in the February 2005 issue of Agricultural Research magazine.