November 01, 1998
by Teresa Acklin
‘Micronutrients' in grain oils suggest future in functional foods.
By Laurie Gorton
Oats, rice and amaranth aren't considered oilseeds, but the “healthy fats” extracted from them could open new markets for cereal grains in the emerging functional foods field, according to scientists reporting new work with these grains.
A symposium at the 1998 annual meeting of the American Association of Cereal Chemists in Minneapolis, Minnesota, U.S., examined these “healthy oils for the new millennium.” Cereal grains were heralded as new sources for economically valuable phytochemicals. Such “micronutrients” include the antioxidant tocotrienol found in oat and rice bran oil; amaranth's squalene, a high-value lipid that resists oxidation at high temperatures, used in cosmetics and thought to inhibit cholesterol-forming compounds; and a variety of other vitamins and vitamin precursors, plus tocopherols and oryzanol.
These materials have high potential, according to symposium speakers. For example, commercially available squalene, extracted from whale and shark oils, costs as much as U.S.$35 to $40 per kilogram. Purified tocopherols and tocotrienols carry price tags of up to U.S.$400 per kg.
“Oat oil is a good source of antioxidant activity,” said David M. Peterson, a scientist at the University of Wisconsin, Department of Agronomy, who also works with the Cereal Crops Research Unit of the U.S. Department of Agriculture, Agricultural Research Service, at Madison. “In oats, the concentrations of tocotrienol, an antioxidant and cholesterol-lowering compound, and oil are highly correlated.”
One drawback, however, is “the high lipase activity in oats, which can cause high acid values in the oil if not inactivated,” he said.
Dr. Peterson noted that oats commonly contain about 6% oil, dry weight, but oat varieties with as much as 18% oil have been bred by scientists. He reported a few early commercial uses for oat oil. These include ConAgra's two-year-old project supplying oat oil to another processor that extracts the oil's phytochemical contents. In Europe, a Swedish yogurt processor is using oat oil components to induce satiety reactions. And Ceapro, a Canadian company, has been working with fractionation of oat oils.
“I expect that commercial interest in oat oil will be for component extraction, rather than oat oil as a primary product,” Dr. Peterson said.
Because amaranth is a drought-tolerant crop, cereal scientists at North Dakota State University have been working with starch and oil aspects of this ancient cereal grain.
“Amaranth seed oil has the highest known concentration of squalene of any plant oil,” said D.P. Wiesenborn of N.D.S.U.'s Agricultural and Biosystems Engineering Department in Fargo. This substance has been shown to reduce levels of serum cholesterol in animals.
The high price of amaranth (30 cents per lb) and its relative scarcity (only 6,000 acres are in current production in the United States) inhibit commercial use. Dr. Wiesenborn worked with oil derived as a byproduct of the extraction of amaranth starch. His techniques were similar to those used to extract rice bran oil: The amaranth was milled to remove its starch, then put through an extruder for concentration and extracted with a solvent.
“Hexane-extracted squalene is not of interest to the health food industry,” he said. So he worked with short-path distillation to concentrate components such as squalene. “Distillates containing up to 80% squalene were obtained, and higher concentrations should be attainable,” Dr. Wiesenborn said.
This is an expensive process, he said, even under non-commercial lab conditions. He added that more work was needed to industrialize the extraction process. “This could be a viable crop if the cost of processing could be reduced,” Dr. Wiesenborn said.
Extraction of rice bran oil, on the other hand, in a cost-effective manner has been achieved. And according to Niazahmed P. Shaikh of InCon Technologies, Inc., Batavia, Ill., new processing technologies now emerging could substantially increase use of this material as a source for valuable micronutrients.
“Rice bran oil is the next big source of tocopherols and micronutrients,” said Mr. Shaikh, “since soy sources are today all but completely consumed by producers of vitamin E and similar compounds.
“Analytical tests have shown rice bran oil to be an excellent source of vitamins, tocopherols, tocotrienols, squalene, and oryzanol, all of which have been shown to dramatically reduce serum cholesterol.”
Commercial extraction technology short path distillation, also called molecular distillation is relatively expensive and limited in capacity. Mr. Shaikh predicted, however, that the cost of this method would decrease in coming years and would eventually replace other distillation and deodorization methods.
“This technology allows you to control how much of the micronutrients are in distillate and how much are in the oil,” Mr. Shaikh said. “It's all a function of the temperature and pressure at which you operate the molecular still.”
Laurie Gorton is executive editor of Baking & Snack, a sister publication to World Grain.