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Better ways to extract value from rice bran

BATON ROUGE, La. -- Extracting vitamin E from rice bran may become more cost effective and provide an expanded market for the rice byproduct if research in the LSU AgCenter’s Department of Biological and Agricultural Engineering proves out.

Rice bran is a good source of antioxidants, but getting it economically has proved to be a stumbling block, said Marybeth Lima, who’s developed a way to get rice bran with higher concentrations of the antioxidant.

Rice bran has been considered a low-value animal feed, but Lima has discovered antioxidants such as vitamin E can be found in different concentrations in different bran layers. She’s devised a method of stripping off the bran in three fractions and measuring the concentration of oil in each.

“Antioxidants aren’t uniform in each fraction,” she said. “So taking only a part of the bran provides buyers with a product with a higher concentration of vitamin E.”

Lima also has learned the concentration of vitamin E varies by layer — outer, middle or inner — depending on the rice variety.

Lima removes the bran in three stages. First, she runs the brown rice through a mill slowly to remove an outer layer. A second pass through the mill at a higher speed yields a second layer. And a final pass at an even higher speed removes the rest of the bran.

“I can adjust the milling settings so that for a batch of rice, I’ll remove a certain percentage of the bran layer,” Lima said. “I then adjust the milling settings to remove 50 percent of the layer and a third setting to remove 85 percent or more of the bran layer.”

She can determine which fraction contains the highest concentrations of the desired antioxidant, she said. This translates into machine settings that will yield a high-value fraction of rice bran from which antioxidants can be extracted.

“We can isolate the high-concentration fraction to sell to pharmaceutical companies,” she said. “The high-concentration fraction has about 25 percent more vitamin E than the entire bran layer — with 66 percent less material to process.”

Lima said her next step is to identify high-value fractions of hypoallergenic proteins, cholesterol-reducing products and rice bran sacchride — an anti-tumor compound — which also are contained in the bran layer.

While pharmaceutical companies can chemically synthesize vitamin E, the rice bran yields oil with the naturally occurring product.

Lima’s research team includes research associate Na Hua and graduate student Becky Schramm.

Cristina Sabliov in the Department of Biological and Agricultural Engineering and Dr. Zhimin Xu in the Department of Food Science are collaborating on the project.

To take the process one step further, Cristina Sabliov is investigating using microwave technology to remove the oil from the bran. Using a novel method of extracting rice oil faster, Sabliov adds a solvent to rice bran and microwaves it. “Over time at a given temperature, the rice bran oil is extracted into the solvent,” Sabliov said. “Then it can be separated.”

She said the process can extract 80 percent of the oil from the bran.

“Increasing the temperature yields more oil,” she said. “Now we’re looking at the threshold to extract the most vitamin E without any degradation.”

Rick Bogren writes for the LSU AgCenter. e-mail: [email protected]

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