Dr. Zhimin Xu is taking what was a relatively useless product and making it a healthful preservative.
Defatted soy flour is a byproduct of producing vegetable oil from soybeans, and until now, it was used only as animal feed – and only in some cases.
"It’s a very low-value waste product," Xu, a food scientist with the LSU AgCenter, said.
He is working with other LSU AgCenter scientists to extract isoflavones from the soy flour.
With Xu’s research, isoflavones can perform double duty. They have many health benefits, and he has proven they work well as a food preservative.
"People are very concerned about their health, and the isoflavones, which act as an antioxidant, can protect against heart disease and lower cholesterol," he said.
Xu has discovered a functional way to get them into the average person’s diet. Artificial preservatives are found in foods such as ground meat and sausage to keep those foods fresher longer. Xu says the isoflavones can act as a natural and healthful food preservative.
"The Food and Drug Administration has questioned the safety of artificial food additives, including food preservatives, for long-term consumption." Xu explained. "Isoflavones can replace the artificial preservatives to keep food fresh."
Before he could test the viability of isoflavones as a food preservative, Xu had to find an efficient way to extract them from soy flour. As part of the project funded in part by the Louisiana Soybean and Grain Research and Promotion Board, he worked with Dr. Cristina Sabliov and a team of LSU AgCenter researchers that includes Dr. Dorin Bolder, Dr. Marybeth Lima, Sundar Balasubramanian, Akanksha Kanitkar and Beatrice Terigar.
Sabliov, a researcher in the LSU AgCenter’s Department of Biological and Agricultural Engineering, has been testing continuous microwave extraction systems as a means of extracting isoflavones from soybeans. Sabliov and colleagues have been working on such a system for several years and recently received exciting results from two different systems they were testing.
Using two different continuous microwave extraction methods, she compared these novel methods with conventional extraction methods – which, in the case of her research, included a water bath to heat the flour-solvent mixture.
The first system used three household microwave units that the Sabliov team specially geared to do batch processing. The units were placed on top of each other, and tubing was inserted through the chambers of the three units to serve as the conduit for the flour-solvent (or extraction) mixture.
"We wanted to see what happens to the extraction yields as the solvent-flour mixture is heated more with the addition of each microwave," Sabliov said.
Sabliov looked at four different isoflavones that could be extracted from the soy flour and heated them for different lengths of time.
"In all cases we extracted more with microwave extraction in less time than using solvent extraction," Sabliov explained.
The second system was set up through a batch extractor, which has "better electric field uniformity than a regular microwave system," Sabliov said, adding that this system allows for more uniform heating and extraction.
With this system, she also found a similar trend to that of the first one – higher extraction in less time with the microwave system.
"It’s fast. It’s easy to use," Sabliov said. "You can control the temperature, and you don’t have to sit there for hours. It’s minutes. Conventional extraction takes hours, and you have to be there for the duration."
Another interesting find in both systems was that after a certain amount of time – 8 minutes in the first system and 4 minutes in the second – extraction rates leveled off.
"So there was no need to heat the mixture for any longer. The maximum extraction was achieved in minutes," she said.
Sabliov said these results answered an important question the researchers had when they started the project.
"We wanted to know if we really would be competitive with conventional systems," she said. "Now we are confident that we are, so now we can move on."
Sabliov’s next step is to work on a larger scale. She has the equipment to begin the process and will start later this year.
Meanwhile, Xu has been testing the antioxidant activity of the extracted isoflavones. He used fish oil as a model to study the stabilizing properties of the isoflavones.
According to Xu, the lipids (fats) in meat oxidize or break down, and that causes the meat to become rancid. He tested his theory that isoflavones could work as a preservative on fish oil, which contains the most susceptible lipids.
Xu was successful in his efforts and also proved that "the defatted soy flour extract could significantly reduce the degradation of health beneficial omega-3 fatty acids in foods fortified with fish oil."
Next, Xu will work on inserting the isoflavones into ground meats such as hamburger patties and sausage.
"If it can stabilize fish oil, then of course it can stabilize meat," Xu said.
Extracting the isoflavones at a high purity is important to Xu’s work. During the extraction process, soy proteins and carbohydrates could be left and produce "soybeany" off-flavors in the meat.
With purer, highly active isoflavones only a small amount (as little as 1 percent) can be added to achieve the desired results – fresher, healthier food.
"It will not affect the taste or texture of the food," Xu said.
But the project could positively affect the value of soybeans post-harvest.–Tobie Blanchard
(This article was published in the 2008 edition of the Louisiana Soybean & Grain Research & Promotion Board Report.)