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Rapidly Measuring Beta-Glucan Content in Oats
USAgNet - 02/13/2018

When it comes to the cholesterol-lowering power of oats, it's the beta glucan that matters. That's why General Mills and Grain Millers joined forces to support research at South Dakota State University to determine beta glucan levels in oats.

A food product must contain at least 0.75 gram of beta-glucan soluble fiber from whole oats per serving to use the "heart healthy" label, according to the Food and Drug Administration. A one-cup serving of Cheerios contains 1 gram, as does a small bowl of hot oatmeal.

To assure that oat products meet this requirement, General Mills research agronomist Tom Rabaey said, "We need a consistent supply of oats that hits the beta-glucan target."

The industry has struggled for 20 years to get a quick, accurate test for measuring beta glucan, explained Bruce Roskens, director of crop sciences at Grain Millers Inc. Rabaey agreed, "Beta glucan is difficult to measure."

General Mills and Grain Millers funded professor Padu Krishnan's proposal, providing $140,000 to develop a near-infrared spectrometer (NIRS) calibration to quantify beta-glucan content in oat samples. Krishnan is a cereals chemist in the Department of Dairy and Food Science.

A chemical procedure known as the Megazyme Method is one of the traditional methods of determining beta-glucan content in oats. Enzymes that mimic the stomach are added to the dried, defatted sample and then the resulting sugars are measured based on color intensity using ultraviolet visible spectrophotometer.

"It costs more than $400 to analyze 50 samples in duplicate--that's very expensive when large numbers of samples are involved," Krishnan said.

NIRS uses reflected energy to quantify beta-glucan levels in a sample of ground, dehulled oats. The nutrients in grain absorb and reflect near-infrared energy. That creates a unique spectra, much like a fingerprint, explained Krishnan.

Known values of beta glucan from chemical analyses are correlated with the spectral files. Calibrations essentially train the software to quantify the reflective values for beta-glucan, according to Krishnan.

To do this, South Dakota State graduate student Devendra Paudel analyzed nearly 500 reference samples. A validation sample set made up of several hundred independent samples is used to determine how close the NIRS-predicted values are to the true values.

"To get a good correlation, we needed a wide range of oats grown in multiple locations, a very diverse population," Krishnan explained. "From high to low beta-glucan levels, the NIRS results must accurately compare with the wet chemistry." A wide range allows for a better linear relationship between NIRS values and true values.

In addition to oat samples from South Dakota breeding lines, the researchers analyzed varieties from Iowa, North Dakota, Minnesota, Illinois and Washington, thanks to Rabaey and Roskens, who are both South Dakota State alumni.

"That's part of the benefit of industry involvement--our supply chain is focused on North America and we get to see various practices," Rabaey said. "That variety in genetic background is what makes this calibration more valuable," added Roskens.

The university researchers also scanned samples from multiple years because the growing conditions also affect the characteristics of the grain. "We have a very robust calibration--and it takes less than a minute to scan a sample," said Krishnan. The next step will be to test the calibration on dehulled, unground oat groats.

The near-infrared calibration can now be used, not only by General Mills and Grain Millers, but also by oat breeders, including South Dakota State's Melanie Caffe-Treml, to screen germplasm early in the breeding process.

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