Background Research, Oats and Wheat in RFC Food and Soil Survey

Guest post from Mason Tucker, Research Assistant in the Real Food Campaign Lab

This winter, the Real Food Campaign has been tasked with adding wheat and oat analysis to our methods to the upcoming year of sample intake. Thanks to guidance from the research and development team at General Mills, they informed us of the primary nutrients within grains that we would benefit from analyzing. These primary nutrients are the types of dietary fiber (total, soluble and insoluble), the ratio of free to bound polyphenols, protein content and tocopherols (vitamin E). Soluble dietary fiber can improve the management of your blood cholesterol and sugar levels, reducing the risk for diabetes while insoluble dietary fiber eases bowel movement; both are found in high quality within wheat and oat products. General phenolic compounds have a variety of health benefits, with the specific ratio of free to bound polyphenols (which are named after the formation these compounds take within biological systems) determining how much it can boost your immune system and how it tastes. Vitamin E is primarily known for its benefits toward skin and hair health, but has a notable effect on preventing a variety of cancers, including breast cancer. Because the Real Food Campaign is dedicated to methods with scalable and cost-effective resources, the most common analytical processes, such as HPLC (High-Performance Liquid Chromatography) are not feasible options to use. The following methods have been singled out for testing in our lab after determining how well they apply to our needs.

For tocopherols and bound/free polyphenol ratios, colorimetric methods can be used within spectral ranges that the bionutrient meter is capable of measuring. The improvements Kanno and Yamauchi suggest for the Emmerie-Engel method provides an accurate and commonly used method for colorimetric tocopherol (vitamin E) analysis as the iron reagent introduced in the paper, PDT, introduces greater sensitivity to the method. For protein measurements, we could pick between the more well known Bradford method and the older Lowry method. The Lowry method was selected over the Bradford method for its relative reagent simplicity and incubation requirements. Lowry has the added benefit of using FC reagent for its measurement of protein content, which we already use for our polyphenol measurements. Measuring dietary fibers is a more difficult process due to the most common methods involving the use of HPLC. Instead, Kays and Barton developed models for NIR analysis of IDF and SDF with high levels of accuracy. Given that most of our processes involve spectral analysis, we saw this method as a perfect fit! We plan to collaborate with another lab to verify our results with this NIR method to a HPLC method. While looking at methods for free and bound polyphenols, evidence was found for measuring bound polyphenols and protein content at the same time in a paper by Winters and Minchin. However, due to our current unfamiliarity with the Lowry method and the complex extraction to get the protein and bound polyphenol content properly separated together, we have opted not to analyze free and bound polyphenols at this time.

We expect to implement tocopherols in the 2020 season starting in May for a subset of our tested crops.

For a more complete link to articles reviewed and general discussion within the RFC Lab team, see here.

• Kanno, C. and Yamauchi, K. 1977. Agric. Biol. Chem., 41: 593
• Sandra E. Kays and, Franklin E. Barton, II. Near-Infrared Analysis of Soluble and Insoluble Dietary Fiber Fractions of Cereal Food Products, Journal of Agricultural and Food Chemistry 2002, 50 (10) , 3024-3029. DOI: 10.1021/jf0116552.
• A.L. Winters, F.R. Minchin, Modification of the Lowry assay to measure proteins and phenols in covalently bound complexes, Analytical Biochemistry, 346 (1) (2005), pp. 43-48