Working Group Meeting Book-Gluten

For the Gluten in Oats Working Group Paul Wehling, General Mills

In the process of developing SMPR 2017.021, the Gluten in Oats Working group agreed on the following definitions for the estimation of gluten in spiking grains to be used for making reference materials for accuracy experiments. Wheat: Gluten = Dumas N2 * 5.68 * 0.80 Barley and Rye Gluten = Dumas N2 * 5.68 * 0.60 We thought the simplicity of this was a positive attribute. During the process, I was asked to justify these 80/60% values with data. Subsequently, we at General Mills developed a wet-chemical method (aka the “Osborne-Dumas” method) to see if the solubility definition in the Codex definition of gluten was appropriate to use in estimating the level of spiked gluten. Accordingly, we ran all the cultivars and mixed spiking blends by this wet chemical method and used these values for making spiked validation samples at 10, and 20 mg/kg levels. At the last meeting of the Stakeholder Panel in Toronto, there was some controversy over this, as some thought the values obtained by the wet-chemical method were too high for barley. In order to move forward, the working group was asked to review the data and the two methods to determine which method should be used, and potentially review the SMPR for possible changes. Subsequent to the Toronto meeting, I have received data from Dr. Katharina Scherf on a 3 rd method – the RP-HPLC method of Wieser. So we can compare all 3 of these methods and decide which set of values should be used on the validation samples. Comparison of results: Blend Dumas Protein

Gluten by calc Dumas * Factor

Gluten by Wet Chem (Gen Mills)

Gluten by HPLC (K. Scherf)

Rye

7.82 g/100g

4.7 g/100g

4.04 g/100g

3.2 g/100g

Barley Wheat

10.17 12.46

6.1

7.93 9.21

5.7 8.2

10.0

Subsequently, since the Wet Chemical values were used to make the validation reference materials, if the WG feels another method is appropriate for use, the reference values of the materials will need to be changed. Blend

Reference Value Dumas * Factor

Reference Value Wet Chemical

Reference Value HPLC

W10 W20 R10 R20 B10 B20

10.8 mg/kg

10 mg/kg

8.9 mg/kg

21.6 11.6 23.2

20 10 20 10 20

17.8

7.9

15.8

7.7

7.2

15.4

14.4