AOAC ERP Gluten Assays - Dec 2018

Annex B

4.1.7.4

Recovery using naturally incurred and processed oat samples

For characterization of recovery from naturally incurred and processed samples, oat cookies and oat-based porridge were produced using oat flour that was contaminated at gluten levels of 2000 mg/kg. The contaminating wheat, rye, and barley were identical to the ones that were used to produce the AOAC Reference Material as described in chapter 3.4. The same estimation for gluten content of each contaminating grain was used that was also used for the preparation of the AOAC Reference Material.

The oat cookies were produced as follows:

95 g grounded gluten-free oat flakes were mixed with 5 g oat flour that was contaminated at a level of 2000 mg/kg gluten from wheat or rye or barley. For each contaminating grain, 60 g sugar, 10 g rice flour and 1 g baking soda were added to the flour mixture and mixed well. Afterwards 60 g melted butter was added and mix well again. Finally, 30 g liquid egg was added and mixed. The total mass of the dough is 261 g so the gluten concentration is 38.3 mg/kg of cookie dough. By using the gluten-free oat flour (see chapter 3.4), gluten-free cookie dough was produced. Since this material was used later on to deplete the high concentrated cookie to approx. 10 mg/kg gluten, this dough was prepared at a fivefold amount. Cookies were formed with two table spoons and mounted on a baking tray that was covered with unused baking paper before. Cookies were baked at 175°C/347°F (upper/lower heat) for 21 minutes. After cooling down to room temperature the weight of all cookie samples was determined. The weight loss was due to evaporation of water as well as probably predominantly fat which deliquesced into the baking paper. Assuming that no gluten proteins deliquesced with the fat and all gluten proteins remained in the cookies, the gluten concentration was calculated to 46 mg/kg. To prepare cookies with a concentration of 11.5 mg/kg gluten, 50 g of the homogenized cookies with a concentration of 46 mg/kg were mixed with 150 g of blank cookies. Table 13 shows the results of the analysis of all gluten-containing cookies as well as for the blank cookies. One replicate for the rye containing cookie with a concentration of 11.5 mg/kg gluten was not included in the calculations since it is obviously an outlier. Table 14 summarizes all values from table 13. It seems that wheat gluten is more susceptible to the heat treatment than the other two gluten containing grains, rye and barley. Nevertheless, all recoveries clearly are within the minimum performance criteria laid down in AOAC SMPR ® 2017.021.

Page 25 of 33

RIDASCREEN ® Total Gluten In-house validation report 2018-10-21