Hi Frauke. We don't have a way of quantifying the measurement of gluten in a cup of sourdough starter. What we can say is that it would turn this gluten-free recipe into a non-gluten-free recipe, so that if someone needed to be eating gluten-free, it would no longer be suited for their diet. Gluten-free bread needs to get to 210°F. The ratio of 1 T flax to 3 T water is the same in our egg replacer blog. This recipe is written for best results. 

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