Oat vary among oat varieties. Also, oats products are frequently cross-contaminated with other gluten-containing cereals during grain harvesting, transport, storage or processing. Pure oats contain less than 20 parts per million of gluten from wheat, barley, rye, or any of their hybrids. Use of pure oats in a gluten-free diet offers improved nutritional value from the rich content of oat protein, vitamins, minerals, fiber, and lipids, but remains controversial because a small proportion of people with celiac disease react to pure oats. Some cultivars of pure oat could be a safe part of a gluten-free diet, requiring knowledge of the oat
Rye bread "Lactobacillus" "sourdough" cultures lowers bread pH, facilitating growth of an acid-tolerant yeast strain, and helping gelatinize starches in the dough matrix. The byproduct of this approach is lighter breads. In areas where high-gluten hard wheat is readily available the need for a complex polyculture of bacteria and yeast can often be reduced or removed by adding a large proportion of hard wheat flour to the rye flour. Its added gluten compensates for amylase activity on the starch in the dough, allowing the bread to retain its structure as it bakes. The "deli rye" tradition in the United States is based