Rye baking flour is a product of milling rye grain, an essential ingredient for traditional rye and rye-wheat bread. Russia is the world's largest producer of rye (more than 2 million tons/year). Flour types: Peeled flour (ash content ≤1.45%) is the main industrial grade for Borodinsky, Darnitsky, Riga, Minsk bread; grayish-white with a creamy tint. Sifted flour (ash content ≤0.75%) is finely milled, white, for light rye bread, flatbreads, gingerbread, bagels. Wholemeal flour (ash content ≤2.0%) is coarsely milled from whole grain with a maximum of fiber. Rye flour doesn't develop an elastic gluten (pentosans and water-soluble proteins form a viscous structure), so the dough is made on sourdoughs — lactic acid fermentation acidifies the environment, stabilizes starch, and gives the bread its characteristic sour taste and aroma. GOST 7045-2017. Moisture content ≤15%. Falling number ≥150 seconds for peeled flour, ≥160 seconds for sifted flour. Packaging: bags 25–50 kg, packets 1–2 kg. Sourdough for rye bread is a culture of lactic acid bacteria and yeast, which is maintained continuously (updated every 4–8 hours). The acidity of the dough (7–12° on the Neiman scale) stabilizes the starch and prevents the crumbling of the crumb. Rye bread stays fresh longer (3–5 days vs 1–2 days for wheat bread) due to increased acidity and pentosan content.