Rye Flour

Rye milling is a shorter, simpler process than wheat milling — fewer passes, less purification, and no expectation of a clean white stream. What comes off is a series of flours differing in how much bran material they carry, and the miller blends and specifies them by extraction. At the coarse end, rye meal and pumpernickel-type meals are essentially the whole grain ground, retaining everything.

Sourdough is not tradition for its own sake in rye baking; it is a technical requirement. Rye starch gelatinises at a relatively low temperature, and rye is rich in amylase, so in a neutral dough the enzymes are still active while the starch is already gelatinising during baking — degrading it and giving a sticky, collapsed crumb. Acidifying the dough lowers the pH enough to suppress the enzyme and to strengthen the pentosan structure, which is what lets a rye loaf hold together at all.

This connects the flour directly back to the grain. Because enzyme activity is the problem, the falling number of the rye a mill buys determines what its flour can do, and the miller has no way to add back what a sprouted lot has already lost. Rye flour quality is set in the field and confirmed at the intake bin.

Rye flours are specified by extraction and ash, by falling number or an equivalent enzyme measure, by particle size, colour, and moisture. Higher-extraction flours carry more bran, more colour, more flavour — and more of whatever was on the outside of the grain, which is where the safety question enters. Ergot alkaloids, if sclerotia were not cleaned out of the grain, report to the flour, and the outer fractions carry proportionally more. Regulatory limits apply to the flour in its own right, and cleaning the grain is the control point.

In handling, rye flour behaves as a cereal flour: hygroscopic, prone to compaction, and a substrate for storage insects. Wholemeal and high-extraction rye flours contain the germ and its oil, so they keep less well than light flours and are rotated more tightly — a familiar trade-off wherever a flour retains the whole grain.