The clearest difference between coarse rye processing and rye flour processing lies in the swelling of the main raw material, rye. The coarser the lots intended for processing, the more important it is to ensure sufficient swelling. This is due to the slow absorption of water by the coarse ingredients and the resulting insufficient gelatinisation of the starch during the baking process. For this purpose, the coarse ingredients are soaked/swollen before the dough is actually prepared. This can take place in the form of soaked grain, hot soaked grain and/or boiled grain, but it is also partly ensured by the coarse grain sourdough. The following types of soaking/swelling have proved successful:
Cold soaked grain is mostly used for coarsely ground coarse grain and rye groats. The quantity of addition is 10 - 20 % (coarse rye proportion of the total grain products that are introduced via the soaked grain). Higher percentages mean that the pouring temperature for dough preparation is too high. For the cold soaked grain, coarse grain and water are mixed in a ratio of 1:1 or 1:2. In the warm summer months in particular, the cold soaked grain is subject to the risk of spontaneous fermentation, which causes an undesirable odour and taste. Spontaneous fermentation can be suppressed by adding dough acidifying agents. The amount of acid already introduced in the soaked grain must be taken into account when calculating the total amount of acid.
Warm soaked grain with pouring temperatures of 40 - 50° C and standing times of 4 - 5 hours is the most common type of pre-swelling. No gelatinisation takes place at these pouring temperatures. The coarse grain/water ratio is 1:1. There is no risk of spontaneous fermentation due to the short standing time. As the warm soaked grain is further processed at temperatures of 25 - 45° C, the temperature of the main dough can be easily adjusted via the pouring water temperature. The amount of warm soaked grain used is 50 - 60 %.
Hot soaked grain means the pre-swelling of the coarse components with hot water. The coarse rye is scalded with water at 60 - 80° C and mixed thoroughly. The temperature in the hot soaked grain is set to 60 - 70° C and the starch in the outer layers of the grain partially gelatinises. As the hot soaked grain cools, the remaining water is quickly absorbed by the grain. The standing times are 2 - 4 hours with a coarse grain/water ratio of 1:2. The gelatinised starch of hot soaked grain is susceptible to enzymatic attack and can be decomposed during the baking process. At higher dosage, this leads to insufficient slicing properties and crumb compaction at the bottom. The quantity of addition of hot soaked grain is therefore limited to a maximum of 20 % of the total amount of coarse grain.
In the production of coarse grain bread, boiled grain (boiled soaked grain) is primarily used for whole grains, and less frequently for rye groats. Here, the grains are boiled with water at a ratio of 1:3 or 1:2 for several minutes. This is done on a large scale with specially designed cooking systems. For cooking systems, the ratio increases to 1:4. In addition, it is often possible to work with high pressure in the system. The grain volume increases by a factor of 3 - 4. The large swollen grains are easily recognisable in the section through the crumb and are particularly attractive. In addition to rye grains, whole wheat, spelt or barley grains are also suitable for this process. The amount of boiled grain added should be a maximum of 10 - 15 %. Especially if the grain-to-water ratio is 1:4. Otherwise, the possible bulk quantity during dough preparation is reduced too much (see chapter on Dough technology).
