# Preliminary Investigations on the Use of a New Milling Technology for Obtaining Wholemal Flows
## 1 Introduction
Typical Central European rye-wheat bread is as difficult to make from common wholemeal flour as wheat bread [15; 16]. It turns out that granulation of particles of outer layers (bran particles) has a fundamental influence on technological behavior and sensory properties. If a sufficiently fine granulation is achieved, which is close to the average granulation of common very fine flours (below 150-200 \(\upmu\)m), the sorption capacity (water binding) of such dough is significantly increased, but its mechanical and sensory properties change minimally. Such finely ground wholemeal flours can then replace conventional flours much better, and at the same time, thanks to the higher water binding, a significantly higher yield of dough and products is achieved. A major problem to keep in mind in the case of production of such flours is the risk of too high a degree of damage to the starch granules. In other words, it is necessary to use a technique that reliably disintegrates the outer layers into very fine fractions, but at the same time does not cause extensive mechanical and especially thermal damage to the starch granules [15]. Damage to starch during disintegration is of two types: (a) mechanical, due to pressure, shear forces, and crash; and (b) thermal, especially due to friction. The deformation to which the grain and its internal structure are subjected during disintegration differs fundamentally depending on the type of mill and grinding parameters used. Grinding in roller mills has a different impact, depending on the parameters (advance, down pressure, specific load) and surface treatment of the rollers (grooving) and their mutual position. In the case of impact mills, other mechanical forces act, and grinding can be both very gentle and very destructive to starch granules, depending on the design of the mill and the process parameters [1; 2]. When the grain is disintegrated in any way, partial deformation and damage to the starch granules always occurs. For bakery purposes, where fermentation is one of the key processes, a certain degree of starch damage is desirable because it becomes more amenable to the amylases present and a sufficient amount of substrate is created for yeast or lactic acid bacteria. In the case of flour for the production of wafers and biscuits, confectionery or pasta, damage to starch is not beneficial. However, with extensive damage, complicationsalso arise in ordinary bakery production (stickiness of the dough, poor structure of the bread crumbs, etc.). Starches of cereals and pseudocereals are easily broken down in the upper part of the human digestive tract. Most starches are completely resorbed in the small intestine, and only some starches may be partially resistant and are classified as indigestible polysaccharidesrides [17; 18]. Starch is gradually cleaved by amylases present in saliva and especially in pancreatic juice to oligosaccharides, which are further hydrolyzed to glucose monosaccharide. In the small intestine, glucose is actively absorbed into body fluids. Dietary starch intake results in a significant increase in blood glucose. Glycaemia is the concentration of glucose in the blood, the value of which in fasting should not exceed 5.5 mol/L (in venous blood) according to the current approach [19]. Starch resorption is rapid, and its rate increases with the degree of damage to the native starch structure. Starch damage can occur biochemically (by enzymatic hydrolysis), chemically (by acid hydrolysis), mechanically, and thermally. The higher the starch resorption rate, the higher the glycemic index (GI) of the food in question [20]. The wholemeal flours tested in this study were produced in a special mill. Physical and chemical analyses of the flours were conducted and the impact of grinding technology on microstructure and properties of the flours was evaluated.