# Glycaemic Index of Bakery Products and Possibilities of Its Optimization
### Increasing the Fibre Content  
Increasing the fibre content primarily results in a relative reduction in the digestible (RDS and SDS) starch content of the final product. However, this alone does not exhaust the full potential effect of fibre addition. While the effect of some fibre components on slowing down the resorption of starch is low and their addition does indeed act almost exclusively as a partial substitution of starch in the total dry weight of a given product, intermediate or raw material (composite flour), other components do indeed act to slow down its resorption and thus slow down the increase in postprandial glycaemia. In particular, it is the fibre components that cause an increase in the viscosity of the intestinal contents [63; 64]. Fibre is one of the factors that can influence the glycaemic index of foods, along with fat and protein. It has the ability to reduce the rate of glucose absorption after eating high glycemic index foods containing carbohydrates: the blood glucose response curve decreases and the need for insulin decreases. Soluble and insoluble fibre may contribute to glycaemic control by reducing gastric emptying, modifying gastrointestinal hormone release, inhibiting amylase activity, interacting with the mucosa to form a barrier layer, and delaying starch hydrolysis, thereby reducing the rate of diffusion of amyloid products into the small intestine [65]. In this case we can speak of an effective substitution of digestible starch. Among the components of cereal fibre, the main ones are arabinoxins and \(\beta\)-glucans, whereas with fibre from other plant sources, apart from \(\beta\)-glucans, the main ones are pectin, guar or gum Arabic or tragacanth, or natural polysaccharides used as hydrocolloid additives, originating from seaweed or of microbial origin (agar, alginate, carrageenan, xanthan); \(\beta\)-glucans originating from certain higher fungi (Pleurotus, Ganoderma species) may also be important in this respect. However, the addition of flours from other sources, in particular certain pseudocereals and legumes, which contain high proportions of resistant starch in their native state, is also becoming increasingly important. Of the pseudocereals, buckwheat [63; 66] is particularly important in this respect. However, hydrocolloid polysaccharides, also used as food additives, which are the result of the physicochemical modification of cellulose or starch, also have a similar effect. This category also includes resistant starch type 4 (RS4) or starch type RS3 obtained by physical modification (HTM) from starch from another source and used as an additive. A great deal of research has been devoted to the physical modification of starch in order to reduce its digestibility or to the production of RS3 starch from various sources (rice, cassava, maize, potato). In particular, heat treatment, often for several hours at temperatures mainly between 80 and 140 \({}^{\circ}\)C with controlled water content (usually less than 40% \(w/w\)), is one of the many possible types of HTS, and the extrusion of starch materials is another, so the source of resistant RS3 starch may thus include, for example, flours produced by milling extruded cereals and semi-finished products [56; 67]. Whichever route is used to increase the fibre content or reduce the GI by the effective substitution of digestible (RDS and SDS) starch in the production of bread or other bakery products, the quality of the resulting product, particularly in terms of its sensory properties,must always be kept in mind. This is where the biggest problem lies in the approaches to reduce the GI of bakery products [68; 69; 70]. The point is that most of the substances, fibre components, through which effective substitution of digestible starch can be achieved, significantly alter the consistency of doughs and consequently the structure and properties of bread and pastry crumb.