# Glycaemic Index of Bakery Products and Possibilities of Its Optimization
###### Abstract
The basic and most abundant component of cereals is starch. Starch occurs in its native state in the form of starch grains composed of ordered amylose and amylopectin molecules. Although the starch content itself is essential for the glycaemic index value (Table 2), the condition of the starch grains and their changes during food processing and production of the final products are equally essential [1; 18]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Cereal** & **Water** & **Proteins** & **Lipids** & **Starch** & **Minerals** \\ \hline Wheat & 13.2 & 11.7 & 2.2 & 59.2 & 1.5 \\ Rye & 13.7 & 11.6 & 1.7 & 52.4 & 1.9 \\ Barley & 11.7 & 10.6 & 2.1 & 52.2 & 2.3 \\ Oat & 13.0 & 12.6 & 5.7 & 40.1 & 2.9 \\ Rice & 13.1 & 7.4 & 2.4 & 70.4 & 1.2 \\ Maize & 12.5 & 9.2 & 3.8 & 62.6 & 1.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Basic chemical composition of cereals (g/100 g: average values for whole grain) [17]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Crops-Whole Grains** & **Starch Content (\% in d.m.)** & **Glycaemic Index** \\ \hline Wheat & 65–75 & 50–60 \\ Rye & 65–75 & 50–60 \\ Barley & 65–75 & 50–60 \\ Oat & 55–65 & 40–50 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Starch content and glycaemic index of cereals, legumes, pseudocoreals and selected cereal products based on data from National Institute of Health, Czech Republic ([[https://szu.cz/wp-content/uploads/2023/12/Glykemicky-index-2003.pdf](https://szu.cz/wp-content/uploads/2023/12/Glykemicky-index-2003.pdf)]([https://szu.cz/wp-content/uploads/2023/12/Glykemicky-index-2003.pdf](https://szu.cz/wp-content/uploads/2023/12/Glykemicky-index-2003.pdf))) (accessed on 23 April 2024) [18; 19; 20; 21; 22]. The processing of cereals for human consumption can be divided into two successive stages. Primary processing, the raw material of which is the sorted and decontaminated grain of the given cereal, generally consists of surface treatment of the grain, hydrothermal treatment and possible disintegration of the grain into flakes, groats, shreds and, in particular, flours and meal. After surface treatment and hydrothermal treatment, the grain may remain whole, usually for direct culinary processing or for use in multigrain breads and pastries and other cereal products. Soaking and germination (or malting) of the grain is also one of the primary processing methods. The most common primary processing method in Europe for wheat (and in Central Europe also for rye) is milling into bakery flours. Oats are mostly processed into oat flakes. Most barley is malted for the production of beer and other alcoholic beverages, and malt is used partly in the bakery industry as a recipe ingredient [23]. Secondary processing is the second stage in which the primary product (flour, meal, whole grain) is processed into final, usually directly consumable products--bread, pastries, other cereal products or pasta, which are cooked in water or steam before consumption. An overview of the basic technological steps is given in Figure 1. The first step in secondary processing is always the preparation of the primary mass (dough) or suspension by mixing the primary cereal product with water or fat and mechanical processing (kneading, whisking, etc.) The secondary processing of cereals always involves some form of heat treatment (baking, frying, drying, cooking, extrusion), which for bread and pastry is preceded by one or more stages of fermentation. The basic fermentation process used in cereal technology for leavening bread and pastry is ethanol fermentation, which produces sufficient carbon dioxide in addition to ethanol. In Central Europe, both traditional rye and wheat sourdoughs undergo homo- and heterofermentative lactic acid fermentation [23]. In all the steps summarized above, during both stages of cereal processing, gradual changes occur at all levels of starch structure.