# Glycaemic Index of Bakery Products and Possibilities of Its Optimization
###### Abstract
Damage and disintegration of native starch grains at the quaternary structure level, changes in the tertiary structure of amylose and amylopectin molecules, and the disintegration of secondary and primary structure due to hydrolysis. Starch grains swell to the extent that the proportion of water in the primary mass or suspension is high, and are subject to partial hydrolysis, mainly enzymatic via amylase, but also to acid hydrolysis during any lactic acid fermentation. The heat supplied results in the formation of a starch slurry and gel and subsequent retrogradation. The first significant damage to starch grains in the processing of cereals in mills occurs mechanically \begin{table}
\begin{tabular}{c c c} \hline \hline
**Crops-Whole Grains** & **Starch Content (\% in d.m.)** & **Glycaemic Index** \\ \hline Rice & 70–80 & 55–60 \\ Maize & 60–70 & 50–60 \\ Sorghum & 65–75 & 55–65 \\ Millet & 70–80 & 55–65 \\ Legumes & 45–55 & 30–45 \\ Buckwheat & 45–55 & 35–45 \\ Amaranth & 55–60 & 30–40 \\ \hline \hline \multicolumn{3}{c}{Bread and bakery products} \\ White wheat bread & 70–75 & 70 \\ Wheat-rye bread (Central Europe type) & 65–70 & 65–70 \\ Dark rye bread & 55–65 & 45–55 \\ Whole grain bread & 55–65 & 45–55 \\ Bread type pumpernickel & 55–65 & 45–55 \\ Buckwheat bread & 50–60 & 40–50 \\ Wheat common bakery products & 70–75 & 70 \\ Croissants & 50–60 * & 60–70 * \\ Donuts & 45–60 * & 70–75 * \\ Muffins and other sweet pastry & 45–60 * & 60–75 * \\ \hline \hline \end{tabular}  
* Starch content and glycaemic index decrease with higher fat content.  
\end{table} 
Table 2: _Cont._and thermally during the actual milling [1]. All of these physico-chemical and biochemical processes acting on starch during cereal processing have an impact on the final GI of the product [24; 25]. In addition to starch, other important components of grain--proteins and fibre components (non-starch polysaccharides, oligosaccharides and lignin)--are also subject to changes during processing. Fibre is concentrated almost exclusively in the grain outer layers and seed coat layers [26; 27; 28; 29; 30]. However, these are removed during the standard processing of wheat (and rye) into common baking and pastry flours before milling. Only wholeneal flours contain all the fibre components. The removal of a significant part or almost all of the grain envelope leads to an increase in the relative starch content of flours and other products, which in itself has a major effect on the glycaemic index [31]. Although the fibre components that remain in the processed grain do not undergo such dramatic changes as the starch during primary and secondary processing, they also swell with water, change their tertiary and, in particular, quaternary structure (the native fibrous structures of the chaff are loosened) and undergo partial enzymatic hydrolysis due to enzymes added in the formulation or produced by certain lactic acid bacteria. These changes, which may potentiate some of the biological functions of the fibre components, may also have an indirect effect on the GI values of the final product [32].