Rye kernel is a source of many nutritionally valuable food components. Among them, there are fructans that show prebiotic properties. However, those components are not included into analytical methods that determine the content of dietary fibre in cereals. In this research study characterized were the selected intermediate products obtained from the industrial milling of rye kernels as regards the content of fructans therein. The effects of technological processes: lactic acid fermentation, extrusion, and baking were analyzed on the amount of fructans in rye products. Furthermore, the content of fructans was determined in the samples of commercial rye crisp bread available in the market in Poland. It was found that the passage rye flours were characterized by a variable content of fructans. The flour fractions obtained from the final break and reducing passages contained substantially higher amounts of those components of dietary fibre than the flours obtained from the initial stages of rye milling process or from commercial flours. Of all the hydrothermal processes studied, only the extrusion process using a one-screw extruder caused the content of fructans to increase by ca. 8 %. The lactic acid fermentation process with the use of pure culture of Lactobacillus plantarum caused the content of fructans to essentially decrease by 10, 32, and 42 % in proportion to the time duration of the fermentation process (18, 24 and 30 h). It was also reported that the content of fructans decreased in the samples fermented with the use of commercial starter cultures. Changes in the amounts of those components were the highest in the products fermented using a baker’s yeast containing starter culture; the level of those changes was from 7 to 32 % depending on the fermentation stage. It was proved that the method of preparing dough and the micro-organism applied impacted the content of fructans in the final product. It is possible to reduce disadvantageous changes in the amounts of those components through the proper selection of the process parameters and the use of proper leaven types.
fructans, rye, extrusion, lactic acid fermentation