The objective of the research study was to determine the effect of the sourdough added into the wheat flour dough and the baking method (traditional baking method and bake-off technology with the application of freezing and frozen storage processes) on the content of starch and total polyphenols in rolls, as well as on the value of glycemic index that was measured in vitro. Four types of wheat flour rolls were analyzed: 1) traditionally baked rolls (TRAD) as a control sample; 2) traditionally baked rolls with 3 % of sourdough (TRAD+SD) added; 3) rolls that were partially baked, frozen, and, next, finally baked (PBF); 4) rolls that were partially baked and frozen, and, next, finally baked with 3 % of sourdough added (PBF+SD). The application of bake-off technology contributed to a reduction in the content of dry matter (DM) (p < 0.05) in the rolls studied from ca. 74 to 65-66 %. The sourdough added and the application of freezing and frozen storage processes caused the content of slowly digestible starch (SDS) to significantly (p < 0.05) increase in the rolls baked using BOT (in PBF rolls by 12.6 % of dry matter; in PBF+SD rolls by 16.10 % of dry matter (DM)) compared to the traditionally baked rolls (in TRAD rolls: 7.4 % of DM; in TRAD+SD rolls: 7.5 % of DM). The content of rapidly digestible starch (RDS) was significantly lower (p < 0.05) in the rolls with the sourdough added: in PBF+SD rolls: 27.4 % of DM and in TRAD+SD rolls: 27.3 % of DM compared to the traditionally baked rolls: 30.8 % of DM, and to the PBF rolls: 29.1 % of DM. The applied freezing and frozen storage processes caused the content of total polyphenols in the rolls studied to significantly increase [mg of gallic acid in 100 g of DM]: in PBF + SD rolls: 105.2 and in PBF rolls: 105.7 vs. in TRAD rolls: 60.2 and in TRAD+SD rolls: 57.7. However, the sourdough added had no impact on the increase in the content of total polyphenols in the rolls studied (p < 0.05). The sourdough added and the freezing and frozen storage processes applied caused the in vitro measured value of glycemic index, expressed as a starch digestibility index (SDI), to decrease. The TRAD rolls were characterized by the highest value of SDI: 76.4 % of DM; and the PBF+SD rolls by the lowest SDI value: 53.2 % of DM. The powdered sourdough added into the white wheat flour and the BOT method with storing the partially baked products under the frozen conditions make it possible to produce wheat flour rolls showing a low value of glycemic index and an increased content of polyphenols.
wheat rolls, method of baking, starch, glycemic index, polyphenols