In vitro glycemic index determination of Turkish sourdough breads and strategies to reduce glycemic index

Glycemic Index (GI) is the percentage of glucose response of food. Low GI has positive effect on health. Turkish white bread with its high glycemic index (87) must be reduced for healthy nutrition. Sourdough is considered as a solution. With this study, GI was decreased by using sourdough and changing fermantation conditions. Firstly, 4 different homemade white sourdoughs (Oguzlu (O), Kastamonu (K), Lüleburgaz (L), Afyon/ Bolvadin 2 (B2)) and one whole wheat sourdough, Safranbolu Yıldız Fırını (SYF) were obtained. Traditional sourdough breads fermented at room temperature (25℃) long time (24hrs). O, K, L, B2, SYF had GI of 50.05±0.3, 51.8±1.65, 50±0.5, 51±0.5 and 46.5 ±0.5, respectively. There was no significant difference among the GI of white sourdough breads except SYF containing dietary fiber. %50 whole wheat sourdough breads containing enzyme were prepared at different fermentation times and temperature. Sourdough breads fermented at the low temperature (4℃) different times (15hrs, 18hrs, 20hrs, 24hrs) had lower GI values (58.1±0.1, 55.05±1.5, 54.25±0.25, respectively) than breads fermented at the room temperature (25℃) different times (15hrs, 18hrs, 20hrs, 24hrs) (65.5±0.7, 66±1, 69±1.5, 69±1.5, 74±0.5, respectively). As a result, while GI of cold fermentation breads gradually decreased, other sourdough breads gradually increased.