RESEARCH ARTICLE The impact of sourdough addition to frozen stored wheat-flour rolls on glycemic response in human volunteers Barbara Borczak 1 , Elz ˙ bieta Sikora 1 , Marek Sikora 2 and Ingrid Van Haesendonck 3 1 Department of Human Nutrition, Faculty of Food Technology, Agricultural University in Krakow, Krakow, Poland 2 Department of Carbohydrate Technology, Faculty of Food Technology, Agricultural University in Krakow, Krakow, Poland 3 Puratos, Groot-Bijgaarden, Belgium The aim of this study was to examine the effect of sourdough addition to partially baked and frozen (PBF) wheat rolls on the glycemic index (GI). The study was performed on healthy humans ( n ¼ 15). The volunteers were asked to attend six times in the early morning, over 3 weeks. Each human tested four types of wheat rolls – two without sourdough addition: (i) fully baked, non-frozen (FBNF); (ii) PBF; and two with the addition of 3% dehydrated sourdough: (iii) FBNF (FBNF þ S), (iv) PBF (PBF þ S). Glucose solution was used as a reference food and tested twice. Blood glucose concentrations were measured before consumption, as well as at 15, 30, 45, 60, 90, and 120 min after the start of the meal. In the study, the addition of 3% dehydrated sourdough to fresh and frozen wheat rolls resulted in a significant decrease in the glycemic response, by 24% – FBNF þ S (GI ¼ 63  7) and PBF þ S (GI ¼ 43  4) – compared to the samples without sourdough: FBNF (GI ¼ 87  11), PBF (GI ¼ 67  3) ( p  0.05). Both factors (freezing and sourdough), applied to the wheat rolls at the same time, statistically significantly reduced the GI, by 44% ( p  0.05). The results of the study show that sourdough supplementation separately and sourdough supplementation combined with frozen storage of white wheat rolls have a significant impact on the glycemic response. Received: April 11, 2011 Revised: July 13, 2011 Accepted: July 13, 2011 Keywords: Frozen storage / Glycemic index / Sourdough / Wheat rolls 1 Introduction Bread plays a fundamental role in human nutrition. After milk products and potatoes, cereals are the third largest group of products in the daily food ration in Poland [1]. According to the latest nutritional recommendations, 5–11 portions of cereal products should be consumed in the daily diet, but mostly whole-grain cereal rich in fiber should be eaten [2]. Since the 1980s attention has been paid to the glycemic index (GI) of foods. Consumption of products with a low GI, and rich in dietary fiber, is recommended in the prevention of diet-related chronic diseases such as type two diabetes, obesity, heart disease, and cancer [3–7]. Wheat is one of the most widely consumed grains in the world, primarily in the form of bread. Unfortunately, white bread has a high GI [8–12]. Current efforts aim to obtain a product characterized by a low glycemic response, good nutritional value, and a quality which is accepted by consumers. Both raw materials and baking processes can influence the glycemic Correspondence: Professor Elz ˙bieta Sikora, Department of Human Nutrition, Agricultural University in Krakow, 122 Balicka Street, 30-149 Krakow, Poland E-mail: rresikor@cyf-kr.edu.pl Fax: þ48-12-662-48-12 Abbreviations: FBNF, fully baked, non-frozen; GI, glycemic index; IAUC, incremental area under the curve; PBF, partially baked and frozen; S, sourdough; TC, total carbohydrates DOI 10.1002/star.201100055 Starch/Sta ¨ rke 2011, 00, 1–7 1 ß 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.starch-journal.com