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Formation of Oligosaccharides and Polysaccharides by Lactobacillus reuteri LTH5448 and Weissella cibaria 10M in Sorghum Sourdoughs

¹University of Alberta, Dept. Agricultural Food and Nutritional Science, Edmonton, AB, Canada T6G 2P5. ²Università degli Studi di Teramo, Dipartimento di Scienze degli Alimenti, Via C. R. Lerici 1, 64023 Mosciano S. Angelo, Italy. ³Corresponding author. Phone: + 1 780 492 0774. Fax + 1 780 492 4265. E-mail: Michael.gaenzle@ualberta.ca

Gluten-free breads, which are composed of gluten-free flours, starch, and hydrocolloids, differ from wheat and rye breads in relation to texture, volume, and crumb structure. Moreover, the dietary fiber content is lower compared with wheat or rye breads. Cereal isolates of lactic acid bacteria frequently produce oligo- and homopolysaccharides from sucrose, which can improve the nutritional and technological properties of gluten-free breads as prebiotic carbohydrates and hydrocolloids, respectively. Sorghum sourdough was fermented with Lactobacillus reuteri LTH5448 or Weissella cibaria 10M, which synthesize fructooligosaccharides (FOS) and levan, and isomaltooligosaccharides and dextran, respectively. The gluten-free bread was produced with 14% sourdough addition. L. reuteri LTH5448 formed FOS and 1.5 g of levan/kg DM in quinoa sourdoughs. FOS were digested by the baker's yeast during proofing, and the levan could be qualitatively detected in the bread. W. cibaria 10M produced >60 g of isomaltooligosaccharides/kg DM and 0.6 g of dextran/kg DM, which could still be detected in the bread. Breads prepared with W. cibaria 10M were less firm compared with breads prepared with L. reuteri LTH5448 or a FOS and levan-negative mutant of L. reuteri LTH5448. The addition of sourdoughs fermented with oligo- and polysaccharide forming starter cultures can increase the content of prebiotic oligosaccharides in gluten-free breads.