Development of novel sourdoughs with in situ formed exopolysaccharides from acetic acid bacteria

Acetic acid bacterial strains were investigated for their ability to grow in aerobic and anaerobic sourdoughs (dough yield = 500) produced from wheat, whole wheat, spelt and rye flour and to produce effectual levels of exopolysaccharides (EPS) within 48 h of fermentation. The strains Kozakia (K.) baliensis DSM 14400 and Neoasaia (N.) chiangmaiensis NBRC 101099 were chosen. Both strains remained in aerobic doughs produced with any of the tested flours. For EPS optimization, 50, 75 and 100 g/l sucrose (sucrose) were added to the doughs and the parameters EPS, pH value, sucrose, acetic acid and gluconic acid were analysed. Results were subjected to statistical data analysis. In sucrose-enriched spelt dough, K. baliensis reached up to 49 g/kg EPS, followed by whole wheat (33 g/kg), wheat and rye dough (32–36 g/kg). N. chiangmaiensis produced 24–29 g/kg EPS in spelt and whole wheat doughs. EPS formation was positively correlated with start sucrose dosage. In contrast to this, a rather negative relation between acetic acid formation and start sucrose was found for both strains, and a positive relation with fermentation time. In spelt doughs, K. baliensis and N. chiangmaiensis produced up to 100 and 21–38 mM/kg acetic acid, respectively. Formation of gluconic acid was positively correlated with start sucrose dosage. K. baliensis produced at maximum 165 mM/kg flour and N. chiangmaiensis at maximum 119 mM/kg flour. Remaining sucrose contents were always positively correlated with start sucrose dosage, whereby both tested strains reached remaining sucrose amounts below 50 g/kg. A subsequent experiment with K. baliensis in backslopped spelt dough showed that this strain can remain in the dough over at least 8 days.