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Enzymatic analysis of levan produced by lactic acid bacteria in fermented doughs
- Shi, Qiao, Hou, Yaxi, Xu, Yan, Mørkeberg Krogh, Kristian B.R., Tenkanen, Maija
- Carbohydrate polymers 2019 v.208 pp. 285-293
- Erwinia, Leuconostoc mesenteroides, Paenibacillus amylolyticus, acid hydrolysis, enzymes, ethanol, faba beans, fermentation, food matrix, fructose, glucose, hydrocolloids, inulin, lactic acid bacteria, levan, models, prebiotics, sourdough, wheat
- Levans and inulins are fructans with mainly β-(2→6) and β-(2→1) linkages, respectively. Levans are produced by many lactic acid bacteria, e.g. during sourdough fermentation. Levans have shown prebiotic properties and may also function as in situ-produced hydrocolloids. So far, levan contents have been measured by acid hydrolysis, which cannot distinguish levans from e.g. inulins. In order to develop a specific analysis for levan in food matrices, a Paenibacillus amylolyticus endolevanase was combined with exoinulinase for levan hydrolysis. A separate endoinulinase treatment was used to detect the possible presence of inulin. Interfering sugars were removed by a pre-wash with aqueous ethanol. Levan content was estimated from fructose and glucose released in the hydrolysis, with a correction made for the residual fructose and glucose-containing sugars. The method was validated using wheat model doughs spiked with commercial Erwinia levan, and tested by analyzing levan content in Leuconostoc mesenteroides DSM 20343-fermented fava bean doughs.