Influence of wheat flour and Lactobacillus strains on the dynamics of by-products from amylolytic activities / Influencia de la harina de trigo y de la especie de Lactobacilo en la dinámicade subproductos de la actividad amilolítica

Amylolytic activity of six flours from three European wheat cultivars (Obelisk, Camp Remy and Fresco, at 70 and 100% extraction level), and five lactobacilli strains (Lactobacillus plantaracm B-39, L-73; L. brevis 25a, L-62, and L. sanfrancisco L-99), as well as the dynamics of by-products from amylolytic degrading action in mixed flour-lactobacilli systems have been investigated. α-Amylase activity of flours depended on ash content; whole flours from the three cultivars had similar values, which were of the order of three to ten times that of white flours. L. sanfrancisco showed the lowest α-amylase activity, and L.plantarum the highest. At the concentrations of lactobacilli used in sourdough processes, flour was the main contributor to final α-amylase action in flour-lactobacilli mixtures. Production of monosaccharides followed variable trends, depending on the extraction level of the flour and on the Lactobacillus strain. The dynamics of monosaccha rides, due to their active and variable involvement in metabolic pathways, could not be adjusted to model regression equations. Maltose levels increased during fermentation, although an effec tive incorporation in Lactobacillus metabolism was observed. A second order polynomy could be used to describe changes in maltose. Low molecular weight dextrins (LMWD) with degrees of polymerization (DP) from three to seven, only appeared and accumulated during the late stages of fermentation. LMWD with a DP of three was the only oligosaccharide capable of being incor porated by lactobacilli, and, of the strains tested, only by L. brevis (25a). The larger dextrins seemed to be involved in further degrading enzymic reactions yielding smaller size fragments. Dynamics of LMWD followed exponential curves, with highly significant regression coefficients.