Bread-dough fermentation by Lactobacillus reuteri CRL 1100.

GEREZ, L., CUEZO, S., ROLLÁN, G. Y FONT DE VALDEZ, G.

Badajoz, España

Congreso; 1ST Internacional Conference on Environmental. Industrial and Applied Microbiology.; 2005

Lactic acid bacteria (LAB) are present in different food ecosystems. LAB have been isolated and used as starter cultures for sourdough breads. Contrary to the European countries, lactic acid starters are not used in bakery in Argentina yet. LAB are able to produce organic acids, mainly lactic and acetic, in variable concentrations depending on the sugar availability present in the dough. In previous works we determined and characterized the invertase activity of Lactobacillus reuteri CRL 1100 which hydrolyses sucrose into glucose and fructose[1]. Proteolysis by LAB during sourdough fermentation may have repercussions on the rheology and staleness; moreover, free amino acids and small peptides are important for rapid microbial growth and acidification [2]. In order to select the mixture of bacteria to be included in the starter culture, it is necessary to know the microorganisms functional characteristics and the biochemical effects that they produce on the dough constituents. The present study was undertaken to determine the effect of Lactobacillus reuteri CRL 1100 on wheat bread – dough fermentation. The carbohydrate and nitrogen compounds metabolisms were evaluated using HPLC and enzymatic commercial kits in the fermented doughs. When L. reuteri CRL 1100 was used to inoculate the dough (D1100), cell viability was increased 3 log units after 24 h of incubation at 30ºC. In D1100, the utilization of carbohydrates by this LAB produced a reduction of the pH value from 6.2 to 3.9, while the pH varied only from 6.2 to 5.7 in the control dough (Dc) after 24 h. The pH decrease in D1100 was mainly correlated with the production of organic acids by L.reuteri with a lactic and acetic acid productions of 2.7 and 1.3 mmol/ 100g dough, respectively, after 6 h of fermentation. In the dough fermented (D1100), the amount of glucose and fructose increased 68 % and 110 %, respectively, while in Dc the glucose and fructose concentrations remained constant. These results should be a consequence of the invertase activity by this LAB strain acting on the sucrose present in the dough. The nitrogen compounds metabolism was evaluated by the free amino acids analysis in Dc and D1100. The concentration of aromatic, basic and dicarboxylic amino acids was increased 357 %, 207% and 13%, respectively, in the fermented dough by L.reuteri CRL 1100. Ornithine, phenylalanine and methionine, important precursors of bread flavor compounds, were also increased 172 %, 287 % and 252%, respectively in D1100 when it was incubated for 24h. Acknowledgements The authors acknowledge the financial support of Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT) and CIUNT from Argentina. References [1] S. Cuezzo de Ginés; M.C. Maldonado and G. Font de Valdez. Current Microbiology ( [2] M. Gobetti. Trends Food Sci. Technol. 9 (1998), p. 267-274