Wheat sourdough fermentation: Metabolism of nitrogen related components by Lactobacillus strains

ROLLÁN, G.,; DE ANGELIS, M.; M. GOBBETTI; FONT DE VALDEZ, G.

Jaen - España

Congreso; Food safety under extreme condition a conference on small scale production units of traditional fermented foods; 2004

Proteolysis by lactic acid bacteria (LAB) during sourdough fermentation can influence rheological parameters, viscosity and gas retention. Moreover, the amino acids released during dough fermentation could stimulate the metabolic activities of microorganisms and the interactions between LAB and yeasts. Furthermore sensorial attributes of bread may be enhanced by the release of nitrogen compounds that represent important flavour precursors influencing the overall aroma of the final product. The LAB strains used in this work were isolated from Argentinean sourdoughs and preliminarily screened for their growth capacity on MBG medium containing gluten as the principal nitrogen source. Lactobacillus reuteri CRL 1098, L. plantarum CRL 778 and L. plantarum CRL 759 were able to grow in these conditions. The proteolytic system of these strains was partially characterized and in vitro effect on the reduction of gliadin like fractions was also observed. The aim of the present work was to determine the proteolytic activity of the selected lactobacilli during sourdough fermentation. A fractionated method of protein extraction and subsequent SDS-PAGE were used to estimate proteolysis in sourdoughs. After 6 and 24 hours of incubation at 30-37°C, the protein profiles of lactobacilli started doughs were compared to un-started acidified dough. The results showed that albumin, globulin and gliadin fractions were partially hydrolysed, while glutenins were not degraded. The concentration of free amino acids also increased in doughs incubated with Lactobacillus strains especially with L. plantarum CRL 759 and L. reuteri CRL 1098. The peptide concentration on water soluble extracts of started dough, determined with RP-FPLC using PepRPC HR 5/5 column, were high in presence of Lactobacillus strains compared to un-started incubated dough. These results would be of interest to prepare wheat sourdough with high levels of amino acids, which have positive influences on bread quality.