Contribution of the microbial mass to the nitrogen profile of wheat bread doughs started with pure and mixed cultures of yeast and lactic acid bacteria

Amino Acid Profiles of Fermenting Wheat Sour Doughs

“…After centrifugation at 23,000 X g for 20 min at 13"C, supematants were made up to 50 mL. Aliquots of extracts (3.5 mL) were deproteinized by ultrafiltration (cut-off 10 KDa) (Collar et al, 1991a) and submitted to cation exchange chromatography on Dowex-5OWx2 (Collar et al, 1991b). Purified dried extracts were derivatized and used for amino acid determination.…”

“…During sour dough fermentation, amino acids and their derivatives may be released into the media by proteolysis Nierle, 1984a, 1984b), by metabolism of sugars (Okuhara and Harada, 1971) and peptides (Nisbet and Payne;1979), and/or by enzymatic synthesis (MacWilliam and Clapperton, 1969). They can also be supplied from the cell mass of microorganisms (Collar et al, 1991a).…”

Amino Acid Metabolism by Yeasts and Lactic Acid Bacteria during Bread Dough Fermentation

“…Freeze-dried UD, FD, and LFD (log) were each extracted twice with 20 mL 40% ethanol (v:v). After ccntrifugation, dcprotcinization (Collar et al, 1991a), and chromatografic purification (Bcnedito de Barber et al, 1989;Collar et al, 1991b), dried extracts were derivatized and used for amino acid determination ( Fig. 2…”

“…Their specific hydrolytic action on dough proteins during fermentation release amino acids and peptides. The microbial mass of microorganisms can also supply low molecular weight nitrogen metabolites by cellular lysis (Thorn, 1971;Rothenbuehler et al, 1982;Collar et al, 1991a). The release of amino acids and peptides by enzymatic reactions (MacWilliams and Clapperton, 1969;Spicher and Nierle, 1984a) and by metabolism of sugars (Okuhara and Harada, 1971) and other components (Nisbet and Payne, 1979), stimulates or inhibits the synthesis of proteases of some species of streptococci (Westhoff and Cowman, 1970).…”

“…The dynamics have been reported in individual low molecular weight nitrogen metabolites during wheat dough fermentation, and the contribution of the inoculum of microorganisms to the nitrogen pattern (Collar et al, 1991a) of doughs started with pure cultures of yeast (Collar et al, 1989) and LAB 1991b). Despite the interest in metabolism of amino acids during fermentation of selected microorganisms in connection with controlled flavor and performance of bread, few papers concerning wheat doughs have been reported.…”