Interactions between sourdough lactic acid bacteria and exogenous enzymes: effects on the microbial kinetics of acidification and dough textural properties

The interactions between lactic acid bacteria and exogenous enzymes were studied to optimize the effects on the microbial kinetics of acidification, acetic acid production and textural properties during sourdough fermentation. Eleven species of lactic acid bacteria were used alone or in association with microbial glucose-oxidase, lipase, endo-xylanase, a-amylase or protease to produce sourdoughs. Data from the microbial kinetics of acidification were elaborated by the Gompertz equation and textural properties of the sourdoughs were analysed by using a Brabender extensograph, a Brabender farinograph and a Chopin alveograph. Only Leuconostoc citreum 23B, Lactococcus lactis subsp. lactis 11M and Lactobacillus hilgardii 51B were positively influenced by the enzymes added. Lactic acidification was increased and accelerated. All the enzymes affected the acidification activity of Lb. hilgardii 51B, including their addition in mixture. The addition of lipase, endo-xylanase and a-amylase increased the production of acetic acid by Lb. hilgardii 51B. Textural analyses pointed out that sourdoughs started with Lb. hilgardii 51B and individual enzymes were characterized by higher stability and softening compared to doughs with enzymes added alone.