Immobilization as a tool to control fermentation in yeast-leavened refrigerated dough

In order to extend the shelf life of refrigerated dough, a new method based on thermo-gelling immobilization is proposed. This slows fermentation at low temperatures (<10 °C) while enabling it at ambient temperature. The principle of immobilization is to create a physical barrier between the substrate and the enzymes or the yeast in order to reduce the production of CO2. In this study, three different immobilization methods were investigated: (1) amylase immobilization, (2) yeast immobilization and (3) global dough immobilization. Enzyme immobilization in alginate/gelatin micro-beads was the least efficient since a high level of amylase leaching was observed. Furthermore, the fermentation process under refrigerated conditions was shown to be yeast limited, thus enzyme immobilization had little impact on the dough leavening. Immobilization of yeast into alginate/gelatin micro-beads enabled the complete arrest of fermentation. Raising the temperature resulted in bead solubilization and resumption of leavening, although the CO2 production rate was only 15% of the normal leavening rate. This is a consequence of sodium alginate, which was demonstrated to be a strong amylase and yeast inhibitor. Global dough immobilization with gelatin proved to be an excellent method to control and improve dough fermentation. Indeed, under refrigerated conditions, no volume increase of the dough was observed, gluten network was preserved, the fermentation potential was recovered by up to 83% and the leavened dough stability was improved. Furthermore, the process is completely reversible. Gelatin was shown to catalyze maltose uptake and thus improve the dough development rate and dough leavening (150%). Gelatin can thus act both as a stopping agent and as a fermentation improver.