Résumé:
This study was led in the aim to set off a technique that enable to follow the fermentation kinetics of the fermented pastes, based on the congelation of the lumps in nitrogen liquidates then freeze-drying.
The Follow-up of fermentation kinetics is done on fermented pastes in a time interval from 0 to 150 min at 38°C. Samples of fermented pastes are preserved in liquid nitrogen, then freeze-dried (- 57°C, 0.05 mbar). The acquisition of the images of the cellular structures is obtained by the use of a medical scanner and by numerical camera. The kinetics of gas expansion is traced. The images obtained are treated by morphological analysis; the grading curves of the corresponding levels of gray are traced. A classification of the structures of the lumps is obtained by Analyze in Principal Components (ACP).
Obtained results showed that the common wheat paste witness expand approximately 3 times more than those of the rice-field bean formula (FRF), fermentation optimum for the common wheat witness is at 120 min with a gas expansion of 195, 79% for the flour1, and 200, 28% for the flour 2, against an fermentation optimum of the ricefield bean formula is at 45 min with a gas expansion of 44.05%.
The grading curves resulting from the image analysis allowed that the finest structure for the two flours of common wheat is at 0 min, and coarsest with 150 min. The finest structure with 5 min., 30 min. coarsest for the FRF. A classification by ACP statistical test made possible to obtain classifications of the structures of the lumps fermented according to their smoothness or their heterogeneity.
In conclusion, and through this word, we could validate the paste congelation freeze-drying technique as a simple tool of following-up the expansion kinetics of materials of different bakers’ qualities.
