Effect of instant controlled pressure drop treatments on the oligosaccharides extractability and microstructure of Tephrosia purpurea seeds

The study of the oligosaccharides extracted from Tephrosia purpurea seeds was undertaken using the instant controlled pressure drop (DIC) as a pre-treatment prior to conventional solvent extraction. This DIC procedure provided structural modification in terms of expansion, higher porosity and improvement of specific surface area; diffusion of solvent inside such seeds and availability of oligosaccharides increase notably. In this paper, we investigated and quantified the impact of the different DIC operative parameters on the yields of ciceritol and stachyose extracted from T. purpurea seeds. The treatment could be optimized with a steam pressure (P) (P = 0.2 MPa), initial water content (W) (W = 30% dry basis (DB)) and thermal treatment time (t) (t = 30 s). By applying DIC treatment in these conditions, the classic process of extraction was intensified in both aspects of yields (145% of ciceritol and 185% of stachyose), and kinetics (1 h of extraction time instead of 4 h for conventional process). The scanning electron microscopy micrographs provided evident modifications of structure of seeds due to the DIC treatment.