Experimental study on the foam-stabilizing advantages and foam stabilization mechanism of novel microbial polysaccharides

Abstract

Microbial polysaccharides are of great interest in improving foam stability due to their excellent physicochemical properties. At present, there are few reports on the improvement of foam stability by novel microbial polysaccharides diutan gum and welan gum, so that the foam stabilization mechanism of microbial polysaccharides in terms of foam drainage, coarsening and coalescence is lacking. In this paper, the foam stabilization mechanism of three microbial polysaccharides was studied in detail from drainage, coarsening and coalescence, and the superiority of diutan gum in foam stabilization was emphasized. Rheological experiments show that the interaction force between diutan gum molecules is very strong, and 0.08 wt% diutan gum can significantly change the viscosity of the solution. The microscopic characteristics of the foam shows that the diutan foam has obvious advantages in foam quality, bubble size and its distribution. For the experimental results of foam drainage, it is found that the critical drainage time of foam is related to the thickening ability of the gum and the liquid drainage half-life of diutan foam is longest. Diutan gum molecule has rod-shaped helical structure and a complex aggregation morphology, which makes diutan gum have good temperature resistance and excellent water retention. These two properties of diutan gum significantly improve its foam stabilization ability. From the analysis of foam coarsening and coalescence, adding microbial polysaccharides can slow down coarsening rate and prevent foam from coalescence. Finally, the morphology of the liquid film at the microscopic scale is observed by SEM, and the thickness of the liquid film of different foams is measured. It is found that the liquid film structure of the foam added with diutan gum is dense and the thickness of the liquid film is the thickest. This study is of great significance to the theoretical exploration of microbial polysaccharides to improve foam performance and the construction of green foam systems.