Effect of fermentation and dynamic high pressure microfluidization on dietary fibre of soybean residue

Soybean residue is the main by-product of making soybean milk and tofu, and there is considerable interest in its recovery, recycling and upgrading. This work was to study the effect of fermentation with lactic acid bacteria and dynamic high pressure microfluidization (DHPM) on fibre fractions, fibre composition, surface topography and X-ray diffraction of dietary fibre in soybean residue. The results show that both fermentation and DHPM increased soluble dietary fibre (6.4-9.7 g/100 g and 6.4-14.0 g/100 g, respectively) and decreased the insoluble:soluble ratio (11.6-7.8 and 11.6-4.5, respectively). The minimum insoluble:soluble ratio (2.5) was obtained in samples with combined fermented and DHPM-treated at 200 MPa. The loss of hemicellulose was observed after fermentation and DHPM, while the cellulose content did not show significant differences. Microstructural and crystal structure analysis indicated that fermentation resulted in the modification of the fibrous structure with reduced crystallinity and DHPM damaged the structure to form rugged surface.