Impact of high-temperature cooking combined with cellulase extraction on the structure and functional properties of soluble dietary fiber from the outer leaves of Chinese cabbage

This study aims to extract soluble dietary fiber (SDF) from discarded outer leaves of Chinese cabbage using a high-temperature cooking combined with cellulase (HC) extraction to promote their high-value utilization. Response surface method was employed to optimize the extraction parameters, yielding an HC-SDF yield of 16.17% under the optimal parameters (material-to-liquid ratio of 1:31 g/mL; cooking time of 20 min, cellulase dosage of 4.6%; enzymatic hydrolysis temperature of 53 ± 1°C, and enzymatic time 90 min). Compared with hot water extraction (HW-SDF, used as a control), HC-SDF yield increased by 97.68%. Structural analysis revealed that HC-SDF exhibited a coarser and loose microstructure, reduced particle size (56.38 μm), and lower molecular weight (6.77 kDa), along with the highest crystallinity and thermal stability, compared to HW-SDF. Functionally, HC-SDF exhibited significantly higher water holding capacity (49.00%), oil holding capacity (51.23%), and glucose adsorption capacity (95.04%) than HW-SDF. Additionally, HC-SDF exhibited superior apparent viscosity, pancreatic lipase inhibitory activity (69.88%), α-amylase inhibitory activity (61.33%), and antioxidant properties. Finally, it was concluded that the HC method not only enhanced the SDF yield but also improved the structural and functional properties, highlighting its potential use as a functional food ingredient in food industries. • RSM optimized the extraction conditions of HC-SDF. • HC-SDF yield increased by 97.68% compared to HW-SDF. • HC-SDF had looser structure, smaller particles, and lower molecular weight. • HC-SDF exhibited higher WHC, OHC, GAC, and CAC than HW-SDF. • HC-SDF showed superior enzyme inhibitory and antioxidant activities in vitro.