Effect of Dynamic High-Pressure Microjet on Physicochemical and Structural Properties of Dietary Fiber from Hawthorn Pomace

In this study, dynamic high-pressure microjet (DHPM) was used to investigate its effect on the structure and physicochemical properties of dietary fiber in hawthorn pomace. The results showed that after DHPM treatment under different conditions, the content of soluble dietary fiber (SDF) in hawthorn pomace increased by 34.59%-73.54% when compared with that of the control group, and the nitrite-adsorbing capability and cation-exchange capacity significantly enhanced (P < 0.05). Meanwhile, water-holding, oil-holding and swelling capacity reached up to the maximum when the pomace was at 200 MPa for 3 cycles, which was increased by 2.08, 8.34, and 2.25 times, respectively, when compared with that of the control group (P < 0.05). Thermogravimetric and rheological analyses showed a decreasing trend in apparent viscosity and a decrease in thermal stability; particle size and scanning electron microscopy analyses showed that the particle size decreased and then increased, the surface was rough, the structure was loose, and the particles agglomerated at the pressure of 250 MPa; infrared spectroscopy and ¹³C NMR analyses showed decreased crystallinity and degradation of some cellulose, hemicellulose and pectin. Therefore, DHPM treatment could increase the soluble dietary fiber content, hydration characteristics, and enhance its nitrite-adsorbing capacity and cation-exchange capacity with reduced thermal stability, particle size, apparent viscosity and crystallinity. This study provides a theoretical basis for the high-value utilization of hawthorn pomace.