*3.2. CLSM*

The microstructure of ISMS-treated PeaF suspensions was first visualized by means of CLSM to analyze the alterations of pea fiber induced by ISMS treatment, and blue fluorescence was observed, as shown in Figure 2A–F. Native PeaF revealed the predominance of a relatively big thick and compact structure, where the centre of some fibers presented weaker fluorescence than their well-defined edges, as shown by arrows in Figure 2A. In accordance with the results of particle size, pre-pulverizer treatment broke the fibers into relatively small structures with bright fluorescence (Figure 2B). Upon ISM treatment, the dense fiber seemed to be disrupted into loose fibers with the increasing of treatment intensity according to the significant change of blue fluorescence. ISM-60 PeaF showed diverse shapes of fluorescence with some strips as depicted in Figure 2C. When ISM pressure reached 90 MPa, the fluorescence intensity of fiber was weakened. ISM-90 PeaF presented a small flake-like structure with weak fluorescence intensity (Figure 2D). The further increasing of the treatment intensity led to a greater degree of tearing fiber, and ISM-120 PeaF (Figure 2E) and ISM-120-T2 PeaF (Figure 2F) displayed more small fragments with faint fluorescence and multiform shape. Overall, as the intensity of the ISMS treatment increased, the fluorescence of ISMS-treated PeaF was weakened and blurred, and the area of fluorescence for most fibers significantly diminished. It was implied that the ISMS treatment disrupted the thick and compact block-like pea fibers into small loose fragments. As pictured in Figure 2G, ISMS-treated PeaF suspensions exhibited a larger sediment volume of fiber at the bottom of the centrifugal tube as the treatment intensity increased, since fibers with smaller and looser structure were more difficult to sink lower to the bottom. These results indicated that the ISMS treatment did cause serious damage to the pea fiber, which confirmed the observation of CLSM images.

**Figure 2.** CLSM images and appearance of native PeaF and ISMS-treated PeaF. (**A**) Native PeaF; (**B**) Pre-PeaF; (**C**) ISM-60 PeaF; (**D**) ISM-90 PeaF; (**E**) ISM-120 PeaF; (**F**) ISM-120-T2 PeaF; (**G**) Appearance of native peaF and ISMS-treated PeaF.
