*2.2. ISMS Treatment of Pea Fiber*

Native pea fiber (native PeaF) suspensions were prepared by mixing pea fiber powder in distilled water using a stirrer for overnight at approximately 500 rpm to completely hydrate, and a concentration of 1.2% (*w*/*w*) was selected according to the investigation of Bruno, et al. [5]. Completely hydrated pea fiber suspensions were added directly into the pre-pulverizer, then the pea fiber suspensions obtained from the pre-pulverizer were treated by ISM for one pass at 60, 90, and 120 MPa and two passes at 120 MPa in series. The temperature of the treated pea fiber suspensions (ISMS-treated PeaF) was less than 54 ◦C, and after ISM treatment, the ISMS-treated PeaF suspensions were immediately cooled to room temperature using an ice bath. Pea fiber treated by ISM at the corresponding intensity was designated as ISM-60 PeaF, ISM-90 PeaF, ISM-120 PeaF and ISM-120-T2 PeaF, respectively. The fiber treated by pre-pulverizer but without ISM treatment was labeled as Pre-PeaF. Part of the suspensions were withdrawn to perform particle size distributions and CLSM analysis. Other suspension samples were freeze-dried and ground into powders. The suspensions were first frozen at −80 ◦C overnight, and then freeze-dried using the FreeZone® 4.5 L freeze-drier (Labconco, Kansas City, MO, USA) at low vacuum (≤10 bar) and temperature (~−40 ◦C). The freeze-dried PeaF was ground into power using a basic

analytical mill (IKA® A11B S025, Merck KGaA, Darmstadt, Germany) by intermittent operating for dozens of seconds. The obtained powders were stored in a desiccator for further analysis.
