**1. Introduction**

The appropriate consumption of dietary fibre has considered to be advantageous to health, such as by preserving gastrointestinal function, lowering blood lipids and cholesterol levels, and reducing the risk of cardiovascular disease [1], so we were encouraged to seek excellent fiber sources for the development of foods supplemented with dietary fibers. Pea fiber is a valuable and attractive food component which has been added to pasta for improving the nutritional value [2]. Commonly, the incorporation of raw pea fiber would negatively impact the sensory characteristics of the food matrix owing to its poor techno-functional properties. One of the areas of focus among researchers and in the field of functional food processing is the modification of fibers to increase their quality or functional properties by adopting physical, chemical and biological approaches [3]. In recent years, superfine pulverization techniques have gained much attention for their modifying properties of fiber. For instance, pulverization methods such as homogenization, microfluidization and ultrafine comminution have been reported to modify fibers from citrus [4,5], purple-fleshed potatoes [6], bamboo shoot shells [7] and carrot pomace [8]. Furthermore, microfluidization showed great potential in modifying fibers such as wheat and corn bran, peach and oat fiber, insoluble soybean fiber and hazelnut skin fiber, as reviewed by Guo, et al. [9] and Ozturk and Turasan [10]. Morales-Medina, et al. [11] also found a continuous

**Citation:** He, X.; Dai, T.; Sun, J.; Liang, R.; Liu, W.; Chen, M.; Chen, J.; Liu, C. Disintegrating the Structure and Improving the Functionalities of Pea Fiber by Industry-Scale Microfluidizer System. *Foods* **2022**, *11*, 418. https://doi.org/10.3390/ foods11030418

Academic Editor: Gian Carlo Tenore

Received: 23 December 2021 Accepted: 29 January 2022 Published: 31 January 2022

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defibrillation of pea hull fiber by microfluidization with the decreasing of particle size. Nevertheless, previous reports were mainly concentrated on treating fibers by small scale microfluidizers. As pointed out by Ozturk and Turasan [10], one of the biggest problems with this technology was the limitation of scale, and additional supporting equipment like a pretreatment miller was necessary if an industry-scale microfluidizer was provided. In our research group, an innovative industry-scale microfluidizer system (ISMS) was developed which combined a pre-pulverizer and an industry-scale microfluidizer (ISM). The schematic diagram and the main functions of the pre-pulverizer and industry-scale microfluidizer were demonstrated in our previous research in greater detail [12–14]. The industry-scale microfluidizer possesses a unique constructional microchannel with large orifice diameters, unusual impact modes and a high processing capacity which could continuously run to reach productivity of five tons per hour. ISMS has been successfully applied to produce stable whole soybean milk and improve the stability of whole corn slurry without filtering and removing any components. This indirectly reflected that the soybean and corn fibers in the whole component systems were modified. With regard to the low utilization of pea fiber, it was worth investigating the effect of ISMS treatment on its structural and functional properties. Ascertaining the efficiency and ability of ISMS to modify pea fiber can provide the possibility for its high-value utilization.

Therefore, the objective of the current work was to investigate the efficiency of ISMS modifying pea fiber. Pea fiber was treated by ISMS at a different intensity (60, 90, 120 MPa for one pass and 120 MPa for two passes after pre-pulverizer treatment). Subsequently, the structure and functionalities of ISMS-treated pea fiber (ISMS-treated PeaF) were determined. The structural properties were characterized by particle size distribution, confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) analysis. The functionalities including swelling capacity (SC), water retention capacity (WRC) and oil holding capacity (OHC) of ISMS-treated PeaF were discussed. This study may identify a new technology that can be utilized to manufacture nutritious foods with high fiber content, thereby promoting the development of new food products.

#### **2. Materials and Methods**

#### *2.1. Material*

Pea fiber powder was provided by Shuangta Food Co., Ltd (Zhaoyuan, China), which contained 80.7% of total dietary fibre. The protein, starch, and ashes accounted for a much lower percentage (0.3, 3.6 and 3.4%, respectively). Calcofluor white was purchased from Aladdin Reagent Company (Shanghai, China). Corn oil was purchased from a local supermarket (Jinlongyu, Shanghai, China). All other chemical agents were of analytical grade.
