Application of Electrical Breakdown in Liquid Process on Inulin Structural Transformations

Abstract

This work proposes a novel technique for biological compound transformation by a circulating electrical breakdown in the liquid (EBL) process. The EBL reactor has been designed with a cylindrical, hourglass-shaped structure that facilitates plasma generation within a 1 mm gap between two pin electrodes at the neck of the reactor. During the EBL process, the inulin solution was flown upward and brought into direct contact with the plasma before recirculating back to the bottom of the reactor for subsequent retreatment. Consequently, it enabled a continuous and thorough inulin treatment. At this time, the influence of the supplied voltage (3.20, 3.76, and 4.32 kVpeak at 50 Hz positive half-wave) for the EBL process generation on the inulin structural transformation was investigated. The most optimal condition in the EBL process was operated at 4.32 kVpeak supplied voltage within the optimal inulin treatment duration of 20 min. Regarding the experimental results, it could be confirmed that the EBL process has the potential to depolymerize the inulin structure. One gram of inulin was dissolved in 100 mL of deionized water and treated under the EBL process for 20 min. Inulin structures were deformed from a 20- $100 \mu \text{m}$ micro spherical shapes into small flakes. Moreover, the DPPH free radical scavenging analysis showed that the antioxidant activity and the prebiotic activity of treated inulin have been improved by 311%, and 35%, respectively.

Keywords

• Inulin
• polysaccharide
• depolymerization
• antioxidant
• plasma–liquid interactions
• solution plasma processing