Kornautchaya Veenuttranon creator Loc Thai Nguyen Chairperson Anal, Anil Kumar Examination Committee Sadiq, Muhammad Bilal Examination committee RTG Fellowship Scholarship donor text series technical report th Pathum Thani, Thailand Asian Institute of Technology 2017 continuing eng 90 leaves : ill. + 1 online resource The aim of this work was to develop a programmable compressed - nitrogen gas flow system combined with electrochemical based assay for assessment of total antioxidant capacity (TAC) using the 2, 2 - diphenyl - 2 - picrylhydrayl hydrate (DPPH{u2022}) solution as a redox indicator on a screen printed carbon electrode ( SPE) . Gallic acid (GA) was chosen as a standard antioxidant. Firstly , the prototype device was designed and fabricated with an internal volume of 1,500 oL . A programmable electronic controlled 3 - way solenoid valve was utilized to control the liquid flow and retention time inside the reaction chamber of the system. A suitable driven pressure for compressed nitrogen gas was 20 kPa which was used to control the volumetric dosage of samples and reagents. There were a good linear relationship between propelled time and volumetric dosage (R 2 > 0.999 ) for all injection ports in which the linear regression equations were used to determine an accurate time for liquid injection . T he electrochemical characterizations of DPPH{u2022} and GA were performed using cyclic voltammetry (CV) , as a result, a suitable applied potential (E) of - 0.05 V was select ed for amperometric determination of TAC. The calibration curve was developed by measuring the constant currents of amperometry ( I ) for different concentration of GA in fixed 0.05 mM DPPH solution, after incubating the mixture for 2 min. One pure compound of ascorbic acid and four liquid food samples (orange juice, pomegranate juice, white wine and green tea) were mixed instead of GA and respective ( I ) were measured to determine the TAC. The results of TAC was then expressed in terms of gallic acid equivalent antioxidant capacity (GEAC). All the above experiments were co - conducted with the spectrophotometric analysis and results were compared. A good linear correlation (R 2 = 0.996 ) was obtained between electrochemical test within flow mixing system and conventional method of DPPH{u2022} scavenged by ascorbic acid, and two methods could be used interch ange (slope = 0.951 ). IC 50 and TAC of four samples were investigated by dif ferentiating the concentration and there was no significant difference (p> 0. 05) between the two methods. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering in Food Engineering and Bioprocess Technology, School of Environment, Resources and Development Thesis (M. Sc.) - Asian Institute of Technology, 2017 Antioxidants Biotechnology Biomaterials Electrochemical apparatus Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B02864 http://203.159.5.9/ait-thesis/detail.php?q=B02864 190827 20260818090754.0