Influence of non-thermal dielectric barrier discharge (DBD) plasma treatment on pectin methylesterase inactivation and ascorbic acid degradation in Citrus sinensis (cv. Malta) juice

Dielectric barrier discharge (DBD)-based atmospheric cold plasma (ACP) technology is an emerging non-thermal approach for fruit juice processing. Therefore, the present investigation involved the application of DBD-ACP to orange juice (cv. Malta), with a range of parameters being examined, including sample depth (2-4 mm), voltage (16-20 kV), and treatment time (2-10 min). The effects of process parameters on the responses of ascorbic acid (AA), residual activity (RA) of pectin methylesterase (PME), and bioaccessibility index (BI) were assessed and optimized using response surface methodology (RSM). The physicochemical properties of ACP-treated juice under optimized conditions were compared with untreated juice. The kinetic study of PME inactivation and AA degradation was also investigated. The optimum conditions achieved by RSM were: voltage of 20 kV, sample depth of 3.29 mm, and treatment time of 2 min. The AA, RA of PME, and BI were obtained under optimum conditions as 31.54 mg/100 mL, 61.33%, and 79.10%, respectively. The principal component analysis demonstrated a better correlation among process and response variables. The results of titratable acidity, pH, and total soluble solids showed an insignificant (p > 0.05) effect. The total phenolic content and total flavonoid content increased by 8.88% and 16.50%, respectively. The AA content and DPPH radical scavenging activity decreased during treatment. A slight change in the total color difference (Delta E) of 0.27 was observed. The Weibull model was found to be the best fit for describing the kinetics of PME inactivation and AA degradation during DBD-ACP treatment.