Comprehensive studies on the properties of apple juice treated by non-thermal atmospheric plasma in a flow-through system

We present an optimized non-thermal atmospheric plasma (NTAP)-based reaction-discharge system for continuous-flow treatment of apple juice (AJ). Using design of experiments with response surface methodology, we optimized discharge current, AJ flow rate, and electrode gap to preserve key spectral features (UV/Vis absorbance at 284 nm) while maximizing temperature below 50 °C. Nutritional, physicochemical, microbiological, and cytotoxic properties of the resulting AJ were assessed. NTAP treatment increased concentrations of Ca, Fe, K, Mg, Na and Sr by 8–10% and Al, B, Ba, Cu, Mn and Zn by 11–15% (differences became insignificant after accounting for 11% water loss). Total phenolic content increased (≈23% unadjusted; ≈11% after water-loss correction), and shelf life was prolonged by up to 12 days. NTAP did not change organic compound structures, °Brix, color, or ferric reducing antioxidant power. NTAP-treated AJ was non-cytotoxic to normal intestinal epithelial cells but induced cytotoxicity in human colorectal adenocarcinoma cells. The study supports potential industrial use of flow-through NTAP for AJ with improved properties.

Anna Dzimitrowicz, Aleksandra Bielawska-Pohl, Pawel Pohl, Piotr Cyganowski, Agata Motyka-Pomagruk, Tymoteusz Klis, Malgorzata Policht, Aleksandra Klimczak, Piotr Jamroz