Cold atmospheric pressure plasma processing of grape juice: Effects on bioactive properties, microbial inactivation, and quality characteristics

This study investigates the effects of cold atmospheric pressure plasma treatment on the bioactive composition, microbial stability, and physicochemical quality of grape juice. Samples were treated for 1–4 min, and changes in total phenolic content (TPC), antioxidant capacity (DPPH and cupric ion reducing antioxidant capacity [CUPRAC] assays), pH, Brix, titratable acidity, and color parameters ( L *, a *, b *) were measured. Microbial analyses, including total mesophilic aerobic bacteria (TMAB) and yeast–mold counts, were conducted both immediately after treatment and during 28 days of refrigerated storage at 4 °C. Plasma treatment reduced TPC from 221.0 to 156.0 mg GAE/L and CUPRAC antioxidant activity from 4.26 to 2.06 µmol TE/L after 4 min. After 28 days of refrigerated storage, yeast–mold counts reached 4.54 log CFU/mL in the control sample, whereas no detectable growth was observed in the sample treated with plasma for 4 min. The TMAB were not detected either before or after plasma treatment. Kinetic modeling revealed that first-order kinetics provided the best fit for TPC degradation and antioxidant capacity, while microbial inactivation also followed a predictable logarithmic decline over treatment time. A treatment duration of 2–3 min preserved over 70% of antioxidant activity and caused minimal changes in quality while effectively reducing yeast and mold growth (by 0.81–1.32 log compared to the control) during refrigerated storage. These results suggest that cold plasma shows promising potential as a nonthermal processing method for fruit juice, with the ability to enhance microbial safety and maintain quality parameters with limited nutrient loss.