Atmospheric cold plasma treatment effects on quality of cloudy apple juice during storage

Abstract

Atmospheric cold plasma (ACP) is a nonthermal technology that shows promise for use in food processing. This study evaluated the effects of ACP treatment on the quality of cloudy apple juice using two different feed gases—simulated air (SA), consisting of 80% nitrogen and 20% oxygen, and combined gas (CG), made up of 90% nitrogen and 10% oxygen—for varying durations (30–150 s). The impact of storage at 4°C for 3 weeks on physicochemical properties (pH, color, viscosity, titratable acidity, soluble solids) and bioactive compounds (total phenolic content [TPC], antioxidant capacity) was assessed. Microbial survival, including total plate count, yeast and mold counts, and Alicyclobacillus acidoterrestris spores, was also evaluated. ACP treatment did not significantly alter pH, °Brix, or viscosity immediately post-treatment; however, pH decreased significantly after storage (e.g., SA at 30 s: 3.66 ± 0.0; CG at 120 s: 3.65 ± 0.01). Post-storage, ACP-treated juices exhibited reduced lightness (L) and increased chroma (C), particularly at longer treatment times (150 s). TPC initially decreased with prolonged ACP exposure but increased post-storage, suggesting plasma-induced cell wall disruption facilitated phenolic release. Antioxidant activity remained stable in ACP-treated juices, in contrast to thermally pasteurized juices, which showed higher DPPH inhibition. ACP achieved limited reduction of A. acidoterrestris spores (1.06 ± 0.35 log CFU/mL with SA for 3 min) and had no significant effect on yeast/mold counts, which increased during storage. No bacterial growth was detected in ACP-treated juices, likely due to the acidic environment.