Combined effects of chlorine dioxide, plasma-processed air, and modified atmosphere packaging on safety and quality of fresh walnuts.

Fresh walnuts are highly perishable after harvest. This work explored hurdle treatment of chlorine dioxide (ClO₂), indirect plasma-processed air (IPPA), and modified atmosphere packaging (MAP) on fresh walnuts with/without husk. Combining IPPA with 10 mg L-1 ClO₂ reduced mold counts by up to 2.06 log CFU g-1 and decreased ClO₂ usage by 80% compared to 50 mg L-1 ClO₂ alone. Subsequent integration with active or passive MAP extended shelf life from 60 to 120 days. A critical storage threshold was identified at day 60, where preservation efficacy among treatments began to diverge significantly. At this point, active-MAP reduced mold incidence by 88.4% or 77.8%, acid value by 0.29 or 0.31 mg KOH g-1, and malondialdehyde by 14.98 or 10.76 nmol g-1 in walnuts with/without husk, respectively. Husk presence initially reduced water loss and conserved fat, but its role reversed after 60 days, promoting discoloration and hydrolytic rancidity, thereby driving overall deterioration.