Impact of relative humidity on ethylene removal kinetics of different scavenging materials for fresh produce industry

Active ethylene scavenging in fresh produce involves the use of adsorbers and oxidizers, such as, potassium permanganate, activated carbon, clays and zeolites, often integrated as sachets, labels, liners, or films. Although many studies have been done to develop novel ethylene scavengers, only a few of them have analyzed the ethylene removal kinetics, especially under different humidity conditions. Kinetic studies can provide information on the ethylene removal rate and ethylene removal at equilibrium which can be highly useful in assessing the efficacy of the scavenger. The main objective of this study was to investigate the ethylene removal kinetics of different scavenging materials at various relative humidity (RH) conditions (0%, 50%, and 100%) at a fixed temperature (13 °C). The active scavenging materials investigated in this study included two commercially available, (potassium permanganate-based and basolite) and three chemically-modified ones (surface modified zeolite with potassium permanganate; surface modified zeolite with zinc, copper and silver; and plasma surface modified titanium dioxide with palladium). Kinetic experiments were conducted with the scavengers placed inside air tight glass jars (1 L) with an initial ethylene concentration of 10 µL L⁻¹. The data obtained was fit to Lagergren pseudo first order kinetic model. Potassium permanganate-based scavengers displayed the highest ethylene removal (~ 8.7–10 mL kg⁻¹) at all three RH conditions. Whereas basolite, zeolite modified with copper, zinc and silver and titanium dioxide modified with palladium were found to be efficient at 0% RH, however, at 50% and 100% RH, a prominent ethylene desorption was observed. Furthermore, a case study of packaging of blueberries with selected scavengers was performed. Blueberry packages containing potassium permanganate and zeolite modified with potassium permanganate had the minimum ethylene concentration of 0.012 ± 0.01 and 0.004 ± 0.00 µL L⁻¹, respectively, at the end of 14 d storage.