Thermal and non-thermal treatments of stone and pome fruit: Towards efficient phytosanitary measures

Conventional postharvest ensures microbiological safety via sterilization however at the cost of partial loss in qualities and crucial public safety concern due to residues. Thus, the aim of this proof-of-concept project is to investigate alternative non-thermal treatments as effective alternative treatment in stone and pome fruits depending on applicability.

Non-thermal postharvest technologies such as electrolyzed water (EW) and microwave (MW) treatments were done to investigate their potential to control decay and maintain quality of apple and nectarine. Cold plasma (CP) optimization trial study was done to find out its decontamination potential for fresh apple and nectarine fruit.

WP1:(A). The EW treatments against B. cinerea resulted in a significant (P ≤ 0.05) reduction in lesion zones in apple. Curative efficacy was most effective at concentrations of 200-500 mg L^-1 for 5 °C and 300-500 mg L^-1 at 24 °C.

WP1:(B). EW treatment of 300 mg/L and treatment time of 10 and 15 min for nectarines resulted in complete inhibition of surface decay compared to 100 mg/L and 200 mg/L concentrations at 10, 15 min treatment time at 1 °C for 21 days.

WP2: MW treatment was effective to maintain quality, eliminated pesticides and/or herbicide derivatives, whereas, chlorine treatment was most effective to inhibit microbial growth.

   WP3: Highest plasma glow discharge was generated at >50 kV. and successfully treated apple and    nectarine fruit without in package with no visible negative effect on the fruit quality.

Electrolyzed water and cold storage has a synergetic effect to eliminate microbial growth and preserve good quality of apple and nectarine.

Microwave treatment showed potential to degrade chemical residues, maintain quality attributes and retard microbial growth on ‘Sunectwentyone’ nectarine stored at 2 °C.

Cold plasma parameter optimization (50 – 80 kV and 5 and 10 min) successfully maintained the visual quality of treated apple and nectarine fruit with or without package.

EW treatment demonstrated the potential as an alternative to chlorine treatment to eliminate fungal growth on fruit. However, optimization of EW concentrations for a specific fruit type is necessary.

Microwave sterilization has an impact on removing pesticide residue/chemicals, but care must be given to the treatment time and duration to avoid the increase in core temperature of the fruit.

Based on the outcomes of this proof of concept, there is a great opportunity for the industry to move away from the use of chlorinated water in the pack-houses.