Optimization of postharvest ultrasonic treatment of kiwifruit using RSM

• The kiwifruits are highly susceptible to spoilage microorganisms.
• Ultrasonic intensity has strong influence on surface microbial reduction.
• Ultrasound treatment increases the post-harvest shelf life of kiwifruits.

This study reports the optimization of ultrasonic treatment combined with sodium hypochlorite (NaOCl) solution on kiwifruit (Actinidia deliciosa) to evaluate its effect on microbial population, respiration rate and its textural quality. Response surface methodology (RSM) based on four factors three level central composite design was applied to investigate the effects of process variables on ultrasonic treatment. Four independent variables include ultrasonic intensity (184–368 W/cm2), temperature (25–40 °C), treatment time (8–15 min) and concentration of the solvent (30–60 ppm) were considered for this study. According to RSM analysis, the optimal treatment parameters obtained were ultrasonic intensity (368 W/cm2), temperature (25 °C), treatment time (8 min) and concentration of the solvent (30 ppm). Microbial population, respiration rate and some quality parameters were compared with NaOCl treated kiwifruits. An ultrasound combined with NaOCl was found to be the most effective treatment in inhibiting the microbial growth (bacteria, yeast and mold) and preserving the quality of kiwifruits, and these results suggest that the ultrasound treatment may provide an alternative for extending the shelf life of whole kiwifruit, maintains the quality of fresh cut kiwifruits and further increases the shelf life of chitosan coated fresh cut kiwifruit.