Impact of packaging materials on bruise damage in kiwifruit during free drop test

Inappropriate packages and packaging materials are the main causes of bruise damage in the postharvest handling of kiwifruit. This study was conducted to identify the suitable materials to be used as collection box during sorting and grading of kiwifruits. Three different materials of box, wooden box, high-density polyethylene (HDPE) box, and expanded polystyrene (EPS) box were used to simulate kiwifruit dropping in grading line. Among three treatments, the lowest weight loss (4.6%) was observed in the EPS box surface-impacted fruits, the bruise index and bruise area of fruits from EPS box were 36.2% and 47.1% less than that of wooden box, respectively. Furthermore, the peak level of ethylene production and respiration rate of fruits from EPS box was 32.6%, 28.9% lower than that of wooden box, respectively. Compared to wooden box and HDPE box surface, EPS box surface slowed softening, reduced electrolyte leakage and malondialdehyde accumulation. Additionally, lower bruise damage by the EPS box surface was also displayed in physiological attributors including hydrogen peroxide (H2O2), superoxide anion (O2–) and the activities of antioxidant enzymes. The collective data indicated that the EPS box surface reduced the adverse physiological changes caused by dropping of kiwifruit. These results indicated the potential of EPS as packaging material of collection box in grading line to reduce bruise damage and to preserve the quality of kiwifruit.