Effects of CaCl2 dipping and pullulan coating on the development of brown spot on ‘Huangguan’ pears during cold storage

Brown spot disorder is a disorder that limits the storage life of the ‘Huangguan’ pear (Pyrus pyrifolia, Nakai). This study aimed to evaluate the effects of postharvest dipping with 2% CaCl2 and coating with 1% pullulan on the development of brown spots during eight months of cold storage at 0 °C. Analysis of calcium extracted using different solvents indicated that fruit dipped with CaCl2 had the highest concentrations of total calcium, water-soluble calcium, calcium pectin and calcium oxalate. Fruit coated with pullulan also had higher concentrations of water-soluble calcium, calcium pectin and calcium oxalate than control fruit, although the total calcium and calcium phosphate concentrations were similar to those of control fruit. Both treatments reduced the incidence of brown spots, inhibited the activities of PPO (polyphenol oxidase) and POD (peroxidase), increased the activities of CAT (catalase) and SOD (superoxide dismutase), and delayed the loss of phenolic compounds, compared with untreated controls. Concomitantly, concentrations of α-farnesene, CTs (conjugated trienes), and MDA (malondialdehyde) were maintained at lower levels in most tissues of treated fruit compared with those of control fruit. These results suggest that both CaCl2 and pullulan treatments inhibited the development of brown spots on ‘Huangguan’ pear by delaying the loss of the polyphenol substances and maintaining the structural integrity of cell membrane.