Ripening of Kiwifruit following Simulated Brushing with Commercial Brushes

Brushing of `Hayward' kiwifruit [ Actinidia deliciosa (A . Chev.) C.F. Liang et A. R . Ferguson var. deliciosa ] to remove trichomes reduced their marketable life. Fruit were brushed with polypropylene brushes having bristles of 0.60, 0.50, 0.30, and 0.25 mm in diameter. The two smallest-diameter bristles removed about 0.1 g of trichomes per fruit. The larger diameter bristles removed 12% more material, including some surface tissue particles. Brushing accelerated ripening during subsequent storage of fruit for 4 days at 4C as indicated by increases in ethylene production and soluble solid concentration and a decrease in firmness. The larger the bristle diameter, the greater the acceleration of ripening. The largest diameter did not accelerate ripening as much as 0.50-mm bristles due to the lower resistance to bending (0.85 N and 2 N for 0.60- and 0.50-mm bristles, respectively) and their greater length. Small surface wounds, visible under the microscope, may have caused the higher ethylene evolution and the consequent ripening response.