Reduction of peduncle detachment surface discoloration in Ananas comosus L. By pre-harvest spraying with potassium phosphite

Abstract

Peduncle detachment surface discoloration (PDSD) in fresh pineapple fruit has rendered serious economic losses in pineapple exports from Taiwan. This experiment was conducted to investigate the post-harvest PDSD process and to evaluate the effect of potassium phosphite (KPhi) solution on pineapple PDSD and fruit quality. PDSD often start to appear in pineapple fruit, especially at room temperature (25 degrees C), quickly between 3 and 4 days after harvest. To evaluate its efficacy in controlling pineapple PDSD, KPhi was sprayed on pineapple leaves at the pre-harvest stage, at four concentrations: 0 (control), 2 g.L-1, 4 g.L-1, and 10 g.L-1. All treated fruits were stored at 18 degrees C and 80-90 % relative humidity for 1 week and then shift to room temperature (25 degrees C) for 4 days to simulate the transportation and shelf-life conditions of exported pineapples. The results showed that KPhi treatment significantly reduced the severity of PDSD compared to that of control (water-only spray). All the KPhi treatments did not affect the total soluble solid content significantly. A pre-harvest spray of 10 g.L-1 resulted in better skin color but yielded the worst crown leaf condition and shell appearance of the just-harvested fruit, however, with no significant difference from the control in skin color or shell appearance after the export condition simulation. Most of the fruit characteristics for the other two KPhi treatments were better than those of the control and 10 g.L-1 treatments. The results indicate that pre-harvest KPhi spraying at 4 g.L-1 is well expected and suggested as a good alternative fungicide treatment to maintain and ensure good pineapple fruit quality for export.