THE EFFECT OF SEASONALITY, MATURITY AND COLOUR TREATMENTS ON INTERNAL BROWNING IN ´PINK LADY´™ APPLES

Abstract

Since 2000, internal browning has been observed in controlled atmosphere stored 'Pink Lady' apples originating from Tasmania. This problem is not usually apparent in fruit immediately after removal from controlled atmosphere, but manifests itself during transport to distant markets. During the 2000 export season, several containers of fruit originating from Tasmania were condemned upon arrival in Europe due to this disorder, causing severe financial losses to growers and marketers, as well as detrimental effects on the marketing program. Internal browning is located in the outer cortex of the flesh; the discolouration can range from a slight grey tinge to a dark brown that follows the vascular traces toward the core of the fruit. Trials over the past four years have shown that this disorder is seasonal and affected by fruit maturity. In the five years studied there has been a yearly variation from 2% to 50% incidence. Fruit maturity appears to be a fundamental factor in the occurrence of internal browning; fruit picked 3 weeks before commercial harvest have a large reduction in the incidence of internal browning and are acceptable in the marketplace. The problem is that fruit are picked over-mature to improve the red colour of the skin, due to supermarket specifications, so trials were conducted to improve fruit colour. These indicated that cincturing, summer pruning, Regalis® and reflective cloth all improved fruit colour. They also significantly increased the incidence of internal browning; however, cincturing had a much greater incidence of internal browning than the other treatments. Importantly, reflective cloth significantly increased colour over the other treatments without advancing maturity, therefore, reflective cloth may be used to improve fruit colour and allow the commercial harvest to be conducted 2-3 weeks earlier to minimise internal browning in Tasmanian 'Pink Lady' apples.