Ethylene biosynthesis and ripening behaviour of ‘Hayward’ kiwifruit subjected to some controlled atmospheres

Abstract

The effects of storage in air (AS), controlled atmosphere (CA) or ultra low oxygen (ULO) on ethylene biosynthesis and ripening of ‘Hayward’ kiwifruit during storage at 0 °C and post-storage at 20 °C, were investigated. Fruit were stored for 60, 120 and 180 days at 0 °C in AS, CA (2%O 2 +5%CO 2 ) and ULO (0.7%O 2 +0.7%CO 2 and 1%O 2 +1%CO 2 ). Freshly harvested fruit and fruit removed from storage were treated with 130 μl/l propylene or propylene-free air for 9 days at 20 °C. Fruit treated with propylene at 20 °C at harvest produced ethylene with a lag period of 3 days, had concomitant 1-aminocyclopropane-1-carboxylic acid (ACC) production, 1-aminocyclopropane-1-carboxylate synthase (ACC synthase) and 1-aminocyclopropane-1-carboxylate oxidase (ACC oxidase) activities, and were ripe after 3–5 days while fruit not treated with propylene were not able to produce ethylene and ripen during the 9 days experiment. AS fruit softened faster during the first 60 days of storage. This effect was reduced in CA and ULO treatments. The soluble solids content (SSC) increased markedly during the first 60 days of storage and remained almost constant thereafter in all treatments. After 9 days shelf life, only AS and CA stored fruit were ripe. Fruit from ULO storage required propylene treatment to ripen fully. When kiwifruit were placed at 20 °C, after 60, 120 or 180 days storage at 0 °C, there was an induction of ethylene production with no lag period in fruit from AS or CA, with or without propylene. There was some ACC content and ACC synthase activity after 60 days storage for all treatments, while ACC oxidase activity increased only upon rewarming of the fruit in AS or CA. Kiwifruit removed from ULO-storage showed drastically reduced capacity to produce ethylene mainly due to low ACC oxidase activity rather than reduced ACC production or ACC synthase activity. Respiration increased upon rewarming of the fruit in all treatments. With storage time, there was a decrease in the capacity of the warmed fruit to produce ethylene and CO 2 as well as in the activities of ACC synthase and ACC oxidase, mostly after 60 days storage.