RATO, A.E.; BARROSO, J.M.    AGULHEIRO, A.C.. Ethylene production by ‘Prunus domestica’ plums during storage at two different temperatures. []. , 30, 1, pp.331-338. ISSN 0871-018X.

Low temperatures interacts with ethylene biosynthesis and ripening in many species. Exposure fruits to low temperatures promotes ethylene biosynthesis in a number of apple and pears cultivars because low temperatures stimulates ACC synthase activity after fruits being warmed up.. Some pears and apples varieties required a cold treatment to achieve good colour, acceptable texture and flavour. In ‘Prunus domestica’ plums cv ‘Raínha Claudia verde’, a climacteric fruit, there is little information about ripening process but we observed after a cold storage period a decrease in ethylene production upon rewarming. The longer the storage period the stronger the depress in ethylene biosynthesis. This cultivar is usually stored at 0-2 ºC, it has small commercial period because of its short postharvest life. In cold chambers fruits became soft very quickly and improper to commercialise. The aim of this study was to compare the effect of two different storage temperatures (1 ºC and 7 ºC ±1º) during 0, 2, 5, 8, and 14 days in ethylene production upon rewarming of ‘Raínha Claudia Verde ‘plums. It was also studied, during cold storage, the evolution of fruits softening rate, % acidity and SSC (soluble solids content). Upon rewarming, it was observed at end of storage period (14 days), in fruits held at 1 ºC, a decrease in ethylene production, relative to controls. In fruits held at 7 ºC the storage period didn’t affected the maximum ethylene production, 0,3 nl/g/h.. A short period of cold (2 days at 7 ºC) induced an enhancement of ethylene production relative to fruits held at 20 ºC. SSC and % acidity showed an expected evolution. At end of storage period fruits showed a higher SSC and lower % acidity due to metabolic processes and transpiration. Fruits held at 7 ºC showed a higher SSC and a lower % acidity than fruits held at 1 ºC. Fruit firmness decrease during the storage period. Fruits held at 7 ºC remained significantly firmer after 14 days storage than fruits held at 1 ºC. Despite SSC and % acidity evolutions suggests that fruit storage conditions are better at lower temperatures, fruits held at 7 ºC showed a lower softening rate and a higher ethylene production rate than fruits held at 1 ºC. The role of ethylene in softening and ethylene cold induction of this cultivar may be clarified by future research on ACC oxidase and ACC synthase and in ethylene sensitivity.

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