The effects of delayed cooling (DC) at 20 ºC for 6 days before cold storage was studied in 'Constanza' plums evaluating development of quality and chilling injuries. At the end of the DC treatment the plums were cold stored at 0 ºC for 7, 14, 21, 28, 35 or 42 days or at 5 ºC for 7, 14 or 21 days and evaluated at harvest, after cold storage periods and after a ripening period at 20 ºC. The control fruits were stored at 0 or 5 ºC. Weight loss was low during storage at 0 or 5 ºC and increased during ripening periods. Firmness changed little in control plums at 0 ºC while in DC plums decreased constantly up to 28 days. Delayed cooling treatment resulted in significant decreases of firmness of plums stored at 5 ºC, which presented 50% of fruit with unacceptable firmness for commercialization after the ripening periods starting from 7 days of storage. Extractable juice was higher in DC fruit than in control fruits at 0ºC, but there were no differences in juiceness in plums stored at 5 ºC. Woolliness was visualized at ripening in DC and control fruits stored at 0 or 5 ºC without differences among treatments. At ripening, control fruit presented internal browning after 42 days at 0 ºC and leatheriness after 28, 35 and 42 days at 0 ºC. Delayed cooling induced an increase of the percentage of healthy fruit after 28, 35 and 42 days at 0 ºC.
Stone fruits; plum; conditioning; cold storage; chilling injury
