Ripening manipulation of ‘Hass’ avocado with ethylene

The long ripening period of ‘Hass’ avocado fruits harvested at the beginning of the harvest can be detrimental to sales. Ethylene is capable of anticipating and accelerating the ripening of climacteric fruits and its application at temperatures between 17 and 20 °C is widely used in the industry to accelerate the ripening of ‘Hass’ avocados. There is no information in the literature about the effectiveness of ethylene when applied at lower temperatures. The main objective of this work was to evaluate the efficacy of ethylene application in accelerating the ripening of 'Hass' avocados harvested at the beginning of the season under treatment tempera- tures of 8°C and 20°C. In experiment I, freshly harvested fruits (n=192) were treated with 1,000 ppm ethylene for 48 hours at 8°C and then kept for 4 days at 8°C to simulate long-dis- tance refrigerated transport. Subsequently, they were stored for 0, 3, 6, or 9 days at 8 °C, and finally kept at 20 °C to simulate shelf life. In experiment II, freshly harvested fruits (n=192) were kept for 4 days at 8 °C to simulate long-distance refrigerated transport and then stored for 0, 3, 6, or 9 days at 8 °C. After the storage period, they were treated with 100 ppm eth- ylene for 24 hours at 20 °C and kept at 20 °C and 85% relative humidity to simulate shelf life. In the first experiment, the initial firmness of the fruits was 190 N and, after 4 days on the shelf, it was 4 and 100 N, respectively, for treated and untreated fruits, that were not stored. Optimum firmness for consumption ranges between 4 and 7 N. Fruits treated with ethylene and stored for 3, 6, and 9 days reached 5.5, 1.3, and 1.9 N of firmness in just 3 days at 20 °C, respectively, while the control reached 50.2, 17.7, and 12.9 N. For all storage times, control fruits showed greater weight loss, ranging from 2.3 to 5.5%, while the weight loss of treated fruits ranged from 1.3 to 2.6%. Control fruits that were stored for 0, 3, and 6 days required, respectively, 4.9, 3 and 2.2 days longer to ripen than treated fruits. Application of ethylene at 8 ℃ accelerates the ripening of ‘Hass’ avocado by up to 4.9 days, and as the fruit ages from harvest, it takes fewer days to ripen when transferred from 8 °C to 20 °C. In experiment II, the number of days for maturation and firmness were affected by ethylene only for 0 and 3 days of storage. Fruits stored for 0 and 3 days at 8 ℃ and treated with ethylene took, respectively, 1.7 and 2.0 days less to ripen than control fruits. Avocados not stored and treated with ethylene reached 48.6 N firmness after 6 days on the shelf, while control fruits had 101.2 N in the same period. Avocados stored for 3 days and treated with ethylene reached 11.9 N in just 3 days on the shelf, while control avocados exhibited 122.4 N. Control fruits showed greater weight loss compared to treated fruits in all periods of refrigerated storage evaluated. Application of ethylene at 20 ℃ accelerates the ripening of ‘Hass’ avocado by up to 2.0 days, and as the fruit ages since harvest, it takes fewer days to ripen when transferred from 8 °C to 20 °C. Keywords: Persea americana Mill.; Ripening control; Ethylene; Cold storage; Pre- conditioning.