Effect of heat shock and quarantine cold treatment with a warm temperature spike on survival of Mediterranean fruit fly eggs and fruit quality in Hawaii-grown `Sharwil' avocado
Eric B. Jang, Harvey T. ChanJr , Kate A. Nishijima, Janice T. Nagata, Michael P. McKenney, Lori A. Carvalho and Esther L. Schneider
Postharvest Biology and Technology Vol: 21 Issue: 3 Pages: 311-320
2001
บทคัดย่อ
The effects of a transient (warming) temperature spike on efficacy of an APHIS approved quarantine cold treatment, T107 (a), against Mediterranean fruit fly, Ceratitis capitata, was tested on Hawaii grown `Sharwil' avocados. Avocados infested with late stage eggs were subjected to a warming temperature spike (ca. 4.2°C for 1 h) at 6¯9 days into the treatment and subsequently allowed to resume the treatment until conclusion (12 days at <1.1°C, 14 days at <1.67°C or 16 days at <2.2°C). Insertion of a ca. 4.2°C temperature spike into the treatment at 6¯9 days had no effect on the efficacy of the quarantine cold treatment when fruit were allowed to resume the treatment to completion. Infested fruit which did not receive a `heat shock' treatment (recommended to improve fruit quality) and subjected to cold treatment for 6¯16 days at either <1.1, <1.67 or <2.2°C (fruit center temperature) had no survivors in the fruit by the 9th day of cold treatment. Infested avocados subjected to a `heat shock' treatment for 10¯12 h at 38°C prior to cold treatment (as above) had no survivors in the fruit by the 8th day of cold treatment. Results of this study indicate that a transient (warm) temperature spike of ca. 4.2°C of the type experienced during an in-transit cold treatment of Hawaii grown `Sharwil' avocados will not compromise the efficacy of the treatment. This study also reconfirmed that the T107 (a) cold treatment (as stated in the APHIS treatment manual) is efficacious against Mediterranean fruit fly eggs in `Sharwil' avocados, and that use of a `heat shock' to prevent chilling injury during the cold treatment did not extend survivorship of fruit fly eggs. Studies on the effects of prolonged (18¯28 day) cold storage on fruit quality indicated that avocados can be stored at quarantine cold temperature (pulp, 1.1¯2.2°C) for up to 24 days without significant loss of external and internal quality compared to fruit quality at 12¯16 days storage. Also, shelf life, Gray Flesh discoloration (of internal tissue), and disease were not affected by the prolonged storage duration.