M. M. C. Tsang

Hot-air induced thermotolerance of red ginger flowers and mealybugs to postharvest hot-water immersion.

Abstract Vase life of red ginger flowers, Alpinia purpurata (Vieill.) K. Schume, subjected to postharvest hot-air conditioning (40°C, 64% r.h.) for 2 h prior to hot-water immersion (49°C for 12 min) equaled or exceeded the vase life of red ginger treated in hot-water immersion only and control flowers in 96% of the trials conducted during a one year period. Reduced flower quality (marketability) (13% of trials) and reduced vase life (4% of trials) from hot-air and hot water treatments occurred in months with high rainfall (≥58 cm month−1) or drought (≤5 cm month−1). Flowers conditioned in hot air before hot-water immersion tolerated 49°C water for up to 13 min, exceeding a proposed 12 min treatment time with no significant loss in vase life or marketability. No apparent benefits were observed for conditioning flowers longer than 2 h in hot air. Hot-air conditioning prior to hot-water immersion increased mealybug survival by 0.4–40%.

HOT AIR TREATMENT FOR CONTROL OF BACTERIAL WILT IN GINGER ROOT

Pseudomonas solanacearum, the pathogen causing bacterial wilt in ginger root, was eliminated when exposed to heat for 30 min at 50°C (122°F) and 45 min at 49°C (120°F), respectively. Exposing ginger seedpieces to hot air at 75% RH until their center temperatures attained 49°C (120°F) for 30 and 60 min and 50°C (122°F) for 30 min, resulted in minimal injury to the hosts. More than 87% of the seedpieces germinated without adverse effect on growth. Rhizomes harvested from plants grown from seedpieces inoculated with P. solanacearum, and subsequently heat treated with hot air at the above time and temperatures, tested negative for P. solanacearum. Heat treatment with 75% RH heated air may prove to be a convenient method to disinfect ginger seedpieces of the bacterial wilt pathogen.

Heated Air Treatment for Meeting Quarantine Regulation with Bulk Papaya Fruits

Papaya fruits were loaded in specially-built bins and treated with heated air to meet quarantine regulations. Two different bin configurations were tested for temperature distribution in the fruit mass. Fruit quality and moisture loss were evaluated. A fruit column of less than 0.6 m (24 in.) produced an acceptable thermal gradient in the fruit mass. Heat treatment was not deleterious to fruit quality.