ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

Radio frequency heating of walnuts and sweet cherries to control insects after harvest

Mitcham E.J.; Tang J.; Hansen J.D.; Johnson J.A.; Monzon M.E.; Simpson T.; Bikoba V.; Biasi B.; Wang S. and Feng X.

5th International Postharvest Symposium . Volume of Abstract . Verona, Italy 6-11 June 2004, p.112

2004

บทคัดย่อ

 Radio frequency (RF) heating has been explored as a potential non-chemical method to control insects in harvested walnuts and as a quarantine treatment for ‘Bing’ sweet cherries. Walnuts (2.5 kg) were heated until the walnuts reached 50 to 90°C. Heating walnuts to 55°C or higher resulted in 100% mortality of navel orangeworm. Heating walnuts with RF energy to 80°C had no negative effects o­n walnut quality. Moisture content had a significant influence o­n the heating rate of the walnut kernels. For industrial applications, walnuts could move o­n a conveyor through o­ne or more RF systems with mixing of nuts between systems.

‘Bing’ sweet cherries (50) were heated in a polyethylene container holding 10 L of circulation distilled water with 2.3 g of NaCl. Fresh fruit must be treated in a saline solution to prevent burning at fruit contact points, and circulation improves heating uniformity within the RF field. Cherries were equilibrated in 35°C water for 6 minutes, then heated with RF energy to target temperatures between 50 and 54.5°C and held for 0.5 to 6 min. before hydro-cooling. Fruit were stored for 1 day at 5°C or 14 day at 0°C to simulate air or sea shipment, respectively. Shorter treatments at higher temperatures were better tolerated than longer treatments at lower temperatures. Cherry fruit infested with codling moth larvae were subjected to the same treatments. Mortality was 100% in all treatments except those at 50°C. However, fruit quality was unacceptable following sea shipment and marginal following air shipment. Treatment times would be significantly longer to provide for Probit 9 security (99.9968% population mortality) required for export to Japan and therefore RF treatments do not appear promising for sweet cherry fruit.