Radio Frequency Heating of Persimmon and Guava Fruit as an Alternative Quarantine Treatment

in HortScience
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  • 1 Univ. of California, Davis, Pomology, Davis, CA 95616
  • 2 Univ. of California, Davis, Pomology, Davis, CA 95616
  • 3 Washington State Univ., Dept. of Biological Systems Engineering, Pullman, WA, 99164
  • 4 Washington State Univ., Dept. of Biological Systems Engineering, Pullman, WA, 99164
  • 5 USDA, USDA-ARS Crop Quality and Research Laboratory, Weslaco, TX 78596
  • 6 Univ. of California, Davis, Pomology, Davis, CA 95616

The Mexican fruit fly infests many tropical and subtropical fruits, consequently fruits must be treated for quarantine security. Although chemical fumigations are the most common quarantine treatments, interest in using cold and heat treatments has increased due to concerns over environment and human health. Recently, shorter heat treatments such as those provided with radio frequency (RF) energy have been studied on walnuts and various fresh fruits as a possible quarantine treatment. Preliminary studies with a heating block system showed that reaching temperatures of 50 °C with a holding period of 2 min. or 48 °C for 6 minutes was required to achieve 100% insect mortality of 600 third instar Mexican fruit flies (the most heat resistant insect stage). Doubling the holding time required to achieve 100% insect mortality would likely be necessary to provide for Probit 9 security. Fresh fruits such as persimmons and guavas are commonly infested by the Mexican fruit fly. Persimmon and guava fruit were treated with RF energy to temperatures ranging from 48 to 52 °C at different holding periods. After treatments fruit were evaluated for external appearance, decay, soluble solids, titratable acidity, internal flesh quality, and ethylene production and respiration rate. Persimmon fruit tolerated the lower temperature, 48 °C for up to 18 min., but temperatures above 50 °C for more than 1 minute caused internal damage. Preliminary studies with guava indicate that fruit may tolerate 50 °C, but fruit quality after storage is still to be evaluated.

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