Walnut Tasting
S. Wang, J. Tang, J.A. Johnson, E. Mitcham, J.D. Hansen, R.P. Cavalieri, J. Bower, B. Biasi
2002
Common in-shell pests of walnuts include the navel orangeworm, codling moth, and Indian meal moth. An initial objective of this study was to determine the most heat tolerant life stage for the navel orangeworm; experiments determined that stage to be the fifth instar. Previous studies indicated that other pests, codling moth and Indian meal moth, are less heat tolerant, so a protocol effective on fifth instar navel orangeworm would be effective for all three species.
A further goal was to develop a practical treatment protocol to control the targeted insects using RF energy and to study the impact of these treatment protocols on walnut quality. A pilot-scale RF system was used to apply various heating protocols to walnuts, pre-infested with navel orangeworm larvae. All protocols killed the larvae. We found no negative quality effects on the walnut kernals. A tasting panel did not detect any difference between treated and untreated walnuts.
A fiber-optic sensor measures kernel temperature
Juming Tang, Shaojin Wang, James Hansen, Judy Johnson, Elizabeth Mitcham, Steve Drake, Guy Hallman
2003
An important key to the development of successful thermal treatments is to identify a delicate balance between minimized thermal impact on product quality and complete killing of insects. The objective of this study was to develop postharvest treatments using RF energy to control common insect pests of in-shell walnuts and cherries based on thermal death kinetics studies of these pests.
To study the thermal death kinetics of pest larvae within nuts, a heating block system with RF as the heat source was used. Embedded fiber optic sensors measured the temperature within the nut. Results indicated that 100% insect mortality could be achieved with no measurable effect on walnut quality.
12kW, 27MHz RF unit in Postharvest lab
E.J. Mitcham, R.H. Veltman, X. Feng, E. de Castro, J.A. Johnson, T.L. Simpson, W.V. Biasi, S. Wang, J. Tang
2004
Heating walnuts using RF treatments to 55 degrees C. or higher resulted in 100% mortality of fifth instar navel orangeworm, which is the most resistant of the three common insect pests. RF treatments slightly reduced the moisture content of walnuts, but this did not affect quality indices. A combined system of radio frequency heating with hot air has the potential to accelerate or even replace batch drying of walnuts.