Summary of Activities at WSU in 2004
1. Three heating method comparisons
2. Preconditioning effects on thermal resistance of navel
orangeworm
3. Improving heating uniformity of fresh fruits
4. Mathematical modeling of RF treatments for walnuts
5. Publications
1. Three heating method comparisons
1. Three heating method comparisons (Cont.)
Temperature time histories of water in the screen metal tube (T1), water
(T2) and apple pulp (T3) in a copper tube together with those of the
heating block system (HBS) at heating rates of 5 and 10°C/min
1. Three heating method comparisons (Cont.)
Ramp-up time and equivalent heating times for different heating
methods
*
*0.6-0.24+0.42=0.78
1. Three heating method comparisons (Cont.)
Thermal mortality (meanSD, %) comparison of fifth-instar navel
orangeworm between using direct immersion, copper tube and
heating block system at a rate of 5°C/min at three temperature-time
combinations
1. Three heating method comparisons (Cont.)
Thermal mortality (meanSD, %) comparison of fifth-instar codling
moth between using direct immersion, copper tube and heating block
system at a rate of 5°C/min at three temperature-time combinations
2. Preconditioning effects on thermal resistance of NOW
Insect mortality after treatment at 50°C+12 min as a
function of preconditioning times at three temperatures
2. Preconditioning effects on thermal resistance of NOW (Cont.)
Arrhenius plot of the preconditioning time for the most
resistance versus the reciprocal of the absolute
preconditioning temperatures
3. Improving heating uniformity of fresh fruits
A fruit mover designed at WSU for oranges in RF systems
3. Improving heating uniformity of fresh fruits (Cont.)
Time temperature history of ‘Valencia’ orange subjected to HW48
and RFA35 (preheating in 35C water for 45 min followed by RF heating
in tap water for 2 min and holding at 48C for 15 min) treatments.
3. Improving heating uniformity of fresh fruits (Cont.)
Thermal images of oranges taken by the infrared imaging camera
during RF assisted hot water heat treatment at the end of preheating,
RF heating, and holding time
3. Improving heating uniformity of fresh fruits (Cont.)
• The quality of treated ‘Navel’ and ‘Valencia’ oranges were
evaluated after 10 days of 4C storage
• The quality parameters included: weight loss, loss in firmness,
color change, total soluble solids, acidity, and change in volatiles.
• The results showed that there was a significant change in
volatile flavor profiles upon RF heat treatments even when
there was no significant difference in the other quality parameters.
• The RF heat treatment (holding for 15 min in 48C hot water)
would meet the quarantine security without unacceptable thermal
damage to the quality of the treated oranges.
3. Improving heating uniformity of fresh fruits (Cont.)
Typical time-temperature history for surface and core of “Red Delicious” apples
(diameter: 8 cm) when subjected to preheating (45°C, 1 m/s), RF heating
(27.12 MHz, 6 kW) for 1.25 min, holding in hot water bath (48°C; 1 m/s)
for 20 min, and 30 min hydro-cooling.
3. Improving heating uniformity of fresh fruits (Cont.)
Thermal images for “Red Delicious” apple cross-sections when subjected to
preheating (45°C), RF heating for 1.25 min, holding in hot water bath
(48°C) for 20 min, and 30 min hydro-cooling
Preheating
Holding
RF heating
Cooling
3. Improving heating uniformity of fresh fruits (Cont.)
•All treatments (48°C for holding 10, 15 and 20 min) resulted in 100%
mortality of codling moth larvae (3 replicates).
•The quality evaluation of “Red Delicious” apples after those treatments
are going on with storage time of 7, 14, 30 and 60 days.
• Those protocols are going to be scaled -up.
3. Improving heating uniformity of fresh fruits (Cont.)
Experimental setup (a) and schematic
view (b) of continuous 25 kW RF-tube
systems for scaling-up studies
4. Mathematical modeling of RF treatments for walnuts
Schematic view of the pilot-scale 27 MHz radio frequency (RF) system used
to treat walnut sample and the infrared imaging system to measure product
surface temperature after RF treatment
4. Mathematical modeling of RF treatments for walnuts (Cont.)
Distribution comparisons of probability density frequency (PDF) of walnut
temperatures between normal (Norm.) and experimental (Exp.) distributions
after 3 min of RF heating without stirring
4. Mathematical modeling of RF treatments for walnuts (Cont.)
Distribution comparisons of probability density frequency (PDF) of walnut
temperatures between using 2 intermittent stirrings and no stirring after 3 min
of RF heating
4. Mathematical modeling of RF treatments for walnuts (Cont.)
Relationship between the rise in standard deviation and the rise in mean of
walnut kernel temperatures with (WS) and without (NS) mixing
4. Mathematical modeling of RF treatments for walnuts (Cont.)
Minimum number of stirrings predicted by the mathematical model as a
function of the mean temperature with different probability levels (p) for
walnut temperatures below the low limit temperature (L)
5. Publications in 2004
• Wang S., Johnson J.A., Tang J., and Yin X., 2005. Heating condition effects on thermal
resistance of fifth-instar navel orangeworm. J. Stored Prod. Res., in press.
• Wang S., Yue J., Tang J., and Chen B., 2005. Mathematical modeling of heating uniformity of
in-shell walnuts in radio frequency units with intermittent stirrings. Postharvest Biol. Technol.,
35(1): 97-107.
• Johnson J.A., Valero K.A., Wang S. and Tang J. 2004. Thermal death kinetics of red flour
beetle. J. Econ. Entomol., 97(6): 1868-1873.
• Hansen J.D., Drake S.R., Heidt M.L., Watkins M.A., Tang J. and Wang S., 2004. RF
treatments for postharvest codling moth control in fresh apples. HortTechnol., 14(4): 533-537.
• Gazit Y., Rossler Y., Wang S., Tang J., and Lurie S., 2004. Thermal death kinetics of egg and
third-instar Mediterranean fruit fly. J. Econ. Entomol., 97: 1540-1546.
• Hansen J., Wang S., and Tang J., 2004. A cumulated lethal time model to evaluate efficacy of
heat treatments for codling moth in cherries. Postharvest Biol. Technol., 33(3): 309-317.
• Birla S.L., Wang S., Tang J., and Hallman G., 2004. Improving heating uniformity of fresh
fruits in radio frequency treatments for pest control. Postharvest Biol. Technol., 33(2): 205-217.
• Mitcham E.J., Veltman R.H., Feng X., de Castro E., Johnson J.A., Simpson T.L., Biasi W.V.,
Wang S., Tang J., 2004. Application of radio frequency treatments to control insects in in-shell
walnuts. Postharvest Biol. Technol., 33(1): 93-101.
• Wang S., Yin X., Tang J., and Hansen J., 2004. Thermal resistance of different life stages of
codling moth. J. Stored Prod. Res., 40(5): 565-574.
Thanks!