Abstract SCHIRACK, ANDRIANA VAIS. The Effect of Microwave ...

RESULTS AND DISCUSSION
Energy Absorption. Microwave blanching involves the generation of heat by
the selective absorption of electromagnetic energy by water molecules and ionic
materials, as reflected in the dielectric properties of the material. In this study, all
treatments were statistically different in the amount of energy absorbed during
microwave blanching (p < 0.0001), although a significant effect occurred within
replicates in Set 1 only. Peanuts in the 11 minute exposure treatment absorbed the
most energy overall (Fig. 1). All other exposure times were significantly different (p
< 0.05) from each other, and the use of a fan made no difference. The amount of
power absorbed depends on the intensity of the electric field, as well as the dielectric
properties of the material. This is often expressed by the equation:
P=2Πfε0E 2 ε”
where f is frequency (Hz), E is electric field intensity (v/m), ε” is the dielectric loss
and ε0 is the dielectric constant of free space (8.854 farad/m). Although the
dielectric properties of shelled peanuts at these experimental conditions are not
found in the literature, Trabelsi and Nelson (2004) found that at frequencies of 12 to
18 GHz, shelled peanuts at 5.1% moisture content had a dielectric constant (ε’) of
2.1 and dielectric loss (ε”) of 0.11. Boldor et al.(2004) found a range of dielectric
constants of 4.5-10 and dielectric loss values from 1.25-2.75 in peanuts at 18-33%
moisture content (dry basis), respectively. Although the dielectric properties will
decrease with frequency and increase with higher moisture content, these studies
give a general range of values for the conditions in this study. These values for
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