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

exposed to the fan to be approximately 10 °C lower than the rest of the peanuts.
This temperature difference was greater in treatments conducted at higher
temperatures, reaching a 17 °C difference in treatments conducted at 98.9 °C
(Adelsberg and Sanders 1997). The difference in the temperatures between the
longer treatments in this study conducted with and without a fan were somewhat
larger, but they were also conducted at much higher temperatures used in
microwave blanching.
In Set 2, the lowest moisture peanuts reached the highest temperatures (Table 2,
Fig. 3). Although all treatments in Set 2 exceeded 100 °C, peanuts in the 5 % MC
treatment had the highest internal temperature (139 °C), followed by 7 %, 9 %, and
11 % MC treatments. The typical temperature profile which is seen in materials
dried using microwave technology has three separate regions: an initial heating
region in which the temperature of the material reaches the wet bulb temperature; a
constant temperature drying region, in which most of the liquid is vaporized and
moves through the sample; and a third region in which the temperature increases
without any further removal of liquid (Metaxa and Meredith 1983). Peanuts with
lower initial moisture contents (5% and 7%) did not absorb as much energy during
processing, because of the relatively lower amounts of polar components in the
sample. However, these low moisture peanuts may be progressing through this
drying curve more quickly as they soon reach an equilibrium moisture content during
the constant drying region. As a result, they spend more of the processing time in
the third region of the curve, increasing in temperature.
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