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

lanchabilities as well as a longer raw peanut shelf life. It has been suggested that
the mechanism of blanching is due to differences in thermal expansion and
subsequent contraction of the seed and seed coat, resulting in a loosening of the
seed coat. In an experiment by Paulsen and Brusewitz (1976), the difference
between the coefficients of cubical thermal expansion of seeds (50 – 60.5 x 10 -5 /°C)
and that for peanut skins (26.5 – 55 x 10 -5 /°C) grew larger at lower moisture
contents. As a result, this explains why peanuts which reached the lowest moisture
content were the most effective treatments for blanchability. In fact, in another
study, Paulsen and Brusewitz (1976b) determined that the effectiveness of
blanching was dependent mainly on the degree of moisture removal, although
Adelsberg and Sanders (1997) did not see an increase in blanchability at moisture
contents below 3.8%. Instead, Adelsberg and Sanders (1997) determined that
differences in blanchability may be affected by thermal expansion or variations in
moisture loss, or possibly a combination of factors. This study was also not able to
separate these factors of temperature and final moisture content, although initial
moisture content does not appear to have much effect on blanchability.
An interplay of temperature and moisture loss must be responsible for the high
rates of blanchability seen in the 8NF treatment. Although this treatment absorbed
significantly less energy and reached lower temperatures than the 11NF treatment
and the peanuts in Set 2, it reached a level of blanchability above the 85% standard.
In order to investigate this, the maximum internal temperatures during processing
were also evaluated, and were found significantly different (p < 0.0001) for each
treatment (Table 3). In this comparison, the maximum temperature of the 8NF
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