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

finish the constant drying region of the temperature profile. Since the lower moisture
peanuts reached this point more quickly, they entered the third phase in the
temperature profile, and reached higher temperatures during processing than the
9% and 11% peanuts (Table 2, Fig. 3). It has been noted that it is difficult to remove
tightly bound water using microwaves, because of the low absorption of energy by
the residual liquid (Metaxas and Meredith, 1983). As a result, the 4% moisture level
may be at a transition between free and bound water in the peanuts, which would
impede further moisture loss during processing at the conditions studied.
Blanchability. Treatments had a significant effect on blanchability
(p < 0.0001). Individually, the treatments of 8NF, 11F, and 11NF were not
significantly different from each other (Fig. 5) but were more blanchable than the
other treatments (p < 0.05). Only 8NF and 11NF consistently exceeded the industry
standard of 85 % blanchability in Set 1, and all variable moisture content peanut
samples in Set 2 exceeded the standard (Fig. 6). In addition, the peanuts with initial
moisture content of 5 % were significantly higher in blanchability (average = 93 %)
than the other 3 lots for each replicate. To ensure that the initial ambient air drying
step for peanuts in Set 2 did not affect blanchability, controls for each moisture
content were also examined, and blanchability was found to average 1 %.
High blanchability resulted from higher process temperatures and lower final
moisture content, with those treatments exceeding 110 °C and reaching a final
moisture content of 5.5 % or below yielding blanchability greater than 85 % (Fig. 7).
Similarly, Rausch et al. (2005), when blanching individual trays of peanuts, found
that microwave treatments resulting in 0.5 – 1.0 % moisture loss provided better
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