the shrinkage of the blanched
banana samples was significantly higher than that of
unblanched samples; the shrinkage of the blanched samples
at the end of processing was in the range 50–65%, depending
on the blanching time and puffing temperature. A
longer blanching time and lower puffing temperature were
responsible for the higher shrinkage. The high shrinkage
for the blanched sample can be explained considering that
some cell components are solubilized and degraded during
blanching[25] and the starch is gelatinized. These effects
cause higher shrinkage of blanched banana during the first
stage of drying and the formation of dense layer with a
rigid structure. When puffed, the expansion of product
volume is rather more difficult. As determined from experiments,
the volume ratio of the sample before puffing
compared to that after puffing at a puffing temperature
of 160C was approximately 121 and 175% for the
blanched and unblanched cases, respectively.