A suitable Xp/Xo ratio resulted to be 0.2 and the optimal kYA and
kXA were adjusted to each kinetic data set. The values are given
in Table 4 together with the average absolute relative deviation
between calculated and experimental caffeine yield.
The optimal Xp/Xo ratio represents a Xk (amount of caffeine
inside cell walls) around 4 times higher than Xp (readily accessible
caffeine), denoting that caffeine is strongly bond in the vegetal
matrix. Furthermore, this is in accordance with the fact that a very
short constant extraction rate period was observed in the extraction
curves (tCER values were 0.96, 0.16 and 0.30 min, respectively, for
EA, EL and ETOH) and thus, mass transport within the solid phase
dominated extraction rate almost from the beginning of the process.
In this respect, the solubility value (Y*) calculated as the slope
of a theoretical linear behavior up to 14 min of extraction should
be considered as an estimated value
A suitable Xp/Xo ratio resulted to be 0.2 and the optimal kYA andkXA were adjusted to each kinetic data set. The values are givenin Table 4 together with the average absolute relative deviationbetween calculated and experimental caffeine yield.The optimal Xp/Xo ratio represents a Xk (amount of caffeineinside cell walls) around 4 times higher than Xp (readily accessiblecaffeine), denoting that caffeine is strongly bond in the vegetalmatrix. Furthermore, this is in accordance with the fact that a veryshort constant extraction rate period was observed in the extractioncurves (tCER values were 0.96, 0.16 and 0.30 min, respectively, forEA, EL and ETOH) and thus, mass transport within the solid phasedominated extraction rate almost from the beginning of the process.In this respect, the solubility value (Y*) calculated as the slopeof a theoretical linear behavior up to 14 min of extraction shouldbe considered as an estimated value
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