2.2.4. Kinetics of solid-liquid extraction
Analysis of the solid-liquid extraction process and comparison
of extraction at different temperatures was performed by implementation
of kinetic modelling. For this reason, kinetic parametersof Peleg’s, Page’s and Logarithmic model, for total polyphenols,
antioxidants and extraction yield were estimated.
Model developed by Peleg (1988), for description of sorption
curves, was adapted for the description of the solid-liquid extraction
process (Eq.(1)):
c (t) = c0 +
t
K1 + K2 · t (1)
where c(t) represents the concentration of total polyphenols/antioxidants/extraction
yield at time t, K1 is Peleg’s rate
constant (relates to extraction rate at the very beginning of the
extraction process), K2 is Peleg’s capacity constant (relates to
maximum polyphenol concentration/antioxidants/extraction yieldduring the extraction process) and c0 is the concentration of total
polyphenols/antioxidants/extraction yield at time t = 0. At t = 0, c0
value equals zero, and thus Eq. (1) can be reduced to (Eq. (2)):
c (t) = t
K1 + K2 · t (2)
The extraction rate in every moment t can be described by solving
the differential equation (Eq. (3)):
dc (t)
dt = K1
(K1 + K2 · t)
2