Effect of temperature and solvent composition on Kobs or
diffusion coefficient. Increase in the temperature caused a negative
effect on Kobs, indicating lower diffusivity at these temperatures
(Table 2). Overall, a higher rate of diffusivity was observed at lower
temperatures. The extraction yield also decreased with increase in
the temperature. This is rather unexpected, as temperature rise
should increase the solubility and diffusivities (Goula, 2013). On
the basis of this behaviour, one could assume that in the extraction
of lycopene from tomato processing waste, the rate determining
step, especially in our case, may be the penetration of solvent into
the matrix or the bond creation between the analyte and the solvent
(the first step of solid–liquid extraction) rather than diffusion
(the second step). Since the matrix contains about 35% water, the
penetration of solvent mixture into the bulk of the matrix may
be hindered, as the solvent mixture contains a non polar hexane
phase. In addition, if the rate determining step was diffusion, the
diffusion coefficient should vary with the temperature in accordance
with the Arrhenius type of relationship