Mathematical modeling of caffeine kinetic during solid–liquid extraction of coffee beans

Grape marc phenolics: Extraction kinetics, quality and stability of extracts

“…The model has been previously applied by Spigno et al (2007) to marc extraction under different mixing and temperature conditions, and could again describe with a good correlation experimental data of the present work prior to equilibrium (120 min) (r 2 = 0.996 and 0.991 for 2006 and 2007 marc, respectively). Continuing with the Fickian approach, as described in detail by Cacace and Mazza (2003), the diffusivity of total phenolics was calculated, giving very similar values for the 2006 and 2007 pomaces: 1.23 Â 10 À10 and 1.50 Â 10 À10 m 2 s À1 , respectively, which is in agreement with other literature values (Cacace and Mazza, 2003;Espinoza-Pérez et al, 2007). The different extraction yields, then, were likely dependent only on differences in the phenolic contents of the raw materials, which in turn depends on the grape variety as well as weather and seasonal variations due to their influence on grape ripening and composition.…”

“…Furthermore, from previous results found in the literature (Bucić -Kojić et al, 2007;Cacace and Mazza, 2003;Espinoza-Pérez et al, 2007;Herodež et al, 2003;Ku and Mun, 2008;Simeonov et al, 1999) it appears that, generally, independent of the extraction conditions (solvent, solid/liquid ratio, mixing rate, temperature and particle size), the equilibrium concentration is reached in less than 2 h or even 1 h. This fast extraction process may be due to the fact that only those phenolic compounds more weakly linked to cellwall structure and those contained in vacuoles can presumably be easily recovered and for which the release efficiency is more liable to be affected by variables such as temperature, solvent-to-solid ratio, type of solvent and mass-transfer conditions in the solidliquid extraction (Pinelo et al, 2006). The recovery of cell-wall linked phenolics, on the other hand, is not possible unless an enzymatically assisted extraction is applied.…”

Improvement of Soybean Oil Solvent Extraction through Enzymatic Pretreatment

“…The equilibrium relationship determined experimentally includes the effect of solid moisture; the volumetric flow is constant because the flow of pure hexane supplied into the system is equal to the flow of miscella extracted from the system. The mass transfer constants in the liquid were estimated using the empirical correlation for fixed beds proposed by Geankoplis [6] and the mass transfer constants in the solid phase were estimated by equaling (5) (mass balance) with the equations that describe the diffusive phenomenon, taking into account the corrections due to material porosity [16]. The solution to (5) and (6) was numerically found using MatLab 2008a.…”

“…The solution to (5) and (6) was obtained through the method of numerical differentiation formula with the MatLab 2008a tool. From these solutions, the simulated profile of oil content evolution in miscella at the column exit and the simulated profile of residual oil content evolution in the solid were estimated [7,15,16,27,28]. Figures 1 and 2 show the simulated data of oil concentration in miscella at the exit of the extraction column according to time for solid flakes and collets without enzymatic pretreatment, respectively.…”

Impact of Instant Controlled Pressure Drop (DIC) Treatment on Drying Kinetics and Caffeine Extraction from Green Coffee Beans

“…Among them are theultraviolet-visible spectroscopy and its derivatives (Belay, 2010), Liquid Chromatography (Pistos & Stewart, 2004;Hywelet al, 2010), and gas chromatography (Espinoza-Perez et al, 2007). However, these works are focused on extraction and monitoring methods.…”