Diffusion phenomena during the decaffeination of coffee beans*

Bichsel, B; Gál, S.; Signer, R.

doi:10.1111/j.1365-2621.1976.tb00767.x

Cited by 18 publications

(20 citation statements)

References 3 publications

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“…Under these conditions and assuming constant caffeine diffusivity (D b ) Eq. Bichel (1979), Udaya-Sankar et al (1983), and Hulbert et al (1998) used Eq. (3), taking only the first term of the series, for fitting the experimental evolution of caffeine concentration in beans during decaffeination process.…”

Section: Modelingmentioning

confidence: 98%

“…Exist patent of this process since 1905 (Bichel, 1979). However its mathematical representation has been limited to caffeine diffusion estimation in coffee beans by using analytical solution of Fick's second law in spherical coordinates and assuming constant boundary conditions (Bichel, 1979;Hulbert, Biswal, Mehr, Walker, & Collins, 1998;Spiro & Selwood, 1984;UdayaSankar et al, 1983). The decaffeination of coffee is a solid-liquid extraction process, in which the caffeine is transferred from the coffee beans solid matrix to the bulk solvent.…”

Section: Introductionmentioning

confidence: 96%

“…Therefore, in this work, a mathematical description of coffee decaffeination based in the mass transfer in both phases was developed. Bichel (1979), Udaya-Sankar et al (1983) and Hulbert et al (1998) proposed the representation of the caffeine diffusion in coffee beans with the analytical solution of the Fick's second law in spherical coordinates…”

Section: Introductionmentioning

confidence: 99%

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

Espinoza-Pérez

Vargas

Robles-Olvera

et al. 2007

Journal of Food Engineering

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Section: Modelingmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Espinoza-Pérez

Vargas

Robles-Olvera

et al. 2007

Journal of Food Engineering

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“…(34) for the calculation of effective moisture diffusivity inside the coffee fruits (D ef ) in m 2 /s. This equation is employed in several works, as for instance: drying of beet powder (Sobreira, Singulani, & Silveira, 2000); drying of soybeans (Souza, Silva, & Barrozo, 2000), anatto (Bixa orellana) drying (Silva & Alsina, 1993) and in the extraction of caffeine from green beans for production of decaffeinated coffee (Bichsel, 1979). Eq.…”

Section: Calculation Of Moisture Effective Diffusivitymentioning

confidence: 99%

“…From the coffee fruit dimensions it was possible to calculate the sphere radius of the same volume as the coffee fruit. Bichsel (1979) also adopted this consideration for calculation of caffeine diffusivity during its extraction.…”

Section: Calculation Of Moisture Effective Diffusivitymentioning

confidence: 99%

Heat and mass transfer in coffee fruits drying

Sfredo

Finzer

Limaverde

2005

Journal of Food Engineering

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Caffeine extraction rates from coffee beans with supercritical carbon dioxide

et al. 1992

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The extraction of caffeine from whole coffee beans with supercritical carbon dioxide was studied in a continuous-flo w extraction apparatus. Decaffeination rates were determined as a function of CO, flow rate, temperature and pressure by continuously monitoring the caffeine in the effluent with a flame ionization detector. Soaking the raw beans in water prior to decaffeination enhanced the rate of extraction, which increased markedly with water content. Using CO, saturated with water also increased the rate of extraction. The rate of decaffeination increased with pressure and temperature and was influenced by both intraparticle diffusion in the water-soaked beans and external mass transfer. A mathematical model based on a linear-driving-force approximation of mass transfer and partitioning of caffeine between the water and the supercritical CO, describes the time-dependent process.The partition coefficient for caffeine distributed between water and supercritical CO, the only parameter determined from the dynamic extraction rate data, increases with temperature and pressure. IntroductionDecaffeination of coffee beans has been carried out with a variety of conventional solvents such as dichloromethane (Stahl et al., 1988;McHugh and Krukonis, 1986), but recently supercritical C 0 2 has been the preferred solvent in large-scale commercial processes (Leyers et al., 1991). The selectivity of supercritical CO, for caffeine in green (unroasted) coffee beans is an important property that is exploited in the decaffeination process, as little else besides caffeine in the raw bean is thought to be soluble in supercritical COz (Stahl et al., 1988). Since extraction is performed on the raw beans, flavor ingredients that are developed only during roasting are not removed. Additionally, use of supercritical C 0 2 precludes any post-decaffeination treatment of the beans to remove the solvent, a necessary step if conventional organic solvents are used.This supercritical fluid process is representative of a wide range of possible extractions: (a) to remove unwanted chemicals from the desired matrix material or (b) to separate and isolate a desired chemical from the matrix. A fundamental understanding is needed of the chemical, physical and transport processes that affect such extractions. The aim of the present research is to develop general experimental and theoretical approaches to study these basic phenomena as well as the particular decaffeination process.Supercritical CO, extraction, including the patents for caffeine extraction, is discussed by McHugh and Krukonis (1986) and Paulaitis et al. (1983). Stahl et al. (1988) also provide useful information about the decaffeination of raw coffee beans, which may contain 0.6 to 3 wt Vo of caffeine. The beans are first soaked in water up to a water content of 45 wt. Yo. Essential for satisfactory extraction, this step may change the texture of the cell walls to enhance diffusion, which is considered a rate-determining step, or the water may free the bound caffeine from the coffee matr...

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Diffusion phenomena during the decaffeination of coffee beans*

Cited by 18 publications

References 3 publications

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

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

Heat and mass transfer in coffee fruits drying

Caffeine extraction rates from coffee beans with supercritical carbon dioxide

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