posted on 2018-12-06, 12:46authored byShima Saffarionpour, Suk-Ying S. Tam, Luuk A.M. van der Wielen, Eric Brouwer, Marcel Ottens
Flavor-active esters, produced during fermentation, are vital components and important contributors to the
aroma of beer. In order to separate trace amounts of esters, their adsorption behavior in the presence of high
concentrations of ethanol and their thermodynamic behavior under the influence of temperature needs to be
understood. This study reports the influence of temperature on single component adsorption isotherms of four
esters (i.e. ethyl acetate, isopentyl acetate, ethyl 4-methylpentanoate, and ethyl hexanoate) on two hydrophobic
resins (i.e. Amberlite XAD16N, and Sepabeads SP20SS) and the estimation of heat, entropy, and Gibbs energy of
adsorption. Higher heat and entropy of adsorption are obtained for ethyl hexanoate and ethyl 4-methylpentanoate
in comparison, due to their higher hydrophobicity, stronger binding, and the exothermic nature of their
adsorption. A higher concentration of ethanol (tested from 1 to 30% (v/v)), lowers the activity coefficient of
esters in the aqueous phase, and subsequently lowers adsorption and Langmuir affinity parameters. Increase of
temperature from 284.15 to 325.15 K shows a reverse influence on maximum adsorption capacity and Langmuir
affinity parameters. Langmuir affinity parameters are obtained at various ethanol concentrations and temperatures.
The reported parameters and thermodynamic properties in this paper, are essential for designing an
industrial scale adsorption step for separation of flavor-active esters under non-isothermal conditions.
History
Publication
Separation and Purification Technology;210, pp. 219-230