Brownian motion and Einstein relation for migration of coffee particles in coffee suspensions

BACKGROUND The migration of particles in a liquid plays an important role in determining the stability of the corresponding suspension. The preparation of a cup of coffee involves the migration/dispersion of coffee particles in aqueous solutions. We investigate the Brownian motion of coffee particle...

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Bibliographic Details
Published in:Journal of the science of food and agriculture 2019-06, Vol.99 (8), p.3950-3956
Main Authors: Lin, Chih‐Yang, Zhou, Wenxiao, Hu, Chen‐Ti, Yang, Fuqian, Lee, Sanboh
Format: Article
Language:English
Subjects:
Activation energy
Aqueous solutions
Beans
Breweries
Brewing
Brownian motion
Coffee
Diffusion
Diffusion coefficient
diffusivity
High temperature
Migration
Organic chemistry
Particulates
suspension
Temperature dependence
Viscosity
Viscous flow
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Summary:BACKGROUND The migration of particles in a liquid plays an important role in determining the stability of the corresponding suspension. The preparation of a cup of coffee involves the migration/dispersion of coffee particles in aqueous solutions. We investigate the Brownian motion of coffee particles in coffee suspensions at different temperatures for three different coffee beans via the migration of the coffee particles of the coffee suspensions in water. RESULTS The activation energies for the Brownian motion of the coffee particles are in the range 23.5–32.0 kJ mol−1, relatively independent of the size of the coffee particles used in the present study. The viscosities of the coffee suspensions are measured as a function of temperature and then used to correlate with the gradient–diffusion coefficient for the Brownian motion of the coffee particles. The activation energies of the rate process controlling the viscous flow of the coffee suspensions are in the range 12.7–14.1 kJ mol−1. CONCLUSION The correlation between the viscosity and gradient–diffusion coefficient of the coffee suspensions generally follows the Einstein relation. A temperature dependence exists for the viscosity and gradient–diffusion coefficient of the coffee suspensions, which can be used to understand the brewing of coffee at high temperatures with respect to product refinement. © 2019 Society of Chemical Industry
ISSN:0022-5142
1097-0010
DOI:10.1002/jsfa.9620