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Modeling of Tea Infusion Kinetics Incorporating Swelling Kinetics

  • Raosaheb A. Farakte , Geeta U. Yadav , Bhushan S. Joshi , Ashwin W. Patwardhan ORCID logo EMAIL logo and Gurmeet Singh
Published/Copyright: January 18, 2017

Abstract

Mathematical model to predict tea infusion kinetics which accounts for swelling kinetics of tea granules is presented. Swelling kinetics of tea granules has never been taken into account for models developed so far. Differential equations (DEs) for concentration of tea constituents inside tea granule with respect to radius and time were derived. Solution methodology for these DEs is developed based on Crank-Nicholson scheme. Tea infusion profile is obtained using this model by knowing the swelling kinetics, partition constant and initial contents in tea granules. Diffusivity and product of interfacial area (As) and backward rate constant (k−1) are the fitting parameters. Model prediction is fitted to the experimental data published previously (R2 = 0.90–0.98). The fitted diffusivity (3.33 × 10−10 m2/s) and Ask−1 (2 m3/(kg.s)) predicted the infusion profile of other sized tea granules very well. This model predicts the infusion during initial stage very accurately without any empirical parameter.

Acknowledgments

Authors would like to thank Unilever Industries Limited for funding the research project. One of the authors would like to thank University Grant Commission (UGC) for providing financial support.

List of symbols

a

empirical parameter in Spiro’s kinetic expression

A

surface area of sphere of radius r (m2)

As

specific surface area of the tea granule (m2/kg)

c

concentration inside liquid phase of shell (kg/m3)

ce

experimental value of infusion concentration (kg/m3)

cp

experimental value of infusion concentration (kg/m3)

cs0

initial soluble content of tea granule (kg/m3)

cs

concentration in the solid phase of shell (kg/m3)

cs

concentration at the solid liquid interface (kg/m3)

cR

concentration at the surface of tea granule and in the bulk infusion (kg/m3)

cR,

concentration at the surface of tea granule and in the bulk infusion at equilibrium (kg/m3)

cs,

concentration in the tea granule at equilibrium (kg/m3)

J

flux of transfer of tea constituents across of shell (kg/(m2.s))

kobs

observed rate constant (1/s)

k–1

1st order rate constant for the transfer of soluble from liquid to solid (m/s)

k1

1st rate constant for the transfer of tea constituents from solid to water (m/s)

K

partition constant

M

mass of tea constituent in shell (kg)

n

number of data points

N

number of tea particles taking part in infusion process

r

inner radius of shell (m)

rm

radius of shell to express the volume of shell (m)

rdiss′′

dissolution rate in the shell (kg/(m2.s))

Δr

thickness of shell (m)

R

radius of tea particle at any time ‘t’ (m)

R0

radius of tea particle at any time ‘t = 0’ (m)

R

radius of tea particle at any time ‘t = ∞’ (m)

sr

ratio of final (after infusion) to initial volume of tea granule

t

time (s)

Δt

time interval (s)

Vb

volume of infusion at time ‘t’ (m3)

Va

amount of water absorbed per unit weight of tea granules (m3/kg)

V

volume of shell (m3)

w

weight of tea granules used for infusion (kg)

x0

initial soluble content of tea granule (kg/kg)

Z

representation of any variable with respect to time as radius

S, T, U, Y, W, X

lumped parameters as per Crank Nicolson scheme (dimensionless)

Greek symbols

ρ

density of tea granule (kg/m3)

λ

rate parameter for swelling process (1/s)

φ

shape parameter for swelling process

References

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Published Online: 2017-1-18
Published in Print: 2017-2-1

©2017 by De Gruyter

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