close

Вход

Забыли?

вход по аккаунту

?

Equilibrium and extraction kinetics of tannins from chestnut tree wood in water solutions.

код для вставкиСкачать
ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING
Asia-Pac. J. Chem. Eng. 2011; 6: 606–612
Published online 7 May 2010 in Wiley Online Library
(wileyonlinelibrary.com) DOI:10.1002/apj.455
Research article
Equilibrium and extraction kinetics of tannins
from chestnut tree wood in water solutions
Claudio Capparucci, Fausto Gironi and Vincenzo Piemonte*
Department of Chemical Engineering Materials & Environment, University of Rome ‘La Sapienza’, Rome, Italy
Received 30 October 2009; Revised 15 March 2010; Accepted 17 March 2010
ABSTRACT: Tannins are natural water-soluble products, characterized by a phenolic structure and the ability to
bind and precipitate proteins. They are widely found in natural products, and their ‘historical’ utilization was in
tanning animal hides into leather. Nowadays, tannins are extensively used in the food and beverage industry and
in pharmaceutical and nutraceutical industries for their positive effects on human health. In conventional processes,
tannins are extracted from vegetable material by using water as a solvent in a temperature range of 40–90 ◦ C; other
polyphenols are always extracted and classified as nontannins. The scope of this work is to characterize chestnut tree
wood in terms of the total extractable tannins. To this aim, analytic methods, reported in the literature, for the quantitative
determination of these compounds in aqueous solution of unknown composition have been assessed. Experimental data
on equilibrium distribution of tannins between solid (wood) and liquid (water) at a temperature of 80 ◦ C are presented.
The obtained results have been correlated by means of the Freundlich isotherm. Experimental data are also reported
on the extraction kinetics of tannins from the solid phase. Experimental extraction curves were simulated by a plug
flow model, and an overall mass transfer coefficient was evaluated.  2010 Curtin University of Technology and John
Wiley & Sons, Ltd.
KEYWORDS: tannins; equilibrium isotherm; fixed-bed column; chestnut wood; solvent extraction
INTRODUCTION
Tannins are defined as water-soluble phenolic compounds having molecular weights ranging from 300
and 5000 Da; they do not constitute a unified chemical group, but have a variety of molecular structures.[1]
Tannins are generally divided into hydrolyzable and
condensed ones and are found in roots, flowers, leaves
and wood of many plants.[2,6,9] Tannins contribute to
the taste of food and beverages by providing a sensation of dryness, which is quite pronounced especially in
some red wines, teas and so on.[14,15]
In recent years, the production of tannins has become
very important because of their increasing commercial interest in the field of pharmaceutical, food
and nutraceutical industries. In particular, tannins can
contribute to the therapeutic effects of some herbal
medicines; beverages rich in tannins have positive cardiovascular effects and, like some other smaller phenolic compounds, tannins may serve as dietary antioxidants. Finally, as is well known, tannins are used for
*Correspondence to: Vincenzo Piemonte, Department of Chemical
Engineering Materials & Environment, University of Rome ‘La
Sapienza’, Rome, Italy. E-mail: piemonte@ingchim.ing.uniroma1.it
 2010 Curtin University of Technology and John Wiley & Sons, Ltd.
Curtin University is a trademark of Curtin University of Technology
converting animal hides to leather because of their ability to interact with and precipitate proteins.[16,17]
The extraction process of tannins from natural matrix
is currently performed by empirical methods; industrially, no process optimization has been carried out.
In order to maximize the recovery of tannins from the
solid matrix, the influence of feed pretreatment (crushing and moisture removal), temperature, extraction time,
and chemical characteristics of the solvent and solventto-solid ratio should be extensively studied.[18] In particular, the reduction of time and temperature in the
process should be a powerful tool to reduce the energy
consumption in the process.
Spigno et al .[11,12] recently published a review paper
on the effect of various process parameters on the
extraction efficiency of phenolic compounds; it is worth
noting that a comparison between different extraction
conditions is very difficult owing to the differences in
the response of analytical methods used to evaluate
the concentration of phenolic compounds in the extract
phase.
Water is the most extensively used solvent for the
extraction of tannins, but organic solvents such as
methanol, ethanol, ethylacetate or acetone and aqueous solutions of the same organic compounds are also
Asia-Pacific Journal of Chemical Engineering
employed. Furthermore, the possibility of utilizing carbon dioxide as a nontoxic, environmentally safe, cheap
solvent has been investigated by Murga et al .[8] and
Luengthanaphol et al .[7] Unfortunately, the solubility of
tannins in supercritical carbon dioxide is low even at
high pressure; therefore, ethyl alcohol is added as an
entrainer to increase the yield from the process. From
an economic point of view, the supercritical CO2 cannot be competitive with classical extraction solvents if
the whole phenolic fraction is to be extracted, i.e. the
supercritical CO2 is competitive to obtain a selective
extraction of a given compound.
In this work, some experimental data on the extraction of tannins from chestnut tree wood, utilizing water
as a solvent at a fixed temperature, are reported. The
choice of water as a solvent was made on the basis
of literature data: in fact, it was verified that the extraction efficiencies of organic solvents are comparable with
that of water, and are also less expensive and polluting.
Moreover, chestnut wood was chosen as raw material
to obtain the tannins because it is characterized by a
rather high concentration of tannins in the solid phase
(about 10% by weight g/g) together with its low cost
and high availability.
The objectives of the paper are as follows:
1. To evaluate the mass of tannins in the solid matrix
utilized in the experimental work (wood characterization).
2. To determine the correlation between the concentration of tannins in the liquid phase and the concentration of the same compounds in the solid phase; in
particular, the Freundlich equilibrium isotherm has
been used to correlate the equilibrium experimental
data collected.
3. To study the extraction process kinetics of tannins
from solid phase, performed in a fixed-bed column
by using a plug flow model.
The obtained results can be considered to be helpful
tools for the optimization of the existing extraction
processes of tannins from solid matrix and for designing
new ones.
MATERIALS AND METHODS
Experimental runs on the extraction of tannins were
performed on samples of 20-year-old chestnut wood.
The wood samples were crushed to obtain a particle
size of approximately 5 × 1 × 1 mm, and then placed
in a vacuum-drying oven for a period of approximately
24 h at a temperature of 40 ◦ C in order to remove the
moisture initially present. An initial moisture content
equal to 0.076 g-H2 O/g-dry-wood was measured.
The concentration of tannins in aqueous solutions was
determined by means of protein [bovine serum albumin
 2010 Curtin University of Technology and John Wiley & Sons, Ltd.
EQUILIBRIUM AND EXTRACTION KINETICS OF TANNINS
(BSA) provided by Sigma–Aldrich] precipitation assay.
This method requires an aqueous solution containing
5% v/v of triethanolamine (TEA) and 1% v/v of sodium
dodecyl sulfate (SDS) provided by Sigma-Aldrich. All
the chemicals used were of reagent grade.
The details regarding the analytical procedure followed for determining the concentration of tannins in
solution are reported in the literature.[10,19] Briefly, a
chemical method was used, which realizes a precipitation of tannins in aqueous solution by adding BSA;
the precipitate is then settled and separated from the
initial solution by centrifugation and filtration by commercially available 0.25-µm filters. The precipitate is
subsequently dissolved in an aqueous solution containing SDS and TEA. The addition of a further solution of
ferric chloride leads to the formation of a compound
chromophore, which has maximum absorbance at a
wavelength of 522 nm. The spectrophotometric analysis
is performed using a spectrophotometer, Perkin-Elmer
Lamba 25.
Calibration was obtained by measuring the absorbance of solutions of known composition at a wavelength of 522 nm. An extinction coefficient, ε =
0.5747, was obtained.
The experimental setup used for the tests (Fig. 1)
consists of a glass column (H = 0.3 m, = 0.025 m)
equipped with a thermostatic jacket, a peristaltic pump
for the flow recirculation, a drum for product accumulation and a thermostat to maintain the temperature at a
fixed value. The experimental setup was used both for
the equilibrium and extraction kinetic runs: the apparatus worked in a closed loop to obtain equilibrium data;
it was operated in an open circuit with a continuous
input of fresh solvent to obtain kinetic data.
The equilibrium tests were carried out at 80 ◦ C by
loading dried and milled wood inside the column
and adding the solvent (deionized water) inside the
accumulation drum. The contact between the liquid and
solid phases was ensured by a recirculation pump. By
means of some preliminary tests, it was shown that a
contact time equal to about 24 h was necessary to reach
equilibrium conditions.
Tests were also carried out to evaluate mass transfer
coefficients between the solid phase and the liquid phase
(at a temperature of 80 ◦ C), using the experimental
apparatus described above. Initially, the column was
rapidly filled with fresh solvent. In this way, the liquid
and solid phases inside the column were contacted
for a long enough time (about 24 h) to ensure the
achievement of equilibrium conditions. Then, pump 5
(Fig. 1) was switched on and a continuous flow rate of
fresh solvent entered the column. At the same time, a
continuous flow rate of the solution exited the column.
At fixed times, samples of this stream, which were
tannin rich, were collected and analyzed in order to
evaluate the concentration of tannins vs time. Low
values of the inlet flow rate were chosen to ensure the
Asia-Pac. J. Chem. Eng. 2011; 6: 606–612
DOI: 10.1002/apj
607
608
C. CAPPARUCCI, F. GIRONI AND V. PEIMONTE
Asia-Pacific Journal of Chemical Engineering
Figure 1. Experimental setup: (1) fixed-bed column, (2) heating jacket, (3) threeway valves, (4) accumulation drum, (5) circulation pump; (A) from thermostat and
(B) to thermostat.
attainment of equilibrium conditions in each column
section. The experimental runs were carried out until the
concentration of tannins in the outlet stream reached a
very low value, that is, of the same order of magnitude
as the tolerance of the instrument (0.035 g/l).
Table 1. Chestnut wood characterization: experimental conditions and mass of tannins extracted in each
run.
Test
Wood
mass (g)
Flow rate
(l/h)
V (l)
Nin (g)
nin (g/g)
231
30
30
10
10
1.20
6.42
6.42
9.00
9.00
2.50
0.20
0.50
0.90
1.10
18.351
2.324
2.373
0.842
0.771
0.079
0.075
0.079
0.084
0.077
Chestnut tree wood characterization
1
2
3
4
5
The initial content of tannins in the wood sample was
determined at 80 ◦ C. On the whole, five tests of wood
characterization were performed by varying the amount
of wood initially loaded in the experimental circuit, the
flow rate and the liquid holdup (Table 1). In each test,
several extraction runs were performed on the same
wood sample in the experimental apparatus operating in
a closed-loop mode. In each run, when equilibrium conditions were reached, the liquid solution was removed,
analyzed and replaced with fresh solvent. Naturally,
owing to the transfer of tannins from the solid to the
liquid phase, the concentration of tannins in the liquid
phase decreased as the number of extractions increased.
The last extraction always showed a concentration of
tannins in the liquid phase around the detectable limit
of the analytical method used to determine the concentration of tannins.
A material balance extended to all the extraction runs
was written to evaluate the mass of tannins extracted
from the solid phase. Therefore, the amount of tannins
RESULTS
 2010 Curtin University of Technology and John Wiley & Sons, Ltd.
Asia-Pac. J. Chem. Eng. 2011; 6: 606–612
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
EQUILIBRIUM AND EXTRACTION KINETICS OF TANNINS
Table 2. Experimental equilibrium data of tannins in
solid and liquid phases (T = 80 ◦ C, flow rate = 6.4 l/h).
1
2
3
4
5
6
7
8
9
10
Wood–solvent
ratio (l/g)
Concentration
of tannins in
the solid
phase (g/g)
9.1
42.9
51.0
63.7
75.0
106.4
149.3
235.8
382.7
481.9
0.712
2.600
3.289
4.089
4.501
6.117
8.161
12.218
18.185
21.081
0.0014
0.0203
0.0161
0.0164
0.0211
0.0239
0.0270
0.0302
0.0349
0.0391
theoretical model
experimetal data
0.05
0.04
neq (g/g)
Sample
Concentration
of tannins in
the liquid
phase (g/l)
0.06
0.03
m = 0.0095 +/- 0.0015
0.02
p = 0.468 +/- 0.065
0.01
0
0
5
10
15
20
25
30
35
40
ceq (g/l)
Figure 2. Equilibrium of extraction of tannins at 80 ◦ C. Line
is obtained with the model described in the text.
initially present in the wood sample Nin is
Nin =
n
Vi Ci ,eq
Table 3. Experimental conditions of kinetic runs
performed at 80 ◦ C.
(1)
i =1
Flow rate
(l/h)
0.50
0.60
0.90
Wood mass (g)
Initial content
of tannins (g)
30
30
30
2.37
2.37
2.37
where Vi and Ci ,eq are the solvent volume loaded in the
circuit and the equilibrium concentration of tannins in
the liquid phase for the extraction run i respectively. In
this way, an average initial content of 0.079 g of tannins
was obtained in 1 g of dry wood (nin ), as reported in
Table 1. This result is in the same order of magnitude
as that in literature data.[13]
Equilibrium data are summarized in Table 2, while
Fig. 2 shows a plot of the adsorbed amount of tannins
vs the concentration of tannins in the liquid phase.
Equilibrium runs
Fixed-bed column runs
Table 2 summarizes the operational conditions used in
the experimental runs reported in this paper; different
equilibrium conditions were obtained by varying the
ratio between the mass of circulating water and the mass
of wood.
The experimental setup used did not allow obtain
experimental data for high concentrations of tannins in
the liquid phase as it is necessary to use a low volume of
solvent; lower than the plant holdup. The concentration
of tannins in the aqueous solution was calculated by the
analytical method described above, while for the solid
phase the equilibrium concentration was calculated by
using the following material balance equation:
M (nin − neq ) = Vceq
Extraction kinetic runs have been carried out to determine the mass transfer coefficients between the solid
and the liquid phases. Table 3 shows the operating conditions used during the kinetic tests.
Figure 3 shows the typical trends of extraction curves
of tannins from the wood. Owing to the procedure
utilized in experimental runs, at t = 0, the concentration
of tannins in the liquid phase is constant in each column
section and is equal to the value obtained by imposing
the equilibrium conditions upon the column.
As the fresh solvent enters the column, the liquid
inside the column is progressively shifted toward the
output section. In the hypothesis of plug flow, the
concentration of tannins in the output stream is constant
from t = 0 to the characteristic time tc given by
(2)
tc =
where M is the total dry wood mass loaded inside
the circuit and neq is the equilibrium concentration of
tannins in the solid phase.
 2010 Curtin University of Technology and John Wiley & Sons, Ltd.
Vs
W
(3)
where Vs is the column liquid holdup and W is
the solvent volumetric flow rate. Subsequently, the
Asia-Pac. J. Chem. Eng. 2011; 6: 606–612
DOI: 10.1002/apj
609
610
C. CAPPARUCCI, F. GIRONI AND V. PEIMONTE
Asia-Pacific Journal of Chemical Engineering
CORRELATION OF EXPERIMENTAL DATA
From a theoretical point of view, the equilibrium data
can be correlated by different adsorption isotherms.
In this work, the Freundlich isotherm was chosen
instead of the Langmuir isotherm because experimental
data do not show the saturation trend typical of the
Langmuir isotherm. Therefore, tannins equilibrium data
were correlated by the following Freundlich isotherm:
P
neq = mceq
(4)
The isotherm parameters, m and p, were evaluated
from the fitting of the experimental data by the least
square method. The parameter values obtained along
with their asymptotic standard errors are reported in
Fig. 2, where the fitted curve and experimental data
are compared. The figure shows that the Freundlich
isotherm gives a satisfactory correlation of the experimental data.
The dynamics of the extraction of tannins in a fixedbed apparatus can be described through a model based
on differential mass balances applied to the liquid and
solid phases and the mass transfer between the liquid
and solid phases. This model was widely developed by
Annesini et al .[1] with the following hypothesis:
(a) isothermal plug flow process;
(b) in each column section, the equilibrium condition
between the liquid and solid phases is assumed;
(c) the axial dispersion is neglected.
Under this hypothesis, the solute mass balance in the
liquid phase is given by
ε
Figure 3. Extraction curves of tannins from chestnut wood
at different flow rates. (a) W = 0.50 l/h, (b) W = 0.60 l/h
and (c) W = 0.90 l/h.
concentration of tannins in the exiting stream decreases
until the tannins in the solid phase are completely
exhausted.
Experimental data reported in Fig. 3 refer to three
values of volumetric flow rates (Table 3). Evidently,
tests performed at higher flow rates show a lower
characteristic time and a more rapid exhaustion of the
column bed.
 2010 Curtin University of Technology and John Wiley & Sons, Ltd.
∂c
∂c
+v
= (1 − ε)aK (c ∗ − c)
∂t
∂z
(5)
where K is the overall mass transfer coefficient covering both liquid and solid phase resistances, c is the
concentration of tannins in the liquid phase, c ∗ is the
concentration of tannins in the solid phase in equilibrium with the liquid phase, a is the specific surface,
ε is the column bed porosity and v is the superficial
velocity.
Similarly, the mass balance in the solid phase gives
the following differential equation:
ρ
∂n
= −aK (c ∗ − c)
∂t
(6)
where n is the concentration of tannins in the solid
phase and ρ is the wood intrinsic density. The equilibrium condition can be added to the previous equations:
n = f (c ∗ )
(7)
Asia-Pac. J. Chem. Eng. 2011; 6: 606–612
DOI: 10.1002/apj
Asia-Pacific Journal of Chemical Engineering
EQUILIBRIUM AND EXTRACTION KINETICS OF TANNINS
Finally, the set of equations can be solved with the
following boundary and initial conditions:
IC :
5t = 0,
BC :
t > 0,
0 ≤ z ≤ H,
z = 0,
in
,
c = ceq
in
n = neq
c=0
(8)
in
is the initial concentration of tannins in the
where ceq
in
liquid phase in equilibrium with the solid phase neq
and
H is the column height.
The derived set of differential equations were implemented and solved by using gPROMS (Process System
Enterprises, London, UK), a general purpose modeling
package capable of describing the dynamic response
of unsteady-state apparatus. A backward finite difference method was selected in order to discrete the spatial
domain (200 nodes) and obtain a set of time-dependent
differential and algebraic equations (DAE). Integration
of the DAE set gives the trends of concentration of tannins as a function of the axial coordinate and time. In
particular, the extraction curves, i.e. the concentrations
of tannins in the outlet stream vs time, are obtained.
These curves depend on the overall mass transfer coefficient K , covering both liquid- and solid-phase resistances. This parameter cannot be predicted theoretically,
but can be evaluated by superimposing model predictions onto experimental results. In particular, K values
can be calculated from the fitting of experimental data
regarding tannins extraction curves.
The overall mass transfer coefficient obviously depends not only on the physicochemical characteristics
of the solute but also on the operating conditions.
Therefore, different values of K were determined for
each run by minimizing the objective function defined
as
(9)
φ=
[ccalc (t, L) − cexp (t, L)]2
where c(t, L) represents the concentration of the solute
in the liquid effluent from the extraction column and
the summation is overall the experimental data of each
extraction curve, evaluated at different solvent flow
rates. In Table 4, the values of operational parameters
used in the correlation of experimental data are reported.
Figure 3 compares the experimental extraction curves
with the theoretical curves obtained with the proposed
model using the fitted values of K (determined by fitting
of the experimental extraction curves). The fitting is
good for the different values of operative parameters.
In order to verify if K changes with the operating
conditions tested in this paper, the values of the
dimensionless mass transfer coefficient aKτ (where τ
is the column residence time) obtained for the water
tannins system are plotted vs the residence time τ for
the different experimental runs in Fig. 4. The results
obtained show a linear dependence of aKτ vs τ . A
constant value of K for the water tannins systems is thus
obtained through correlation of the experimental data
(K = 0.00091 ± 0.000073 m/h). Therefore, a constant
value of K , independent of the liquid-phase velocity
(i.e. liquid flow rate), corresponds to an extraction rate
controlled by the internal resistance of the solid phase,
as also reported by other authors.[5]
CONCLUSIONS
This paper deals with an experimental and theoretical
study, performed in order to assess the feasibility of
an extraction process to recover tannins from chestnut
tree wood. Firstly, a simple procedure was proposed to
evaluate the content of tannins in solid matrices: a value
of 0.079 g-tannins/g-dried-chestnut-wood was obtained.
Then, at 80 ◦ C, both batch equilibrium tests and breakthrough experiments were carried out to obtain information on equilibrium and kinetic conditions. The hypothesis of an equilibrium condition of tannins between liquid
and solid phases was adopted and the Freundlich equation was chosen to fit experimental data.
Experimental data on the fixed-bed extraction process
show that the extraction rate can be described with
0.3
0.25
Table 4. Parameters used in the correlation of
experimental data by the proposed model.
Operative parameter
Column bed porosity, ε
Column liquid holdup, Vs (l)
Specific surface, a (m−1 )
Wood intrinsic density, ρ (g/l)
Freundlich parameter, p
Freundlich parameter, m
Column height, H (m)
Column diameter, (m)
Numerical value
0.64
0.09
4400
560
0.468
0.0095
0.3
0.025
 2010 Curtin University of Technology and John Wiley & Sons, Ltd.
aKτ
0.2
0.15
0.1
0.05
0
K = 0.00091 +/- 0.000073 m/h
0
0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 0.2
τ (h)
Figure 4. Dimensionless mass transfer coefficient, K, vs the
column residence time τ .
Asia-Pac. J. Chem. Eng. 2011; 6: 606–612
DOI: 10.1002/apj
611
612
C. CAPPARUCCI, F. GIRONI AND V. PEIMONTE
an overall mass transfer coefficient K from the liquid
to the adsorbed phase. A constant value of K has
been obtained from correlation of experimental data
obtained with different solvent flow rates. This result
clearly indicates that the rate of the extraction process
is controlled by the internal resistance of the solid phase.
The results reported in this paper can be helpful in
the designing of industrial processes for the extraction
of tannins from natural solid matrix. In particular, it is
possible to identify the optimum extraction time and
the yields of tannins that can be obtained once the
temperature and the flow rate of the extraction solvent
is fixed.
Asia-Pacific Journal of Chemical Engineering
V
W
H
a
ε
v
ρ
τ
p
m
K
solvent volume loaded inside the circuit (l)
solvent volumetric flow rate (l/h)
column height (m)
column diameter (m)
specific surface (m−1 )
column bed porosity
superficial velocity (m/s)
wood intrinsic density (g/l)
column residence time (h)
Freundlich parameter
Freundlich parameter (l/g)
overall mass transfer coefficient (m/h)
REFERENCES
Acknowledgement
This study was financially supported by the Ministero
della Università e della Ricerca Scientifica (MURST)
NOMENCLATURE
BSA
SDS
TEA
Nin
nin
neq
n
in
neq
in
ceq
ceq
c
c∗
M
Vs
Bovin serum albumin
sodium dodecyl sulfate
triethanolamine
tannins amount initially present in the wood
samples (g)
initial content of tannins (g/g)
tannins equilibrium concentration in the solid
phase (g/g)
tannins concentration in the solid phase (g/g)
initial concentration of tannins in the solid
phase in equilibrium with the liquid phase
(g/g)
initial concentration of tannins in the liquid
phase in equilibrium with the solid phase (g/l)
tannins equilibrium concentration in the liquid phase (g/l)
tannins concentration in the liquid phase (g/l)
tannins concentration in the solid phase in
equilibrium with the liquid phase (g/l)
total dry wood mass loaded inside the circuit (g)
column liquid holdup (l)
 2010 Curtin University of Technology and John Wiley & Sons, Ltd.
[1] M.C. Annesini, F. Gironi, B. Monticelli. Water Res., 2000;
34(11), 2989–2996.
[2] U.D. Chavan, F. Shahidi, M. Naczk. Food Chem., 2001; 75,
509–512.
[3] A.E. Hagerman, Y. Zhao, S. Johnson. In Antinutrients and
Phytochemicals in Food, Shahidi Editor, Washington, DC,
Oxford University Press, New York, 1997; pp.209–222.
[4] A.E. Hagerman. Tannins Handbook, Oxford University press,
New York, 2002.
[5] S.S. Herodez, M. Hadolin, M. Skerget, Z. Knez. Food Chem.,
2003; 80, 275–282.
[6] B. Lapornik, M. Prosek, A.G. Wondra. J. Food Eng., 2005;
71, 214–222.
[7] S. Luengthnaphol, D. Mongkholkhajornslip, S. Douglas, P.L.
Douglas, L. Pengsopa, S. Pongamphai. J. Food Eng., 2004;
63, 247–252.
[8] R. Murga, R. Ruiz, S. Beltran, J.L. Cabezas. J. Agric. Food
Chem., 2001; 48, 3408–3412.
[9] J.P. Salminen. J. Chem. Ecol., 2003; 29(6), 1289–1305.
[10] P. Schofield, D.M. Mbugua, A.N. Pell. Anim. Feed Sci.
Technol., 2001; 91, 21–40.
[11] G. Spigno, L. Tramelli, M.D. De Faveri. J. Food Eng., 2007;
81, 200–208.
[12] G. Spigno, L. Tramelli, M.D. De Faveri. J. Food Eng., 2007;
78, 793–801.
[13] S. Zahari, A. Moubarik, F. Charrier, G. Chaix, H. Bailleres,
G. Nepveu, B. Charrier. Holzforschung, 2008; 62(6),
679–687.
[14] S. Muetzel, K. Becker. Food Sci. Technol., 2006; 125,
139–149.
[15] N. Turkmen, F. Sari, Y.S. Velioglu. Food Chem., 2005; 99,
835–841.
[16] Q. He, K. Yao, D. Sun, B. Shi. Biodegradation, 2008; 18,
465–472.
[17] N. Mateus, E. Carvalho, C. Luis, V. de Freitas. Anal. Chim.
Acta, 2004; 513, 135–140.
[18] M.S. Guerrero, J.S. Torres, M.J. Nuniez. Bioresour. Technol.,
2008; 99, 1311–1318.
[19] P. Rautio, U.A. Bergvall, M. Karonen, J.P. Salminen. Biochem.
Syst. Ecol., 2007; 35, 257–262.
Asia-Pac. J. Chem. Eng. 2011; 6: 606–612
DOI: 10.1002/apj
Документ
Категория
Без категории
Просмотров
1
Размер файла
162 Кб
Теги
water, solutions, extraction, wood, tanning, kinetics, chestnut, tree, equilibrium
1/--страниц
Пожаловаться на содержимое документа