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The use of activated charcoal in combination with other fining agent and its influence on the organoleptic properties of sherry wine

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Fining experiments have been conducted on fino sherry wine from the Jerez-Xrs-Sherry region (southern Spain), in which the combined use of activated charcoal with proteinaceous fining agents (casein, potassium caseinate, albumin, and gelatin) has been studied. The effect of these fining agents on the polyphenolic content, the aromatic profile, and the resistance to browning of the treated wine has been determined. The polyphenolic content suffers significant decreases following the use of activated charcoal; these decreases are only increased slightly by the subsequent use of the other fining agents. The aromatic profile was not found to be altered by the clarification agents used. Despite the reduction in the polyphenolic content, the treated wines show a tendency to suffer browning similar to that observed in non-clarified wine.
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Abstract Fining experiments have been conducted on
fino sherry wine from the Jerez-Xérès-Sherry region
(southern Spain), in which the combined use of activated
charcoal with proteinaceous fining agents (casein, potas-
sium caseinate, albumin, and gelatin) has been studied.
The effect of these fining agents on the polyphenolic
content, the aromatic profile, and the resistance to
browning of the treated wine has been determined. The
polyphenolic content suffers significant decreases follow-
ing the use of activated charcoal; these decreases are
only increased slightly by the subsequent use of the other
fining agents. The aromatic profile was not found to be
altered by the clarification agents used. Despite the
reduction in the polyphenolic content, the treated wines
show a tendency to suffer browning similar to that
observed in non-clarified wine.
Keywords Fining treatments · Activated charcoal ·
Phenolic compounds · Browning · Sherry wine
Introduction
The “fino” sherry wines typical of the Jerez-Xérès-Sherry
region (southern Spain), protected from the action of
oxygen thanks to their special system of biological aging
under the “velo de flor” [1], are affected, as other white
wines, by the phenomenon of browning once they have
been bottled. It has been known for many years [2, 3]
that this deterioration of the organoleptic and sensorial
characteristics accompanying this browning is due to the
oxidation of the polyphenolic compounds present in the
wine. As a result of these alterations in the organoleptic
properties, the product is often rejected for consumption,
implying both immediate economic losses and longer-
term loss of confidence in wines of this type by consumers.
To date, a wide variety of enological techniques have
been employed to counter this undesirable evolution
(bottling under inert atmosphere [4, 5], addition of anti-
oxidants (ascorbic acid, sulfur dioxide [6, 7]), etc.). The
use of clarifying agents is another of the techniques
aimed at avoiding the browning of wines. These act upon
the phenolic compounds encouraging their precipitation.
In the field of enology, many different substances have
been employed as fining agents over time.
Notable among these is bentonite, the effect of which
on the protean content of the wine has been well-proven.
There are authors who state that the use of bentonite not
only facilitates the precipitation of the thermolabile
proteins [8] but also produces a reduction in the poly-
phenolic content of the wine [9, 10, 11]. The more widely-
used proteins employed as clarifying agents include
casein, gelatin [12], potassium caseinate, and albumin.
Due to the chemical nature of activated charcoal, this
is another clarifying agent that tends to adsorb compounds
of low polarity, causing it to react easily with the
benzene groups present in the wine [13]. It would seem
that, depending on the type of charcoal and the dosage
applied, its use may entail significant losses of aroma in
the treated wines [14] together with a destabilization of
the color caused by the presence of chemically-adsorbed
oxygen which may produce oxidation of the wine [15],
reaching levels of color intensity above than those of
untreated wine [16]. In spite of these problems, and given
its powerful decolorizing action [17], this clarifying
agent has come into common use in the enological
industry in recent years, in the stages prior to the
bottling, for the purpose of achieving wines with ever-
paler tonalities.
In the case of fino sherry wines, some studies have
shown that the use of activated charcoal does not alter
its organoleptic characteristics. However, it has been
observed that the treated wines undergo a considerable
increase in color intensity, even when they begin with
S. López · R. Castro () · C.G. Barroso
Analytical Chemistry Department, Faculty of Sciences,
University of Cádiz, P.O. Box 40, 11510. Pol. Rio San Pedro,
Puerto Real, Cádiz, Spain
e-mail: remedios.castro@uca.es
E. García · J.A.S. Pazo
Sandeman – Coprimar. Jerez de la Frontera. Cádiz, Spain
Eur Food Res Technol (2001) 212:671–675
DOI 10.1007/s002170100300
ORIGINAL PAPER
Sebastián López · Remedios Castro · Esmeralda García
Jose Antonio S. Pazo · Carmelo G. Barroso
The use of activated charcoal in combination with other fining agents
and its influence on the organoleptic properties of sherry wine
Received: 2 October 2000 / Revised version: 30 November 2000 / Published online: 26 April 2001
© Springer-Verlag 2001
initial values considerably lower than those observed for
the same wine without this treatment [18].
This article describes a study conducted on the use of
activated charcoal in combination with other clarifying
agents: casein, potassium caseinate, gelatin, and albumin,
with the objective of determining whether such
combined application leads to a reduced tendency of the
“fino” sherry wine to browning, and of observing if the
use of these substances influences the organoleptic
characteristics of the wine.
Material and methods
Samples. “Fino” sherry wine (ethanol content of 15 vol.%) from
the Jerez-Xérès-Sherry region (SW Spain) that had been biologically
aged for two-and-a-half years, was subjected to various different
clarification treatments.
Fining process. Activated charcoal (180 mg/l) was added to the
wine. After being left to act for a day, the second clarifying agent
was added, leaving aside one part of the wine with only the activated
charcoal added. Each of the different clarification processes tested
was applied to a quantity of 30,000 l.
The four clarification treatments tested were:
1. Treatment CA: soluble casein (120 mg/l)
2. Treatment CK: soluble caseinate (120 mg/l)
3. Treatment AH: egg albumin (120 mg/l)
4. Treatment GE: liquid gelatin (100 mg/l)
After these additions, all of them were treated with sodium
bentonite (1 g/l).
The activated charcoal (Acticarbone CX), obtained from
Laffort (Guipúzcoa, Spain), had a BET surface area of
950–1250 m2/g and a particle diameter of 10–100 Å. Both the
sodium bentonite (Volclay, particle size of 1–2 mm), and the casein
(FT/1107), instant potassium caseinate (FT/1109), egg albumin
(Ovoclaryt FT/1100), and gelatin (concentrated liquid superclari-
fying) were supplied by Laffort (Guipúzcoa, Spain).
After leaving the various different clarification agents to act
for four days, the wines were filtered through diatomaceous earth
and chilled to facilitate the precipitation of tartrates (1 week,
4 °C). After this stage and once filtered (1.2 µm and 0.45 µm) the
wines were then bottled. All these steps were carried out following
the daily routines of the wine cellar in which the study was
conducted. In all cases, a control wine was retained, subjected to
the same conditions but not clarified.
The wines were sampled after the addition of the activated
charcoal, after completing the process of clarification and at the
time of release for bottling.
Determination of the polyphenolic profile. Samples (80 µl) of
wine after filtration (0.45 µm pore size) were analyzed by HPLC,
in duplicate. The elution phases used were solvent A (95% water,
5% methanol) and solvent B (95% methanol, 5% water) at pH 2.5
(extra pure sulfuric acid). The elution gradient was from 100% to
85% solvent A in 5 min, from 85% to 50% solvent A in 40 min,
and isocratic elution for 35 min. The analyses were carried out
using a C18 column (Lichropher 100 RP-18, 250 mm¥3 mm, 5 µm
particle size) at a flow rate of 0.5 ml/min and detection at 280 nm
and 320 nm.
The various polyphenolic compounds present were identified
by comparison with a library of DAD spectra and retention times
of standards. Commercial standards were purchased from Fluka
(Buchs, Switzerland) and Eastman Kodak (Rochester, NY). Caftaric
and coutaric acids were isolated by the method described by
Singleton et al. [19]. Each compound was quantified by comparison
with a calibration curve obtained with the corresponding standard,
except GRP (2(S)-glutathionyl caftaric acid), which was quantified
as caftaric.
Determination of the aromatic profile. The aromatic profiles were
determined, in duplicate, using a prior stage of continuous rotatory
liquid-liquid extraction for 150 min (0.8 rpm). The extraction was
performed on 100 ml of wine diluted to 200 ml with distilled
water. The mixture was saturated with NaCl, at which time 50 µl
of the internal standard, 4-methyl-2-pentanol, was added. A mixture
(2:1) of ether-n-pentane (90 ml) was used as the organic extractant.
The extract obtained was concentrated under an atmosphere of N2
in a TurboVap II (Zymarck) station until reaching a final volume
of 2 ml.
Subsequently the extract obtained was subjected to gas
chromatography using an HP 5890 series II gas chromatograph
with flame ionization detection (FID). The injection volume was
1 µl, splitless for 0.5 min. The column used was a JW-DBWAX,
60 m and 0.25 mm internal diameter, split flow 30 ml/min and
purge flow 1.5 ml/min. The carrier gas used was helium (column
head pressure of 14 psi). The temperature of the detector during
the analysis was 250 °C, while the injector was held at 200 °C.
The temperature gradient used began at 45 °C for 20 min, and was
then raised to 95 °C at a rate of 10 °C/min. After 1 min it was
increased to 130 °C (2 °C/min). This temperature was held for
1 min and then increased to 210 °C (1 °C/min) and held at this
temperature for 20 min.
A Voyager (Thermoquest) gas chromatograph with a mass
detector (electronic impact and quadrupole) was used for the identi-
fication of the various signals obtained. The signal was recorded
and processed with a Masslab software supplied with the Wiley
6.0 MS library. Chromatography conditions as before. Peak identifi-
cation was carried out by analogy of mass spectra and confirmed
by retention indices of standards when they were available or by
retention data from the literature. Quantitative data from the identi-
fied compounds were obtained by measuring the relative peak area
in relation to that of 4-methyl 2-pentanol, the internal standard.
The concentration of those compounds for which there was a
standard available was obtained by means of a calibration curve.
For those compounds whose standard was not available, the relative
peak area was used.
Determination of susceptibility to browning. Quantities of 120 ml
of wine, were subjected, in duplicate, to a process of electrochemical
oxidation using equipment devised by our research group [20]. In
this, the susceptibility to browning is quantified as the increase in
absorbance recorded at 420 nm (“y”) against the electrical current
(“x”) applied [21]. This equipment allows the susceptibility of a
wine to browning to be determined rapidly and reliably, without
having to wait the length of time taken for this phenomenon to
evolve naturally.
Statistical treatment. Variance and cluster analyses were performed
on polyphenolic and volatile data from the replicated samples
using the Statgraphics Statistical Computer Package “Statgraphics
Plus 3.1” for Windows 95.
Results and discussion
In order to check if there were significant differences
between the initial wine and those treated with the various
fining agents, the concentrations of the different poly-
phenolic compounds under study, identified in the wines,
were subjected to variance analysis. The results obtained
are given in Table 1.
Almost all the polyphenolic compounds were found
to be affected by the clarification, with significant
decreases being recorded. For those compounds that
differed significantly (p<0.05), the diminution percentage
by compound and by treatment in respect of the initial
wine has been calculated; the values obtained are given
in Table 1. The content of catechin was reduced most by
672
the clarification CK (activated charcoal+potassium
caseinate+bentonite). The hydroxycinnamic acids (caftaric,
cis- and trans-p-coutaric), together with GRP (2-(S)-
glutathionyl caftaric acid) showed the greatest decreases
with the treatments CA (activated charcoal+casein+
bentonite) and GE (activated charcoal+gelatin+bentonite).
Cluster analysis was performed in order to establish
the degree of similarity between the different clarification
treatments in function of the polyphenolic variables
studied. The results obtained are presented in Fig. 1.
As can be seen, there exists a high degree of similarity
between treatments CA, CK, GE, and AH, which are
grouped in the same cluster. This one is, later, grouped
together with the wine that had been treated with charcoal.
This could be due to the fact that the greatest decreases
are produced after the application of activated charcoal,
as can be observed from a comparison of the diminution
percentages of the various polyphenols reached after the
use of charcoal and after the completion of the process
of clarification (Table 1). The decrease in the different
polyphenols after the use of activated charcoal is only
seen to be slightly reinforced by the subsequent use of
the different fining agents tested.
In respect of the study of the aromatic profiles
obtained for the wines after the clarification treatments,
Table 2 presents the results of the variance analysis to
which the principal aromatic compounds studied were
subjected, corresponding to the control wine and the
treated wines.
No significant differences were detected between the
profiles obtained for the wine before and after its clarifi-
cation. In addition, a tasting study made by a group of
experts of the wine cellar in which these tests were
carried out did not reveal any appreciable negatives
673
Table 1 Variance analysis.
(GRP=2-(S)-glutathionyl caftaric
acid) and diminution percentage
for polyphenols which are
significantly different at p<0.05.
CA=activated charcoal+casein+
bentonite; CK=activated
charcoal+potassium caseinate+
bentonite; AH=activated
charcoal+albumine+bentonite;
GE=activated charcoal+
gelatin+bentonite
Compound Variance analysis Diminution percentage
Fp Charcoal CA CK GE AH
Gallic acid 0.86 0.055
Tyrosol 2.89 0.138
Catechin 53.31 0.000b19.56 31.81 82.26 14.17 38.13
Protocatechualdehyde 22.52 0.002b34.77 52.46 46.89 46.71 46.93
p-Hydroxybenzaldehyde 23.65 0.002b4.88 11.78 4.39 0.16 7.21
Syringic acid 3.94 0.083
Epicatechin 1.31 0.381
Caftaric acid 10.41 0.012a10.63 16.13 9.96 13.57 11.47
cis p-Coutaric acid 15.04 0.005b6.45 10.41 5.53 13.43 9.70
trans p-Coutaric acid 54.28 0.003b23.31 29.11 24.20 26.25 20.49
GRP 5.98 0.039a7.8 16.87 12.21 19.47 12.64
Chlorogenic acid 16.43 0.004b11.29 30.60 29.63 31.46 26.97
Caffeic acid 18.26 0.004b24.72 25.51 25.79 27.74 24.93
cis p-Coumaric acid 52.98 0.000b21.73 27.01 28.80 25.85 27.17
trans p-Coumaric acid 11.64 0.010b8.19 12.61 11.84 13.34 16.34
iso-Ferulic acid 24.02 0.002b30.28 41.76 39.92 43.74 43.66
Ferulic acid 60.56 0.000b28.83 35.57 32.22 33.99 32.87
aValues are significantly
different at p<0.05
bValues are significantly
different at p<0.01
Fig. 1 Cluster analysis applied to the control and treated wines.
Polyphenolic variables. Keys in Table 1
Table 2 Variance analysis applied to volatile compounds in the
control and treated wines
Compound Variance analysis
Fp
Isobutanol 0.35 0.791
3-Methylbutanol 0.47 0.719
3-Hydroxybutanone 0.21 0.885
Ethyl lactate 0.23 0.872
1-Hexanol 0.16 0.917
Acetic acid 0.35 0.795
2,3 Butanediol 0.47 0.720
2-Methylpropanoic acid 0.08 0.970
1,3 Butanediol 0.69 0.602
Butyric acid 0.15 0.927
Isovaleric acid 0.08 0.968
Diethyl succinate 0.20 0.894
Methanol 0.37 0.781
Hexanoic acid 0.41 0.754
Benzyl alcohol 0.36 0.785
Phenol 0.26 0.852
Octanoic acid 0.43 0.744
Diethyl glutarate 0.36 0.785
Diethyl malate 0.47 0.722
regarding the typical aroma of “fino” sherry wines. Other
authors have found that adsorption capacity of activated
charcoal depends on the dosage [22], and therefore its
application at a high dosage could affect the components
of the aroma, although these negative effects on the aroma
of the wines have only been confirmed at concentrations
much higher than those applied in this study [14].
In respect of the resistance to browning, from the
decreases produced in the polyphenolic content of the
clarified wines it would be expected that these would
present a reduced tendency to suffer this deterioration.
This susceptibility to oxidative phenomenon was deter-
mined by means of the electrochemical test of accelerated
browning.
Figure 2 shows the differences in behavior observed
for the wines treated with activated charcoal alone, acti-
vated charcoal combined with other clarifying agents,
and the control wine.
The addition of activated charcoal produced a marked
reduction in color intensity (Fig. 2), but this reduction
was not seen to be reinforced by the subsequent addition
of any of the other clarifying agents.
No differences exist in respect of the levels of suscepti-
bility to oxidation reached by the wines subjected to the
combined treatment with activated charcoal and the rest
of the clarifying agents tested in this study. All reached
similar color levels (at 420 nm) after the browning test.
The control wine reached a level of susceptibility to oxi-
dation similar to that observed in the clarified wines,
showing an increase in color that was less than the
increases observed in the clarified wines, but starting from
an initial value (absorbance at 420 nm) that was higher.
The behavior observed for the wine treated with activated
charcoal alone was similar to that observed for the wines
subjected to the combined clarifying treatments. It would
appear, therefore, that the addition of the other agents
after the application of activated charcoal does not provide
any reduction in the tendency to suffer browning.
These results were corroborated by the natural evolu-
tion of the color observed for the different wines along
one year in the bottle (Fig. 2).
It appears, therefore, that despite the reduction of the
oxidizable polyphenolic content, the application of acti-
vated charcoal has caused a destabilization of the wine’s
resistance to the oxidation processes that characterize the
phenomenon of browning; this destabilization was not
resolved by the later use of others fining agents.
Some studies of clarification conducted on white
wines have postulated that this destabilization observed
in respect of color could be due to the presence of
oxygen adsorbed onto the activated charcoal, which
would facilitate its solution in the wine [16].
This observation, together with the reduced protection
generated in the wines treated with activated charcoal as
a result of its great power of adsorption over other
components of the wine [23], could explain that the addi-
tion of charcoal in combination with other clarifying
agents gives rise to a wine which reaches levels of
susceptibility to oxidation equal to or slightly greater
than those observed in untreated wines.
In conclusion, the treatment of fino sherry wine with
activated charcoal, at the dosage studied (180 mg/l), in
combination with other clarifying agents, produces a
wine with a lower polyphenolic content, good organoleptic
characteristics, but its susceptibility to browning is similar
to that observed in untreated wine, despite commencing
from lower levels of color intensity.
Acknowledgements We gratefully acknowledge the collaboration
from “Sandeman-Coprimar”, which allowed these experiments
to take place. This work was supported by Spanish CICYT
(ALI97–0795).
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Charcoal is an important source of renewable biomass and has great industrial importance as a bio-thermo-reducer in the production of pig iron and steel. To increase the quality and yield of charcoal, it is necessary to invest in the continuous improvement of kilns and in the control of the carbonization process. However, there is a lack of studies that characterize the technologies currently used in the production of charcoal to achieve the ideal balance, considering advances and limitations. This balance is the starting point for the improvement of current carbonization kilns and development of new proposals for kilns. This study aims to fill this research gap. In this context, the main kilns used worldwide for the production of charcoal were characterized. A total of 21 types of carbonization kilns were found, and the majority presents technological improvements. However, even with carbonization kilns with technological advances available, most of the world charcoal production still uses from traditional kilns with low technology, which results in worse charcoal yield and quality. Therefore, several aspects are discussed that involve the production of charcoal and help to explain the difficulty in the consolidation of kilns with better technology.
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Charcoal is an important source of renewable energy with great industrial importance as a bio-thermo-reducer in the production of pig iron and steel. To increase the quality and yield of charcoal, it is necessary to invest in the continuous improvement of carbonization kilns and in the control of the carbonization process. However, studies to characterize the technologies currently used in the production of charcoal are lacking. This paper aims to fill this research gap by searching for patent documents of kilns used worldwide in the production of charcoal. A total of 172 carbonization kiln patents have been found and most of them contain technological improvements. The following were emphasized: information on the structure of the kiln, means of mechanizing the loading and unloading of kiln, the reuse of gases and vapors from the carbonization process, control of the carbonization process, rapid cooling of the produced charcoal while it is still inside the kiln, and possible advantages of adopting such technologies. However, despite these technological advances, most of the world's charcoal production still comes from low-technology, traditional kilns, resulting in lower yield and variable charcoal quality. Also discussed are the reasons for the lack of consolidation in the production environment of technologies proposed by kiln patents, considering the fact that they could increase the yield and quality of charcoal and, consequently, reduce the demand for wood.
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Puerta del Viento (PdV) Organic Wines has been making wine since 2009. The wines were made by Jorge Vega, a wine-grower from the Bierzo, who produced handcrafted wines using organic farming techniques. Organic wines produced from Mencía and Godello grapes created a market niche for Puerta del Viento, one of only five organic wineries in the Bierzo region. These local varieties were only grown in the Bierzo and in a smaller appellation nearby. In late 2014, Vega was concerned that gaining consumer acceptance for his unique and as-yet unknown wines was proving to be difficult.
Article
The impact of fining on the sensory and chemical properties of Washington State white wine was investigated. Unfilled, commercially prepared Chardonnay and Gewurztraminer wines were treated with bentonite (1000 mg/L), isinglass (60 mg/L), Sparkalloid (360 mg/L), activated charcoal (450 mg/L), whole milk (500 mg/L), or wheat gluten (400 mg/L). Ethyl dodecanoate was the only volatile compound to significantly differ among Chardonnay treatments, which was highest in the control (0.031 mg/L) and lowest in Chardonnay treated with bentonite (0.017 mg/L). Conversely, a number of volatile compounds varied significantly among Gewurztraminer treatments. Ethyl acetate was significantly highest in the activated charcoal treatment (25.4 mg/L), while lowest in the Sparkalloid treatment (22.1 mg/L). In addition, Gewurztraminer treated with activated charcoal contained high concentrations of higher alcohols. Wheat gluten significantly decreased the concentrations of I-hexanol, 3-methyl-1-butanol acetate, and 2-methyl-1-butanol. Benzeneethanol was significantly lower in the Sparkalloid, wheat gluten, and bentonite treatments. Conversely, benzeneethanol was highest in the isinglass (85.2 mg/L) and activated charcoal (74.7 mg/L) treatments. 2-Phenylethyl acetate and linalool were lowest in Gewurztraminer fined with bentonite. No significant differences were found among treatments for either varietal when the wines were subjected to difference testing (duo-trio) by an untrained panel (p >= 0.05). No differences were found among Gewurztraminer treatments evaluated by a trained panel, whereas differences in spicy aroma and floral/honey flavor were observed among Chardonnay treatments (p <= 0.05). This study demonstrated the impact fining can have on the chemical and sensory properties of wine and confirmed the importance of selecting the appropriate type of fining agent in order to maintain wine quality.
Article
A new accelerated browning method that allows the prediction of the evolution of white wine was developed. The determination of similarities between natural browning phenomena and accelerated browning is a critical point for the introduction of this new method for control purposes. Since phenolic compounds are the main substances responsible for browning, their evolution in both the natural process and accelerated browning was investigated. HPLC is used to quantify the phenolic composition and about 40 peaks are obtained for each analysis. Since the amount of information obtained is fairly large, chemometric techniques (cluster analysis of cases and principal component analysis) were used to analyse the evolution of phenolic compounds. It was demonstrated that the effects of accelerated browning on samples of wine have the same characteristics as natural browning.
Article
White sherry wines were treated with three fining agents (activated charcoal, PVPP and Riduxhigh), in addition to an initial treatment with casein and bentonite, in four different combinations. The wines were stored at 20 or 30 °C for 1 year with a view to examining changes in their flavan-3-ol fraction and differences in their degree of sensitivity to browning. Flavan-3-ol monomers and dimers, as well as browning measured as absorbance at 420 nm, increased during storage in all the wines. After this period the wines treated with fining agents containing activated charcoal, PVPP and Riduxhigh exhibited less marked browning, with no significant differences among them at both 20 and 30 °C. However, taking into account the higher initial colour of bottled wines treated with Riduxhigh in relation to those treated with activated charcoal or PVPP, this fining agent showed higher capacity to control browning.© 2000 Society of Chemical Industry
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