Autores
Pino Ramos, L.L. (UNIVERSIDAD DE TALCA) ; Peña Martínez, P.A. (UNIVERSIDAD DE TALCA) ; Laurie Gleisner, V.F. (UNIVERSIDAD DE TALCA)
Resumo
Lately, there has been an increasing interest in using plant-derived proteins for
wine phenolic fining. This work aimed at determining the fining ability of protein
extracts from the Andean pseudocereals quinoa (Chenopodium quinoa Willd.) and
kiwicha (Amaranthus caudatus L.) (QP and KP respectively) at different doses and
contact times on C. Sauvignon wine compared to commercial fining agents. QP and KP
were effective in reducing the turbidity, total phenolics and total tannins
similarly than commercial fining agents. Some treatments with QP and KP slightly
decreased the color intensity similarly to other vegetable proteins. The fining
ability of QP and KP has been studied for the first time. Results showed that they
could be used as effective fining agents alternatives to animal proteins.
Palavras chaves
plant-derived proteins; fining; red wine
Introdução
In the wine industry, proteinaceous fining agents are commonly used to modulate
the wine composition by removing unwanted substances that may affect its clarity
or organoleptic characteristics such as astringency. Traditionally, animal
protein-based preparations (e.g., gelatin, albumin, casein) have been used for
this purpose. The efficacy of these proteins has been widely proven, but their
use in wines has been questioned due to the risks they may pose to allergic
consumers, the removal of color, and their trade focus on vegan consumers
(DECKWART et al., 2014; WEBER et al., 2007). Lately, there has been a rising
interest in finding new methods for wine fining, and plant-derived proteins such
as those from cereals, potatoes, and legumes have received increasing attention.
Proteins extracted from several plant sources have been proposed as effective
phenolic fining agents, but due to their allergenic potential, only the ones
obtained from wheat, pea and potatoes have become commercially available (OIV-
OENO 495-2013). Quinoa (Chenopodium quinoa Willd.) and kiwicha (Amaranthus
caudatus L.) are native pseudocereals to the Andean highlands. Quinoa and
kiwicha have a higher protein content than traditional cereals such as rice,
corn and wheat (BRESSANIi, 1994; KOZIOL, 1992) and they are considered gluten
free products with low allergenic potential (DRZEWIECKI et al., 2003, GORINSTEIN
et al., 2002). Given their high concentration, and the types of proteins they
contained, quinoa and kiwicha seeds might be good sources of proteins for wine
phenolic fining. Therefore, the aim of this work was to determine the fining
ability of quinoa and kiwicha protein extracts on red wines, and to compare them
against commercial proteinaceous fining agents.
Material e métodos
Quinoa and kiwicha seeds were grounded to obtain the flour. Next, 50 g of each
flour was defatted with n-hexane for 24 h. The defatted meal was subjected to
alkaline extraction with water (10% w/v) at pH 9.5 and subsequent isoelectric
precipitation (pH 5) to obtain the protein extracts QP and KP. The protein
content of the extracts was determined by the Dumas method in a LECO TruSpec CN
Carbon Nitrogen Determinator element analyzer, using a 5.85 g protein/g nitrogen
conversion factor and alfalfa as standard. Fining experiments were carried out
in triplicate at 20°C using 50 mL Falcon tubes and included treatments with the
QP and KP extracts at different doses (20 and 30 g hL-1) and different contact
times (48 and 96 h) in comparison with gelatin. Fining agents were dispersed in
75 μL of water, added to 40 mL of C. Sauvignon wine, and mixed. The control
treatment consisted of 40 mL of wine treated with 75 μL of water. After
clarification, the samples were centrifuged at 14,000 rpm for 10 minutes. Tannin
concentration was determined spectrophotometrically using the methylcellulose
precipitable tannins assay. The monomeric fraction of flavan3-ols was analyzed,
using the p-DAC assay, with the catechin kit COD 12834 on a Y15 automatic wine
analyzer (Biosystems). Total phenolics were determined by the Folin–Ciocalteu
microassay using a SYNERGY HTX multi-mode reader. The CIELab parameters, color
intensity and hue were calculated from the absorption spectra using the software
MSCV (University of La Rioja, Spain. Low molecular weight phenolics were
analyzed on an Agilent 1200 series HPLC equipped with a LiChrosorb RP-18 column,
250 x 4 mm, 5 μm, and diode array (DAD) and fluorescence (FLD) detectors,
according to GÓMEZ-ALONSO et al., (2007).
Resultado e discussão
The effect of the clarification treatments on the content of total phenols,
total anthocyanins, total tannins, and catechins (monomeric flavan-3-ol) of
Cabernet Sauvignon wine is shown in Table 1. Treatments with QP significantly
reduced the content of total phenols at the two doses and contact times tested,
while KP only did so when applied at 30 g hL-1 for 48 h. All treatments
significantly decreased the content of precipitable tannins with
methylcellulose, being QP at 20 g hL-1 for 96 h the most effective treatment.
Treatments with QP and KP did not affect the content of total anthocyanins,
while gelatin was the only treatment that produced a significant decrease in
these compounds. In the case of flavan-3-ol monomers, all treatments
significantly decreased their concentration. The effect of the clarification
treatments on the concentration of low molecular weight phenols such as
flavonols and anthocyanins was analyzed by HPLC (data not shown). The treatments
did not significantly decrease the concentration of the analyzed compounds. Our
results allow us to hypothesize that the fining agents used are more likely to
bind high molecular weight tannins than to those of low molecular weight or
monomers. Colorimetric parameters were also analyzed and are shown in Table 2.
Treatment with QP at 30 g hL-1 for 48 h produced the greatest increase in the
luminosity of the wine under study, followed by treatment with gelatin.
Consistently, gelatin and QP treatments for 48 h significantly increased the a*
and b* coordinates. None of the treatments applied affected the colorimetric
parameters, color intensity and hue. The use of QP and KP as fining agents has
the advantage that they are non-allergenic products.
Total phenolics, tannins, anthocyanins and catechins of Cabernet Sauvignon wine treated with different fining agents at two contact times (48 and 96h)
Colorimetric parameters of Cabernet Sauvignon wine treated with different fining agents at two contact times (48 and 96 h)
Conclusões
The fining ability of quinoa and kiwicha protein extracts has been studied for the
first time. Results showed that QP and KP could be used as effective fining agents
for red wines as alternatives to animal proteins such as gelatin. The use of QP
and KP as fining agents has the advantage of being non-allergenic products. More
studies have to be performed to investigate the effects of the treatments with QP
and KP on the sensorial attributes of wines.
Agradecimentos
The study was supported by the Chilean National Agency of Research and Development
(ANID) through FONDECYT Postdoctoral 3200396 (L.L. Pino-Ramos), FONDECYT 1190301
(V.F. Laurie), and the doctoral grant 21190245 (P. Peña-Martínez)
Referências
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