Enological Parameters and Total Phenolic Compounds in Fetească Neagră Wines Aged with Oak Chips

Focusing on Modern Food Industry (FMFI), Volume 5 2016 www.fmfi‐journal.org doi: 10.14355/fmfi.2016.05.004

Enological Parameters and Total Phenolic Compounds in Fetească Neagră Wines Aged with Oak Chips Georgiana‐Diana Dumitriu1, Nieves Lopez de Lerma*2, Valeriu V. Cotea3, Marius Niculaua4, Rafael A. Peinado5 University of Agricultural Sciences and Veterinary Medicine “Ion Ionescu de la Brad” Iași, Department of Viticulture and Oenology, 700490, no 3, Mihail Sadoveanu Alley, Iaşi, România 1,3,4

University of Cordoba, Department of Agricultural Chemistry Edificio Marie Curie, Campus of Rabanales, E‐ 14104, Cordoba, Spain 2,5

dumitriu.diana22@yahoo.com; 2*b92lolem@uco.es; 3vcotea@uaiasi.ro; 4niculaua@gmail.com; 5rafael.peinado@uco.es

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Abstract Aging process in winemaking is a crucial component in defining the quality of resulted products. In the last years alternative practices (oak chips) started to become more useful, due to their benefits. In this paper we study the impacts of various oak chips on the red wines enological parameters and phenolic compounds. Fetească neagră variety grape (V.vinifera) was growing in North‐East Romania wine region and harvested in 2013. Thirteen technologic variants followed the same classical winemaking process and were separated into a control sample (without chips) and samples aged with various types of oak chips for of 1.5 and 3 months. Phenolic compounds we determinated using spectrophotometric measurements to evaluate the total quantity of anthocyans and the total polyphenolic index. Wine constitutes a dynamic system, in continuous evolution, in which numerous reactions involving polymerization and condensation take place between its phenolic compounds during the aging process. These reactions, undoubtedly affect its structure and, very probably, its phenolic compounds. In our study, phenolic compounds quantities presents a low variation among samples, but are influenced by the time of aging, decreasing at 3 months. Cluster analysis of Fetească neagră wines differentiated the variants in two major groups (aged wines at 1.5 months and aged wines at 3 months).

Keywords Red Wines; Oak Chips; Total Phenolic Compounds; Anthocyans

Introduction One of the most important practices in the production of alcoholic beverages is the aging process, where a series of physical, chemical and biological changes take place that improve wines stability and also modification to the compositional and organoleptic characteristics. Simpler and more affordable aging practices, alternative to barrels, such as the use of pieces of oak wood, have gained increased significance in the wine industry in the last time period. The role of wood is crucial because during the maturation process changes take place: flavor complexity increases due to the elimination of compounds present in wood and the phenolic compounds from wood are solubilised.

The phenolic composition of wines is strongly influenced by the experimental conditions of the aging. It is well known that the final chemical and organoleptic characteristics of wines depend on the wood used (botanical and geographical origin, seasoning, toasting degree) (Schumacher et al., 2013), the contact surface (size, amount of chips) and the duration of contact between wood pieces and wine (Rodríguez‐Bencomo et al., 2008; Cejudo‐ Bastante et al., 2011; Ortega‐Heras et al., 2010). In the case of treatment with oak chips, additional parameters such as the size, toasting, type have an important influence in the phenolic spectrum of the final product. Therefore, the phenolic composition can help to characterise and detect wine aging styles. Recent studies have suggested that some wines containing phenolic compounds are capable of preventing aging and diseases such as arteriosclerosis, diabetes and inflammatory processes Ghanta et al., 2007; Ulrich‐Merzenich et al., 2009).

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Wine colour changes during aging process, from the initial red of young wines to a more reddish‐brown hue of aged wines, are attributed to reactions that take place between anthocyanins, a type of flavonoids responsible for the colour of red grapes and young wines, and other molecules present in the medium, leading to the formation of new more stable pigments.

This work was carried out in order to investigate the influence of enological parameters and phenolic compounds of wines (Fetească neagră grape variety) aged with specific oak chips for 1.5 and 3 months.

Materials and Methods Winemaking Process Experimental material used is Fetească neagră grapes from North‐East Romania, harvested in 2013. The marc obtained was subjected to maceration–fermentation process at temperature of 10‐12˚C, for 7 days. In the next step, the marc was pressed and the wines obtained were transferred in fermentation tanks for the completing of alcoholic and malolactic fermentation. At the end of the fermentation processes, a batch was used as control wine (without chips) and the other batches were aged with different oak wood chips (table 1) for 1.5 months and 3 months. The dimensions oak chips in centimetres was 0.5 x 1.5 x 0.2 (width x length x thickness) and the wines were aged during 1.5 and 3 months.

TABLE 1. ORIGIN, DOSE (G/L) AND TYPE OF OAK CHIPS USED WINE AGING.

Geographical origin

Type

Toasting level

Dosage

Code

Control wine

V0

Pure

Untoasted

3

V1

5

V2

Fruity

Medium

3

V3

5

V4

Vanilla

Medium plus

3

V5

5

V6

3

V7

5

V8

Quercus petraea /France

Spice

Tannin

Heavy

Medium plus

Quercus alba/ United States

3

V9

5

V10

3

V11

5

V12

Analytical Parameters The analytical methods used to characterize the above parameters are in accordance with European and O.I.V. standards (2015). Wine sample, at 1.5 and 3 months, was analysed for determining the basic physico‐chemical parameters: pH (OIV‐MA‐AS313‐15), titratable acidity (OIV‐MA‐AS313‐01), volatile acidity (OIV‐MA‐AS313‐02), ethanol (OIV‐MA‐AS312‐01A) and reducing sugar (OIV‐MA‐AS311‐01C).

Determination of Total Phenolic Compounds and Total Anthocyans To characterize the phenolic compounds we used a spectrophotometric measurement, in order to evaluate the total quantity of anthocyans and the total polyphenolic index of wines. Principle of method for total quantity of anthocyans is based on the existence of a acidic medium where there is an equilibrium between colored and incolor forms of anthocyans. This equilibrium depends on the pH values. Color intensity variation between two pH values (pH = 0.6 and pH = 3.5) is proportional to the anthocyans content. This variation is not affected by the phenolic functions or other phenolic compounds (like tannins).

Photometric measurements were made using Analytik Jena S200 spectrometer (at 280 nm, respectively 520 nm), after filtering the samples through a HA‐0.45 μm paper (Millipore, Milford, MA).

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Statistical Analyses A homogeneous group analysis was made to identify significant differences in the analysed parameters among the wine samples using the statistical package Statgraphics Centurion XVI from StatPoint Technologies, Inc. (Warrenton, VI, USA). Cluster analysis was made to establish differences among wines aged for 1.5 and 3 months, using total anthocyans content as classifying variables.

Results and Discussion Enological Parameters Table 2 shows the values of the enological parameters analyzed in wines containing different dosage and type of chips during the aging process. pH values usually increased during aging in most samples.

TABLE 2. ENOLOGICAL PARAMETERS OF FETEASCĂ NEAGRĂ AGED WINES AT 1.5 AND 3 MONTHS

V0

V1

V2

V3

V4

V5

V6

1.5 Months pH

3.68±0.01

3.71±0.01

3.73±0.01f

3.74±0.00g

3.74±0.01g

3.65±0.01a

3.65±0.02a

5.8±0.04b

5.8±0.04b

6.0±0.06i

5.68±0.04a

5.83±0.03c

5.98±0.08h

5.95±0.04g

0.56±0.01d

0.58±0.04e

0.55±0.01c

0.53±0.01b

0.52±0.01a

0.53±0.01b

0.52±0.02a

Ethanol (% v/v)

14.96±0.17a

14.96±0.01a

14.96±0.02a

14.96±0.06a

14.96±0.1a

14.96±0.05a

14.96±0.01a

Reducing sugar (g/L)

2.36±0.01b

2.35±0.06a

2.37±0.01c

2.36±0.04b

2.35±0.01a

2.36±0.03b

2.36±0.01b

Titratable acidity (g tartaric/L) Volatile acidity (g acetic/L)

d

e

3 Months pH

3.7±0.01f

3.72±0.01g

3.76±0.00i

3.74±0.00h

3.76±0.01i

3.66±0.01b

3.65±0.01a

5.78±0.00f

5.73±0.04e

5.7±0.00d

5.62±0.08a

5.65±0.00c

5.88±0.00i

5.85±0.04g

0.57±0.01c

0.58±0.00d

0.57±0.01c

0.56±0.00b

0.55±0.01a

0.57±0.00c

0.57±0.02c

Ethanol (% v/v)

14.96±0.12a

14.94±0.03a

14.94±0.03a

14.94±0.05a

14.94±0.0a

14.94±0.05a

14.94±0.01a

Reducing sugar (g/L)

2.36±0.02b

2.35±0.08a

2.37±0.02c

2.36±0.01b

2.35±0.05a

2.36±0.02b

2.36±0.01b

V7

V8

V9

V10

V11

V12

Titratable acidity (g tartaric/L) Volatile acidity (g acetic/L)

1.5 Months pH

3.67±0.01c

3.66±0.01b

3.66±0.00b

3.66±0.01b

3.66±0.02b

3.66±0.01b

5.83±0.08c

5.95±0.04g

5.91±0.05e

5.89±0.04d

5.92±0.08f

5.91±0.04e

0.53±0.03b

0.52±0.01a

0.52±0.01a

0.52±0.01a

0.52±0.01a

0.52±0.01a

Ethanol (% v/v)

14.96±0.07a

14.96±0.05a

14.96±0.09a

14.96±0.14a

14.96±0.01a

14.96±0.1a

Reducing sugar (g/L)

2.35±0.01a

2.37±0.03c

2.36±0.01b

2.37±0.02c

2.35±0.01a

2.36±0.05b

pH

Titratable acidity (g tartaric/L) Volatile acidity (g acetic/L)

3 Months 3.69±0.00

c

3.61±0.01

3.66±0.01b

3.66±0.00b

3.66±0.00b

3.66±0.01b

5.63±0.04b

5.7±0.00d

5.86±0.00h

5.85±0.04g

5.89±0.00j

5.85±0.02g

0.78±0.00f

0.81±0.03g

0.84±0.01h

0.84±0.01h

0.69±0.02e

0.81±0.00g

Ethanol (% v/v)

14.94±0.05a

14.94±0.05a

14.94±0.02a

14.94±0.01a

14.94±0.01a

14.94±0.0a

Reducing sugar (g/L)

2.35±0.05a

2.36±0.02b

2.36±0.01b

2.36±0.04b

2.35±0.01a

2.35±0.05a

Titratable acidity (g tartaric/L) Volatile acidity (g acetic/L)

e

Data expressed as mean ± standard deviation. Different superscript letters indicate significant differences at 95% of confidence level (homogenous groups analysis)

Ethanol content it is not influenced by the types and amount of chips. Along the aging time, it has been reported a decreased content in ethanol, mainly due to evaporation and or to oxidation and esterification phenomena. In our

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study, no significant differences were obtaioned among wines aged for 1.5 and 3 months.

Slight differences can be observed, in general terms, in the volatile acidity due to the type of chips used at 1.5 months of aging. However, at 3 months, wines aged with heavy toast chips and medium plus chips type tannin show significant increased values (V7 to V12 wines) in relation to the wines aged for 1.5 months. This increased values can be due on one hand to the non‐enzymatic oxidation of ethanol first into acetaldehyde and them into acetic acid. On the other hand, the hydrolysis of acetyl groups present in hemicelluloses that occurs during toasting can also increase the levels of acetic acid in wine during ageing (Moreno & Peinado, 2012).

Total acidity values (g tartaric/L) decreased due probably to the precipitation of the tartaric salts (Moreno & Peinado 2012). Lastly, wines show a small quantity of reducing sugar (between 2.35 g/L and 2.37 g/L) which are typical of dry wines.

Phenolic Compounds The main phenolic compounds responsible of the colour of the red grapes. are extracted from the grape skin during fermentation but anthocyanins levels decrease during maturation and aging as a result of the formation of new anthocyanin‐derived pigments (Moreno & Peinado, 2012).

As can be seen in Fig. 1 only wines aged with tannin chips (V9 to V12) increased their total phenolic contents (TPI) in relation to the control. Whereas, TPI decreased in wines aged with medium plus or heavy toast chips (V5 to V8).

So it can be assumed that in wines aged with tannin chips the diffusion of polyphenols from the oak chips to the wine prevailed versus precipitation and the opposite is true for V5 to V8 wines.

Also, we observed that wines aged in presence of oak chips during 1.5 months showed higher total phenolic amount than the control wine. At 3 months of aging, the wines increased their phenolic concentration than the control wines.

The phenolic compounds content of the wine decreased with wine age, due to their participation at different chemical reactions like: condensation between the specific phenolic compounds found in wine; condensation reactions between the phenolic compounds in the presence of acetaldehyde; oxidation reactions of the phenolic compounds with the formation of some xantiliu derivates of yellow color that conducts to the modification of the colour from red‐purplish to red brick like.

FIG. 1 TOTAL POLYPHENOLS INDEX (MG CATECHIN/L) DURING AGEING AT 1.5 AND 3 MONTHS FOR FETEASCĂ NEAGRĂ WINES

It can be observed that the quantity of anthocyans decreases in all tehnological variants at 3 months. Thought, this variation is small we can conclude that types of chips don`t influence their amount (Fig. 2). The variation is caused by the chemical changes in the wines composition that take place like, condensation, oxidation, insolubilization and sedimentation of phenolic compounds.

At 1.5 months the quantity of anthocyans ranges between 494.25 mg/L (V1) and 419.32 mg/L (V10) and at 3 months varies from 449.84 mg/L (V0) to 374.15 mg/L (V12).

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During red wines aging colored polymeric anthocyans are formed and the presence of monomeric anthocyanins decreases. In the same time, the anthocyanin equilibrium is affected while transforming their red color into polymer (Salas et al., 2004). Also, these polymeric pigments are relevant for the sensorial feel of red wines in the mouth, due to their increased solubility compared to the pure polymeric proanthocyanidins meanwhile limiting the precipitation of these condensed tannins.

FIG. 2 TOTAL QUANTITY OF ANTHOCYANS DURING AGEING AT 1.5 AND 3 MONTHS FOR FETEASCĂ NEAGRĂ WINES

Previous studies reported that at the end of alcohol fermentation about 25% anthocyanins may have polymerized with flavonoids, and approximatly 40% by the end of the first year of aging. This phenomen continues at a decreasing rate for approximatly a number of years, when total polymerization has been achived (Jackson, 2008).

Even after long aging periods wine continue to be red of red‐brown, when if we donʹt find monomeric anthocyanins. Therefore, the polymerization process is shifting in time the anthocyanin absorption properties, transforming red to brown, or in some cases orange and yellow (Santos‐Buelga et al., 1999).

Cluster Analyses

FIG. 3 CLUSTER ANALYSES OF FETEASCĂ NEAGRĂ AGED WINES

Cluster analysis is the most popular from the multivariate techniques with many applications in the field of food science and technology (Müller & Hamm, 2014).

In the cluster analysis the primary purpose is to aggregate individuals based on their characteristics, forming groups with greatest possible internal homogeneity (within groups) and greatest possible external heterogeneity (between groups).

In this work, the Ward´s method was used to assess similarity between wines treated with various type of oak chips aged 1.5 and 3 months. Anthocyans content of the whole sample were used as classifying variables (Fig. 3).

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As can be seen in Fig. 3 two distinct clusters were formed, where the first one distinguished the wines aged 1.5 months and in the second cluster, the wines aged 3 months.

Conclusions Enological parameters of aged wines are in the same range as regular Fetească neagră red wines values and showed no significant differences when compared with control wine.

The evolution of phenolic compounds quantities presents a low variation and does not have major differences between variants. Though a decrease of total phenolic compounds is registered for variants at 3 months compared to samples at 1.5 months. Also, aging time decreased the total amount of anthocyans in all technological variants.

Cluster analysis of Fetească neagră wines separated the variants in two major groups (aged wines at 1.5 months and aged wines at 3 months).

Alternative products in winemaking, as oak chips, prove a important potential for producing red wines with a increased cost‐effectiveness and simple use, by accelerating the manufacture process and shortening the time of contact with wine.

ACKNOWLEDGMENTS

This paper was published under the frame of European Social Fund, Human Resources Development Operational Programme 2007‐2013, project no. POSDRU/159/1.5/S/132765. We are grateful to Campus de Excelencia Internacional Agroalimentario (ceiA3) and the International Doctoral Program of the University of Córdoba, in collaboration with Vitenol research Group.

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