ns

Xu

Chinnces

Received in revised form 9 September 2014Accepted 19 September 2014Available online 28 September 2014

Keywords:Bottle stoppers

ing 18-month aging in bottle. The wines were sealed with six types of bottle stoppers. The results showed

determines red hues in wine (Revilla, GarcA-Beneytez, & Cabello,2009). Typically, the reactions between anthocyanins and otherphenolic compounds in wine change its purple tints toward rubyred (Boulton, 2001; Fulcrand, Duenas, Salas, & Cheynier, 2006).These reactions also promote the stability of wine colour andreduce the astringency of wine (Boulton, 2001). Meanwhile, the

outhfeel mainlybottle s

ati, 2000;conrme

wine maturation in bottle was affected by the sealing sysbottle stoppers (Godden et al., 2001), and oxygen transf(ORT) signicantly determined the development of wine(Godden et al., 2001; Skouroumounis et al., 2005). The increaseof ORT can markedly enhance the degradation speed of anthocy-anins and monomer avan-3-ols, accelerate the sulphite con-sumption, and increase the chromaticity (related to the decreaseof sulphite content) (Wirth et al., 2010). A continuous micro-aer-obic condition with appropriate OTR in bottled wine can also helpto increase the accumulation of pyranoanthocyanins and remove

Corresponding author. Tel.: +86 10 62736191; fax: +86 10 62738658.E-mail address: panqh@cau.edu.cn (Q.-H. Pan).

1 Both of authors equally contributed to this work.

Food Chemistry 172 (2015) 565574

Contents lists availab

Food Che

lsenamic acids, avan-3-ols, avonols and stilbenes). Besides, poly-meric phenolics can be formed through condensation reactionsbetween avan-3-ols and anthocyanins during aging period.Amongst these compounds, anthocyanins are the main factor that

pounds on development of wine colour and mdepends on transferring oxygen through the(Castellari, Matricardi, Arfelli, Galassi, & AmJulien, Jourdes, & Teissedre, 2011). It has beenhttp://dx.doi.org/10.1016/j.foodchem.2014.09.1150308-8146/ 2014 Elsevier Ltd. All rights reserved.topperSilva,

d thattem ofer ratequality1. Introduction

Phenolic compounds are responsible for sensory characteristicsin wine, such as colour, mouthfeel, and avour, and they undergomany compositional and content changes in the process of wineaging (Li et al., 2009). Generally, wine phenolic compounds arecomposed of two main groups, anthocyanins and non-anthocyaninphenolic compounds (namely, hydroxybenzoic acids, hydroxycin-

unstable anthocyanins from grape skins are converted into stableoligomeric and polymeric pigments via the combination with vinylphenol and/or pyruvic acid during wine fermentation and agingprocesses (Fulcrand, Benabdeljalil, Rigaud, Cheynier, &Moutounet, 1998). Flavan-3-ols and hydroxycinnamic acids areinvolved in redox reactions, causing browning reactions and hazeformation (Cheynier & Ricardo-da-Silva, 1991).

During bottle aging, the effect of evolution of phenolic com-Bottle agingPhenolic compoundsSensory qualitythat phenolic compounds presented four evolution patterns along with wine aging in bottle, mainlydepending on their chemical nature. Most of the anthocyanins had signicant differences in concentra-tion amongst the wines sealed with the six bottle stoppers at the 18-month point. Analysis of partial leastsquares (PLS) revealed that wine appearance quality was positively correlated with the levels of malvi-din-3-O-(6-O-acetyl)-glucoside-4-vinylguaiacol, gallocatechin and dihydrokaempferol-3-O-rhamnos,while the development of mouthfeel properties was positively associated with the evolutions ofmalvidin-3-O-glucoside-ethyl-(epi)catechin, peonidin-3-O-(6-O-acetyl)-glucoside, malvidin-3-O-(6-O-coumaryl)-glucoside-pyruvic acid and peonidin-3-O-glucoside-4-vinylphenol. No obvious associationwas observed between the development of wine sensory characteristics and the evolution of dissolvedoxygen in wine.

2014 Elsevier Ltd. All rights reserved.Article history:Received 6 June 2014

This study aimed to assess the correspondence between the evolution of phenolic compounds and thedevelopment of appearance and mouthfeel in Cabernet Sauvignon (Vitis vinifera L. cv.) dry red wines dur-Evolution of phenolic compounds and seand their co-development

Yuan Gao a,1, Yuan Tian a,1, Di Liu a, Zheng Li b, Xiao-Jun Wang a, Qiu-Hong Pan a,aCenter for Viticulture & Enology, College of Food Science and Nutritional Engineering,b Food Science and Human Nutrition Department, Institute of Food and Agricultural Scie

a r t i c l e i n f o a b s t r a c t

journal homepage: www.eory in bottled red wines

Zhang a, Jing-Ming Li a, Jing-Han Huang a,

a Agricultural University, Beijing 100083, China, University of Florida, Gainesville, FL 32611, USA

le at ScienceDirect

mistry

vier .com/locate / foodchem

animal odors (Wirth et al., 2012). However, some different opin-ions suggested that OTR only affected visual and olfactory percep-tions of wine, but had little impact on in mouth attributes(Caill et al., 2010).

The level of dissolved oxygen in bottled wine mainly dependsupon oxygen concentration in the headspace at bottling and theingress rate of oxygen into the bottle through stoppers (Goddenet al., 2001). Therefore, bottle stoppers determine the dissolvedoxygen concentration in wine to a large extent. Generally, syn-thetic plugs lead to higher oxygen transmittance, whereas thelower oxygen concentration is observed in screw-cap bottled

2. Materials and methods

2.1. Wine samples

The wine samples used for this trial were produced in BeijingDragon Seal Winery Company during a 2009 vintage from Caber-net Sauvignon (Vitis vinifera L. cv.) grapes grown in Huailai County,Hebei Province, China. These wines had been aged in French oakbarrels (Shenyang Fresh Wood Industry Co., Ltd. China) for12 months prior to being bottled. Bottling was performed in mid

Four bottles (considered four biological replicates) were used for

plugs is smaller than that of the other three corks. The synthetic

etic

522 284 288 256

566 Y. Gao et al. / Food Chemistry 172 (2015) 565574wines, compared to other types of stoppers, such as technicalcorks and natural corks (Lopes, Saucier, Teissedre, & Glories,2006, 2007). Polymer synthetic plugs have a good sealing capacitydue to good performance on pullout force and resilience, whichleads wines to a good quality at least within 24 months after bot-tle aging (Silva, Lambri, & Faveri, 2003). Synthetic plugs tend toretain more volatile acid and free and total SO2 in wine after8 months of bottling. Beyond these, some studies suggested thatwines sealed with synthetic plugs lacked fruity aroma and exhib-ited weak anti-oxidative activity (Godden et al., 2001;Kwiatkowski, Skouroumounis, Lattey, & Waters, 2007; Marin,Jorgensen, Kennedy, & Ferrier, 2007; Silva et al., 2003). However,it also has been reported that synthetic plugs effectively pre-vented the generation of corked taste and provided white winewith fruity aromas (Francis, 2003). Besides bottle stoppers, stor-age temperature also can cause some differences in aroma,mouthfeel, and colour of bottled wines (Hopfer, Buffon, Ebeler,& Heymann, 2013).

Bottle-aging is a necessary stage in the production process ofwines because it helps to modify various organoleptic propertiesfor good wine quality. The amount of oxygen ingress related to bot-tle stopper types plays an important role in development of wineorganoleptic properties. However, most of the studies so far havebeen undertaken to study the impact of stopper types on the chem-ical composition, colour, and avour of the bottled wines. The lit-erature is scarce on the establishment of the association betweenthe variation of phenolic compounds and the development of winecolour and mouthfeel properties in bottled wines. In the presentstudy we used the wine aged in advance in oak barrels for12 months, and sealed the wine with six types of bottle stoppersto provide different oxygen environments for post-bottling matu-ration. Phenolic compounds were qualitatively and quantitativelyexamined using high performance liquid chromatography-massspectrometry (HPLCMS). Sensory evaluation was carried out bya trained panel (20 tasters). The co-development between phenoliccompounds and the properties of colour and mouthfeel wasassessed by means of statistical tools. The results screened outsome phenolic compounds that played a critical role in the evolve-ment of colour and mouthfeel in wine during bottle-aging, andthus provided important references for improvement of Chinesewine quality.

Table 1Physical index of various bottle closures used in this study (n = 10).

Physical index Closure types

Synthetic plug-1

Synth2

Diameter (mm) 21.74 21.58Length (mm) 44.72 36.41Ovality (mm) 0.18 0.2Moisture content (%) 1 0.9Density (kg/m3) 514 501

Percentage of compression to the original diameter (%) 72 72Rebound rate (%) 98 99plugs showed much lower moisture content and much higher den-sity compared with the other three corks, indicating that the poly-mer synthetic plugs possess poor elasticity.

2.3. Chemicals and standards

Ethyl acetate (analytical grade) was purchased from BeijingChemical Reagent Company (Beijing, China). Acetonitrile, metha-nol, formic acid, and acetic acid (HPLC grade) were obtained fromFisher Scientic Co. (Fairlawn, NJ, USA). Deionised water (

2.4.1. Anthocyanins

2000, Shanghai Yarong Biochemistry Factory, Shanghai, China) at

Wine colour was evaluated using CIELab space, and CIELab

istrvalues were determined according to a published method (Ayala,Echavarri, & Negueruela, 1997). The wine sample was lteredthrough a 0.45 lm lter (cellulose acetate and nitrocellulose,CAN) prior to analysis. Absorbance at 440 nm, 530 nm, and600 nm were measured through a 0.2 cm light path length on aT6 Spectrophotometer (Shanghai, China). Distiled water was used30 C and re-dissolved in 5 mL methanol. The resultant methanolsolution was ltered through 0.22 lm nylon membrane ltersprior to HPLCMS analysis. A Zorbax SB-C18 column (3 50 mm,1.8 lm) was used for the separation of non-anthocyanin phenoliccomponents. The mobile phase consisted of (A) aqueous 1% aceticacid and (B) acetonitrile containing 1% acetic acid. The gradientelution was performed at the ow rate of 1 mL/min as follows:05% B for 5 min, 58% B for 5 min, 812% B for 5 min, 1218% Bfor 5 min,1822% B for 2 min, 2235% B for 2 min, and 35100%B for 4 min. Injection volume was 20 lL and the detection wave-length on DAD was 280 nm. Mass spectrometry (MS) conditionswere set as follows: negative electro-spray ionisation (ESI) inter-face mode, 30 psi nebuliser pressure, 10 mL/min dry gas ow rate,325 C dry gas temperature, andm/z 1001500 all mass scan mode.External standard catechin, quercetin, gallic acid, caffeic acid, andtrans-resveratrol were used for quantication of avan3-ols, avo-nols, hydroxybenzoic acids, hydroxycinnamic acids and stilbenes,respectively.

2.5. Characterisation of colour fractionAnthocyanins were examined according to our previously pub-lished method (Han et al., 2008). The wine samples were lteredthrough 0.22-lm lters (cellulose acetate and nitrocellulose,CAN) and the resulting ltrates were directly injected into an Agi-lent 1200 LC-UV-MS equipped with a reversed-phase column [Kro-masil C18; 250 lm (length) 4.65 lm (diameter)]. A gradientconsisting of solvent A [water:formic:acetonitrile, 92:2:6 (v/v)]and solvent B [water:formic:acetonitrile, 44:2:54 (v/v)] wasapplied at a ow rate of 1 mL/min as follows: 010% B for 1 min,1025% B for 19 min, 2540% B for10 min, 4070% B for 5 min,70100% B for 5 min. Injection volume was 30 lL and the detectionwavelength on a diode array detector (DAD) was 525 nm. Massspectrometry (MS) conditions were set as follows: positive elec-tro-spray ionisation (ESI) interface mode, 30 psi nebulizer pressure,12 mL/min dry gas ow rate, 300 C dry gas temperature, and m/z1001500 all mass scan mode. Anthocyanins were quantied usingmalvidin-3-O-glucoside as an external standard, and expressed asmilligram per litre on the basis of malvidin-3-O-glucoside.

2.4.2. Non-anthocyanin phenolic compoundsThe wine sample (100 mL), diluted with an equal volume of

distiled water, was extracted three times with ethyl acetate in suc-cession and then separated by a separating funnel. The ethyl ace-tate phase was evaporated to dryness in a rotary evaporator (SY-Malvidin-3-O-glucoside was purchased from Extra synthese SA(Genay, France), whereas gallic acid, catechin, caffeic acid, querce-tin, and trans-resveratrol were received from Sigma Chemical Co.(St. Louis, MI, USA). All the standards used for identication andquantication in this study were of HPLC quality.

2.4. Determination of phenolic compounds

Y. Gao et al. / Food Chemas the blank. The colour parameters that dene the CIELab spaceare lightness (L), redness/green component (a), yellowness/bluecomponent (b), and hue angle (Hab).

2.6. Determination of dissolved oxygen in wine

The dissolved oxygen was immediately measured at the open-ing the bottle through an inoLabOxi730 dissolved oxygen instru-ment equipped with an automatic mixing electrode (WTW,Germany). The scale of sensor measurement ranges from 0 to50 mg/L. The electro-chemical equipment was calibrated beforeevery measurement. Measures were obtained from the mean valueof three readings after it was stabilised on a certain value.

2.7. Sensory evaluation

Sensory evaluation of the wines was carried out using 100 posi-tive points provided by International Organisation of Vine andWine (OIV) (NN106/04, 2004). The attributes were composed ofappearance (20 score points), fragrance (30 points), mouthfeel(40 points), and overall impressions (10 points) of wines. In thepresent study, the values of appearance and mouthfeel were espe-cially taken into account to explore correlation between theseattributes and phenolic compounds. Twenty panelists (ten malesand ten females) participated in the sensory sessions every timeand they were students with ages between 21 and 24, majoringin Viticulture and Enology of our college. The participants hadacquired the knowledge of wine tasting and completed a 40-htraining course of wine sensory evaluation. In each session the par-ticipants were seated in separated booths and the wines, sealedunder six different types of the stoppers, were presented in a ran-dom order. The appearance characteristics (clarity, chroma andhue) and mouthfeel characteristics (purity, intensity, structure,harmony and aftertaste) were documented and scored. A 10 minbreak was taken between samples. To minimise the systemic var-iance caused by tasters and to make data more objectively reectthe difference amongst the wine samples, we performed the stan-dardisation of the raw data according to condence intervals. For awine sample sealed under the same type of stoppers (named aswine-j), the average (named asMj) of the sensory evaluation scoresfrom all the tasters was calculated and their standard derivation(rj) was attained as well. The condence interval of sensory eval-uation for this wine-j sample was in the range of Mj rj. When asensory evaluation score of the wine-j sample that an individualtaster gave was within this range of the condence interval, theraw score was considered to be valid and did not need to performstandardisation conversion. But when the score was outside thisrange, the standardisation conversion was applied via the rawscore plus or minus the rj value. As a result, a new set of datawas generated for the sensory evaluation of the wine-j sample,and these data were used for subsequent statistical analysis.

2.8. Statistical analysis

In this study, quantitative analysis of phenolic compounds andCIELab values was performed in four experimental sample repli-cates for each stopper type. Cluster analysis was used to highlightthe similarities and differences in the wines sealed under differentstoppers using phenolic compounds as variables. Based on the sen-sory description and principal component analysis (PCA) of thewine samples with different stoppers and different bottle agingperiods, a loading Biplot was provided to visualise the positioningof sensory quality of various wine samples. Partial least squares(PLS) regression was applied to establish the correspondence

y 172 (2015) 565574 567between sensory characteristics and phenolic components. Full

cross-validation was used to validate the PLS model. From vari-ables importance plot (VIP) value, regression coefcients and load-ing weights, we can determine that effects of phenolic compoundson the development of sensory quality in bottle-aged wines sealedwith different stoppers. All statistical analyses were performed bySPSS 14.0 software (Chicago, IL, USA).

3. Results and discussion

3.1. Evolutions of dissolved oxygen and phenolic compounds in winesduring aging in bottle

The dissolved oxygen concentration in the wine rapidlydropped within the rst three months of the post-bottling, andsubsequently remained at a low level (Fig. 1). The initial dissolvedoxygen amount was obtained from the wines that were bottledand held upright for 12 h. It was observed that the technical cork

568 Y. Gao et al. / Food Chemistrand natural cork allowed more oxygen to stay inside the bottlecompared to the other stoppers just after the bottling point. Fromthe 12th month of post-bottling, the dissolved oxygen content inthe wines using the synthetic plug-3 exhibited an obviousincrease. At 18 months, the wines using the synthetic plug-1, syn-thetic plug-3, and natural cork contained higher levels of the dis-solved oxygen compared with the wines sealed with the otherthree types of stoppers (Fig. 1). This indicated that both of thesynthetic plugs provided a poor sealing environment and allowedoxygen to enter the bottles after a year of bottle storage, which isin agreement with a previous report (Mas, Puig, Lladoa, & Zamora,2002).

The evolution of phenolic compounds during the wine bottle-aging was assessed and heatmap cluster analysis was performedusing package R based on 34 anthocyanins and 33 non-anthocyaninphenolic compounds detected in this study (Appendix Figs. 16).Although therewere certain differences in composition and concen-tration of phenolic compounds amongst thewines using these typesof stoppers, similar variation patterns were observed over the agingperiod. They could be grouped into four changing trends. Firstly,phenolic compounds only appeared at high levels during 9ththrough 12th month of post-bottling, but stayed at a low level inthe other periods, suggesting that no gradual evolvement occurred.These compounds mainly included dephinidin-3-O-glucoside-4-vinylcatechol, (epi)gallocatechin-(epi)catechin, gallocatechin, epi-catechin, quercetin, isorhamnetin, and dihydrokaempferol-3-O-rhamnos. The second trend showedagradual increase in the concen-Fig. 1. Changes in dissoluble oxygen of Cabernet Sauvignon dry red wines with thesix types of stoppers during bottle aging (mg/L).tration in 12 or 15-month of the post-bottling and then a decrease.These compounds following such a trend included cyanidin-3-O-glucoside, procyanidin B3 (P3), dihydroquercetin-3-O-rhamnoside,malvidin-3-O-glucoside-(epi) catechin, myricetin, cis-resveratrol,syringetin-3-O-glucoside, and ethyl caffeate. The third trend wascharacterised by high concentration at the early period of the winebottle-aging, followed by a continuous decrease with the aging per-iod. Many anthocyanin compounds followed this trend, such aspeonidin-3-O-glucoside, malvidin-3-O-glucoside, dephinidin-3-O-(6-O-acetyl)-glucoside, petunidin-3-O-(6-O-acetyl)-glucoside, mal-vidin-3-O-(6-O-acetyl)-glucoside, peonidin3-O-(cis-6-O-couma-ryl)-glucoside, and malvidin-3-O-(cis-6-O-coumaryl)-glucoside.Similarly, procyanidin B2 (P2), ethylgallate and ethyl p-coumaratealso exhibited such a variation trend. Fourthly, other phenolic com-pounds, such as malvidin-3-O-(6-O-coumaryl)-glucoside-pyruvicacid, syringic acid, kaempferol-3-O-glucoside, and glucose ester oftrans-p-coumaric acid, showed the relatively high levels in the rst6 months of bottle aging, and then dramatically dropped to a lowlevel. It can be concluded from the above results that most of avo-nols and avan-3-ols contributed to the rst and second variationtrends, whereas some anthocyanins, benzoic acids, and cinnamicacids affected the third and fourth trends during the wine bottle-aging. In a word, most of the phenolic compounds had a low levelat the later periodof aging inbottle (1518 months), except for somepolymeric pigments such as peonidin-3-O-(6-O-acetyl)-glucoside,peonidin-3-O-glucoside-4-vinylphenol, malvidin-3-O-glucoside-ethyl-(epi) catechin, gallic acid, andmalvidin-3-O-(6-O-acetyl)-glu-coside-4-vinylguaiacol.

Phenolic composition differences amongst the wines using thedifferent types of stoppers were observed in these four variationtrends. Compared to the agglomerated cork, the other types ofstoppers caused more phenolic compounds to follow the secondand third trends during the bottle-aging. For example, malvidin-3-O-glucoside-pyruvic acid, cyanidin-3-O-(6-O-acetyl)-glucoside,malvidin-3-O-(6-O-acetyl)-glucoside-pyruvic acid, malvidin-3-O-glucoside-4-vinylguaiacol, malvidin-3-O-(6-O-coumaryl)-gluco-side-4-vinylphenol, trans-resveratrol, and caftaric acid ester com-plied with the fourth variation trend in the wines using theagglomerated cork. However, these phenolic compounds followedthe third trend in the wines sealed with the other bottle stoppers.

It has been demonstrated that some phenolic compoundsdiminished irreversibly or were converted into bigger pigmentmolecules along with wine aging. Generally, phenolic compoundswith low molecular weight showed a signicant reduction in theconcentration, such as (+)-catechin, ()-epicatechin, trans-resvera-trol and anthocyanins, whereas polymeric pigments started to beaccumulated in aged wines (Castellari et al., 2000). Our resultswere in accordance with these reports. The changes of phenoliccompounds resulted from various chemical reactions, some ofwhich were associated with the presence of oxygen dissolved inwine (Escribano-Bailn, lvarez-Garca, Rivas-Gonzalo, Heredia, &Santos-Buelga, 2001). Oxygen has been considered to be capableof causing the oxidation of ethanol to acetaldehyde (Wildenradt& Singleton, 1974), resulting in the formation of ethyl-linkedanthocyanins-avanols in wine, such as methylmethineanthocya-nincatechin polymers and pyranoanthocyanincatechin polymers(Escribano-Bailn et al., 2001; Mateus et al., 2003). The polymeri-sation reactions of tannins and anthocyanins mainly occur in theperiod of aging in barrel or bottle, which leads wines to a more sta-ble colour and a better mouthfeel and sensory quality (Mateuset al., 2003). Polymerisation reactions can cause a rapid declineof free anthocyanins in wine. Since polymerisation reactions arerelated to the dissolved oxygen in wine, the evolution of phenolic

y 172 (2015) 565574compounds in wines using different types of stoppers can be differ-ent during bottle-aging period due to the different oxygen transferrate through different stoppers.

interpretation of the interaction amongst sensory characteristics

value. Six of seven indices, apart from the value of L, were all

istr3.2. Main difference of phenolic compounds amongst different stoppersealed wines

To understand which component in various aging periods hasstatistically signicant difference (p 6 0.05 or p 6 0.01) in the con-centration amongst the wines sealed with these six stoppers, one-way analysis of variance (ANOVA) was conducted based on theconcentrations of individual phenolic compounds. As shown inTable 2, most of the anthocyanins had statistically signicant dif-ference amongst the wines using these stoppers at six samplingpoints. In particular, ve basic anthocyanins and seven of ten acyl-ated anthocyanins were obviously differentiated at 18-month ofthe post-bottling. This result indicated that the wine colouringcomponents were easily affected by the stopper types, whichwas consistent with the previous reports (Gambuti, Rinaldi,Ugliano, & Moio, 2013; Godden et al., 2001; Mas et al., 2002;Skouroumounis et al., 2005). Only a few avan-3-ols, avonolsand phenolic acids exhibited statistically signicant differenceamongst these six stopper-sealed wines. Apart from catechin, ethylp-coumarate and p-coumaric acid, the other avan-3-ols and phe-nolic acids as well as all avonols did not have signicant differ-ence amongst the wine samples at 18-month of the post-bottling(Table 2).

To understand overall similarities and differences in the varia-tion of phenolic compounds during bottle storage amongst thewines with six types of bottle stoppers, we performed hierarchicalcluster analysis using these identied phenolic compounds as vari-ables (Fig. 2). The wines with the same bottle storage time wereclustered together within the shortest distance, regardless of thebottle stopper types used, further demonstrating that the winesunder different sealing systems possessed the similar variationtrends of phenolic compounds. The wines aged in the bottle for0, 3 and 6 months were closer at hierarchical distance and thewines bottle-aged up to 15 and 18 months were also clustered ina short distance. The wines bottle-aged for12 months were closeto the wines aged in the bottle for 0, 3 and 6 months. The farthesthierarchical distance was observed between the 9-month bottle-aged wines and the other aging-period wines. This suggested thatthe 9-month period might be a key turning point to the variation ofphenolic compounds in the bottle-aged wines. The results abovealso showed that most of the phenolic compounds in the winesdecreased to a relatively low concentration after 9 or 12 monthsof the post-bottling. Combined with the varying trends of dissolvedoxygen throughout the bottle storage, we speculated that theimpact of bottle stopper types on wine phenolic compounds beganto be highlighted after 9 months of the bottle aging.

3.3. Variation of colour characteristics in bottled wines

Wine colour characteristics were evaluated using the CIELabmethod (Appendix Fig. 7). For the wines using different bottle stop-pers, the value of L all increased within the rst 3-month aging,decreased in succession during the aging period of 615 months,and nally rose slightly during the following 3 months. As similarto a previous report (Skouroumounis et al., 2005), the wines usingthe agglomerated corks, technical corks, and natural corks hadhigher L value than those sealed with the synthetic plugs. Thewines with the synthetic plug-2 showed the most obvious uctua-tion of L value over the bottle-aging period. This suggested thatstopper types could affect the evolution of colour intensity duringbottle aging, and synthetic plugs can be more suitable for short-term bottling due to a fast oxidation process (Mas et al., 2002).Stopper types appeared to affect the redness (a value) of the bot-

Y. Gao et al. / Food Chemtle-aging wines as well. The wines with the three synthetic plugshad higher a value than those with the other three corks. The syn-thetic plugs enhanced the a value of the wines within 3 months oflocated at the right side of the plot, corresponding to the principalcomponent 1 (PC1) scores from 6.8 to 8.8. In particular, clarity, col-our depth, and hue were all distributed in the fourth quadrant andrelatively close to each other, suggesting that there was an interde-pendent relationship amongst these three appearance attributes. L

value was in the left of the plot, opposite to the other index. Thewines at 3-month aging had the highest brightness (L), especiallythe wines sealed with the natural corks. Overall, the wines sealedwith the different bottle stoppers gradually proceeded towardthe six colour index along with the bottle aging process. Fromthe positioning of these wine samples in the plot, it could be con-sidered that the wines aged in bottle for 15 months, except thewines with the synthetic plug-2 (B15), attained a relatively goodappearance evaluation in terms of clarity, colour depth, and colourhue. However, the 18-month bottle-aged wines showed a slightdecrease in appearance quality. The wines using the syntheticplug-2 for 9 months or longer (B9-B18) appeared at the rst quad-rant near to a and b values in the plot, representing deeper red-ness and yellowness. However, these wines were all given poorappearance description. According to the distance between thepoints representing the wine samples and wine appearance attrib-uters, we observed that the wines with the technical cork (D1218), agglomerated cork (E1218), and natural cork (F1218)and was allowed to understand how these index affected overallsensory quality of the wine samples analysed.

3.4.1.1. Positioning analysis of appearance characteristics. Fig. 3Ashows a loading Biplot of three appearance attributes and four col-our parameters. Appearance attributes include clarity, colourdepth (saturation), and colour hue (shade or tint), whereas fourcolour parameters consist of L value, a value, b value, and Habthe post-bottling, whereas the opposite observations were found inthe wines sealed by the other three types of corks. The value of b

continually increased during the 18 months of bottle-aging, and itsenhancement showed the largest in the wines using the syntheticplug-2. Meanwhile, the wines with the synthetic plug-2 had highervalue of Hab in comparison with the other wine samples. In short,amongst six bottle stoppers used in this study, the short syntheticplug-2 imparted the lowest lightness (L), strongest redness (a),deepest yellowness (b), and highest hue (Hab) to the wines at18 months (Appendix Fig. 7). Mas et al. reported that syntheticplugs allowed oxygen to enter the bottles after a year of bottle-aging (Mas et al., 2002). The effect of OTR on colour change inred wine has been reported, and the wine aged with the minimalheadspace presented the least redness and lightness throughoutthe bottle-aging period of 24 months (Kwiatkowski et al., 2007).These explained why the wine using the short synthetic plug hadthe highest colour parameters after 18-month bottle aging in thisstudy. However, there are also some different viewpoints. Forexample, Hopfer et al. thought that the changes in yellownessand hue value, expressed as b and h values, greatly differedamongst the wines mainly owing to the difference in the bottle-aging temperature rather than the sealing systems (Hopfer et al.,2013).

3.4. Correlation between phenolic compounds and development ofsensory characteristics

3.4.1. Positioning analysis of sensory characteristicsLoading Biplot of PCA on sensory characteristics provided an

y 172 (2015) 565574 569showed better appearance quality in comparison with the winesusing the polymeric synthetic plugs. Combined with the variationof dissolved oxygen during this period (Fig. 1), the development

Table 2One-Way ANOVA of various phenolic compounds amongst red wines sealed with different stoppers.

Numbers Phenolic compounds Aging time (months)

3 6 9 12 15 18

1 Dephinidin-3-O-glucoside 1.329 35.586 1.581 2.872 57.773 6.873

2 Cyanidin-3-O-glucoside 7.952** 0.810 1.130 0.745 n.s. 3358.897

3 Petunidin-3-O-glucoside 17.715 26.736 0.543 1.202 202.259 17.512

4 Malvidin-3-O-(6-O-caffeoyl)-glucoside 35.360 7.945** n.s. n.s. n.s. n.s.5 Peonidin-3-O-glucoside 2.082 3.448* 0.820 1.038 3.818* 23.898

6 Malvidin-3-O-glucoside 3.401* 69.962 14.198 5.219** 20.944 20.936

7 Dephinidin-3-O-(6-O-acetyl)-glucoside 3.934* 1.979 1.105 0.833 7.983** 20.277

8 Peonidin-3-O-glu-pyruvic acid 6.112** 46.072 8.235** 46.696 n.s. n.s.9 Malvidin-3-O-glu-pyruvic acid 2.600 81.967 1.309 0.506 0.130 0.927

10 Malvidin-3-O-glu-acetaldehyde 3.166* 6.510** 9.969** 20.086 n.s. 1871.357

11 Cyanidin-3-O-(6-O-acetyl)-glucoside 9.164** 5.062* 3.939* 3.678* 2180.576 0.08512 Malvidin-3-O-(6-O-acetyl)-glu-pyruvic acid 5.035* 2.389 1.454 0.801 58.921** 77.680

13 Petunidin-3-O-(6-O-acetyl)-glucoside 4.032* 2.025 1.345 1.951 n.s. 62.484

14 Malvidin-3-O-(6-O-acetyl)-glu-acetaldehyde n.s. 17.005 41.852 58.278 467.753 4.000*

15 Malvidin-3-O-glu-ethyl-(epi)catechin 28.052 12.756 87.849 n.s. 85.008 171.002

16 Peonidin-3-O-(6-O-acetyl)-glu-pyruvic acid 50.318 n.s. 243.992 57.384 n.s. n.s.17 Dephinidin-3-O-glu-4-vinylphenol 4.146* 1.756 n.s. n.s. 75.358 853.884

18 Peonidin-3-O-(6-O-acetyl)-glucoside 17.912 1.363 1.403 1.388 24.304 62.067

19 Malvidin-3-O-(6-O-acetyl)-glucoside 0.867 9.324** 1.100 9.610** n.s. 92.382

20 Cyanidin-3-O-(6-O-coumaryl)-glucoside n.s. n.s. n.s. n.s. n.s. 103.458

21 Malvidin-3-O-(6-O-coumaryl)-glu-pyruvic acid 12.094 5.976** n.s. n.s. n.s. 151.857

22 Dephinidin-3-O-glu-4-vinylcatechol 2.353 n.s. 15.644 3.198* n.s. n.s.23 Malvidin-3-O-(trans-6-O-coumaryl)-glucoside 58.450 4.365* n.s. n.s. 2.319 16.668

24 Peonidin-3-O-glu-4-vinylcatechol 36.021 141.544 4.440* 7.711** 11.472 465.777

25 Peonidin-3-O-(cis-6-O-coumaryl)-glucoside 2.443 1.908 4.090* 7.452** 730.251 3.01726 Malvidin-3-O-(cis-6-O-coumaryl)-glucoside 19.100 4.747* 0.316 9.199** n.s. 451.876

27 Peonidin-3-O-glu-4-vinylphenol 1.039 511.079 4764.110 614.620 4.376* n.s.28 Malvidin-3-O-glu-4-vinylphenol 1.541 1.826 0.825 15.010 n.s. 3.00829 Malvidin-3-O-glu-4-vinylguaiacol 10.491 200.526 829.226 402.542 3.424* n.s.30 Malvidin-3-O-(6-O-acetyl)-glu-4-vinylphenol 1.839 94.123 1.379 11.137 490.006 1.77931 Malvidin-3-O-(6-O-caffeoyl)-glu-4-vinylphenol 23.030 293.783 n.s. n.s. n.s. n.s.32 Malvidin-3-O-(6-O-acetyl)-glu-4- vinylguaiacol n.s. n.s. n.s. 4.638* n.s. 1.11233 Malvidin-3-O-(6-O-coumaryl)-glu-4-vinylphenol 1.097 6.776** 2.542 5.806** n.s. n.s.34 Cinnamic acid 9.819** 3.501* 1.061 0.792 2.601 n.s.35 Gallic acid 4.924* 0.213 0.674 0.558 3.908* 2.40736 Dimer(epi)gallocatechin-(epi)catechin 6.175** 61.307 10.190** 0.601 1.389 n.s.37 Gallocatechin n.s. n.s. n.s. 0.875 0.924 n.s.38 Procyanidin B2 (P2) 0.725 1.191 2.162 1.607 2.923 n.s.39 Catechin 2.705 0.425 n.s. 0.720 4.956* 109.755

40 Caffeic acid 2.644 0.327 0.741 1.230 0.807 2.58041 Procyanidin B3 (P3) n.s. 1.501 15.936 1.698 n.s. n.s.42 Syringic acid 4.666* 0.693 n.s. n.s. n.s. n.s.43 Enthylgallate 1.317 0.130 0.436 1.668 0.982 n.s.44 Epicatechin 2.019 n.s. 0.189 n.s. n.s. n.s.45 p-Coumaric acid 5.468** 0.413 n.s. 0.316 1.861 4.547*

46 Dihydroquercetin-3-O-hexoside n.s. n.s. 5.749** n.s. n.s. n.s.47 Dihydroquercetin 2.218 0.270 6.418** 0.359 0.508 n.s.48 Myricetin-3-O-glucoside n.s. 668.961 n.s. n.s. 1.347 n.s.49 Ethyl protocatechuate 1.002 0.417 0.960 0.292 1.265 n.s.50 Dihydroquercetin-3-O-rhamnoside 2.092 0.027 1.692 1.179 n.s. n.s.51 Quercetin-3-O-glucuronide 2.654 0.110 1.641 0.051 n.s. n.s.52 Malvidin-3-glucoside-(epi)catechin 9.238** 10.933 5.169** 0.736 n.s. n.s.53 Laricitrin-3-O-glucoside 309.525 63.657 0.807 1.117 n.s. n.s.54 Dihydrokaempferol-3-O-rhamnos n.s. n.s. n.s. 0.610 1.402 n.s.55 Myricetin 8.907** 2.865 1.173 1.353 2.983 n.s.56 Cis-resveratrol 2.942 0.273 2.992 n.s. 1.786 n.s.57 Syringetin-3-O-glucoside 13.881 3.862* 69.260 0.424 2.759 n.s.58 Kaempferol-3-O-glucoside 2.937 6.462** n.s. n.s. n.s. n.s.59 Isorhamnetin-3-O-glucoside n.s. n.s. n.s. n.s. n.s. n.s.60 Ethyl caffeate 3.081 0.747 2.226 0.378 1.160 2.12961 Trans-resveratrol 0.218 0.142 1.431 0.364 1.011 n.s.62 Quercetin n.s. n.s. 1.583 n.s. n.s. n.s.63 Iaricitrin 4.839* 0.106 1.225 0.180 n.s. n.s.64 Ethyl p-coumarate 1.490 0.089 2.346 0.805 0.964 10.914

65 Isorhamnetin n.s. n.s. 1.513 n.s. n.s. n.s.66 Caftaric acid ester n.s. 9.756** 302.282 2.576 4.635* n.s.67 Glucose ester of trans-p-coumaric acid 27.149 26.323 347.375 n.s. n.s. n.s.

n.s. No signicant differerce there. The data in bold are highlighted due to very high F-value.** A signicance level of p < 0.01.* A signicance level of p < 0.05.

570 Y. Gao et al. / Food Chemistry 172 (2015) 565574

istrY. Gao et al. / Food Chemof the wine appearance quality did not seem to have the directassociation with dissolved oxygen content.

3.4.1.2. Positioning analysis of mouthfeel features. In this study themouthfeel terms included genuineness, positive intensity, struc-ture, harmony, and aftertaste. These mouthfeel features were allpositioned at the right side of the plot, scoring from 0.75 to 0.95of PC1 (Fig. 3B). There was a synergistic effect as to structure andharmony of wine, the two being close to each other in the plot.Overall, most of the wines bottle-aged for 36 months had a rela-tively good genuineness and aftertaste, especially for the winesusing the technical corks (E6), natural corks (F6), and syntheticplug-3 (C6). The 15-month bottle-aged wines with the syntheticplug-1(A15), synthetic plug-3 (C15), agglomerated cork (D15),and technical cork (E15) were the nearest to the points represent-ing wine structure and harmony. Relative to the 12-month wines,the 15-month wines with the short synthetic plug-2 (B15) and nat-ural cork (F15) also had a good mouthfeel description. In contrast,most of 9- and 18-month wines were separated from the pointsrepresenting six mouthfeel features, implying that these wineshad a poor mouthfeel performance at the two aging periods. Com-bined with the result of PCA, we speculated that the poor overallmouthfeel description of the 9-month wines might be related toa dramatic alteration of phenolic compounds (Lorrain et al.,2013; Marquez, Serratosa, & Merida, 2014). The point representing

Fig. 2. Cluster analysis based on phenolic compounds in bottle-aged dry red winessealed with different bottle stoppers. Letters represent six bottle stoppers: syntheticplug-1 (A), synthetic plug-2 (B), synthetic plug-3 (C), aglomerated cork (D), 1 + 1technical cork (E) and natural cork (F), respectively. Numbers after the letterrepresent aging time (months).the 18-month bottle-aged wines with the synthetic plug-2 (B18)was at the far left, which indicated that the mouthfeel quality ofthe wines declined signicantly.

3.4.2. Correlation between variation of phenolic compounds anddevelopment of sensory attributes3.4.2.1. Correlation between phenolic compounds and appearancecharacteristics. Partial least squares (PLS) regression analysis wasused to establish the association between the variation of com-pounds and the development of sensory properties during the wineaging in bottle. The correlation between matrix X (phenolic com-pounds) and matrix Y (sensory properties) was reected by a load-ing plot (Fig. 4). A series of numbers (167) in this plotcorresponded to these phenolic compounds in Table 2. The rsttwo principal components (PCs) accounted for about 62% of thetotal variables. As shown in the loading plot (Fig. 4A) and variablesimportance plot (VIP) value of the rst two PCs (Appendix Table 1),the points representing these appearance characteristics, exceptfor L value, were all positioned at the right side of the loading plot,and they had a closely positive correlation with malvidin-3-O-(6-O-acetyl)-glucoside-4-vinylguaiacol (No. 32), gallocatechin (No.37), and dihydrokaempferol-3-O-rhamnos (No. 54). These sug-gested that the increase in the concentration of these three com-pounds might improve the appearance characteristics of thewine, but could cause the reduction of the wine lightness. Previousreports provided some explanations regarding the promotion ofthe phenolic compounds on wine appearance quality. For example,pyranoanthocyanins, like malvidin-3-O-(6-O-acetyl)-glucoside-4-vinylguaiacol (No. 32), have been conrmed to have the visiblemaximum absorbance at a higher wavelength than their corre-sponding anthocyanins (e.g. malvidin-3-O-(6-O-acetyl)-glucoside),which imparted a reddish tonality to red wine. Moreover, thesevinyl pyranoanthocyanins were relatively more stable and stayedlonger in aged red wines (de Freitas & Mateus, 2011; Mateuset al., 2003). In the present study, the above three phenolic com-pounds all followed the rst varying trend along with the processof the bottle-aging for all the wines, that is, high levels appeared at12 months of the post-bottling and stayed at a low level in theother periods. It can be concluded that the attenuation of wineappearance quality in the late period of bottle-aging might berelated to the decline of these three compounds.

Except for these three components, other phenolic compoundswere distributed at the left side of the plot and they were nega-tively correlated with ve appearance indicators, especially peoni-din-3-O-glucoside (No. 5), malvidin-3-O-glucoside (No. 6),dephinidin-3-O-(6-O-acetyl)-glucoside (No. 7), petunidin-3-O-(6-O-acetyl)-glucoside (No. 13), malvidin-3-O-(6-O-acetyl)-glucoside(No. 19), gallic acid (No. 35), caffeic acid (No. 40), and ethyl p-coumarate (No. 64). This suggests that wines develop toward agood appearance evaluation accompanying the reduction in theconcentrations of these compounds during bottle-aging. Thisobservation can be explained by the previous reports. For example,it has been observed that the content of the free or monomericanthocyanins gradually decrease or even disappeared with aging(Eiro & Heinonen, 2002; Gutirrez, Lorenzo, & Espinosa, 2005).Instead, the stable pigments, such as pyranoanthocyanins andpolymeric pigments, as red wine aged, were formed through chem-ical modications of anthocyanin molecules, or condensation reac-tions between avan-3-ols and anthocyanidins (Carvalho, Oliveira,De Freitas, Mateus, & Melo, 2010). On the other hand, these mono-meric anthocyanins could be oxidised and degraded. These reac-tions produced brick redness in red wine with a long time aging(Rentzsch, Schwarz, & Winterhalter, 2007). Furthermore, the poly-

y 172 (2015) 565574 571merisation reaction of anthocyanins protected from nucleophilicattack or oxidisation by other molecules in aqueous solution, hencemaintaining the wine colour (Somers, 1971). The present study

istr572 Y. Gao et al. / Food Chemalso showed that gallic acid presented a signicant decline alongwith aging time, which is probably due to the esterication andacetylation as previously reported (Bentez, Castro, & GarcaBarroso, 2003). Similarly, caffeic acid and ethyl p-coumarate alsoexhibited a concentration decline, which might result from theincorporation of hydroxycinnamic acid into pyranoanthocyaninsand even hydroxyphenylpyranoanthocyanins (Pinotin)(Rentzsch, Schwarz, Winterhalter, & Hermosn-Gutirrez, 2007;Schwarz, Hofmann, & Winterhalter, 2004). Considering the occur-rence of these reactions during wine bottle-aging, it is easy tounderstand the negative correlation between the reduction of themonomeric anthocyanin and phenolic acid components, and thedevelopment of wine appearance during wine bottling.

3.4.2.2. Correlation between phenolic compounds and mouthfeelperceptions. Fig. 4B reects a weak correlation between phenolic

Fig. 3. Loadings BiPlot of appearance characteristics (A) and mouthfeel characteristics (bottle stoppers: synthetic plug-1 (A), synthetic plug-2 (B), synthetic plug-3 (C), aglomerafter the letter represent aging time (months).y 172 (2015) 565574compounds (matrix X) and mouthfeel characteristics (matrix Y),because the rst two PCs only explained 40.1% of the total vari-ables. It was still observed that the mouthfeel indicators were con-centrated on the rst quadrant of the diagram corresponding to thepositive scores in PC1 and PC2, and wine structure and harmonyinuenced each other. Malvidin-3-O-glucoside-ethyl-(epi)catechin(No. 15), peonidin-3-O-(6-O-acetyl)-glucoside (No. 18), malvidin-3-O-(6-O-coumaryl)-glucoside-pyruvic acid (No. 21), and peoni-din-3-O-glucoside-4-vinylphenol (No. 27) were located in the mostright side, which indicated that these four compounds were posi-tively related to the development of the mouthfeel, particularlythe aftertaste and genuineness of the red wine. Additionally, mal-vidin-3-O-(6-O-acetyl)-glucoside-4-vinylguaiacol (No. 32) wasassociated with the wine intensity, whilst gallocatechin (No. 37),dihydrokaempferol-3-O-rhamnos (No. 54), and glucose ester oftrans-p-coumaric acid (No. 67) had a positive correlation with

B) of bottle aged dry red wines sealed with different stoppers. Letters represent sixated cork (D), 1 + 1 technical cork (E) and natural cork (F), respectively. Numbers

istrY. Gao et al. / Food Chemthe wine structure and harmony. Oppositely, cyanidin-3-O-(6-O-coumaryl)-glucoside (No. 20), malvidin-3-O-(6-O-acetyl)-gluco-side-4-vinylphenol (No. 30), malvidin-3-O-(6-O-coumaryl)-glucoside-4-vinylphenol (No. 33), dimer(epi)gallocatechin-(epi)catechin (No. 36), procyanidin B3 (P3) (No. 41), dihydroqu-ercetin-3-O-hexoside (No. 46), malvidin-3-glucoside-(epi) catechin(No. 52), and isorhamnetin-3-O-glucoside (No. 59) were positionedin the most left side, far away from the points of the mouthfeelcharacteristics, suggesting that wines developed toward goodmouthfeel as these phenolic compounds decreased or were con-verted into the lager molecules during bottle-aging.

4. Conclusions

In conclusion, four groups of phenolic compounds (phenolicacids, avonols, avan-3-ols, and anthocyanins) and sensory char-acteristics in the wines sealed with six types of stoppers wereassessed during 18-month of the bottle aging. Phenolic compounds

Fig. 4. Loading plot of partial least squares regression analysis between phenolic compoaged dry red wines sealed with different stoppers. Numbers represent the phenolic comy 172 (2015) 565574 573in the red wines followed four evolution patterns, depending onthe group of these compounds. The ninth month of the bottle agingwas a key turning point for the overall evolution of phenolic com-pounds. Both the appearance and mouthfeel attributes of the winesin bottle developed toward a good quality during the 15-monthperiod, regardless of the types of bottle stoppers used. This sensorydevelopment appeared to have fair association with the variationof dissolved oxygen in the aged wines. The phenolic compoundspositively or negatively correlated with the development of thewine appearance and mouthfeel characteristics were bothscreened out through the analysis of Partial least square. Furtherconcern would be focused on how these compounds affect winesensory attributes.

Acknowledgement

This work was nancially supported by the project of ChinaAgriculture Research System (CARS-30).

unds and appearance characteristics (A), and mouthfeel characteristics (B) of bottlepounds listed in Appendix Table 1.

Appendix A. Supplementary data

Supplementary data associated with this article can be found, inthe online version, at http://dx.doi.org/10.1016/j.foodchem.2014.09.115.

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Evolution of phenolic compounds and sensory in bottled red wines and their co-development1 Introduction2 Materials and methods2.1 Wine samples2.2 Stoppers2.3 Chemicals and standards2.4 Determination of phenolic compounds2.4.1 Anthocyanins2.4.2 Non-anthocyanin phenolic compounds

2.5 Characterisation of colour fraction2.6 Determination of dissolved oxygen in wine2.7 Sensory evaluation2.8 Statistical analysis

3 Results and discussion3.1 Evolutions of dissolved oxygen and phenolic compounds in wines during aging in bottle3.2 Main difference of phenolic compounds amongst different stopper sealed wines3.3 Variation of colour characteristics in bottled wines3.4 Correlation between phenolic compounds and development of sensory characteristics3.4.1 Positioning analysis of sensory characteristics3.4.1.1 Positioning analysis of appearance characteristics3.4.1.2 Positioning analysis of mouthfeel features

3.4.2 Correlation between variation of phenolic compounds and development of sensory attributes3.4.2.1 Correlation between phenolic compounds and appearance characteristics3.4.2.2 Correlation between phenolic compounds and mouthfeel perceptions

4 ConclusionsAcknowledgementAppendix A Supplementary dataReferences