The influence of different closures on volatile composition of a white wine

Food Packaging and Shelf Life 23 (2020) 100465

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The influence of different closures on volatile composition of a white wine

T

Ana Sofia Oliveira*, Isabel Furtado, Maria de Lourdes Bastos, Paula Guedes de Pinho, Joana Pinto* UCIBIO/REQUIMTE, Department of Biological Sciences, Laboratory of Toxicology, Faculty of Pharmacy, University of Porto, 4050-313 Porto, Portugal

A R T I C LE I N FO

A B S T R A C T

Keywords: White wine Closures Volatile organic compounds HS-SPME-GC/MS Metabolomics Sensory analysis

The impact of different closures on wine volatile composition was assessed by headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC/MS) analysis of a white wine. The sealing systems studied comprised 1 + 1 cork, microagglomerated cork and synthetic closures. A descriptive sensory analysis and measurement of some oenological parameters were also performed. The main differences on wine volatile profile were observed between cork and synthetic closures, comprising statistically significant alterations in the levels of six volatile compounds. Two compounds, namely 2,4-di-tert-butylphenol and trans-4tert-butylcyclohexanol, were identified for the first time, to our knowledge, in wines sealed with synthetic closures and a microagglomerated cork, respectively. In addition, the sensory analysis of wine sealed with cork stoppers unveiled highest scores in aroma intensity, aroma quality and balance. On the other hand, wine sealed with synthetic closures were described with oxidative sensory attributes, lowest levels of SO2 and highest colour intensity.

1. Introduction Wine is a mildly acidic hydroalcoholic solution produced from alcoholic fermentation of grape juice or must by yeasts, characterized by unique sensory properties that have attracted consumers for centuries (Waterhouse, Sacks, & Jeffery, 2016). Compounds derived from grapes and others formed during fermentation, winemaking and wine storage are the main contributors for wine flavour and colour, depending on their odour-active features and interactions (Lopez, Aznar, Cacho, & Ferreira, 2002; Moreira, Lopes, Ferreira, Cabral, & de Pinho, 2016; Waterhouse et al., 2016). Higher alcohols, acids and esters are quantitatively dominant in aroma (Zhu, Du, & Li, 2016) especially in quality criteria of white wine (Moreira, Lopes, Ferreira, Cabral, & de Pinho, 2018). Nevertheless, it is during the bottle storage that wine composition gradually changes until it reaches the maximum of its sensory quality (Liu et al., 2015). The initial wine composition, as well as the storage conditions (e.g., temperature, light, humidity, bottle position and pH), are the main factors that determine wine evolution in bottle, but the choice of the packaging should also be taken into consideration (Liu et al., 2015; Skouroumounis et al., 2005). Indeed, the closure type can shape the organoleptic wine properties by different ways due to different oxygen permeation (Hopfer, Ebeler, & Heymann, 2012), absorption and/or migration of compounds from the closure into the wine

(Silva, Jourdes, Darriet, & Teissedre, 2012). Cork has been reported to be the perfect closure for sealing wine bottles due to its unique physical properties, namely high flexibility, elasticity, compressibility, recovery and impermeability to liquids (Prat, Besalú, Bañeras, & Anticó, 2011). In addition, some volatile and phenolic compounds (Azevedo et al., 2014; Pinto et al., 2019) can be extracted from cork by wine, thus positively contributing to flavour, colour and astringency during wine development. However, 2,4,6-trichloroanisole (TCA) contamination, characterized by a musty and mouldy odour usually referred as “cork taint”, has brought up alternative sealing systems into the closures market, namely synthetic closures and screw caps (Hopfer et al., 2012). Since the oxygen is extremely important in wine development, especially in white wine due to its ability to reduce the levels of fruity flavours and develop oxidative characters (Lopes et al., 2009), several studies have focused on oxygen transmission rate of closures. In general, these studies had concluded that synthetic closures are the less effective barriers to oxygen transfer compared to other closures (He, Zhou, Peck, Soles, & Qian, 2013; Lopes, Saucier, Teissedre, & Glories, 2007, 2009; Silva, Julien, Jourdes, & Teissedre, 2011). In fact, the increased levels of some oxidation markers in wines sealed with synthetic closures, including Strecker aldehydes, (E)-2-alkenals, sotolon, furfural (Mayr et al., 2015) and acetaldehyde (He et al., 2013) has been demonstrated, confirming the acceleration of wine development towards

⁎ Corresponding authors at: UCIBIO/REQUIMTE, Department of Biological Sciences, Laboratory of Toxicology, Faculty of Pharmacy, University of Porto, Rua Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal. E-mail addresses: aoliveira@ff.up.pt (A.S. Oliveira), jipinto@ff.up.pt (J. Pinto).

https://doi.org/10.1016/j.fpsl.2020.100465 Received 18 September 2019; Received in revised form 2 December 2019; Accepted 3 January 2020 Available online 17 January 2020 2214-2894/ © 2020 Elsevier Ltd. All rights reserved.

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2.3. Oenological parameters

oxidation in comparison to cork stoppers and screw cap. Furthermore, higher levels of several alcohols (1-butanol, 2-phenylethanol, 1-pentanol, (Z)-3-hexen-1-ol and 2-nonanol) were also reported in a Chardonnay wine under synthetic stoppers compared to natural and technical corks, unveiling grilled and toasty characters in the sensory evaluation (Liu et al., 2015). The levels of ethyl decanoate, 2-phenylethanol, (S)-3-ethyl-4-methylpentanol, ethyl hexanoate, styrene and isoamyl lactate (Liu, Xing, Li, Yang, & Pan, 2016) were found increased in wines bottled with natural cork stoppers compared to those sealed with synthetic closures in two different studies (Liu et al., 2015, 2016). Esters and 2-phenylethanol were described to be responsible for the floral and fruity odour observed in wines sealed with cork stoppers (Liu et al., 2016), suggesting that cork is the most suitable closure to preserve these aromas. Screw cap is the only closure type that has a significant impact on the prevention of oxygen entrance (He et al., 2013; Lopes et al., 2007, 2009; Silva, Jourdes, & Teissedre, 2011), however, some authors observed the development of undesirable reduced characters, as struck flint and rubber aromas, due to the insufficient oxygen exposure (Lopes et al., 2009). Concerning the effects of different closures on wine volatile composition, this study aims to perform a holistic approach, based on untargeted metabolomics, to determine the volatile profile of white wine sealed with different closures at 48 months post-bottling. Wine sealed with 1 + 1 cork, microagglomerated cork and synthetic closures was analysed by HS-SPME-GC/MS to assess the volatile wine composition. A descriptive sensory analysis was also performed in order to understand the results obtained from volatile profiling, as well as the measurement of free and total SO2 content and colour intensity.

Some wine chemical parameters were measured by the winery, including pH (3.30), ethanol content (12.7%), density (0.9901), and total and volatile acidity (6.80 and 0.25 g/L, respectively). After 48 months post-bottling, free and total SO2, and colour intensity were evaluated. SO2 analysis was determined by amperometric titration corrected with acetaldehyde. Colour intensity was assessed by measuring the absorbance at 420 nm using a UV–vis Varian, Cary 50 scan spectrophotometer (Palo Alto, CA, USA). 2.4. Analysis of volatile compounds by HS-SPME-GC/MS For the assessment of volatile composition at 48 months post-bottling, 250 μL of wine were placed in a 20-mL vial and analysed by HSSPME-GC/MS (method adapted from (Barros et al., 2012)). Briefly, the volatile compounds were extracted by a 50/30 μm divinylbenzene/ carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber (Supelco Inc., Bellefonte, Pennsylvania, USA), using a Combi-PAL autosampler (Varian Pal Autosampler, Switzerland). The extraction was carried out for 30 min at 45 °C, with a stirring speed of 250 rpm, after a 5 min incubation at the same temperature. Finally, the analytes were thermally desorbed into the GC injector over 6 min at 250 °C. GC–MS analysis was performed on a 436-GC model (Bruker Daltonics) coupled to a SCION single quadrupole mass spectrometer (Bruker Daltonics), using a fused silica (Rxi-5Sil MS) capillary column (30 m × 0.25 mm internal diameter × 0.25 mm; Restek Corporation, U.S., Bellefonte, Pennsylvania, USA) for chromatographic separation (Pinto et al., 2018). The carrier gas was high purity helium (Gasin, Porto, Portugal) at a constant flow of 1 mL/min. The initial column temperature was 40 °C kept for 1 min, followed by an increase of 5.0 °C/ min from 40 to 250 °C (5 min) and from 250 to 300 °C (0 min). Single quadrupole mass spectrometry was conducted in the electron ionization (EI) mode at 70 eV. The analysis was performed in full scan mode from m/z 40 to 250 with a scan time of 500 ms. The identification of volatile compounds was performed based on matching the retention time and mass spectra obtained from the sample with the commercial standards injected at the same conditions. For compounds not commercially available, the comparison of MS fragmentation with the mass spectra in the NIST 14 spectral database (version 2.2, 2014), and a comparison of Kovats retention indices (RI), determined using a commercial hydrocarbon mixture (C6–C20), with the RI reported in the literature, were performed for compound identification. For quantification of the volatile compounds contributing to the discrimination of wine samples, commercial standards were dissolved in ethanol (HPLC grade) and successively diluted in wine model solution (12% ethanol, 5 g/L of tartaric acid at pH 3.2) to prepare the different levels of a calibration curve for each compound. Volatile compounds of each calibration level were analysed using the same method as the wine samples, and the regression analysis method was applied to calculate the respective concentration. Ionone-like compound was quantified using a calibration curve of α-ionone commercial standard. 1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) was not quantified due to the unavailability of commercial standard, hence the statistical analysis was performed using the area of the quantifier ion (m/z 157). The limit of quantification (LOQ) of the discriminant compounds can be found in (Barros et al., 2012), except for trans-4-tert-butylcyclohexanol and 2,4-di-tert-butylphenol which were determined in this study.

2. Materials and methods 2.1. Chemicals All chemicals used were purchased from Sigma-Aldrich, Inc. (Steinheim, Germany). Ethanol (99.9%) was supplied by CARLO ERBA Reagents (Val de Reuil, France). Ultrapure water was obtained from a Milli-Q Millipore purification system (Millipore, Billerica, Massachusetts, USA). 2.2. Wine and closures Wine used in this study was produced during 2013 vintage from a blend of white wine varieties. Fermentation was carried out in stainless steel tanks under 18 °C over 20 days. Tartaric precipitation was carried out in isothermal tanks under constant temperature (3 ± 1 °C) over 7 days. After filling, the bottles were stored horizontally under cellar conditions for 48 months. Six sealing systems were tested (n = 3 per type of stopper), including two different 1 + 1 cork (A and B), microagglomerated cork stoppers (A and B) and co-extruded synthetic closures (A and B). 1 + 1 Cork stoppers (44 mm length and 23.5 mm diameter) consisted of granulated cork of different sizes, 2–4 mm (A) and 1–2 mm (B), agglutinated with a binder with two end cork discs. The microagglomerated cork stoppers (A and B) (44 mm length and 24 mm diameter) consisted of granulated cork agglutinated with two different polyurethane food grade binders. The two co-extruded synthetic closures (A and B) (44 mm length and 23 mm diameter) comprised polyethylene-based closures with two different oxygen permeabilities (A has lower permeability than B). Later on, another essay was designed including wine model solution (12% ethanol, 5 g/L of tartaric acid at pH 3.2) sealed with the same closures mentioned above (n = 3 per group in 375 mL bottles), in order to evaluate the potential extraction of compounds from closures to wine model solution after 16 months postbottling. All closures were taken from a range representing commercial stocks supplied by their manufactures.

2.5. Sensory analysis Before the HS-SPME-GC/MS analysis, descriptive sensory analysis was carried out by a panel of seven judges with an extensive experience in wine tasting, from the Comissão de Viticultura da Região dos Vinhos Verdes and the University of Porto (Porto, Portugal). The sensory 2

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Table 2). The ionone-like compound and TDN were also responsible for the discrimination of wine sealed with synthetic vs. microagglomerated cork A (Fig. 1b–ii), being present at higher levels in microagglomerated cork A compared to synthetic closures (Table 2). These results suggest that 1 + 1 cork and microagglomerated cork A may preserve more efficiently some esters and other volatile compounds in white wine compared to synthetic closures. In addition, L-camphor was only detected in wine sealed with 1 + 1 corks (A and B) (Table 2), whereas 2,4di-tert-butylphenol was only quantified in wines sealed with synthetic closures (A and B) since it was present in trace amounts in the remaining sealing systems (Table 2). trans-4-tert-Butylcylohexanol was only detected in wine sealed with microagglomerated cork A, thus appearing as very important in the discrimination of wine sealed with this type of closure compared with 1 + 1 corks (Fig. 1b–ii, Table 2) and synthetic closures (Fig. 1b–iii, Table 2). L-Camphor was also the compound responsible for discrimination between microagglomerated cork B and 1 + 1 corks (Fig. 1b–iv), since it was only detected in wine sealed with 1 + 1 corks as mentioned above. The extraction of 2,4-di-tert-butylphenol (Fig. S4), trans-4-tert-butylcylohexanol (Fig. S5) and L-camphor (Fig. S6) from synthetic closures, microagglomerated cork A and 1 + 1 corks, respectively, into wine model solution (375 mL bottles) was also confirmed at 16 months post-bottling. The levels of free and total SO2 and the absorbance at 420 nm (A420) were also measured in the same wine samples (Fig. 2). The wine sealed with synthetic closures unveiled significantly lower levels of free and total SO2 compared with the remaining sealing systems (Fig. 2a and b). Regarding wine colour intensity, a significantly higher A420 (Fig. 2c) was found for wine sealed with synthetic closures compared with the remaining closures. The results of the descriptive sensory analysis (Fig. 3, Table 3) unveiled statistically significant differences among the wine sealed with different closures. Cork stoppers (1 + 1 corks and microagglomerated A and B) were distinctly differentiated from synthetic closures, being scored with higher aroma intensity, aroma quality and balance, whereas the synthetic closures were scored with higher oxidation attributes. Since ethyl esters and acetates (e.g., 2-phenylethyl acetate) are produced during wine fermentation in high quantities, their levels tend to decrease during wine ageing usually through hydrolysis towards reaching chemical equilibria with the corresponding alcohol and organic acid (Linsenmeier, Rauhut, & Sponholz, 2010). In the present study, higher levels of ethyl hexanoate, ethyl octanoate, ethyl decanoate and 2-phenylethyl acetate were observed in 1 + 1 corks compared with synthetic closures. This difference may be associated with the scalping phenomenon promoted by the polyolefinic nature of synthetic closures (Sajilata, Savitha, Singhal, & Kanetkar, 2007). These closures have been reported as highly capable of sorbing ethyl hexanoate, ethyl octanoate and ethyl decanoate when compared to natural and technical cork stoppers (Capone, Sefton, Pretoius, & Høj, 2003). Furthermore, the lower levels of esters in wine sealed with synthetic closures may be associated with oxidation through higher oxygen ingress into the bottle, since synthetic closures have been reported as being considerably more permeable to oxygen than cork stoppers in general (He et al., 2013; Liu et al., 2015; Lopes et al., 2007, 2009). Lower levels of some acetate and ethyl esters, including ethyl hexanoate, ethyl octanoate and ethyl decanoate, have been found decreased in a white wine (Chardonnay) under semi-oxidative and forced oxidative conditions (Patrianakou & Roussis, 2013), possibly due to the direct attack of hydroxyl radicals or by interaction with polyphenol quinones (Patrianakou & Roussis, 2013). Other studies have already reported higher amounts of ethyl hexanoate, ethyl decanoate and 2-phenylethanol in Chardonnay sealed under cork stoppers (natural, agglomerated and 1 + 1 technical cork) compared to synthetic closures (Liu et al., 2015, 2016). Some norisoprenoids, TDN and an ionone-like compound, were detected at the highest concentrations in wines sealed with cork stoppers. These compounds contribute to the fruity and floral scents of wines (Moreira et al., 2018) and are produced from direct degradation

assessments were performed in blind tasting conditions at the tasting room of Comissão de Viticultura da Região dos Vinhos Verdes (Porto, Portugal) in individual booths (18 ± 1 °C at daylight). Wine samples (50 mL) were served in standard ISO 3591 ‘XL5-type’ tasting glasses, labelled with three-digit random codes and evaluated independently within one hour of pouring. The sensory attributes scored were aroma intensity (the overall wine aroma), aroma quality (the overall fruitiness and freshness of wine), acidity, bitterness, balance, oxidized and reduced (scents related with the presence of volatile sulphur compounds) characters. Panellists were trained to assess first the aroma and then the palate of wines, scoring each attribute on a scale of 0 to 5, where 0 indicated that the attribute was not perceived and 5 the high intensity of the attribute. Each panel member assessed three wine bottles (repetitions) per type of closure in three sessions. 2.6. Statistical analysis The GC–MS data was converted to CDF file format and pre-processed using MZmine-2.34 (Pluskal, Castillo, Villar-Briones, & Orešič, 2010). Pre-processing steps consisted in crop filtering (m/z 50–200 and RT 3.70–40.00 min), peak detection (noise level 5.0 × 104), chromatogram deconvolution (peak range 0.03–0.5, baseline level 1.0 × 106) and alignment (m/z tolerance 0.1, RT tolerance 0.05 min). Artefact peaks from the chromatographic column and SPME fiber (e.g., cyclosiloxanes, siloxanes and phthalates) were manually removed and the data matrix was normalized by total area and scaled to Pareto. Principal component analysis (PCA) and partial least-squares discriminant analyses (PLS-DA) were applied with a default seven-fold internal cross validation (SIMCA 13.0.3, Umetrics, Sweden). Based on Variable Importance to the Projection (VIP) values, the volatile compounds responsible for the discrimination were obtained. The individual significance of concentration levels or peak areas of selected compounds were assessed using the nonparametric Mann-Whitney test, considering statistical relevance for p-value < 0.05 (GraphPad Prism 6, USA). The sensory results (each attribute) were submitted to analyses of variance (ANOVA) followed by Fisher’s least significant difference tests. 3. Results and discussion The volatile composition of a white wine bottled with six different closures at 48 months post-bottling was assessed by HS-SPME-GC/MS analysis, being the volatile profile of 1 + 1 cork represented in Fig. 1a. As listed in Table 1, a total of 69 volatile compounds were identified, including 10 alcohols, 8 aldehydes, 32 esters, 4 organic acids, 2 ketones, 3 lactones, 3 norisoprenoids, 1 phenol derivative and 6 terpenes. Most of these compounds have been described as a part of volatile wine composition contributing for its sensory properties (Lengyel & Sikolya, 2015). Though, trans-4-tert-butylcyclohexanol (Fig. S1) and 2,4-di-tertbutylphenol (Fig. S2) were identified in wine samples for the first time, to our knowledge, in the present study. Multivariate analysis was applied to differentiate the volatile profile of wine sealed with the six different types of closures, namely 1 + 1 cork A and B, microagglomerated cork A and B, and synthetic closures A and B. Due to the lack of separation observed in PLS-DA models of 1 + 1 cork A vs. B and synthetic closure A vs. B (Fig. S3), two new groups were created: 1 + 1 cork (A and B, n = 6) and synthetic closures (A and B, n = 6). A clear separation of the remaining groups can be observed in PLS-DA models (Fig. 1b), while no clear separation was evidenced in PCA (data not shown). The volatile compounds potentially relevant for the discrimination (VIP > 1) were quantified and the ones found statistically different between the different closure groups are presented in Table 2. The volatile profile of wine bottled with 1 + 1 cork showed higher levels of ethyl hexanoate, ethyl octanoate, ethyl decanoate, 2-phenylethyl acetate, an ionone-like compound and TDN compared with those in wine sealed with synthetic closures (Fig. 1b–i, 3

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Fig. 1. a) Representative HS-SPME-GC/MS chromatogram of volatile compounds identified in white wine sealed with 1 + 1 cork. Compound identification: 1- isoamyl alcohol, 2furfural, 3- 1-hexanol, 4- isoamyl acetate, 5benzaldehyde, 6- ethyl hexanoate, 7- hexyl acetate, 8- ethyl 2-furoate, 9- 1-octanol, 10phenylethyl alcohol, 11- L-camphor, 12- diethyl succinate, 13- ethyl octanoate, 14- phenylethyl acetate, 15- diethyl malate, 16- iononelike compound, 17- 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN), 18- decanoic acid, 19ethyl decanoate, 20- isoamyl octanoate. b) PLSDA scores scatter plot obtained for the volatile profile of white wine sealed with i) 1 + 1 corks (A and B, n= 6) vs. synthetic closures (A and B, n= 6), ii) synthetic closures (A and B, n= 6) vs. microagglomerated cork A (n= 3), iii) 1 + 1 corks (A and B, n= 6) vs. microagglomerated cork A (n= 3) and iv) 1 + 1 corks (A and B, n= 6) vs. microagglomerated cork B (n= 3).

attribute in some aged white wines. This compound is produced during fermentation, depending on the yeast strain, but its production also continues during bottle storage (Sacks et al., 2012). In addition, this C13-norisoprenoid has been described as one of the main wine

of carotenoids and the hydrolysis of glycoside molecules (Oliveira, Barbosa, Ferreira, Guerra, & Guedes de Pinho, 2006). TDN has been reported to contribute to the characteristic “kerosene” and “petrol” aroma of aged Riesling (Sacks et al., 2012), being considered a positive 4

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Table 1 List of volatile compounds identified in white wine sealed with different closures by HS-SPME-GC/MS. Compound Alcohols Isoamyl alcohol 3-Hexen-1-ol 1-Hexanol 1-Heptanol (S)-3-Ethyl-4-methylpentan-1-ol Benzyl alcohol 1-Octanol trans-Linalool oxide Phenylethyl alcohol cis-4-tert-Butylcyclohexanol trans-4-tert-Butylcyclohexanol Aldehydes Furfural Benzaldehyde 5-Methyl-2-furfural Phenylacetaldehyde Nonanal Decanal β-Cyclocitral Dodecanal Esters Ethyl 2-methylpropanoate (isobutyrate) Ethyl butanoate Ethyl 2-methylbutanoate Ethyl 3-methylbutanoate (isovalerate) Isoamyl acetate Methyl hexanoate Ethyl hexanoate Hexyl acetate Ethyl 2-furoate Ethyl 2-hydroxy-4-methylpentanoate Propyl hexanoate Ethyl heptanoate Methyl octanoate Diethyl succinate Ethyl octanoate Ethyl phenylacetate Isopentyl hexanoate 2-Phenylethyl acetate Diethyl malate Diethyl glutarate Ethyl nonanoate Vinyl decanoate Ethyl 9-decenoate Ethyl decanoate Ethyl isopentyl succinate Isoamyl octanoate Ethyl dodecanoate Isopropyl laurate Methyl dihydrojasmonate Ethyl myristate Isopropyl myristate Ethyl palmitate Organic acids Hexanoic acid Octanoic acid Nonanoic acid Decanoic acid Ketones 2-Heptanone 2-Nonanone Lactones γ-Butyrolactone trans-β-Methyl-γ-octalactone Norisoprenoids Ionone-like compound 1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) β-Damascenone Phenol derivative 2,4-Di-tert-butylphenol Terpenes α-Pinene 3-Carene

CAS

RT (min)

RI

Reported RI

Most abundant ions (m/z)

Identification method

123-51-3 544-12-7 111-27-3 111-70-6 38514-13-5 100-51-6 111-87-5 34995-77-2 60-12-8 98-52-2 98-52-2

3.91 6.45 6.82 9.72 11.25 11.64 12.75 13.24 14.00 16.70 17.06

– 853 867 969 1020 1033 1069 1085 1111 1203 1215

736 856 868 970 1023 1036 1071 1086 1116 1214 1214

55 55 56 55 69 79 71 59 65 57 57

/ / / / / /

70 67 / 82 69 / 84 70 84 108

/ / / /

94 91 81 81

/ / / /

111 122 123 123

STD STD STD NIST 14 NIST 14 STD STD STD STD STD STD

98-01-1 100-52-7 620-02-0 122-78-1 124-19-6 112-31-2 432-25-7 112-54-9

5.84 9.44 9.46 11.94 13.78 16.74 17.14 22.24

830 959 960 1042 1103 1204 1218 1406

833 962 962 1045 1104 1206 1220 1409

67 51 53 65 57 57 67 57

/ / / / / / / /

95 77 81 91 70 70 81 67

/ / / / / / / /

96 105 110 120 82 / 98 82 / 112 123 / 137 / 152 82 / 96

STD STD STD STD STD STD STD NIST 14

97-62-1 105-54-4 7452-79-1 108-64-5 123-92-2 106-70-7 123-66-0 142-92-7 614-99-3 10348-47-7 626-77-7 106-30-9 111-11-5 123-25-1 106-32-1 101-97-3 2198-61-0 103-45-7 626-11-9 818-38-2 123-29-5 4704-31-8 67233-91-4 110-38-3 28024-16-0 2035-99-6 106-33-2 10233-13-3 24851-98-7 124-06-1 110-27-0 628-97-7

4.26 5.11 6.31 6.41 7.01 8.34 10.56 10.97 12.12 12.30 13.45 13.54 14.34 15.93 16.50 17.74 17.97 18.07 18.30 18.74 19.22 21.53 21.64 21.86 22.67 23.17 26.72 27.46 27.96 31.12 31.75 35.11

– 802 848 852 875 922 997 1011 1047 1054 1092 1095 1121 1176 1196 1240 1248 1252 1260 1276 1293 1379 1383 1392 1424 1444 1591 1623 1644 1787 1828 1990

755 802 849 854 876 925 1000 1011 1048 1060 1094 1097 1126 1182 1196 1246 1252 1258 1244 1283 1296 – 1387 1396 1436 1446 1595 1617 1649 1794 1827 1993

71 / 116 60 / 71 / 88 57 / 74 / 85 / 102 57 / 60 / 85 / 88 55 / 70 59 / 74 / 87 / 99 60 / 88 / 99 56 / 84 95 / 112 / 140 69 / 87 61 / 99 / 117 88 / 101 / 113 74 / 87 / 127 101 / 129 88 / 101 / 127 65 / 91 / 164 55 / 70 / 99 91 / 104 77 89 117 87 115 143 88 / 101 / 141 57 / 71 / 155 55 / 69 / 88 / 110 88 / 101 71 / 101 / 129 70 / 127 / 145 88 / 101 60 / 102 / 200 83 / 153 88 / 101 60 / 102 / 228 88 / 101 / 157

STD STD STD STD STD NIST STD STD STD NIST NIST STD NIST STD STD STD NIST STD NIST NIST STD STD NIST STD NIST NIST NIST NIST NIST NIST NIST NIST

142-62-1 124-07-2 112-05-0 334-48-5

10.28 16.24 18.50 21.19

988 1187 1267 1367

990 1180 1273 1373

60 60 57 60

STD STD STD STD

110-43-0 821-55-6

7.36 13.55

888 1089

891 1092

58 / 71 58 / 71

STD STD

96-48-0 39638-67-0

8.06 19.87

913 1317

915 1302

56 / 86 71 / 87 / 99

NIST 14 NIST 14

– 30364-38-6 23726-93-4

18.87 20.84 21.49

1280 1353 1378

– 1354 1386

93 / 121 / 136 / 177 / 192 142 / 157 / 175 69 / 121

NIST 14 NIST 14 STD

96-76-4

24.64

1503

1519

57 / 191 / 206

STD

80-56-8 13466-78-9

8.65 10.90

933 1008

937 1011

77 / 93 79 / 93 / 121 / 136

STD NIST 14

/ / / /

73 73 60 73

/ / / /

87 101 115 / 129 129

14

14 14 14

14 14 14

14 14 14 14 14 14 14 14 14

(continued on next page) 5

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Table 1 (continued) Compound

CAS

RT (min)

RI

Reported RI

Most abundant ions (m/z)

Identification method

1,4-Cineole D-Limonene L-Camphor Nerol oxide

628-97-7 5989-27-5 464-48-2 1786-08-9

11.05 11.49 15.05 15.18

1013 1028 1146 1151

1016 – 1142 1153

111 / 55 / 71 / 125 57 / 68 / 93 / 121 81 / 95 / 108 67 / 68 / 83

STD STD STD NIST 14

RI: retention indices determined using a commercial hydrocarbon mixture (C6-C20); Reported RI: retention index reported in literature; RT: retention time; STD: standard compound; NIST 14: National Institute of Standards and Technology standard reference database, version 2.2, 2014.

with 1 + 1 cork stoppers in the present work. Indeed, the extraction of L-camphor from cork by wine model solution was recently reported (Pinto et al., 2019). Nowadays, this monoterpene is used in aromatherapy (Chen, Vermaak, & Viljoen, 2013) and over-the-counter products (Hausner & Poppenga, 2012), due to its antimicrobial, antiviral and antitussive properties (Chen et al., 2013). To our knowledge, 2,4-di-tert-butylphenol was identified and quantified in white wine sealed with synthetic closures for the first time in this study. This compound has been routinely used as an intermediate for the preparation of antioxidants and ultraviolet stabilizers in the plastic industry and manufacturing of pharmaceuticals and fragrances (Choi et al., 2013). However, its odour properties and potential impact on wine sensory properties are completely unknown. 4-tert-Butylcyclohexanol is derived from hydrogenation of 4-tert-butylphenol and is an intermediate of 4-tert-butylcyclohexyl acetate synthesis, an ester widely used in cosmetics and fragrance industry (Sekiguchi & Tanaka, 1999). According to our knowledge, its trans-isomer was identified in wine volatile composition for the first time in this study, being only present

compounds that can be scalped by different closures (Capone et al., 2003; Godden et al., 2001; Skouroumounis et al., 2005). Several authors described that synthetic closures display the highest scalping capacity, absorbing 96 to 98% of TDN compared to 50% scalping capacity of natural cork stoppers in a Semillon white wine (Capone et al., 2003; Godden et al., 2001; Skouroumounis et al., 2005). These results are in agreement with the highest TDN levels obtained in wine sealed with cork stoppers in the present study. The ionone-like compound seems to follow the same scalping tendency of TDN, as it belongs to the norisoprenoids family as well. However, the undefined identification of the ionone-like compound makes it difficult to recognize its direct impact on white wine development. Other three volatile compounds showed clear differences among wine sealed with different closures, namely L-camphor, 2,4-di-tert-butylphenol and trans-4-tert-butylcyclohexanol. L-Camphor was only detected in white wine sealed with 1 + 1 cork (A and B) stoppers. LCamphor is a monoterpene ketone with a strong and pleasant odour (fresh, minty and camphor) and was only detected in white wine sealed

Table 2 List of volatile compounds changing in white wine sealed with 1 + 1 corks (A and B, n = 6), synthetic closures (A and B, n = 6), microagglomerated cork A (n = 3) and microagglomerated cork B (n = 3). Class/Compound

Alcohol trans-4-tert-Butylcyclohexanol Esters Ethyl hexanoate

Concentration

d

a

Units

1 + 1 Corks

Synthetics

Microaggl. cork A

Microaggl. cork B

ND

ND

52.5 ± 7.0

ND

2.38 ± 0.58

1.53 ± 0.55

2.29 ± 0.61

1.88 ± 0.34

% variation (p-value b) 1 + 1 Corks vs. synthetics

Microagglo. cork A vs. synthetics

μg/L

–

–

mg/L

56.0 ± 16.5 (*)

–

Odour descriptor

Odour detection threshold

NR

NR

Green apple

14 μg/L

c

e

e

Ethyl octanoate

7.34 ± 2.53

3.15 ± 1.36

6.73 ± 2.82

5.16 ± 1.31

mg/L

133 ± 22 (*)

–

5 μg/L

–

Fruity, peach e Flowery, rose f Fruity e

2-Phenylethyl acetate

55.4 ± 3.0

46.8 ± 3.5

52.5 ± 3.8

54.1 ± 4.7

μg/L

18.4 ± 3.8 (**)

–

Ethyl decanoate Phenol derivative 2,4-Di-tert-butylphenol g Monoterpenes L-Camphor Norisoprenoids Ionone-like compound i 1,1,6-Trimethyl-1,2dihydronaphthalene (TDN)

1.81 ± 0.49

0.866 ± 0.355

1.97 ± 0.76

1.71 ± 0.50

mg/L

109 ± 18 (**)

BLOQ

59.4 ± 13.5

BLOQ

BLOQ

μg/L

–

–

NR

NR

780 ± 244

ND

ND

ND

ng/L

–

–

Camphor

14.6 ± 5.1 NQ

7.85 ± 2.99 NQ

15.4 ± 2.4 NQ

10.5 ± 1.6 NQ

μg/L –

85.5 ± 17.5 (*) 186 ± 23 (**)

96.7 ± 13.5 (*) 113 ± 10 (*)

– Kerosene, petrol d

h

e

250 μg/L

f

200 μg/L

e

NR NR 2 μg/L

k

j

*p-value < 0.05, **p-value < 0.01. BLOQ: below limit of quantification, ND: not detected; NQ: not quantified (no commercially available standard), NR: not reported. a Average concentration and standard deviation. b Statistical significance assessed using the Mann-Whitney test. c Odour thresholds were determined in wine model solution (12% (v/v) ethanol containing 5 g/L tartaric acid, pH 3.5) (Sacks et al., 2012); 10% water/ethanol solution containing 7 g/L glycerine, pH 3.2 (Waterhouse et al., 2016) and 10% (v/v) ethanolic solution (Sumby, Grbin, & Jiranek, 2010). d LOQ=10 μg/L. e (Waterhouse et al., 2016). f (Sumby et al., 2010). g LOQ=10 μg/L. h (Arn & Acree, 1998). i Quantified using the calibration curve obtained for α-ionone commercial standard. j Percentage of variation and p-value computed using the area of the quantifier ion (m/z 157). k (Sacks et al., 2012). 6

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Fig. 2. Bar charts of a) free SO2, b) total SO2 and c) absorbance at 420 nm measured in white wine sealed with different closures after 48 months post-bottling (expressed in average and standard deviation, n = 6 for 1 + 1 cork stoppers (A and B) and synthetic closures (A and B), n = 3 for microagglomerated cork A and B). Statistical significance assessed using the Mann-Whitney test. * p-value ≤ 0.05, ** p-value ≤ 0.01.

7

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Fig. 3. Sensory descriptive profile of white wine sealed with different closures after 48 months post-bottling. Results are expressed in average of intensity ratings for seven panelists (n = 6 for 1 + 1 corks (A and B) and synthetic closures (A and B), n = 3 for microagglomerated cork A and B).

development towards oxidation which is also corroborated by higher A420 (browning state) (Ghidossi et al., 2012; Godden et al., 2001). Furthermore, the sensory evaluation showed that the white wine sealed with cork stoppers presented the highest scores in aroma intensity, aroma quality and balance, whereas the synthetic group was scored with higher oxidation, confirming the analytical assessments of a faster development in wine sealed with the later type of closure. Several studies have also showed that synthetic closures promote the fastest decrease of SO2 content (Godden et al., 2001; Liu et al., 2015; Lopes et al., 2009; Skouroumounis et al., 2005), the highest increase in brown colour (Lopes et al., 2009; Skouroumounis et al., 2005) and the fastest development of wine towards oxidized sensory characters (Godden et al., 2001; Liu et al., 2015; Lopes et al., 2009; Mayr et al., 2015; Skouroumounis et al., 2005).

in wine sealed with microagglomerated cork A. Since the trans-4-tertbutylcyclohexanol was not detected in wines and wine model solution sealed with microagglomerated cork B, one possible origin may be the composition of the binder used in the formulation of microagglomerated cork A. Nevertheless, there is a lack of information about the chemical and sensory properties of 4-tert-butylcyclohexanol and more studies should be performed to understand its influence in white wine evolution. SO2 is the main antioxidant used to protect wine from oxidation, thus there is a relationship between the SO2 decrease and the wine oxidation degree as a result of the storage conditions (Sanmartin, Ying, Quartacci, Andrich, & Venturi, 2018). The wine oxidation index is given through the measure of total SO2, which represents both free and bound forms of SO2 that reacts with several wine constituents, such as acetaldehyde, anthocyanins and others (Sanmartin et al., 2018). The wine sealed with synthetic closures showed lower levels of free and total SO2 compared to cork stoppers, suggesting an acceleration in wine

Table 3 Intensity ratings resulted from quantitative descriptive analysis of white wine sealed with 1 + 1 corks (A and B, n = 6), synthetic closures (A and B, n = 6), microagglomerated cork A (n = 3) and microagglomerated cork B (n = 3), at 48 months post-bottling. Attributes

Aroma intensity Aroma quality Acidity Bitterness Balance Oxidation Reduction

Sensory scores

a

p-value

b

1 + 1 Corks

Synthetics

Microagglo. cork A

Microagglo. cork B

1 + 1 Corks vs. synthetics

Microagglo. cork A vs. synthetics

Microagglo. cork B vs. synthetics

3.1 2.9 2.4 1.3 2.9 1.3 0.3

2.5 2.2 2.0 1.1 2.0 2.6 0.2

3.3 3.0 2.4 1.2 2.8 1.0 0.9

2.9 2.7 2.4 1.0 2.7 1.2 0.6

ns * ns ns * * ns

** * ns ns ns * ns

* ns ns ns ns * ns

± ± ± ± ± ± ±

0.7 0.7 0.7 0.6 0.4 0.9 0.3

± ± ± ± ± ± ±

0.3 0.4 0.8 0.7 0.5 0.8 0.2

± ± ± ± ± ± ±

0.5 0.6 1.0 0.7 0.6 1.0 1.0

± ± ± ± ± ± ±

0.4 0.5 0.8 0.5 0.4 0.7 0.5

a

Average sensory scores and standard deviation (seven panellists). Statistical significance assessed using the Mann-Whitney test. ns: not significant. * p-value < 0.05. ** p-value < 0.01.

b

8

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4. Conclusions

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This study showed that bottle closures have an impact in the volatile profile, SO2 content, colour intensity and sensory attributes of a white wine after 48 months post-bottling. Differences in volatile composition, chemical and sensory assessments were mainly observed between cork stoppers and synthetic closures. Wines sealed with 1 + 1 corks were characterized by higher contents of some ethyl esters (ethyl hexanoate, octanoate and decanoate) and 2-phenylethyl acetate, as well as norisoprenoids (TDN and an ionone-like compound), which were also present in higher amounts in microagglomerated cork A when compared with synthetic closures. L-Camphor was specifically identified in wine sealed with 1 + 1 corks. Due to their fruity, floral and pleasant odour descriptors, these volatile compounds may contribute to global aroma quality, aroma intensity and balance described in the sensory evaluation of wines sealed with 1 + 1 corks and microagglomerated cork. On the other hand, synthetic closures were associated with oxidized descriptors, which is in accordance with the oenological parameters measured (free and total SO2, colour intensity). For the first time, to our knowledge, 2,4-di-tert-butylphenol and trans-4-tert-butylcyclohexanol were described in the volatile composition of wines sealed with synthetic closures and microagglomerated cork A, respectively. Both compounds are widely used in plastics, cosmetics and fragrance industries, but more studies should be performed to understand their sensory impact on wine chemical and sensory properties. Declaration of Competing Interest None. Acknowledgements This work received financial support from the European Union (European Regional Development Fund POCI/01/0145/FEDER/ 007728) and National Funds (FCT/MEC, Fundação para a Ciência e a Tecnologia and Ministério da Educação e Ciência) under the Partnership Agreement PT2020 UID/MULTI/04378/2013. The study is a result of the project NORTE-01-0145-FEDER-000024, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement (DESignBIOtecHealth—New Technologies for three Health Challenges of Modern Societies: Diabetes, Drug Abuse and Kidney Diseases), through the European Regional Development Fund. Appendix A. Supplementary data Supplementary material related to this article can be found, in the online version, at doi:https://doi.org/10.1016/j.fpsl.2020.100465. References Arn, H., & Acree, T. E. (1998). Flavornet: A database of aroma compounds based on odor potency in natural products. Developments in Food Science, 40(C), 27. Azevedo, J., Fernandes, I., Lopes, P., Roseira, I., Cabral, M., Mateus, N., et al. (2014). Migration of phenolic compounds from different cork stoppers to wine model solutions: Antioxidant and biological relevance. European Food Research and Technology, 239(6), 951–960. Barros, E. P., Moreira, N., Pereira, G. E., Leite, S. G. F., Rezende, C. M., & de Pinho, P. G. (2012). Development and validation of automatic HS-SPME with a gas chromatography-ion trap/mass spectrometry method for analysis of volatiles in wines. Talanta, 101, 177–186. Capone, D., Sefton, M., Pretoius, I., & Høj, P. (2003). Flavour’ scalping’ by wine bottle closures–the’ winemaking’ continues post vineyard and winery. Australian and New Zealand Wine Industry Journal, 18(5), 16–20. Chen, W., Vermaak, I., & Viljoen, A. (2013). Camphor - a fumigant during the black death and a coveted fragrant wood in ancient Egypt and Babylon – a review. Molecules, 18(5), 5434–5454. Choi, S. J., Kim, J. K., Kim, H. K., Harris, K., Kim, C.-J., Park, G. G., et al. (2013). 2,4-Ditert-butylphenol from sweet potato protects against oxidative stress in PC12 cells and in mice. Journal of Medicinal Food, 16(11), 977–983.

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