Article pubs.acs.org/JAFC
Aromatic Characterization of Pot Distilled Kiwi Spirits Cristina López-Vázquez,† Laura García-Llobodanin,‡ José Ricardo Pérez-Correa,§ Francisco López,*,‡ Pilar Blanco,† and Ignacio Orriols*,† †
Estación de Viticultura y Enología de Galicia (EVEGA)-Ingacal, Ponte San Clodio, 32427 Leiro, Spain Departament d’Enginyeria Química, Facultat d’Enologia, Universitat Rovira i Virgili, Av. Països Catalans 26, Campus Sescelades, 43007 Tarragona, Spain § Departamento de Ingeniería Química y Bioprocesos, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22, Chile ‡
ABSTRACT: This study contributes fundamental knowledge that will help to develop a distillate of kiwi wine, made from kiwis of the Hayward variety grown in the southwest of Galicia (Spain). Two yeast strains, L1 (Saccharomyces cerevisiae ALB-6 from the EVEGA yeast collection) and L2 (S. cerevisiae Uvaferm BDX from Lallemand) were assessed to obtain a highly aromatic distillate. The kiwi spirits obtained were compared with other fruit spirits, in terms of higher alcohols, minor alcohols, monoterpenols, and other minor compounds, which are relevant in determining the quality and taste of the kiwi spirits. It was found that the kiwi juice fermented with yeast L1 produced a more aromatic distillate. In addition, kiwi distillates produced with both yeasts had the same ratio of trans-3-hexen-1-ol and cis-3-hexen-1-ol, which is lower than that found in other fruit distillates. KEYWORDS: kiwi spirit, alcoholic beverages, fermentation, aromatic composition
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not comply with the minimum commercialization weight of 62 g, as indicated in the Official Journal of the European Communities, 2004.10 Before processing, the fruit was kept in storage at 2 °C for less than 3 months. At 24 h prior to sampling, fruits were taken out of storage and allowed to warm to ambient temperature (around 20 °C). The fruits were processed at the eating-ripe stage, having an average flesh firmness of 0.5 kgf. The flesh firmness was evaluated using a firmness texture analyzer FTA/GS-14 (Infoagro Systems, S.L., Madrid, Spain). A hand-held refractometer with ATC 0-32 Brix (Auxilab S.L., BeriainNavarra, Spain) was used to measure soluble solids content. Kiwi Processing. Kiwi fruits were sorted by size and washed with plenty of running water in order to remove foreign material from the skin (pesticides, hairs, and particles). Next, the kiwi fruits were crushed with an ENO-2 crusher (Magusa, Vilafranca del Penedès, Spain). Previously the mash was treated with a pectolytic enzyme (Uvazym Arom MP, Sepsa Enartis, Vilafranca del Penedés, Spain) to favor juice extraction. The mash obtained was divided into 6 batches of 55 kg and put into 6 fermentation tanks of 50 L. After pulping, 35 mg/L of SO2 was added. Fermentation. Two types of kiwi wines (KW) were produced: KWL1, fermented with L1 yeast (Saccharomyces cerevisiae ALB-6 from the yeast collection of the Estación de Viticultura e Enoloxiá de Galicia, EVEGA, Leiro, Spain), and KWL2, fermented with L2 yeast (S. cerevisiae Uvaferm BDX, an active dry yeast from Lallemand, Zug, Switzerland). L1 yeast was previously grown in YEPD medium [1% (w/v) yeast extract, 2% (w/v) peptone and 2% glucose (w/v)] at 28 °C for 24 h, and the cells were recovered by centrifugation, washed with sterile water, and added to kiwi juice at a concentration of 106 cells/mL. Following manufacturers’ indications, L2 yeast was added to the kiwi juice in the fermentation tanks at a concentration of 25 g of yeast/hL, after rehydratation for 20 min in 250 mL of sugared water at 37 °C and finally acclimatizing in 1 L of kiwi juice. Three tanks were inoculated with each strain. All fermentations were carried
INTRODUCTION Kiwi or kiwi fruit, botanically known as Actinidia chinensis, originates from the Yangtze River valley in China,1 where it has been grown for 2000 years. Spanish kiwi production, over 10,000 tons, is mainly located in Galicia, which has more than 60% of the 900 ha cultivated in Spain. The Spanish kiwi is highly valued in the European market, since it is harvested and immediately consumed, an aspect that differentiates it from kiwis imported from other parts of the world.2 Recently, the development of cultivation techniques and production management in Spain and other countries have significantly increased kiwi production, which, in turn, has led to an excess of supply. Consequently, although kiwis are still mainly consumed fresh, there is an increasing trend to develop new kiwi-based products, such as nectar, jams, and preserves.1,3 Moreover, some studies have been done on kiwi wine, particularly in Asia. This opens up the possibility of developing kiwi distillates3−6 that preserve or enhance the aromatic characteristics of the ripened fresh fruit. The kiwi aroma is a combination of different volatile compounds such as ethyl butanoate, unsaturated aldehydes, and alcohols of six carbon atoms.7 The aromatic profile varies with fruit maturity, which increases the fraction of esters.8 In general, the Hayward variety is aromatically characterized by C6 aldehydes and alcohols, with some esters produced upon ripening.9 Academic research on kiwi wines and distillates is scarce. We found only two papers dealing with kiwi wine in Europe3,6 and one paper dealing with a distillate of a kiwi enriched grape wine.3 Therefore, this research aims to provide fundamental knowledge that will help to develop kiwi distillates characterized by an aromatic profile that meets market standards.
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MATERIALS AND METHODS
Received: Revised: Accepted: Published:
Kiwi Samples. We used kiwi fruits with 7% soluble solids (SS) of the Hayward variety grown in the southwest of Galicia (Spain) and harvested in November 2009. The kiwi fruit used in this study does © 2012 American Chemical Society
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July 9, 2011 January 21, 2012 February 10, 2012 February 10, 2012 dx.doi.org/10.1021/jf204310v | J. Agric. Food Chem. 2012, 60, 2242−2247
Journal of Agricultural and Food Chemistry
Article
out at a room temperature of 12 ± 1 °C, and the evolution of the fermentations was monitored by daily measurements of temperature and density in the tanks. When the density reached a plateau, the fermentations were stopped by adding 50 mg/L of SO2. The kiwi mashes obtained were stored at 4 °C for less than two weeks, until distillation and chemical characterization of the distillates. Distillations with a Charentais Alembic. In total, 50 kg of fermented kiwi mash was distilled in a 50 L copper Charantais alembic. The base of the boiler was heated by an open flame, and tap water was used to cool the total condenser. The heating power was set to obtain an average distillation rate of 8 mL/min. The first 300 mL of distillate was collected as head, the heart was collected when the ethanol concentration reached 40% v/v, and the tail was obtained and discharged when the ethanol concentration reached 28% v/v. Three distillations were carried out for each wine type, KWL1 and KWL2. Chemical Analysis. Classical Parameters. In the initial mash and in the kiwi wines, the usual parameters were determined in accordance with the Office International de la Vigne et du Vin, OIV,11 and the Official Journal of the European Communities, 1990:12 ethanol (steam-distillation of kiwi wine made alkaline by a suspension of calcium hydroxide, and measurement of the alcoholic strength of the distillate by electronic densimetry), reduced sugars (cupric-alkaline method), density (DMA 5000, Anton Paar, GmbH, Graz, Austria), pH (Crison micropH 2000, Barcelona, Spain), total acidity (acid−alkali titration, Crison TitroMatic 1S, Barcelona, Spain), volatile acidity (titration of the volatile acids separated by steam-distillation with sodium hydroxide), citric and malic acid (enzymatic-spectrophotomety, LISA 200 autoanalyzer, TDI, Barcelona, Spain). Anton Paar densimeter (DSA 5000 M, Anton Paar, GmbH, Graz, Austria) was used to determine both the probable alcohol strength of the kiwi juice and the alcoholic strength of the kiwi wines and kiwi distillates as a function of density using conversion charts.11,12 GC Analysis. The heart fractions obtained were analyzed using gas chromatography coupled with flame ionization detection (GC−FID) with direct injection of the distillate. Analyses were carried out using two different columns. Macroconstituents (methanol, higher alcohols, acetaldehyde, 1,1-diethoxyethane, ethyl acetate, ethyl lactate, 1-hexanol, isobutyraldehyde, ethyl formate, methyl acetate, 2-propenal, 2-butanol, allylic alcohol) were analyzed using a CP Wax-57 CB capillary column (50 m × 0.32 mm i.d. × 0.2 μm film thickness, Varian Medical Systems, Barcelona, Spain) on a GC Agilent 6890 (Agilent Technologies, Waldbronn, Germany) equipped with split/splitless injector with an electronic flow control (EFC) and a FID; conditions were reported in a previous study.13 The other compounds were separated using a Supelcowax 10 capillary column (30 m, 0.32 mm, 0.25 μm film thickness; Supelco Inc., Bellefonte, PA, USA) in a GC Varian CP3900 (Varian Medical Systems Barcelona, Spain), and the method used was the one described by López-Vázquez et al.14 Samples were analyzed in triplicate. Statistical Analysis. One-way analysis of variance (ANOVA) was applied to the data obtained from the GC analysis. The aim was to ascertain whether there are significant differences (at 5% level) between the kiwi spirits produced with the two different yeast strains. All the statistical analyses were performed with the SPSS statistical package (version 17.0).
Table 1. Physical and Chemical Characteristics of Kiwi Winesa KWL1
citric acid (g/L) density (g/mL) alcoholic strength (% v/v) reduced sugars (g/L)* total acidity (mequiv/L)* volatile acidity (g/L acetic acid)* pH* malic acid (g/L)*
KWL2
initial mash
mean
SD
mean
SD
7.60 1.0415 5.4b 59.6 152.0 nd 3.54 nd
6.40 1.012 4.63 2.70 128.4 1.39 3.88 3.53
0.53
