The flavour of fruit spirits and fruit liqueurs: a review

Review Received: 7 May 2014, Revised: 24 November 2014, Accepted: 21 December 2014 Published online in Wiley Online Library: 13 February 2015 (wileyonlinelibrary.com) DOI 10.1002/ffj.3237 The flavour of fruit spirits and fruit liqueurs: a review Magdalena Śliwińska,* Paulina Wiśniewska, Tomasz Dymerski, Waldemar Wardencki and Jacek Namieśnik ABSTRACT: Fruit spirits and liqueurs are among the most popular spirit-based beverages made from fruits such as plums, cherries, melon, apple, citrus and pear. The types of fruits and production methods have a great significance for the quality of the final product. The production process of spirits consists of the following stages: fermentation, distillation and maturation. For this reason scientists started to investigate the composition of fruit spirits and liqueurs in order to monitor the changes occurring in the production process and to control the content of selected compounds negatively affecting human health as well as compounds influencing the flavour and aroma of spirits. Furthermore, studies investigating the authenticity of the products and the identification of their botanical and geographical origin were performed. This article is a summarized description of fruit liqueurs and spirits produced from the above-mentioned fruits and the characteristics of commonly used techniques for quality assessment of both types of product. Keywords: fruit spirits; fruit liqueurs; quality; sensory ; authenticity tests; review Introduction Spirit-based beverages are very popular worldwide. They are produced in various countries from various raw materials. Fruit spirits and liqueurs belong to this group of beverages. According to European Community Regulation EC 110/2008 fruit spirit is a spirit-based beverage produced exclusively via ethanol fermentation and distillation of fleshy fruit or must of such fruit, with or without stones. It is distilled at less than 86% volume so that the distillate has an aroma and taste derived from the raw materials. The minimum ethanol content in fruit spirits is 37.5% volume. In most cases, the maximum allowed methanol content of fruit spirit is 1000 g/hl of 100% volume alcohol. Fruit spirits made from stone fruits cannot contain hydrocyanic acid more than 7 g/hl of 100% volume alcohol. These spirit-based beverages are not allowed to be flavoured artificially. In most cases, the brand name of a given fruit spirit should be stated, together with the name of the fruit from which the beverage had been made, for example cherry spirit or kirsch, plum spirit or slivovitz, peach spirit, apple spirit, or grape spirit. [1] The word spirit can be substituted with the word wasser (Germany) and eau de vie (France). The fruits most frequently used in the production of fruit spirits are cherries, plums, apricots, pears (Barlett and Williams varieties) and apples (Golden Delicious and Cox Orange). Fruit spirits made from the fruits of low sugar content, for example quince and strawberries are rarely manufactured. [2] Plum spirits constitute the most popular fruit spirits, and is a spirit-based beverage manufactured on a large scale mainly in central and eastern Europe. The largest producers of plum spirit are Czech Republic, Poland, Slovakia, Hungary, Bulgaria, Serbia and Romania. Depending on the country of origin, plum spirit can be called śliwowica (Poland), tuica (Romania), slivovica (Slovakia) or sljivovica (Bosnia and Herzegovina). Plum spirit is also produced in western Europe, but in smaller amounts. It is known under the name eau-de-vie de prunes (France), zwetschgenwasser (Germany) and pflaumliwasser (Switzerland). [3] In some publications the name plum brandy can be found, however, according to the Regulation EC 110/2008 the aforementioned alcoholic beverages are classified as fruit spirits. [1] Cherry spirits are another popular kind of fruit spirit. They are mostly produced in southern parts of Germany, France, Switzerland and Serbia. A bitter almond aroma and flavour [4] are characteristic of this spirit. Fruit spirits made from apples include, among others, Calvados, which comes from the Normandy region of northern France along the English Channel. It is made from fermented apple juice, possibly with addition of pears. [5] According to regulations [1] the spirits manufactured from citrus fruits, pears and apples are also classified as fruit spirits. Spain is the leader in terms of sales of this spirit because of this country s vast pear production. [6] Italy is well known for its production of spirits made from citrus fruits, particularly from oranges. A melon spirit is also a very popular in Europe. Large quantities of melons are produced in Castilla La Mancha in Spain. Market saturation with this product has resulted in diversification by producers, including a production of melon spirit. [7] However, so far no information about this spirit has been incorporated in Regulation EC 110/2008. Liqueurs are another group of alcoholic beverages made from fruits, amongst other things. The name liqueur comes from the Latin word liquefacere, which means to melt or to dissolve. [8] Liqueurs are made via concurrent dissolution or mixing of a * Correspondence to: Magdalena Śliwińska, Gdansk University of Technology, Department of Analytical Chemistry, 11/12 Narutowicza Street, 80-233 Gdańsk, Poland. E-mail: m.e.sliwinska@gmail.com Gdansk University of Technology, Department of Analytical Chemistry, 11/12 Narutowicza Street, 80-233 Gdańsk, Poland 197

M. Śliwińska et al. 198 number of components. According to legal regulations, liqueurs are colourless or coloured sweetened spirit-based beverages produced by flavouring ethanol or the distillate of agricultural origin. The minimum ethanol content in liqueurs is 15% volume, while the sugar content, expressed as inverted sugar, in most cases equals 100 g/l of liqueur. [1] However, there are numerous traditional liqueurs that contain 35 45% of ethanol. Products of agricultural origin, such as herbs (roots, seeds and flowers), fruits (whole fruit, peel and stones) and fruit juices, as well as other food products, inter alia, dairy products and wines, are used in the production of liqueurs. Moreover, essential oils, and natural and synthetic aromas are also used. There are three possible ways to obtain natural extracts, that is, infusion, percolation and distillation. The production of natural extracts begins with the soaking of the selected product (e.g. fruit) in ethanol at 40 60 C for a couple of days. Next, the filtered solution undergoes maceration, followed by the distillation process. Most frequently, liqueurs are coloured by adding, inter alia, caramel and honey. [2,8] The most popular liqueurs are made of apple, cherry and plum. For many years, scientists have investigated the complex composition of fruit spirits and liqueurs made from fruits, in order to monitor the changes that occur in the production process, control the content of selected compounds that negatively affect human health (e.g. methanol, ethyl carbamates), authenticate the products, and possibly identify their botanical and geographical characteristics. Constituents of Possible Concern Constituents present in fruit spirits that may be seen as potentially having a negative influence on health include methanol, hydrogen cyanide and ethyl carbamate. In this context, however, it should be noted that their potential for harm is generally minimal, compared with that of alcohol itself. Methanol is formed during the production process by the enzymatic hydrolysis of fruit pectin. The scheme of this reaction looks as follows: pectin þ H 2 O pectin methylesterase pectic acid þ methanol: An increase in methanol concentrations is influenced by, amongst other things, the content and level of methylation of pectins and the activity of the original pectin methylesterase in the fruit. Methanol is contained in all alcoholic beverages. Its concentrations are usually at a low level, however, in the case of fruit spirits produced together with stones and skins, the content of this compound may reach up to 1000 g/hl of 100% volume alcohol, and even more. [3,9 13] According to EU directives for plum spirits, the concentration of methanol must not exceed 1200 g/hl of 100% volume alcohol. [1] Cyanogenic glycosides are a natural ingredient, but they are also contained in fruit stones. Stones may become damaged during mash preparation and cyanogenic glycosides from the stones may come into contact with enzymes in the fruit mash. As a result, cyanogenic glycosides are then degraded to hydrocyanic acid. Prolonged storage of the fermented mash may lead to the release of hydrocyanic acid from intact stones. Small amounts of hydrogen cyanide have an advantageous effect on the aroma of alcoholic beverages. In larger amounts, however, it can be harmful to the body. Regulation EC 110/2008 states that the HCN content should not exceed 7 g/hl of 100% volume alcohol. [14,15] Ethyl carbamate is a potential genotoxic carcinogen in humans. This compound is formed during the fermentation of food products. [16] It has been proven that the highest concentrations of ethyl carbamate occur in spirit-based beverages made of stone fruits. [17] In certain environmental conditions, such as exposure to light and high temperatures, ethyl carbamate can be formed from various substances, including hydrogen cyanide, urea and citrulline, which are present in food and beverages. [14] The highest ethyl carbamate content is observed in the final stage of fermentation, when the ethanol concentration peaks. [18,19] The allowed ethyl carbamate content in fruit spirits is 400 μg/l. [15] Research on methanol, HCN and ethyl carbamate is described in a further part of this publication. Origins of Flavour The quality of spirits is influenced by a natural aroma of fruits used for their production. The general aromatic profile of fruits is influenced by many factors: the geographical origin, the method of cultivation, storage and time of harvest. Fruits contain several hundred compounds, which have a cumulative influence on the general aroma. In many cases, fruit aroma is influenced by a mixture of several compounds, which do not show such properties individually, for example, hexyl 2-methylbutanoate, hexyl acetate and ethyl hexanoate contribute to apple aroma. [20] In many cases, some compounds occur in many kinds of fruits and they are not a distinguishing feature of one aroma, for example linalool, nonanal, (E)-2-hexenol and limonene. Additionally, aromatic compounds are characterized by a different aroma depending on the concentration of a given compound, for example eugenol, which has a fruity aroma at lower concentrations, and a pungent aroma at higher ones. [21] The botanical origin, that is, the difference in the composition between various cultivars of one kind of fruits, also makes it more difficult to determine the general aromatic profile of fruits, for example a compound from the terpene group, α-farnesene, was identified only in plums from the P. salicina and P.domestica cultivars but was not detected in the P. cerasifera, P. ussuriensis and P. spinosa cultivars. [22] Compounds with a description of the aroma that is probably responsible for the aroma of a given fruit are presented in Table 1. Production The quality of fruit spirits is influenced by four main production stages: the first involves the selection of the raw material and its form; the second is the selection of appropriate parameters for the fermentation process; the third pertains to the distillation process (the selection of appropriate equipment and fraction); the fourth is the process of the beverage maturation under appropriate conditions and the period of time. [31] Selection of Raw Material The first stage of the production of spirits is the selection of an appropriate selection of the type of fruit and form of this raw material. Fruits in the classic form (whole fruits), pulp and juice are used in production. Spirits are most often made from plums, melons, apples, cherries and pears. wileyonlinelibrary.com/journal/ffj

The flavour of fruit spirits and fruit liqueurs Table 1. Compounds responsoble for fruit aroma Compound Aroma Raw material Reference γ-decalactone Plum Plum 22 Octyl acetate Pear, fruity Pear 23 Ethyl (2E,4Z)-2,4-decadienoate Pear Pear 23 (E, Z)-2,6-nonadienal Melon, cucumber Melon 24 Hexyl 2-methylbutanoate Green Apple 25, 26 Nonanal Floral, fruity, green, woody Different fruits 22, 26 (R)-limonene Citrus Grapefruit 27 2-Phenylacetaldehyde Sweet, floral Melon 24 (E)-2-hexenol Green, apple Apple 2, 28 Ethyl cinnamate Fruity Stone fruits 2, 28 Benzaldehyde Almond Stone fruits 2, 28 Hydrocyanic acid Bitter almond Stone fruits 2, 28 Isopentyl propanoate Fruity, plum, sweet, Plum 29 1-Hexanol Grass, herbaceous, fruity Different fruits 20, 23 6-Methyl-5-hepten-2-one Floral Plum 30 (E,E)-2,4-decadienal Green Pear 23 Linalool Floral, plum Different fruits 22 Plums are the most popular fruits used for the production of fruit spirits. Previous studies [9,32] have checked the influence of the selection of the appropriate cultivar and form of plums. One study [9] presented results pertaining to methanol content in fruit spirits, depending on the plum cultivars used: Geneva Mirabelle, French Damson, Pozegaca, Oblinaya, Early Golden, Lohr, and Rosy Gage plums growing in the New York region. The methanol concentration was measured by means of highperformance liquid chromatography (HPLC). The results presented showed that the fruit spirit made of Early Golden plum had the highest methanol content, while that produced from Pozegaca plum, contained the lowest methanol level. Moreover, it was demonstrated that the efficiency of plum spirit production and the methanol content are influenced by factors such as date of harvest and geographical location of the harvested fruits. [9] Research has focused on the influence of the selected form of plums for the production of spirits. One study [32] described the effect of different preliminary treatments of plums with varying sucrose content (Węgierka Zwykła) on the quality of Śliwowica Łącka, namely, plum mash, plum concentrate and plum syrup after crystallization. The content of sugars and ethanol was monitored during the fruit fermentation by HPLC. The analysis of volatile compounds in plum spirits was conducted by using gas chromatography (GC) equipped with a flame ionisation detector (FID). The application of spectrophotometric techniques allowed the determination of hydrogen cyanide content (HCN). In addition, a sensory was performed to precisely assess the aroma and colour of the plum spirits. The results presented showed that plum spirits of the highest quality were produced from plum mash and plum concentrate. [32] The next review is of a study of the relationship between the composition of cherry spirit and the type of cherries used in its production, for example sour cherries (P. cereseus). [4] The purpose of this research was to compare the composition of five cherry spirits made of sour cherry varieties (Oblačinska, Celery s 16, Rexle, Heiman s Ruby and Heiman s Conserve) originating from Serbia, and to evaluate the influence of cherry variety on organoleptic properties of the final product. Identification of volatile compounds was undertaken using GC-FID and GC MS, whereas benzaldehyde content was determined using HPLC. A sensory was employed to assess the organoleptic properties of the beverages. The statistical method of ANOVA was used to investigate the differences between the samples. Thanks to the application of GC, 32 aromatic compounds were quantitatively analysed. Benzaldehyde and linalool occurred at the highest concentrations in the spirits investigated. Spirits made of the Celery s 16 and Rexle cherry varieties displayed such high concentrations: both spirits scored the best notes in the sensory. The lowest content of aromatic compounds was determined in spirits produced from Oblačinska cv and Heiman s Ruby cv cherries. The spirit made from Oblačinska cherries had the worst score in the sensory. The authors stated that it could have been caused by the high contents of ethyl octanoate and ethyl hexadecanoate. [4] Apart from research concerning the influence of pulp and juice on spirit production, the literature contains information on the effect of fruit pits on the quality of cherry and plum spirits produced under laboratory conditions was described. Dollenseppler cherries and Ersinger Frühzwetschge plums were used to make the investigated fruit spirits. The contents of sugars, ethanol and acids (acetic, propanoic and lactic acids) during the fermentation of fruit mash (with and without pits) with different yeast strains were determined by HPLC. The volatile compounds were quantitatively analysed in the fermentation products and post-distillation spirits by using a GC-FID technique. In addition, the content of ethyl carbamate was determined by means of GC MS/MS. Total HCN in the spirits was photometrically determined. Finally, the end product was subjected to sensory by 25 people. The results obtained were statistically analysed using ANOVA. Based on the study results, it was concluded that the spirits produced from the pitcontaining fruit mash can be distinguished from those obtained from mash without pits. [33] There is also information available in the published literature on comparing the production processes of melon spirit. [7,34,35] Three forms of melon were used in the fermentation process leading to the production of melon spirit, that is, pulp, juice and pulp without the skin. In each case, ph and degrees Brix 199 wileyonlinelibrary.com/journal/ffj

M. Śliwińska et al. 200 were measured. Distillation was conducted by using either column stills or copper-pot stills. The analysis of volatile compounds was performed by means of GC MS [34] and GC-FID. [7,35] Moreover, in other studies [34,35] a sensory was also applied. Principal components analysis (PCA) was mainly used for processing the data collected. [7,34,35] Pulp fermentation turned out to be more efficient, however, the final product scored low in the sensory analysis, and had high methanol content. The use of melon pulp without the skin is a better solution for the industry because the waste produced has less impact on the environment. [34,35] The influence of the form of apples on cider production was also investigated. Whole apples and apples in the form of concentrate were used for research. Using GC MS [36] and GC FID [37] and HPLC, [38] it was shown that ciders made in the traditional manner contained higher concentrations of decanoic and dodecanoic ethyl esters and long-chain fatty acids. [36] Higher concentrations of furan compounds, methanol and furfural were found in ciders made from apple juice concentrate. [37,38] It is evident from the studies quoted that the quality of spirits is influenced by the choice of the cultivar and form of fruits used for their production. In the case of plum spirits, the highest quality was produced from plum mash and plum concentrate, while in the case of melon spirits, the final product made from pulp scored low in the sensory analysis and had a high methanol content. In the case of apple spirits, higher concentrations of selected compounds, including methanol, were identified in ciders made from apple concentrate. As regards stone fruits, research was also conducted to determine the influence of stones on the quality of the spirit. The research results showed that the presence or absence of stones in the mashes should not be used as a general quality criterion, as the preference for one or the other spirit will remain a matter of personal taste. It turns out the decisive influence on the selection of fruits used for production influences its quality, but the choice of fruit cultivars mostly depends on consumer preferences. Fermentation and Distillation Processes Fermentation and distillation processes influence the formation of aromatic compounds in spirits, which, as a result, influences their quality. The fermentation stage consists, amongst other things, of appropriate selection of yeast strains and the selection of fermentation parameters, and the distillation process depends on the type of equipment used. The effect of yeast on the fermentation of the Węgierka Zwykła plum is presented by Satora and Tuszyński. [39] The quantitative and qualitative analyses of volatile compounds, inter alia, methanol, ethyl acetate, acetaldehyde, amyl alcohol, butanol and hexanol were performed by means of GC MS. The highest ethanol concentration was detected after spontaneous fermentation with Saccharomyces cerevisiae (yeast used in wine making), however, after distillation, the ethanol concentration increased over several dozens of times, as in the case of samples containing Kloeckera apiculata yeast. It was demonstrated that non-saccharomyces yeasts are responsible for the high concentration of esters and methanol, while the use of S. cerevisiae yeast results in the high content of higher alcohols in plum spirits. The beverage produced via fermentation with S. cerevisiae scored the highest note in the sensory. The data obtained were processed by PCA. [39] Due to the considerable influence of the fermentation process on the product quality, research is often conducted to check the influence of fermentation parameters. The ph of fermentation is one of these parameters. Such research was conducted on spirits manufactured from pears. The influence of ph on the quality and sensory value was estimated using GC-FID, HPLC and sensory. [40] Thanks to the use of the ANOVA and PCA methods, it was demonstrated that pear spirits obtained from fermentation of fruit juice with acidified ph have a higher content of fruity esters and higher alcohols, inter alia, 2-methyl-1- butanol, 3-methyl-1-butanol and 2-methyl-1-propanol, and a lower content of ethyl acetate, as compared with pear spirits made from fermentation of fruit juice with a native ph. The aforementioned differences in the composition of these two kinds of pear spirits, however, were not identified using sensory (both smell and taste). [40] There are publications in the literature describing the influence of the equipment used during the distillation process on the quality and composition of spirits. A study on the effect of different distillation techniques used in the production of Croatian plum spirits from the Slavonija region was conducted by means of GC and sensory. It was proven that the distillation type has a huge impact on the spirit quality. The samples of plum spirits made by using a distillation column had higher content of the main aromatic compounds. Moreover, these samples received the highest score in the sensory. [41] Another article describes research on volatile compounds in which a comparative composition analysis was conducted on the samples of different plum spirits originating from Serbia. Four plum spirits were researched, that is, commercially available Manastrika originating from Belgrade, homemade Sokolova rakija and Karanka from the Užice region, and Valjevka from the Valjevko region. The percentage content of ethanol in all samples was 45%. The aforementioned plum spirits were distilled in the 1990s, namely, Manastrika in 1990, Sokolova in 1992, Karanka in 1993 and Valjevka in 1997. The analysed inter alia spirits differed with respect to the distillation type. Manastrika plum spirit was produced with apparatus consisting of a short distillation column, which allows for obtaining a distillate with the optimal content of components, whereas the device used in the production of Sokolova, Karanka oraz Valjevka plum spirits did not have a column. A comparative analysis of spirit compositions was performed using GC-FID. In oldest plum spirit (Manastrika) a higher concentration of aromatic compounds was detected: benzyl alcohol, β-phenyl ethyl alcohol. In addition, the aromatic terpene compounds, α-pinene and β-myrcene, were detected only in that plum spirit. Moreover, a sensory was also conducted in order to organoleptically assess the spirits. Based on the presented results, it was concluded that the distillation type has a significant effect on the quality of the spirit produced. The sample of Manastrika, the plum spirit produced by using the apparatus with a distillation column, scored the highest note in the sensory. [31] The influence of the equipment used on the distillation process has been described in another study. [42] This study considered the composition of the middle run distillate, which was analysed in relation to the distillation apparatus and the type of fermented pear juice (with and without sediment) used. The juice fermentation was monitored by HPLC, while the quantitative and qualitative analyses of volatile compounds were performed by means of GC. Pear wine, used as a raw material, was distilled in three different devices, that is, glass pot wileyonlinelibrary.com/journal/ffj

The flavour of fruit spirits and fruit liqueurs equipped with a glass column, copper-pot still, and glass pot with copper shavings added to the distillation vessel. The ANOVA method was applied to determine the differences in the composition of middle run distillates dependent upon the equipment used and the presence of yeast sediment. Based on the results obtained, it was demonstrated that the concentrations of compounds negatively affecting the quality of distillate (methanol, ethyl acetate and furfural) decreased or remained unchanged when using wine with sediment in the production process and distillation in a copper-pot still. Moreover, the concentration of the aforementioned compound responsible for pear aroma, that is, ethyl (2E,4Z)-2,4-decadienoate was high in the presence of yeast sediment during the production process. These results confirmed that the best way to produce pear spirit is by fermenting juice with sediment, followed by distillation in a copper-pot still. [42] It is evident from the studies quoted that the use of the S. cerevisiae yeast strain for the production of plum spirits results in a higher alcohol content. In the case of pear, acidic ph has no influence on sensory, but only on the composition. The use of fermenting juice with sediment, followed by distillation in a copper-pot still for the production of pear spirits, allows for an increase in concentrations of compounds responsible for the pear aroma, that is, ethyl (2E,4Z)-2,4-decadienoate, which shows better quality of the product. Additionally, the use of equipment with a distillation column contributes to the highest note in the sensory. It turns out that for the production of good quality spirits, it is necessary to use an appropriate strain of yeast and selection of appropriate fermentation parameters and distillation equipment. The proper performance of these activities not only ensures a high-quality flavour and aroma, but also limits the number of undesirable and sometimes harmful substances. Maturation Process Fresh distillates are often characterized by a raw and pungent odour and taste. For this reason, maturation is the last process influencing aromatic compounds and, as a result, influences the organoleptic values of spirits. The influence of maturation time and different types of storage barrels on the composition and organoleptic qualities of plum spirits originating from Serbia was studied by Pecić et al. [43] The content of phenolic and polyphenolic compounds, organoleptic qualities, colour and antioxidant properties of the spirits were determined. HPLC was used in the analysis of the aforementioned compounds, while the spectrophotometric methods were applied to assess antioxidant properties. Homemade plum spirits (Prepečenica and Šlijvovica), which had been heated in barrels made of different types of wood from 10 to 47 years, were investigated. The difference in composition of the aforementioned spirits is their ethanol content, for example the ethanol content of Šlijvovica is not less than 25%, whereas that of Prepečenica is not less than 40%. All spirits sampled were made of Prunus plum variety. Ten samples of plum spirits (nine samples of Prepečenica and one sample of Šlijvovica) with a similar range of ethanol concentrations (45%) were analyzed; Šlijvovica with a 28% ethanol content was an exception. Based on the results presented, it was demonstrated that Prepečenica, which had been matured in the barrel made of oak tree (Quercus petreate L.) from the Kučaj Mountains, displayed the highest content of phenolic compounds and high values of antioxidant activity. The statistical results of sensory from ANOVA indicated that the barrel type used in the production of plum spirit has no effect on the organoleptic. Moreover, it has been proved that the duration of maturation period has a positive effect on the taste and smell of plum spirit. In the case of spirits matured longer than 35 years, however, no differences in the sensory were found. Additionally, owing to the use of sensory, it was found that the ethanol concentration also influences organoleptic properties, as Šlijvovica, which contained the lowest ethanol concentration, obtained the lowest scores from the survey respondents. [43] Results concerning a cider composition analysis (from apples and apple juice concentrate) obtained in the maturation process have been presented in previous studies. [36 38] The cider maturation process took place in oak barrels at 9, [36] 12 [37] and 15 [38] months. Research was performed using GC MS, [36] GC-FID [37] and HPLC. [38] It was shown that in the maturation process, the concentrations of acetate esters, acetaldehyde and long-chain fatty acids decrease, while the concentrations of diethyl butanedioate, ethyl 3-methylbutanoate, ethyl esters of long-chain fatty acids, carbonyl compounds, benzoic acid, cinnamic acid, benzaldehyde, cinnamaldehyde, and furanoids and 1-hexanol increases. [36 38] It was shown that the cider maturation process increases the alcohol strength. [37] Serbian plum spirits were also analysed for the presence of seven elements, that is, Cu, Fe, Zn, Mn, Ca, Se and As [44] by using the atomic absorption technique. Thirty-one samples of commercial and homemade plum spirits were investigated. In addition, the spirits were matured in barrels made of various wood types (oak and mulberry). The determinations of arsenic and heavy metals are very important with regard to the toxicity and organoleptic of spirits. The maturation time of the spirit has an effect on its copper concentration. Copper is an element that has a considerable influence on sensory qualities. The content of this micronutrient improves the odour and taste of spirits. In this study the relationship was described by the following equation: [44] age of plum spirit ðyearsþ ¼ 2:602 ðcu concentrationþ þ 2:610: The type of wooden barrels had no influence on the content of the analysed metals. It was also demonstrated that the concentrations of toxic elements (Cd, As, Pb) in these spirits were infinitesimal, that is, below the quantitative limit of the method. [44] It can be concluded from the aforementioned studies that the ageing period of spirits influences the composition and organoleptic qualities of spirits. The ageing period, no longer than 35 years, however, does not affect the sensory assessment, for example, in the case of plum fruits. Additionally, alcohol concentrations in beverages do not influence the extraction process of compounds originating from wood, including vanillin with the vanilla fragrance and (Z)-β-methyl-γ-octalactone and (E)-βmethyl-γ-octalactone with the oak and wood fragrance. The kind of wooden barrel influences the composition and, in particular, volatile compounds and medium-volatile compounds and organoleptic values of fruit spirits, however, the use of wooden barrels (oak and mulberry) does not influence the composition of micronutrients. 201 wileyonlinelibrary.com/journal/ffj

M. Śliwińska et al. 202 Examination of the Composition of the Finished Product The literature contains many publications describing research on comparing the composition of spirits. Such research is aimed at checking the composition and sensory qualities of spirits made from the same or different kinds of fruits. In two studies, [3,45] the composition and organoleptic qualities of plum spirits from eastern and central European countries and former Yugoslavia were compared. In the later study [3] Śliwowica Łącka made from Węgierka Zwykła plum harvested from two orchards in different time periods (in Jazowsko in 2001 2002, and in Łącko in 2002 2004) and the Slovak Pravá Bošacka Slivovica and Romanian Tzuica from Clej-Napoca were compared, based on compositional analysis and sensory of the spirits. The primary aim of the study was to determine the content of the main volatile compounds, that is, methanol, acetaldehyde, esters and higher alcohols. Moreover, the content of HCN originating from stone fruit fermentation was also assessed by a photometric method. The qualitative and quantitative analyses were performed using GC MS. The sensory analysis proved that compounds such as 1-propanol, isobutanol and amyl alcohol influence the characteristic smell of plum spirit from the Polish city of Łącko. The high content of volatile compounds, in particular of carbonyl compounds, in the Polish plum spirit has a negative effect on the organoleptic characteristics because of a pungent and sharp odour. It is worth mentioning that in southern Poland the plum spirit is traditionally consumed together with hot tea. The high temperature causes the release of aromatic compounds responsible for the plum aroma, therefore the consumer senses a unique and pleasant smell. The statistical data analysis was performed using ANOVA. [3] A compositional analysis of the three fractions of Jelinek traditional plum spirit from the former Yugoslavia was carried out by Velíšek et al. [45] The volatile compounds in the first fraction were characterized by low intensity. In the second fraction, a large content of compounds, such as aldehydes (hexanal, octanal, heptanal), benzaldehyde, 2-undecanone and damascenone, was noted. The mixture of all these substances forms an ideal plum aroma. The compounds in the third fraction were characterized by an intense rose fragrance. The qualitative analysis was performed by means of GC MS, while a sensory was used to determine aromatic compounds. [45] In further studies, research on comparing the composition of plum spirits with other fruit spirits, including apples, pears and grapes. [46,47] In Kostik et al. [46] the composition of homemade plum spirits and grape spirits made in Macedonia was compared by analysing congeneric compounds, the latter being volatile and non-volatile substances without ethyl alcohol. The quantitative analysis of, inter alia, methanol, 1-propanol, 2-propanol, 1-butanol and n-amyl alcohol was conducted by using GC-FID. It was demonstrated that the contents of congeners in different fruit spirits were very similar [46] A similar set of samples was investigated by Rusu Coldea et al. [47] In this case, GC-FID was used to compare the composition of the main volatile compounds in apple, pear and plum spirits from Romania. Besides ethanol, the following compounds were quantitatively and qualitatively analysed: acetaldehyde, ethyl acetate, methanol, 1-propanol, 2-propanol, isobutyl alcohol, active amyl alcohol, 1-butanol and furfural. The results obtained were analysed statistically using ANOVA. It was demonstrated that compounds such as acetic aldehyde, ethyl acetate and amyl alcohol are responsible for the taste and smell of the beverage. Moreover, the concentration of these compounds influence the quality of the spirit. [47] Another study compared the contents of flavanoids in samples of, inter alia, cherry and plum (sloe plum) liqueurs from Bavaria by using HPLC-CRD. [48] These compounds have an influence on organoleptic characteristics such as astringency and, indirectly, also on color. Based on the comparison of the chromatograms obtained, it was concluded that the composition of flavonoids present in the analysed beverages was very similar. [48] Cherry spirits were most frequently analysed for the presence of ethyl carbamate. Studies have considered the possible application of different analytical techniques for analysing the content of ethyl carbamate in cherry spirits originating from southern Germany (vicinity of Karlsruhe in Baden- Württemberg). [18,49,50] Lachenmeier et al. [49] carried out a quantitative analysis of ethyl carbamate in cherry spirit samples using GC MS/MS. It was demonstrated that the technique applied can be used in the future for routine analysis of ethyl carbamate content instead of GC MS/SIM as previously used. [18,49] Moreover, investigations conducted by means of the headspace solid phase microextraction (HS-SPME) method combined with GC MS/MS also confirmed the applicability of GC MS/MS for ethyl carbamate analysis. [51] Lachenmeier [50] determined ethyl carbamate content by using Fourier transform infrared (FTIR) spectroscopy. In addition, a comparative analysis of FTIR and GC MS/MS techniques with regard to quantitative analysis of ethyl carbamate was performed. It was demonstrated that FTIR enables fast [ca. 2 min] but imprecise analysis. It was necessary to additionally use GC MS/MS, which is a more precise method although it takes longer time (2 h). [50] The qualitative analysis of ethyl carbamate in different cherry spirits was described Andrey, [52] who demonstrated that ethyl carbamate concentration in beverages stored in translucent glass bottles increases with increasing exposure of sunlight. In the case of cherry spirit, the content of ethyl carbamate increased ten times after a 14-day exposure. [52] Cherry liqueurs have been investigated using various techniques. Studies have been undertaken on the analysis of phenolic compounds displaying antioxidant properties. [53 55] These compounds have an influence on organoleptic characteristics such as astringency and also, indirectly, colour. Rødtjer et al. [53] investigated extracts from Prunus cerasus species used in the production of cherry liqueurs. Analysis of phenolic compounds during the Fenton reaction was conducted by means of HPLC with electrochemical detection (ECD). Rødtjer et al. also studied, [54] inter alia, cherry liqueurs originating from Denmark and made from the same fruit type, again using HPLC-ECD. Based on the mixture of reference compounds, ten compounds were identified in the analysed liqueurs, that is, 4-hydroxycinnamic acid, caffeic acid, protocatechuic acid, vanillic acid, taxifolin, gallic acid, cyanidin 3-galactoside, catechins and epicatechins. [54] Samples of Mirinello di Torremaggiore, an Italian cherry liqueur produced from the P. mahaleb L. cherry according to traditional recipes, were analyzed by Ieri et al. [55] The analysis of phenolic compounds was performed using HPLC with a diode-array detector (DAD), HPLC MS and HPLC MS/MS. Based on the measurements obtained, the percentage composition of the aforementioned liqueurs was determined as follows: anthocyanins (16.5%), phenolic acid (43.3%), coumarin (36.2%) and flavonoids together with other compounds (4%). [55] Commercial apple liqueurs were analysed in terms of acidity, alcohol strength, micronutrient and sucrose content, and wileyonlinelibrary.com/journal/ffj

The flavour of fruit spirits and fruit liqueurs methanol and furfural concentrations. The presence of compounds such as citric, lactic and malic acid, which are added during the production process, is connected with acidity regulation. The main sugars contained in such beverages are β-fructose, α- and β-glucose. Furfural is a carbonyl compound that has a considerable influence on the quality and organoleptic properties of this beverage. The content of this compound increases during the maturation process. The presence of micronutrients, such as iron, manganese, copper and zinc, influences the organoleptic properties of the product and is caused by incorrect manufacturing processes. The presence of sodium is caused by the addition of acidity regulators, such as sodium citrate or sodium bicarbonate. Potassium, calcium and magnesium, on the other hand, derive from fruits. [56] Ladauphin et al. [57] presents results concerning the quantitative analysis of acrolein in fresh Calvados distillates. Acrolein is a compound contained in apples and it has a negative effect on organoleptic properties of spirits produced from these fruits. This research was performed by means of derivatization using 3-methylbenzothiazolone hydrazine. The use of this compound made it possible to produce stable hydrazones, which are easily detected by GC using a nitrogen phosphorus detector (NPD). [57] A quantitative analysis of aldehydes in Calvados and Cognac was performed using 3-methylbenzothiazolin-2-one hydrazone as the derivative agent using GC MS. [58] The results obtained showed that 3-methylbutanal and hexanal are potential key aroma compounds of freshly distilled Calvados and Cognac. Low concentrations of 2-methylbutanal, pentanal and heptanal, on the other hand, do not influence organoleptic properties of drinks. [58] Another group have described research on spirits made from citrus fruits. Da Porto et al. [59] compared direct injection GC MS and SPME/GC MS techniques. They demonstrated that GC MS is more sensitive in detecting polar compounds with low and medium molecular weight, for example methanol, isobutane, n-butanol and isoamyl alcohol. On the other hand, the investigations conducted using SPME/GC MS showed this technique to be highly sensitive for detecting non-polar and medium-polar compounds, and long-chain alcohols. Moreover, the application of SPME/GC MS enables the identification of trace compounds that affect the beverage aroma. For this reason, SPME should be considered a perfect supplementary technique for GC MS in the analysis of fruit spirits. [59] Moreover, volatile compounds formed during the production of orange spirits were analysed in relation to the sweeteners used. The effect of the following sweeteners was assessed: sucrose, glucose, fructose, honey, maple syrup, aspartame, sorbitol and acesulfame K. By using HS-SPME/GC MS it was proven that nine compounds produce an orange aroma, that is, acetaldehyde, benzaldehyde, ethyl octanoate, ethyl nonanoate, n-octyl acetate, nonanol, linalool, δ-3-carene and valencene. Based on these results, it was concluded that the presence of sweeteners such as, sucrose, glucose, maple syrup and aspartame influences the solubility of some compounds, which results in their lowered concentration in the headspace phase, because of that the orange spirits sweetened with these substances have a weaker orange aroma. The effect of sweeteners on the content of volatile compounds in orange spirits was statistically estimated using ANOVA. [6] Another large group of fruit spirits comprises spirit-based beverages made from pears. Spain is the world leader in terms of sales of this spirit because of their vast pear production. In order to improve product quality, investigations of the effect of sunlight on product quality were conducted by analysing the composition of pear spirits stored in green and translucent bottles. [60] By using HS-SPME/GC it was discovered that ethyl (2E,4Z)-2,4-decadienoate, the compound responsible for pear aroma, is transformed mostly to its (2Z,4E)- and (2E,4E)- isomers in UV light, which worsen the aroma. The results presented demonstrated that pear spirit should be stored in colored bottles in order to retain its intense fruit aroma. [60] Chemical composition tests make it possible to identify compounds responsible for the odour and aroma as well as toxic compounds. The compound concentration levels also influence the sensory assessment of such beverages. Specific mixtures of compounds in appropriate proportions also influence the odour. It is evident from articles describing the comparative analysis of spirits produced from various fruits that the contents of cogeneric compounds are similar to each other, which shows that this type of compound does not influence the aroma characteristic of a given fruit. The compositional analysis made it possible to identify compounds influencing the odour of beverages, including benzaldehyde, furfural and ethyl (2E,4Z)-2,4- decadienoate. Phenolic compounds are usually analysed using HPLC coupled with various detectors. These compounds influence the quality of spirits because they cause bitterness and astringency of the taste and odour and also influence the colour. Beverages made from stone fruits, most often cherry spirits, were tested for the presence of ethyl carbamate, a compound with carcinogenic properties, using various analytical techniques. It is evident from the aforementioned studies that GC is the most appropriate technique for detecting ethyl carbamate. In finished spirit products produced from fruits, the content of sugars is also analysed. If the sugar content is too high, it reduces the intensity of volatile aromatic compounds, which are detected using GC. In addition to studying compositional aspects, research has also been conducted concerning the influence of external factors on finished spirits, for example Cigić et al. [60] Such research evaluated the stability and quality of products and verified the influence of improper storage on the aroma of products. Compositional tests also make it possible to test the authenticity of spirits, and examples of such tests are described in the next part of this review. Authenticity Tests of Spirit-based Beverages Made from Fruits Authenticity tests allow for distinguishing spirits made from various kinds and species of fruits. There are numerous articles describing the authenticity tests of plum spirits made from various plum cultivars. The first example is the study by Spaho et al., [61] that is, distinguishing between plum spirits produced in Bosnia and Herzegovina from Stanley, Pozegaca and Bilska rana (Buhler) plum varieties. The content of volatile compounds was measured at all three stages of distillation. Based on the analysed data, differences in the content of esters and higher alcohols between the distilled fractions were detected. The composition of the volatile fraction depended on the plum variety and ethanol concentration, that is, 40, 45 and 50% v/v. It was demonstrated that the head fraction contained large amounts of 1-propanol, ethyl acetate and isobutyl acetate, while the tail fraction was characterized by the presence of 1-hexanol, 1-pentanol and isopentyl acetate. Slijvovica made of Bliska rana plum had a significantly higher content of esters and higher alcohols compared 203 wileyonlinelibrary.com/journal/ffj

M. Śliwińska et al. 204 with the plum spirits made from Pozegaca and Stanley plums. It was shown the ratio of the isobutyl (2-methyl-1-propanol) and iso-amyl (3-methyl-1-butanol) alcohol compounds in plum spirits made from two cultivars Stanley and Pozegaca is 1:1. In beverages from the Bilska rana (Buhler) cultivar, the ratio of the aforementioned compounds is 1:2. Moreover, plum spirit made from Bliska rana plum scored the highest note in the sensory. This is caused by a high total content of two esters: isopentyl acetate and ethyl lactate. These investigations will contribute to the development of research in the field of plum spirit authentication. The aforementioned spirits were quantitatively and qualitatively analysed by using GC-FID, and the results obtained were statistically analysed using ANOVA and PCA. [61] In an earlier study, [3] high methanol concentrations were determined in samples of Polish and Romanian plum spirits, with the highest content of esters being observed in ţuica. In another study, [62] a comparative analysis of traditional plum spirits made in Romania, that is, ţuica, palinca and şliboviţa, was conducted based on the spirit composition and sensory. Ţuica is produced exclusively from plums in the Subcarpathian region of Muntenia; it is prepared in a copper-pot still over an open fire in a simple distillation process. Palinca is made from various fruits, but when only plums are used the spirit is called plum palinca. Şliboviţa is the third spirit produced in the Balcans. Nine types of plum spirit were analysed, that is, Bucium plum ţuica, Vinia old plum ţuica, Vlad extra fine ţuica, Tomeşti plum ţuica, Maramureş şliboviţa, Maramureş palinca, Zalău palinca, Bocşiţa palinca and traditional homemade distillates made of plums. Based on a comparative analysis of all samples, it was concluded that Bucium plum ţuica has neutral ph and the lowest ethanol content (36.8% v/v). Due to the short maturation of Bucium plum ţuica, it contained the lowest amount of polyphenols. On the other hand, the samples of Tomeşti plum ţuica, Maramureş şliboviţa, Maramureş palinca and Vinia old plum ţuica displayed the highest concentrations of polyphenols and esters. It was stated that the high content of these compounds results from the long maturation period of these plum spirits. The highest ethanol concentration was observed in the samples of Vlad extra fine ţuica, Zalău palinca and Bocşiţa palinca. The results of this study are applicable to the identification and authentication of spirit-based beverages made from plums. [62] Authenticity tests have also been performed while comparing various fruit cultivars. Rusu Coldea et al. [63] investigated 26 homemade spirits produced from various fruits (plums, apples, pears) in the Transylvania region of Romania. UV-Vis spectroscopy and HPLC were used to analyse phenolic compounds as authenticity markers. This study was aimed at distinguishing between spirits with regard to their botanical origin. By using UV-Vis spectroscopy, it was demonstrated that the highest concentration of phenolic compounds is a characteristic of plum spirits. Moreover, the application of liquid chromatography allowed the identification of botanical characteristics. In the case of apple spirits, protocatecuic acid turned out to be such a distinctive compound. The presence of quercetine was detected only in pear spirits, while kaempherol was found exclusively in plum spirits. [63] In another study the volatile fractions were compared in samples of apple spirits produced from different apple varieties. [64] Apple spirits originating from Sardinia (Malus pumila, L. cvs. Miali and Appio) and the northern part of Trident Province (Canadian Rennet, Golden Delicious, Royal Gala, Morgenduft and Gravenstein) were compared. One manufacturer produced the Sardinian apple spirits over four consecutive years (2002 2005), whereas those from Trident were made by two producers in 2003, using the same production method. Analysis of the volatile fractions was performed using high-resolution GC-FID and highresolution GC MS, with direct sample injection. The results were analysed statistically using ANOVA and PCA. It was demonstrated that the presence of compounds such as ethyl octanoate, hexyl 2-methylbutyrate, 1-hexanol, furfural and benzaldehyde enable distinguishing between the apple varieties. [64] Further studies tested the authenticity of the French Calvados beverage made from apples. Two studies [5,65] presented results of research on the analysis of compounds responsible for the Calvados aroma on the basis of distillates of good, neutral and bad quality using GC-FID, GC-O (olfactometric detection) and GC MS. [5,65] A list of compounds were presented that are responsible for the aroma of this beverage: 1,1-diethoxybutane, 1,1- diethoxyethane, 1,1-diethoxy-3-methylbutane, ethyl butanoate, β-damascenone; sweat floral:hexyl acetate; bind cider floral: decanol; fermented apple:ethyl 2-methyl butanoate. It was also demonstrated that high concentrations of the following compounds could cause deterioration of the organoleptic quality of the beverage: 3-methylbut-2-en-1-ol herbaceous ; 1,1,3- triethoxypropane acrolein ; 3-methylthiopropanal potato. [5,65] Other studies that describe Calvados and Cognac authenticity tests are based on a comparative analysis of the content of selected groups of compounds. In the first study, Girard s T reagent was used for the identification of carbonyl and sulfur compounds and the analysis was performed using GC-SCD (sulfur chemiluminescence detector) and GC MS. The presence of 48 aldehydes and ketones as well as 28 sulfur compounds was revealed by means of the method used. A comparative analysis of the results obtained revealed carbonyl compounds characteristic of a given type of beverage: 2-thiophenecarboxaldehyde and pentan-2-one are compounds detected only in Cognac; heptanal and hexan-2-one were detected in Calvados samples. The studies also revealed 12 compounds identified in both types of alcohol: octanal, nonanal, furfural, decanal, benzaldehyde, β-cyclocitral, heptan-2-one, 6-methyl-5-hepten-2-one, nonan-2- one, 2-acetylfurane, undecan-2-one and β-demascenone. The total concentration of sulfur compounds in Cognac samples was five to six times that of Calvados samples. [66] In the second study, two identification methods were used for the analysis of trace volatile compounds. The first method was performed using extracts directly identified in dichloromethane obtained by liquid liquid extraction and GC MS. The second method consisted of two stages: groups of compounds were separated by preparative GC and the fractions were analysed on a polar stationary phase by GC MS. In the next step, silica gel fractionation was used to separate them by polarity and analysed by GC MS. The first method identified 169 compounds, whereas the second method allowed identification of 331 compounds. Compounds identified in the Calvados composition included: 4-ethylphenol, 4-ethylguaicol, 4-vinylguaiacol, eugenol, methylegenol, 4-vinylanisole, geraniol, 4-terpineol, camphor, 2-methylbut-2-enole and 3-methylbut-2-en-1-ol, which causes the herbaceous defect. The following compounds were identified in the Cognac composition: 2-pentylfuran, rose oxide, myrcenol, β-terpineol, γ-terpineol, hex-3-enyl acetate, hex-3-enyl propanoate, hex-3-enyl butanoate and β-farnesene. [67] The authenticity of fruits made from melon [68] and lemons [69] has also been examined. Research concerning the authentication of melon spirits was presented by Hernández Gómez wileyonlinelibrary.com/journal/ffj