**4. Distillation procedure and analysis of spirits**

Upon completion of alcoholic fermentation, the fermented were immediately distilled with yeast lees in two ways in previous assays: in rectifying glass column and in French type copper pot. In the first case, a glass column of 50 cm of length and filled up to 50% with Raschig rings and a round bottomed 10 L flask were used. The flask was filled with 5 L of every type of fermented fruit. To ensure a homogenous heat distribution during the distillation process, boiling stones were added and the flow rate was adjusted at 10mL min-1. In the second case, a 30 L French type copper pot filled with 15 L of fermented fruit was used and the flow rate was adjusted at 25 mL min-1. In both cases the fermented were double distilled. The first distillation was stopped when the alcohol degree was lower than the fermented fruit, obtaining a distillate around 17-20% (v/v). In the second distillation, the first phase was the collection of 0.8% of distillate (heads) which was discarded. This distillation was stopped at around 30% (v/v), so the final distillate (heart fraction) reached an alcohol concentration around 55% (v/v). The tails were formed adding the fractions ranging from 30 % (v/v) to 5 % (v/v). The distillate was collected in fractions of different volums depending of the equipment used. In these kind of processes and in order to avoid the loss of aromas all the fractions were collected on ice and kept at 4ºC until their analysis. The percentage alcohol content in all of them was determined by electronic densimetry in all the fractions (European Union, 2000). The heart fraction alcohol degree values are shown in Table 1. In both distillations (copper pot and column) the alcohol degree of the paste was lower because the initial degree of the fermented was also inferior.


Table 1. Alcohol degree of second distillation for different fractions collected in the copper pot and in the glass column

Respecting the chemical analysis of major volatiles, the glass column samples possessed higher concentrations of Propanol, 2-Methyl 1-Propanol and 3-Methyl 1-Butanol. Moreover, the sensory analysis of the first batch of distillates offered conclusive results so as to the distillation type. 100% tasters preferred the samples distilled in the copper pot due to its aroma intensity while the other ones coming from glass column were rejected on basis of their pungent and /or "not sufficiently intensive" aroma.

With regard the type of substrate, even though the "paste" type offered a better yield in the process, it does not seem to be the ideal substrate due to the sluggish of fermentation, a high methanol content and the negative sensory characteristics. Juice distillate was more appreciated due to its aroma intensity (Hernández-Gómez et al., 2008).

To compare the results with those from previous years using a glass column, and thus narrow down the production processes, a pilot-plant copper pot, *alquitara*, was used. At the

Upon completion of alcoholic fermentation, the fermented were immediately distilled with yeast lees in two ways in previous assays: in rectifying glass column and in French type copper pot. In the first case, a glass column of 50 cm of length and filled up to 50% with Raschig rings and a round bottomed 10 L flask were used. The flask was filled with 5 L of every type of fermented fruit. To ensure a homogenous heat distribution during the distillation process, boiling stones were added and the flow rate was adjusted at 10mL min-1. In the second case, a 30 L French type copper pot filled with 15 L of fermented fruit was used and the flow rate was adjusted at 25 mL min-1. In both cases the fermented were double distilled. The first distillation was stopped when the alcohol degree was lower than the fermented fruit, obtaining a distillate around 17-20% (v/v). In the second distillation, the first phase was the collection of 0.8% of distillate (heads) which was discarded. This distillation was stopped at around 30% (v/v), so the final distillate (heart fraction) reached an alcohol concentration around 55% (v/v). The tails were formed adding the fractions ranging from 30 % (v/v) to 5 % (v/v). The distillate was collected in fractions of different volums depending of the equipment used. In these kind of processes and in order to avoid the loss of aromas all the fractions were collected on ice and kept at 4ºC until their analysis. The percentage alcohol content in all of them was determined by electronic densimetry in all the fractions (European Union, 2000). The heart fraction alcohol degree values are shown in Table 1. In both distillations (copper pot and column) the alcohol degree of the paste was

> Alcohol degree (% v/v) 1st fraction 2nd fraction 3th fraction Average value

Juice 68.6 61.5 44.2 58.1 Pws 65.6 52.1 27.9 48.5 Paste 69.8 62.8 44.6 59.1

Juice 79.5 60.5 12.3 50.8 Pws 80.0 61.3 11.2 50.8 Paste 75.0 54.0 10.6 46.5

Table 1. Alcohol degree of second distillation for different fractions collected in the copper

Respecting the chemical analysis of major volatiles, the glass column samples possessed higher concentrations of Propanol, 2-Methyl 1-Propanol and 3-Methyl 1-Butanol. Moreover, the sensory analysis of the first batch of distillates offered conclusive results so as to the distillation type. 100% tasters preferred the samples distilled in the copper pot due to its aroma intensity while the other ones coming from glass column were rejected on basis of

With regard the type of substrate, even though the "paste" type offered a better yield in the process, it does not seem to be the ideal substrate due to the sluggish of fermentation, a high methanol content and the negative sensory characteristics. Juice distillate was more

To compare the results with those from previous years using a glass column, and thus narrow down the production processes, a pilot-plant copper pot, *alquitara*, was used. At the

**4. Distillation procedure and analysis of spirits** 

lower because the initial degree of the fermented was also inferior.

their pungent and /or "not sufficiently intensive" aroma.

appreciated due to its aroma intensity (Hernández-Gómez et al., 2008).

Copper pot

Column

pot and in the glass column

same time, the volatile compounds in the distillates obtained were compared with those in other commercially available spirits.

The fermented juice was immediately distilled in a traditional 130-L "*alquitara"*, (reflux still) (Silva, Macedo & Malcata, 2000) filled to 70-80 % of capacity, equipped with a series of temperature sensors. Distillation flow rate was set at 170 mL/min, and the condenser was kept at below 21 °C throughout. The distillate was collected in volumes of 1 L each, except for the head fraction. The first distillation was stopped when the alcohol content in the volume collected had reached 8-10 % (v/v), which yielded a distillate with an alcohol content of 18.5-25 % (v/v), depending on the source substrate from which it had been made. The head-fraction (200 mL), usually discarded, was not rejected.

The second distillation was carried out in a traditional 30-L alembic copper still filled with 15 L of the first distillate. Distillation flow rate was set at 35-40 mL/min. The heads, 0.8 % of the distillate, were discarded, and distillation was stopped at 40 % (v/v), thus yielding a final distillate (hearts) of 58-69 % (v/v), again depending on the source substrate from which it had been made. The tails comprised the fractions from 40 % (v/v) to 5 % (v/v). For all the distillates the alcohol content of the last volume collected was between 9.2 and 11.8 % (v/v), and the final alcohol content was between 18.5 and 25 % (v/v). In the second distillation, the alcohol content decreased from 74.5 % (v/v) to 40.0 % (v/v) in the last volume collected. The total distillation time for all the fractions was around 4 h. The highest value was for the juice distillate (pH-adjusted) and the lowest for the paste (pH-unadjusted) distillate.

After the second distillation the major volatiles present in the heads, hearts, and tails fractions of the different spirits are depicted in Figure 1.

Fig. 1. Evolution in major volatile compounds during the second distillation. Methanol. Higher alcohols: 2M1P, 2M1B, 3M1B, and 1-Propanol. Esters: Ethyl lactate, Ethyl acetate, and Ethyl butyrate (mg/L of EtOH). h, heads; H, hearts; t, tails. pws = paste without skins

Methanol was collected in nearly the same proportion in all the fractions, most likely due to the formation of azeotropic mixtures (Orriols, 1994). Nevertheless, methanol concentrations were higher in the distillates from the pH-unadjusted wines except for "juice" tails. High levels of methanol in the paste distillate were observed (pH-unadjusted). The higher alcohols (HA)

Spirits and Liqueurs from Melon Fruits (*Cucumis melo* L.) 189

Esters are associated with pleasant odours. This is particularly true of Ethyl acetate, which contributes to aroma complexity and has a positive impact at very low levels (50-80 mg/L) (Steger & Lambrechts, 2000). Ethyl acetate was higher in the distillates pH-unadjusted. Ethyl lactate contributes intense, long-lasting aromas (Tourliere, 1977). The content in distillates is linked to lactic fermentation, in general it was lower in pH-adjusted distillates (Briones et al., 2002). Ethyl butyrate adversely influence the organoleptic quality of distillates (Soufleros, 1978,1987). Paste distillates at both pH had the highest concentrations. Concentrations of the minor esters, other than Ethyl lactate and Ethyl acetate, were higher in the pH-adjusted distillates, due principally to Ethyl caprylate, Ethyl palmitate, Ethyl

Respecting carboxylic acids, short-chain (C4-C12) fatty acids produce unpleasant odours, and high concentrations are an indicator of poor quality (Orriols, 1992,1994). Decanoic and octanoic acids were the most abundant fatty acids and were present at higher concentrations

The major volatile compounds of melon spirit were compared with other commercial spirits such grappa, orujo, and other fruit distillates from cherry, raspberry and pear (Hernández Gómez et al, 2005a) . In general, 1-Propanol was higher in melon distillates, being similar to those in grappa and cherry spirit. In like fashion, Ethyl acetate was much higher in the juice distillate with a concentration nearly three times more than in the other spirits. Acetaldehyde and Ethyl lactate were present in similar amounts in most of the spirits considered, with the exception of much higher concentration of Ethyl lactate found out in the cherry spirit, most probably as a result of the lengthy maceration time. 2-Methyl 1- Propanol and Amyl alcohols were somewhat higher in the melon distillates, pear spirit, and grappa. The melon distillates had appreciably lower methanol contents than the rest of the spirits considered, particularly as compared to the pear spirit (11216 mg / L of ethanol), most likely because of the high pectin content of pears. 1-Butanol was detectable in the pear spirit and, to a lesser extent, in the melon distillates. 2-Butanol and Ethyl butyrate were not

Sensory analysis was performed in a standard tasting room [Spanish standard 87004:1979 (Aenor, 1977). Distillates were diluted with distilled water to alcohol strength of 28 % (v/v) and served at a temperature of 15 ºC. Evaluations were carried out at daily sessions between

There were significant differences between juice distillates and pws and conversely, there were no significant differences between the paste distillates. The tasters preferred pws or juice distillates, but there was no preference between them. The expert tasters from a distilling company likewise expressed no preferences, possibly because the spirits being

The effect of maceration in increasing and improving aroma intensity in a melon (*Cucumis* 

caproate, Ethyl laurate and Ethyl decanoate.

**4.1 Comparison with commercial spirits** 

present in detectable amounts in any of the spirits analysed.

10:00 a.m. and 12:00 noon to prevent taster fatigue.

tested were new to them and had an unfamiliar flavour.

**5. Maceration for improving melon spirit** 

*melo* L.) spirit was studied.

in the pH-adjusted distillates.

content was higher in the heads and hearts than in the tails. All the distillates displayed the same behaviour, with no considerable differences among them. In addition, the HA content was not related to the fermentation pH and substrate types. The ester content (Ethyl acetate, Ethyl lactate, and Ethyl butyrate) was higher in the heads, decreasing in the hearts and the tails. Fermentation pH had a pronounced influence on the ester content.

Respecting the concentrations of the volatiles in the final spirits, high amounts of methanol and 2-Butanol were noticed. They can make spirits hazardous to consumers health. Moreover, methanol imparts a cooked cabbage odour, with a threshold of 1200 mg/L (Ribéreau-Gayon, et al., 2000). The methanol content was higher in the distillates made from the pH-unadjusted in all substrates. The paste distillates exhibited the highest levels, probably owing to the action of certain pectinases on the substantial amount of melon skins present (Cortés Diéguez, et al, 2000). However, in no case did the levels exceed the limits for fruit spirits set by the legislation currently in force (European Union, 1989).

Higher alcohols are responsible for imparting complex sensory attributes to spirits (Silva et al., 2000). The Amyl alcohols and 2-Methyl 1-Propanol contribute positive to the sensory characteristics (Bertrand, 1975; Orriols, 1992, 1994). They are detectable organoleptically at concentrations below 15 mg/L of ethanol (Tourliere, 1977). 1-Propanol has a pleasant, sweetish odour, but excessive concentrations will introduce solvent notes that mask all the positive notes in distillates (Fundira, Blom, Pretorius, & van Rensburg, 2002). The highest 1- Propanol contents were recorded in the distillates made from the pH-adjusted fermentation substrates, in contrast, 2M1P was lower in the pH-adjusted distillates at levels similar to those reported in previous years. Amyl alcohol contents were very similar in all cases. 1- Butanol has a heavy, penetrating odour, and 2-Butanol is associated with low-quality raw materials (Orriols & Bertrand, 1990; Cortes Dieguez et al., 2000). 1-Butanol concentrations were higher in the pH-adjusted distillates. Conversely, 2-Butanol was not detected in any of the distillates produced. 2-Phenylethanol imparts a very clinging, rose-like aroma (Nykänen & Suomalainen, 1983), and was not influenced by pH, except in the juice distillates. 1- Hexanol, cis-3-Hexen-1-ol, and 3-Methyl-3-buten-1-ol impart strong herbaceous aromas. Hexanol and cis-3-Hexen-1-ol perception thresholds in spirits are 20 mg/L and 3.5 mg/L, respectively (Jouret & Cantagrel, 2000), and the concentrations did not exceed those values. Smoked or burnt wood aroma is conferred by 4-Methyl-guaiacol (Dubois & Dekimpe, 1982), and it was present in all distillates except the pH-adjusted juice. Benzyl alcohol is related to the quantity of benzaldehyde, the latter being important because it imparts a bitter almond aroma to wines at levels above 2-3 mg/L (Blaise, 1986). In the melon spirits, concentrations were nowhere near that perception threshold reported for wines.

Otherwise, Acetaldehyde is 90 % of the total aldehyde content in distillates (Versini, Monetti, dalla Serra & Inama, 1990, Orriols, 1991; Silva, Malcata, & Hogg, 1995). More than 1200 mg/L of ethanol is evidence of oxidation of the ethanol during alcoholic fermentation or a enzymatic pyruvic acid decarboxylation (Baro & Quiros-Carrasco, 1977; Cantagrel, Lablanquie, Snakker, & Vidal, 1993). Its importance derives from its pungent odour and its chemical reactivity (Silva et al., 2000). pH had no effect in juice and pws substrates, in contrast, it was doubled in pH-adjusted paste distillate. Furfural may be formed as a result of oxidation of ascorbic acid (Bayonove, Baumes, Crouzet, & Günata, 2000). A slightly higher furfural content in the distillates from the pH-unadjusted substrates was observed.

content was higher in the heads and hearts than in the tails. All the distillates displayed the same behaviour, with no considerable differences among them. In addition, the HA content was not related to the fermentation pH and substrate types. The ester content (Ethyl acetate, Ethyl lactate, and Ethyl butyrate) was higher in the heads, decreasing in the hearts and the

Respecting the concentrations of the volatiles in the final spirits, high amounts of methanol and 2-Butanol were noticed. They can make spirits hazardous to consumers health. Moreover, methanol imparts a cooked cabbage odour, with a threshold of 1200 mg/L (Ribéreau-Gayon, et al., 2000). The methanol content was higher in the distillates made from the pH-unadjusted in all substrates. The paste distillates exhibited the highest levels, probably owing to the action of certain pectinases on the substantial amount of melon skins present (Cortés Diéguez, et al, 2000). However, in no case did the levels exceed the limits for

Higher alcohols are responsible for imparting complex sensory attributes to spirits (Silva et al., 2000). The Amyl alcohols and 2-Methyl 1-Propanol contribute positive to the sensory characteristics (Bertrand, 1975; Orriols, 1992, 1994). They are detectable organoleptically at concentrations below 15 mg/L of ethanol (Tourliere, 1977). 1-Propanol has a pleasant, sweetish odour, but excessive concentrations will introduce solvent notes that mask all the positive notes in distillates (Fundira, Blom, Pretorius, & van Rensburg, 2002). The highest 1- Propanol contents were recorded in the distillates made from the pH-adjusted fermentation substrates, in contrast, 2M1P was lower in the pH-adjusted distillates at levels similar to those reported in previous years. Amyl alcohol contents were very similar in all cases. 1- Butanol has a heavy, penetrating odour, and 2-Butanol is associated with low-quality raw materials (Orriols & Bertrand, 1990; Cortes Dieguez et al., 2000). 1-Butanol concentrations were higher in the pH-adjusted distillates. Conversely, 2-Butanol was not detected in any of the distillates produced. 2-Phenylethanol imparts a very clinging, rose-like aroma (Nykänen & Suomalainen, 1983), and was not influenced by pH, except in the juice distillates. 1- Hexanol, cis-3-Hexen-1-ol, and 3-Methyl-3-buten-1-ol impart strong herbaceous aromas. Hexanol and cis-3-Hexen-1-ol perception thresholds in spirits are 20 mg/L and 3.5 mg/L, respectively (Jouret & Cantagrel, 2000), and the concentrations did not exceed those values. Smoked or burnt wood aroma is conferred by 4-Methyl-guaiacol (Dubois & Dekimpe, 1982), and it was present in all distillates except the pH-adjusted juice. Benzyl alcohol is related to the quantity of benzaldehyde, the latter being important because it imparts a bitter almond aroma to wines at levels above 2-3 mg/L (Blaise, 1986). In the melon spirits, concentrations

Otherwise, Acetaldehyde is 90 % of the total aldehyde content in distillates (Versini, Monetti, dalla Serra & Inama, 1990, Orriols, 1991; Silva, Malcata, & Hogg, 1995). More than 1200 mg/L of ethanol is evidence of oxidation of the ethanol during alcoholic fermentation or a enzymatic pyruvic acid decarboxylation (Baro & Quiros-Carrasco, 1977; Cantagrel, Lablanquie, Snakker, & Vidal, 1993). Its importance derives from its pungent odour and its chemical reactivity (Silva et al., 2000). pH had no effect in juice and pws substrates, in contrast, it was doubled in pH-adjusted paste distillate. Furfural may be formed as a result of oxidation of ascorbic acid (Bayonove, Baumes, Crouzet, & Günata, 2000). A slightly higher furfural content in the distillates from the pH-unadjusted

tails. Fermentation pH had a pronounced influence on the ester content.

fruit spirits set by the legislation currently in force (European Union, 1989).

were nowhere near that perception threshold reported for wines.

substrates was observed.

Esters are associated with pleasant odours. This is particularly true of Ethyl acetate, which contributes to aroma complexity and has a positive impact at very low levels (50-80 mg/L) (Steger & Lambrechts, 2000). Ethyl acetate was higher in the distillates pH-unadjusted. Ethyl lactate contributes intense, long-lasting aromas (Tourliere, 1977). The content in distillates is linked to lactic fermentation, in general it was lower in pH-adjusted distillates (Briones et al., 2002). Ethyl butyrate adversely influence the organoleptic quality of distillates (Soufleros, 1978,1987). Paste distillates at both pH had the highest concentrations. Concentrations of the minor esters, other than Ethyl lactate and Ethyl acetate, were higher in the pH-adjusted distillates, due principally to Ethyl caprylate, Ethyl palmitate, Ethyl caproate, Ethyl laurate and Ethyl decanoate.

Respecting carboxylic acids, short-chain (C4-C12) fatty acids produce unpleasant odours, and high concentrations are an indicator of poor quality (Orriols, 1992,1994). Decanoic and octanoic acids were the most abundant fatty acids and were present at higher concentrations in the pH-adjusted distillates.

### **4.1 Comparison with commercial spirits**

The major volatile compounds of melon spirit were compared with other commercial spirits such grappa, orujo, and other fruit distillates from cherry, raspberry and pear (Hernández Gómez et al, 2005a) . In general, 1-Propanol was higher in melon distillates, being similar to those in grappa and cherry spirit. In like fashion, Ethyl acetate was much higher in the juice distillate with a concentration nearly three times more than in the other spirits. Acetaldehyde and Ethyl lactate were present in similar amounts in most of the spirits considered, with the exception of much higher concentration of Ethyl lactate found out in the cherry spirit, most probably as a result of the lengthy maceration time. 2-Methyl 1- Propanol and Amyl alcohols were somewhat higher in the melon distillates, pear spirit, and grappa. The melon distillates had appreciably lower methanol contents than the rest of the spirits considered, particularly as compared to the pear spirit (11216 mg / L of ethanol), most likely because of the high pectin content of pears. 1-Butanol was detectable in the pear spirit and, to a lesser extent, in the melon distillates. 2-Butanol and Ethyl butyrate were not present in detectable amounts in any of the spirits analysed.

Sensory analysis was performed in a standard tasting room [Spanish standard 87004:1979 (Aenor, 1977). Distillates were diluted with distilled water to alcohol strength of 28 % (v/v) and served at a temperature of 15 ºC. Evaluations were carried out at daily sessions between 10:00 a.m. and 12:00 noon to prevent taster fatigue.

There were significant differences between juice distillates and pws and conversely, there were no significant differences between the paste distillates. The tasters preferred pws or juice distillates, but there was no preference between them. The expert tasters from a distilling company likewise expressed no preferences, possibly because the spirits being tested were new to them and had an unfamiliar flavour.
