Innovation in Continuous Rectification for Tequila Production

processes

Communication Innovation in Continuous Rectiﬁcation for Tequila Production

Estarrón-Espinosa Mirna, Ruperto-Pérez Mariela, Padilla-de la Rosa José Daniel * and Prado-Ramírez Rogelio *

Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco (CIATEJ), Av. Normalistas No. 800, C.P. 44720 Guadalajara, Jalisco, Mexico; [email protected] (E.-E.M.); [email protected] (R.-P.M.) * Correspondence: [email protected] (P.-d.l.R.J.D.); [email protected] (P.-R.R.); Tel.: +33-33455200 (P.-d.l.R.J.D.)

Received: 23 March 2019; Accepted: 6 May 2019; Published: 14 May 2019

Abstract: In this study, a new process of continuous horizontal distillation at a pilot level is presented. It was applied for the first time to the rectification of an ordinario fraction obtained industrially. Continuous horizontal distillation is a new process whose design combines the benefits of both distillation columns, in terms of productivity and energy savings (50%), and distillation stills in batch, in terms of the aromatic complexity of the distillate obtained. The horizontal process of continuous distillation was carried out at the pilot level in a manual mode, obtaining five accumulated fractions of distillate that were characterized by gas chromatography (GC-FID). The tequila obtained from the rectification process in this new continuous horizontal distillation process complies with the content of methanol and higher alcohols regulated by the Official Mexican Standard (NOM-006-SCFI-2012). Continuous horizontal distillation of tequila has potential energy savings of 50% compared to the traditional process, besides allowing products with major volatile profiles within the maximum limits established by the regulation for this beverage to be obtained.

Keywords: horizontal continuous distillation; rectiﬁcation; tequila; energy saving

1. Introduction Tequila is a traditional Mexican alcoholic beverage recognized around the world. It is obtained from distillation of the fermented juice of the Agave tequilana Weber blue variety. The production process consists of five stages: cooking, grinding, fermentation, distillation, and resting or aging [1]. According to the percentage of sugars belonging to agave used in the production of Tequila, it can be classified as one of the following categories: Tequila and Tequila 100% Agave [2]. In the case of Tequila, 51% of the total sugars in the fermentation process must belong to agave, and the rest of the sugars may be obtained from other sources [3]. The Tequila aroma depends on the amount and type of volatile compounds present [4]. Tequila’s composition is very complex. Different volatile compounds have been reported as responsible for the sensorial characteristics of tequila, among which the most important are alcohols, esters, terpenes, fatty acids, aldehydes, ketones, furans, sulphur compounds, lactones, and phenols [4,5]. This composition is affected by each of the stages of its production process, where the distillation process plays an important role. Based on the Official Mexican Standard regulating tequila composition, the maximum permissible concentration of methanol is 300 mg/100 mL of anhydrous alcohol, while for higher alcohols, it is 500 mg/100 mL of anhydrous alcohol [3]. The alcohol concentrations of tequila can be regulated during the distillation process. Most spirits’ production processes use either batch distillation columns or alembics [6]. The latter are the most frequently used in small-scale production facilities. In these systems, three cuts (head, heart, and tail) are collected sequentially; high-quality spirits are produced from the heart cut. Even though

Processes 2019, 7, 283; doi:10.3390/pr7050283 www.mdpi.com/journal/processes Processes 2019, 7, x FOR PEER REVIEW 2 of 8

ProcessesMost2019 spirits’, 7, 283 production processes use either batch distillation columns or alembics [6]. The latter2 of 8 are the most frequently used in small-scale production facilities. In these systems, three cuts (head, heart, and tail) are collected sequentially; high-quality spirits are produced from the heart cut. Even thethough operation the operation of alembics of isalembics relatively is simple relatively compared simple to compared batch distillation to batch columns, distillation it involves columns, many it uncontrolledinvolves many and uncontrolled unmeasured disturbancesand unmeasured that generate disturbances variability that ingenerate the composition variability of thein finalthe productcomposition [7]. Tequila of the final is obtained product after [7]. Tequila two consecutive is obtained di ffaftererential two distillationsconsecutive indifferential pot stills [distillations1]. The first one,in pot named stills [1]. stripping, The first allows one, named a product stripping, called ordinario allows ato product be obtained, called whose ordinario ethanol to be content obtained, is 20–30% whose inethanol volume. content The secondis 20–30% one, in named volume. rectification, The second consists one, named of distilling rectification, the ordinario consistsagain of and distilling obtaining the threeordinario products: again and head, obtaining tail, and three heart, products: the latter ofhead, which tail, has and an heart, ethanol the content latter of close which to 55%has an in volume,ethanol whichcontent basically close to constitutes55% in volume, a tequila which beverage basically [8 ].constitutes a tequila beverage [8]. The use of batch distillation columns results in a higher productivity and higher eefficiencyfficiency of ethanol recovery compared to the traditional batch process, but a lower presence of compoundcompound complexity in the Tequila productproduct [[9].9]. Recently, innovations have emerged in the distillationdistillation area focused on energy reduction, consumption, andand process process time time [10 [10–12].–12]. A A new new patented patented technology, technology, called called Continuous Continuous Distillation Distillation [13], has[13], been has shownbeen shown to be more to be effi morecient andefficient more and cost-e moffectivere cost-effective than the traditional than the process.traditional Continuous process. horizontalContinuous distillation horizontal combines distillation the distillationcombines the columns distillation and batch columns distillation and batch process. distillation This system process. has reducedThis system the energyhas reduced consumption the energy by 50%consumption based on a by study 50% where based citruson a study essential where oils citrus were obtainedessential [oils14]. Currently,were obtained an equipment [14]. Currently, prototype an equipment of continuous prototype distillation of continuous has beenbuilt, distillation which has consists been of built, five stages,which consists built in of stainless five stages, steel 304built with in stainless an operation steel 304 volume with ofan 60 operation L which volume operates of continuously 60 L which (Figureoperates1). continuously (Figure 1).

Figure 1. Equipment prototype of continuous distillation.

The informationinformation aboveabove has has led led us us to to apply apply this this distillation distillation process process in tequilain tequila production, production, since since it has it ahas great a great potential potential for application for application in the tequila in the industry.tequila industry. This study This aims study to produce aims higherto produce productivity higher andproductivity energy savings and energy while savings preserving while the preserving tequila aroma. the tequila aroma. In thisthis study, study, we we evaluate evaluate the compositionthe composition of the distilledof the distilled fractions obtainedfractions duringobtained the rectificationduring the processrectification by continuous process by distillationcontinuous of distillation the ordinario of theobtained ordinario at obtained the industrial at the level, industrial in order level, to in know order if thisto know distillation if this systemdistillation allows system tequila allows with tequila the quality with specified the quality in thespecified Official in Standard the Official for tequilaStandard to befor obtained.tequila to be obtained.

2. Materials and Methods 2.1. Raw Material. 2.1. Raw Material. A total of 250 liters of ordinario with an alcohol content of 26.0% Alc. Vol. was provided by Tequila A total of 250 liters of ordinario with an alcohol content of 26.0% Alc. Vol. was provided by San Matías Inc., from the state of Jalisco. Tequila San Matías Inc., from the state of Jalisco. 2.2. Continuous Distillation of Ordinario at Pilot Level. 2.2. Continuous Distillation of Ordinario at Pilot Level. The process was operated in manual mode over a period of 4 h for two experimental runs under the followingThe process conditions: was operated in manual mode over a period of 4 h for two experimental runs under the followingFeed Flow: conditions:60 mL/min (T = 16.67 h). Distilled–FeedFeed Flow: 60 mL/min Ratio (D (T/F) = =16.670.2 Lh). distilled /L ordinario Feed.

Processes 2019, 7, x FOR PEER REVIEW 3 of 8 Processes 2019, 7, 283 3 of 8 Distilled–Feed Ratio (D/F) = 0.2 L distilled/L ordinario Feed. ItIt was was decided decided to to workwork atat aa lowlow flowflow (high(high residenceresidence times)times) toto ensureensure thethe stabilitystability ofof thethe processprocess sincesince it it waswas operatedoperated in in manualmanual mode mode without without the the control control system. system. InIn laterlater phases,phases, wewe intendintend toto workwork atat shortershorter residenceresidence times times by by making making modifications modifications to to the the equipment. equipment. ProcessProcess DescriptionDescription TheThe liquidliquid toto bebe distilled,distilled, inin thisthis casecaseordinario ordinario(product (product ofof thethe firstfirstdistillation), distillation), isis fedfed (F)(F) ininthe the firstfirst stagestage (Figure(Figure2 )2) and and goes goes through through each each of of the the five five stages stages of of the the equipment equipment until until obtaining obtaining the the wastewaste streamstream (W).(W). InIn eacheach ofof thethe stages, stages, bothboth heatheat exchangersexchangers carrycarry outout evaporationevaporation ofof thethe volatiles,volatiles, whichwhich are are recovered recovered in in each each of of the the five five condensers condensers to to obtain obtain the the distillate distillate (D). (D). ThisThis equipmentequipment has has a a heat heat recovery recovery system system that that allows allows us us to to recover recover the the heat heat of theof the waste waste (W) (W) to preheatto preheat the the feed feed (F), (F), which which achieves achieves anadditional an addition energyal energy saving saving in the in processthe process when when recovering recovering the sensiblethe sensible heat. heat. In each In each of the of condensers,the condensers, a distilled a distilled fraction fraction (D) is (D) obtained, is obtained, which which is characterized is characterized and which,and which, according according to the to desired the desired profile pr orofile composition, or composition, can be can mixed. be mixed.

Figure 2. Schematic diagram of continuous distillation. Figure 2. Schematic diagram of continuous distillation. The accumulated volume of the five distilled fractions obtained was collected and analyzed by gasThe chromatography accumulated volume to determinate of the five the distilled content fractions of methanol, obtained higher was collected alcohols, and esters, analyzed furfural, by andgas aldehydes.chromatography to determinate the content of methanol, higher alcohols, esters, furfural, and aldehydes. 2.3. Alcoholic Content 2.3. Alcoholic Content Alcohol content expressed as % ethanol (v/v) at 20 ◦C was measured with a portable density meter DMA-35Alcohol (Anton content Paar, Graz,expressed Austria). as % ethanol (v/v) at 20 °C was measured with a portable density meter DMA-35 (Anton Paar, Graz, Austria). 2.4. Chromatographic Characterization 2.4. Chromatographic Characterization The distilled fractions and products (accumulated fractions) were analyzed by gas chromatography (GC) usingThe distilled an Agilent fractions Technologies and 7890Bproducts gas chromatograph(accumulated (Palofractions) Alto, CA,were USA) analyzed equipped by withgas achromatography flame ionization (GC) detector using (FID). an Agilent Separation Technologies was performed 7890B gas onchro anmatograph INNOWAX (Palo capillary Alto, CA, column USA) (60equipped m 250 withµm i.d.a flame0.25 ionizationµm film thickness) detector with(FID). nitrogen Separation as the was carrier performed gas (1 mL on/ min).an INNOWAX The oven × × temperaturecapillary column was programmed (60 m × 250 initially μm i.d. at× 500.25◦C µm for 7film min, thickness) and was thenwith increased nitrogen at as a the rate carrier of 10 ◦C gas/min (1 tomL/min). 165 ◦C. FollowingThe oven temperature this, the temperature was programmed was raised initia fromlly 165 at 50◦C °C to for 220 7◦ min,C at aand rate was of 20then◦C /increasedmin and heldat a rate for 5of min. 10 °C/min A volume to 165 of 1°C.µL Following was injected this, in the split temperature mode with was a split raised ratio from of 1:50.165 °C The to injection220 °C at porta rate and of 20 detector °C/min temperatures and held for were5 min. 220 A volume and 250 of◦ C,1 µL respectively. was injected A in mixture split mode of air with (400 a mLsplit/min), ratio hydrogenof 1:50. The (40 injection mL/min), port and and nitrogen detector as temperatures the auxiliary were gas (25220 mLand/min) 250 °C, was respectively. also fed to theA mixture detector. of Chromatographicair (400 mL/min), datahydrogen was collected (40 mL/min), and recorded and nitrog usingen as Mass the Hunterauxiliary GC gas/MS (25 software mL/min) (B.07.02.1938). was also fed Quantificationto the detector. of majorChromatographic volatiles in samples data was was co basedllected on and the internalrecorded standard using Mass method, Hunter as described GC/MS insoftware the Offi cial(B.07.02.1938). Mexican Standard, Quantification NOM-006-SCFI-2012. of major volatiles The analyses in samples were performedwas based inon duplicate the internal and the results were expressed as mg/100 mL of anhydrous alcohol.

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Processes 2019, 7, x FOR PEER REVIEW 4 of 8 standard method, as described in the Official Mexican Standard, NOM-006-SCFI-2012. The analyses werestandard performed method, in asduplicate described and in the the results Official were Mexican expressed Standard, as mg/100 NOM-006-SCFI-2012. mL of anhydrous The alcohol. analyses Processes 2019, 7, 283 4 of 8 were performed in duplicate and the results were expressed as mg/100 mL of anhydrous alcohol. 2.5. Statistical Analysis. 2.5. Statistical An analysis Analysis. of variance was done to identify differences in the concentration of compounds regulated by the Official Standard (NOM-006-SCFI-2012) for each fraction using the statistical An analysis of variance was done to identify didifferencesfferences inin thethe concentrationconcentration ofof compoundscompounds software STATGRAPHICS CENTURION XVI. regulated byby the the O ffiOfficialcial Standard Standard (NOM-006-SCFI-2012) (NOM-006-SCFI-2012) for each for fractioneach fraction using the using statistical the statistical software STATGRAPHICSsoftware STATGRAPHICS CENTURION CENTURION XVI. XVI. 3. Results and Discussions 3. Results and Discussions 3.1. Alcoholic Concentration of Distilled Fractions 3.1. Alcoholic The average Concentrat Concentration distillatesion of of Distilled the fractions Fractions of continuous distillation had an alcoholic grade of 57.2% ± 12.6The Alc. average average Vol., which distillates distillates was similar of of the the fractions to fractions the distillate of continuous of continuous obtained distillation by distillation batch distillationhad hadan alcoholic an [8] alcoholic (Figure grade 3). gradeof 57.2% of 57.2%± 12.6 Alc.12.6 Vol., Alc. which Vol., whichwas similar was similar to the distillate to the distillate obtained obtained by batch by distillation batch distillation [8] (Figure [8] (Figure 3). 3). ± Alcoholic Content 100 Alcoholic Content 100 50 50 0 0 12345 Ethanol (% Vol.) Ethanol 12345Fraction Ethanol (% Vol.) Ethanol Fraction Figure 3. Alcoholic degree of the distilled fractions obtained in the continuous distillation. Figure 3. Alcoholic degree of the distilled fractions obtained in the continuous distillation. 3.2. Chromatographic Characterization 3.2. Chromatographic Characterization 3.2.1. Content of Higher Alcohols and Aldehydes 3.2.1. Content of Higher Alcohols and Aldehydes 3.2.1.The Content five ofaccumulated Higher Alcohols fractions and Aldehydes of distillate obtained in the continuous distillation process The five accumulated fractions of distillate obtained in the continuous distillation process showed showedThe statistically five accumulated significant fractions differences of distillate among themselves obtained regardingin the continuous the content distillation of aldehydes process and statistically significant differences among themselves regarding the content of aldehydes and higher highershowed alcohols, statistically with significant fraction 1 differencesshowing the among highes themselvest amount of regarding higher alcohols the content and ofaldehydes, aldehydes with and alcohols, with fraction 1 showing the highest amount of higher alcohols and aldehydes, with an average anhigher average alcohols, content with of fraction253.66 ± 1 86.51 showing and the2.87 highes ± 1.02t mg/100amount mLof higher of anhydrous alcohols alcohol,and aldehydes, respectively with content of 253.66 86.51 and 2.87 1.02 mg/100 mL of anhydrous alcohol, respectively (Figure4). (Figurean average 4). The content variation± of 253.66 of acetaldehyde ± 86.51± and (Figure 2.87 ± 1.024b), whichmg/100 is mLa very of anhydrousvolatile compound, alcohol, respectivelymay be due The variation of acetaldehyde (Figure4b), which is a very volatile compound, may be due to changes to(Figure changes 4). inThe the variation temperature of acetaldehyde of the process (Figure due to 4b), the which equipment is a very that volatile was operated compound, in manual may bemode. due in the temperature of the process due to the equipment that was operated in manual mode. to changes in the temperature of the process due to the equipment that was operated in manual mode.

Higher Alcohols Aldehydes 800.0 Higher Alcohols 60.0 Aldehydes 600.0800.0 40.060.0 400.0600.0 20.040.0 200.0400.0 20.0 200.00.0 0.0 mg/100 mL mL a.a. mg/100 mg/100 mL mL a.a. mg/100 12345F2345 0.0 1 2 3 4 5 F2345 0.0 Fraction

mg/100 mL mL a.a. mg/100 Fraction mg/100 mL mL a.a. mg/100 1 2 3 4 5 F2345 12345F2345 Fraction Fraction (a) (b)

FigureFigure 4. 4. ConcentrationConcentration(a) of of higher higher alcohols alcohols ( (aa)) and and aldehydes aldehydes ( (bb)) in in different diﬀerent(b collected) fractions.

FractionFigure 14. obtainedConcentration in the of continuoushigher alcohols distillation (a) and aldehydes system ( wasb) in equivalentdifferent collected to heads fractions. in the batch distillation and could be removed to obtain a ﬁnal product with a better aromatic proﬁle.

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ProcessesFraction2019, 7, 2831 obtained in the continuous distillation system was equivalent to heads in the batch5 of 8 distillation and could be removed to obtain a final product with a better aromatic profile.

3.2.2. Content of of Methanol, Methanol, Esters, Esters, and and Furfural Furfural The fourfour accumulatedaccumulated fractions fractions 2, 3,2, 4,3, and4, and 5 (F2345) 5 (F2345) of distillate of distillate obtained obtained in the distillationin the distillation process didprocess not showdid not statistically show statistically significant significant differences differences with a 95% confidencewith a 95% level. confidence An average level. concentration An average ofconcentration 95.17 4.59, of 11.67 95.17 ±3.56, 4.59, and 11.67 1.18 ± 3.56,0.35 and mg /1.18100 mL± 0.35 of anhydrousmg/100 mL alcohol of anhydrous was determined alcohol was for ± ± ± methanol,determined esters, for methanol, and furfural, esters, respectively and furfural, (Figure respectively5). (Figure 5).

Volatile Compounds 140.0 120.0 100.0 80.0 60.0 40.0

mg/100 mL mL a.a. mg/100 20.0 0.0 1 2 3 4 5 F2345 Fraction

Aldehydes Methanol Esters Furfural

Figure 5. ConcentrationConcentration of methanol, esters, and furf furfuralural in different diﬀerent collected fractions.

The ﬁnalfinal distillate obtained, which consisted of the mixture of fractions 2, 3, 4, and 5 (F2345), was belowbelow thethe maximum maximum permissible permissible limits limits regarding regarding the contentthe content of methanol, of methanol, higher higher alcohols, alcohols, esters, andesters, aldehydes and aldehydes established established by the by O theﬃcial Official Mexican Mexican Standard Standard for Tequilafor Tequila (NOM-006-SCFI-2012) (NOM-006-SCFI-2012) [3] (Table[3] (Table1). 1).

TableTable 1. Results 1. Results of the of major the major volatile volatile profile profile for the for final the distillate final distillate obtained obtained by continuous by continuous distillation. Mean concentration ofdistillation. Continuous Distillation NOM-006-SCFI-2012 Compound (ΣMeanFractions concentration 2, 3, 4 and of 5).mg Continuous/100 mL Distillation of a. a. mg/100NOM-006-SCFI-2012 mL of a. a. Compound Aldehydes(Σ Fractions 2, 2.87 3, 4 and1.02 5).mg/100 mL of a. a. mg/100 40 mL of a. a. ± Methanol 95.17 4.59 300 Aldehydes 2.87± ± 1.02 40 Esters 11.67 3.56 200 Methanol 95.17± ± 4.59 300 Higher alcohols 253.66 86.51 500 Esters 11.67± ± 3.56 200 Furfural 1.18 0.35 4 Higher alcohols 253.66± ± 86.51 500 Furfural 1.18 ± 0.35 4 Different authors have reported the concentration increase of several compounds during distillationDifferent [5], authors while with have this reported process the (Table concentration1), the content increase of methanol of several and compounds higher alcohols during is maintaineddistillation [5], below while the with limits this established process (Table by the 1) Mexican, the content regulation of methanol of tequila and [3higher]. In additionalcohols tois reducingmaintained the below energy the consumption, limits established multiple by options the Mexi are generatedcan regulation by being of tequila able to mix[3]. theIn addition fractions ofto interestreducing to the reduce energy methanol consumption, contents multiple and/or higheroptions alcohols are generated at the end by being of the able process to mix (Table the2 fractions). of interest to reduce methanol contents and/or higher alcohols at the end of the process (Table 2).

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Table 2. Chromatographic characterization of tequila fractions of continuous distillation.

Fraction 1 Fraction 2 Fraction 3 Fraction 4 Fraction 5 Compound Mean S.D. Mean S.D. Mean S.D. Mean S.D. Mean S.D. ± ± ± ± ± Acetaldehyde 27.97 24.40 5.05 1.44 4.97 3.35 1.57 0.36 1.50 1.23 ± ± ± ± ± Ethyl acetate 76.48 35.56 13.04 8.35 11.83 7.26 2.91 0.66 2.87 3.77 ± ± ± ± ± Methanol 87.28 8.53 81.11 17.03 93.02 4.58 108.10 7.42 99.84 11.48 ± ± ± ± ± 2-Butanol 1.19 0.04 0.41 0.23 0.39 0.41 0.21 0.08 0.34 0.36 ± ± ± ± ± 1-Propanol 30.49 2.35 20.62 7.21 22.42 3.79 20.43 1.07 20.66 5.65 ± ± ± ± ± Isobutanol 148.66 13.97 72.08 32.46 74.63 22.91 52.47 6.06 59.21 34.63 ± ± ± ± ± 1-Butanol 0.99 0.15 0.60 0.21 0.59 0.20 0.56 0.03 0.64 0.33 ± ± ± ± ± Isoamyl alcohol 350.58 38.21 180.16 80.52 186.35 55.65 131.83 17.22 152.55 88.84 ± ± ± ± ± 1-Pentanol 0.32 0.12 0.37 0.06 0.55 0.22 0.36 0.09 0.46 0.12 ± ± ± ± ± Ethyl lactate 1.87 0.55 2.82 0.50 3.38 1.07 4.70 1.09 4.72 2.53 ± ± ± ± ± Furfural 1.35 0.11 1.00 0.36 0.81 0.26 0.86 0.16 1.92 0.96 ± ± ± ± ±

3.3. Energy Consume Distillation uses a lot of energy; however, with a good design of the system, the energy requirements can be reduced or recovered for other operations [14]. Another alternative used is mechanical re-compression, but it is costly to install and run so the savings must make it cost eﬀective. About 25% (depending on design) of the steam emitted from the thermocompressor is recovered heat from the liquid [14]. The horizontal column distillation reduces the consumption of steam by approximately 50% with respect to the traditional process. The energy consumption of this technology (horizontal continuous distillation) is within the consumption range of the distillation columns and its consumption is approximately 50% lower than the traditional processes (Table3).

Table 3. Energy consumption of the diﬀerent distillation processes.

Process Energy Consume Reference Batch 0.87 Kg. Vap./Kg Ordinario [15] Conventional Column 0.5–0.6 Kg.Vap./Kg Feed [16] Kaibel column 0.4 Kg. Vap./Kg Feed [17] Horizontal Continuous Distillation 0.4 Kg. Vap./Kg Ordinario This study

The energy saved resides in two main aspects: 1. Multistage distillation is more eﬃcient than one-stage distillation for the same consumption of steam for both alternatives, due to an increment of mass transfer by a higher gradient between concentrations of phase liquid to phase vapor during the distillation process and the better distribution of vapor in each stage; 2. In this technology, it is possible recuperate about 15% of sensible heat of the eﬄuent using a heat exchanger to preheat the feed, which is a possibility to implement in the beverage industry.

Another potential benefit could be the production of vinasse at a low temperature of 55 ◦C, facilitating its disposition. Comparatively, a typical Tequila distillery generates 7 to 10 L of this effluent per liter of Tequila, with a low pH of 4.5, high temperature of 95 ◦C, and high organic loads, which represent a significant disposal problem [18]. In terms of the economic aspect, the distillation represents around 50% of energetic consumption in the elaboration process of tequila. A reduction of 50% of the energy of distillation results in an energy consumption reduction of 25% in the global process. For a 100% tequila producing plant of 852,120 L/year where steam consumption represents 0.29% of the cost structure [19], these numbers are apparently low, permitting us to keep distillated fractions of high value-added and the potential control of the compounds responsible for the aroma of tequila within the limits allowed [3]. Processes 2019, 7, 283 7 of 8

4. Conclusions The tequila obtained from the rectification process in this new continuous horizontal distillation process complies with the content of major volatiles (methanol and higher alcohols) regulated by the Official Mexican Standard. The five accumulated fractions of distillate obtained in the continuous distillation process did not show statistically significant differences with a 95% confidence level (p-value > 0.05) with respect to the content of methanol, esters, and furfural. However, these fractions showed statistically significant differences with a 95% confidence level (p-value < 0.05) among themselves regarding the content of aldehydes and higher alcohols, with the fraction of 1 being the one that showed the highest amount of both groups of compounds. Continuous horizontal distillation constitutes a potential alternative for the distillation of tequila with the benefit of energy savings of 50% compared to the traditional process and the potential control of the compounds regulated by the Official Mexican Specification for tequila.

Author Contributions: P.-d.l.R.J.D. and P.-R.R. directed the research, E.-E.M. and P.-d.l.R.J.D. supported work in the redaction and reviewed the paper, and R.-P.M. realized the experimentation. Funding: This research received no external funding. Acknowledgments: We acknowledge CIATEJ for the facilities and support during the development of the present work; Tequila San Matías Inc., from the state of Jalisco, for providing the ordinary tequila; and Tec. Abiel Alba and Ing. Ernesto Rodríguez for the technical support during the development of the experiment. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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