molecules Article Innovation in a Continuous System of Distillation by Steam to Obtain Essential Oil from Persian Lime Juice (Citrus latifolia Tanaka) José Daniel Padilla-de la Rosa 1 , Magaly Dyanira Manzano-Alfaro 2, Jaime Rosalío Gómez-Huerta 3, Enrique Arriola-Guevara 2, Guadalupe Guatemala-Morales 4,* , Anaberta Cardador-Martínez 5,* and Mirna Estarrón-Espinosa 1,* 1 Unidad Zapopan, Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco (CIATEJ), Av. Camino Arenero No. 1227, Col. El Bajío, Guadalajara C.P. 45019, Mexico; [email protected] 2 Departamento de Ingeniería Química, CUCEI, Universidad de Guadalajara, Blvd. Marcelino García Barragán #1421, esq. Calzada Olímpica, Guadalajara C.P. 44430, Mexico; [email protected] (M.D.M.-A.); [email protected] (E.A.-G.) 3 Departamento de Química, CUCEI, Universidad de Guadalajara, Blvd. Marcelino García Barragán #1421, esq. Calzada Olímpica, Guadalajara C.P. 44430, Mexico; [email protected] 4 Unidad Normalistas, Centro de Investigación y Asistencia en Tecnología y Diseño del Estado de Jalisco (CIATEJ), Av. Normalistas No. 800, Guadalajara C.P. 44720, Mexico 5 Escuela de Ingeniería y Ciencias, Tecnologico de Monterrey, Epigmenio González 500 Fracc. San Pablo, Querétaro C.P. 76130, Mexico Citation: Padilla-de la Rosa, J.D.; * Correspondence: [email protected] (G.G.-M.); [email protected] (A.C.-M.); Manzano-Alfaro, M.D.; [email protected] (M.E.-E.) Gómez-Huerta, J.R.; Arriola-Guevara, E.; Guatemala-Morales, G.; Abstract: The citrus industry is one of the most important economic areas within the global agricul- Cardador-Martínez, A.; tural sector. Persian lime is commonly used to produce lime juice and essential oil, which are usually Estarrón-Espinosa, M. Innovation in a obtained by batch distillation. The aim of this work was to validate a patented continuous steam dis- Continuous System of Distillation by tillation process and to both physically and chemically characterize the volatile fractions of essential Steam to Obtain Essential Oil from Persian lime oil. Prior to distillation, lime juice was obtained by pressing the lime fruit. Afterwards, Persian Lime Juice (Citrus latifolia the juice was subjected to a continuous steam distillation process by varying the ratio of distillate Tanaka). Molecules 2021, 26, 4172. flow to feed flow (0.2, 0.4, and 0.6). The distillate oil fractions were characterized by measuring their https://doi.org/10.3390/ density, optical rotation, and refractive index. Gas chromatography GC-FID was used to analyze the molecules26144172 chemical compositions of the oil fractions. The process of continuous steam distillation presented high oil recovery efficiencies (up to 90%) and lower steam consumption compared to traditional Academic Editor: Laura De Martino batch process distillation since steam consumption ranged from 32 to 60% for different steam levels. Received: 11 June 2021 Moreover, a reduction in process time was observed (from 8 to 4 h). The oil fractions obtained via Accepted: 3 July 2021 continuous steam distillation differed significantly in their composition from the parent compounds Published: 9 July 2021 and the fractions. Publisher’s Note: MDPI stays neutral Keywords: essential oils; distillation by steam; continuous processes with regard to jurisdictional claims in published maps and institutional affil- iations. 1. Introduction Citrus is the most abundant crop of fruit trees around the world, with annual pro- duction in 2015 totaling approximately 130,947 million tons. The main citrus fruits grown Copyright: © 2021 by the authors. globally are oranges, mandarins, lemons, limes, and grapefruits. Brazil, China, India, Licensee MDPI, Basel, Switzerland. Mexico, Spain, and the USA produce over two-thirds of the world’s citrus fruits [1]. In This article is an open access article 2017, the worldwide production of acid lime fruit was 17,218,173 tons, among which Mex- distributed under the terms and ico contributed 2,528,174 tons and was thus considered the main producer of lime fruit, conditions of the Creative Commons comprising 14.7% of the total production [2]. Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Molecules 2021, 26, 4172. https://doi.org/10.3390/molecules26144172 https://www.mdpi.com/journal/molecules Molecules 2021, 26, x 2 of 19 Molecules 2021, 26, 4172 2 of 18 1.1. Industrial Use of Lemons 1.1. IndustrialFor many Use years, of Lemons the citrus processing industry has focused on the production of juices and essential oils. It was estimated that 33% of citrus harvested in the world is used For many years, the citrus processing industry has focused on the production of juices to produce juices [3]. In the processing of citrus fruits (orange, lemon, lime, grapefruit, and essential oils. It was estimated that 33% of citrus harvested in the world is used to etc.) for juice and essential oil extractions, peels represent between 50 and 65% of the total produce juices [3]. In the processing of citrus fruits (orange, lemon, lime, grapefruit, etc.) weight of the fruits and remain the primary byproduct [4]. This solid residue, referred to for juice and essential oil extractions, peels represent between 50 and 65% of the total as citrus waste, is estimated to total 15 million tons per year worldwide [5]. Although weight of the fruits and remain the primary byproduct [4]. This solid residue, referred to as citrus peels are used as cattle feed and as a source of essential oils, the correct management citrus waste, is estimated to total 15 million tons per year worldwide [5]. Although citrus of this residue remains an ongoing problem for the citrus industry [3]. The major compo- peels are used as cattle feed and as a source of essential oils, the correct management of nents of dry citrus peel waste include sugars (23%), cellulose (22%), pectin (25%), hemi- this residue remains an ongoing problem for the citrus industry [3]. The major components cellulose (11%), flavonoids (4.5%), and up to 4% essential oil, often referred to as citrus of dry citrus peel waste include sugars (23%), cellulose (22%), pectin (25%), hemicellulose essential oil [6]. (11%), flavonoids (4.5%), and up to 4% essential oil, often referred to as citrus essential oil [6]. 1.2. Production of Essential Oils 1.2. ProductionDifferent industries of Essential appreciate Oils citrus essential oils because of their pleasant aroma and incredibleDifferent industries variety of appreciate applications citrus [7]. essential In the food oils industry, because of citrus their pleasantessential aromaoil is used and incredibleas the main variety aromatic of applications ingredient in [7 ].non-alcoholic In the food industry, carbonated citrus drinks, essential cola oildrinks, is used pastries, as the mainsweets, aromatic and biscuits. ingredient In the in pharmaceutical non-alcoholic carbonated industry, this drinks, type cola of essential drinks, pastries, oil is used sweets, as a andflavoring biscuits. to mask In the the pharmaceutical unpleasant taste industry, of drugs this [8]. type In ofthe essential chemical oil industry, is usedas these a flavoring oils are toused mask as fragrances the unpleasant in air tastefresheners of drugs and [8 cleani]. In theng products. chemical industry,In the perfume these oilsindustry, are used citrus as fragrancesessential oils in airare freshenersused as the and primary cleaning raw products. materials In to the formulate perfume industry,toiletries citrusand perfumes essential oils[7]. are used as the primary raw materials to formulate toiletries and perfumes [7]. Citrus oil generally contains over 90% terpenes, about 5% oxygenated compounds, and less than than 1% 1% non-volatile non-volatile compounds, compounds, such such as as waxes waxes and and pigments pigments [9,10]. [9,10 ].Essential Essen- oilstial consist oils consist of mixtures of mixtures of volatile of volatile and non-volatile and non-volatile components, components, such as suchterpenes, as terpenes, sesquit- erpenes,sesquiterpenes, higher higheralcohols, alcohols, aldehydes, aldehydes, ketones, ketones, acids, esters, acids, esters,camphor, camphor, and waxes. and waxes. The volatilevolatile fractionfraction of of Persian Persian lime lime oil oil is characterizedis characterized by higherby higher levels levels of d-limonene, of d-limo- nene,γ-terpinene, γ-terpinene, esters, esters, and monoterpene and monoterpene aldehydes aldehydes and lower and amounts lower amounts of β-pinene of β +-pinene sabinene + sabinenesesquiterpenes sesquiterpenes and aliphatic and aliphatic aldehydes aldehydes than key than lime key oils lime [11 oils]. Interestingly, [11]. Interestingly, although alt- houghd-limonene d-limonene comprises comprises more than more 90% thanw/w 90%of the w/w volatile of the compositionvolatile composition of the essential of the essen- oil, its tialcontribution oil, its contribution to the final aromato the final of the aroma mixture of isthe limited mixture by itsis limited instability by andits instability the possibility and theof forming possibility off-flavor of forming compounds off-flavor [7]. compounds [7]. Some ofof thethe representative representative compounds compounds in thein essentialthe essential oil from oil Persianfrom Persian lime are lime shown are shownin Figure in1 Figure. 1. Figure 1. Compounds in in the the essential essential oil oil of of Persian Persian lime: lime: (a ()a d-limonene,) d-limonene, (b ()b γ)-terpinene,γ-terpinene, (c) (βc) -pinene,β -pinene, (d) (αd-terpineol,)