Extraction of carotenoid-rich palm pressed fiber oil using mixtures of hydrocarbons and short chain alcohols

Journal Pre-proofs Extraction of Carotenoid-Rich Palm Pressed Fiber Oil using Mixtures of Hydrocarbons and Short Chain Alcohols Gabriela Lara Alvarenga, Maitê Sarria Cuevas, Maria Carolina Capellini, Eduardo José Crevellin, Luiz Alberto Beraldo de Moraes, Christianne Elisabete da Costa Rodrigues PII: DOI: Reference:

S0963-9969(19)30696-9 https://doi.org/10.1016/j.foodres.2019.108810 FRIN 108810

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Food Research International

Received Date: Revised Date: Accepted Date:

1 August 2019 16 October 2019 6 November 2019

Please cite this article as: Lara Alvarenga, G., Sarria Cuevas, M., Carolina Capellini, M., José Crevellin, E., Alberto Beraldo de Moraes, L., Elisabete da Costa Rodrigues, C., Extraction of Carotenoid-Rich Palm Pressed Fiber Oil using Mixtures of Hydrocarbons and Short Chain Alcohols, Food Research International (2019), doi: https://doi.org/10.1016/j.foodres.2019.108810

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Extraction of Carotenoid-Rich Palm Pressed Fiber Oil using Mixtures of Hydrocarbons and Short Chain Alcohols

Gabriela Lara Alvarenga1, Maitê Sarria Cuevas1, Maria Carolina Capellini1, Eduardo José Crevellin2, Luiz Alberto Beraldo de Moraes2, Christianne Elisabete da Costa Rodrigues1,*

¹ Laboratório de Engenharia de Separações (LES), Departamento de Engenharia de Alimentos (ZEA), Faculdade de Zootecnia e Engenharia de Alimentos (FZEA), Universidade de São Paulo (USP), 13635-900 Pirassununga, São Paulo, Brazil. ² Departamento de Química, Universidade de São Paulo (USP), 14040-901 Ribeirão Preto, São Paulo, Brazil.

*Corresponding author at: Laboratório de Engenharia de Separações (LES), Departamento de Engenharia de Alimentos (ZEA), Faculdade de Zootecnia e Engenharia de Alimentos (FZEA), Universidade de São Paulo (USP), 13635-900 Pirassununga, Sao Paulo, Brazil. Tel.: +55 1935654354. E-mail address: [email protected].

Abstract Solvent extraction is the most efficient method for recovering residual oil from palm pressed fiber (PPFO), which may contain up to eight times the carotenoid content of that found in crude palm oil. The objective of the present study is the use of binary mixtures of hydrocarbons (HC), hexane (Hex), cyclohexane (CHex) or heptane (Hep), and alcohols (ALC), ethanol (Eth) or isopropanol (IPA), in order to promote the highest recovery of a carotenoidrich PPFO, in which the compositions of the mixtures are defined based on the calculation of solute-solvent distance (Ra) considering β-carotene as the solute. The extraction experiments were conducted in batch, at 60 ± 2 °C, or in a fixed-bed packed column, at 55 ± 3 °C. Hex and Hep:IPA provided 80% of batch PPFO extraction yield, while in column, the highest yields were obtained with Eth and Hex:IPA (66%). The total carotenoid content obtained was the same independent of the solvent and extraction configuration (from 1790 ± 230 up to 2539 ± 78 mg β-carotene/kg PPFO). In terms of the carotenoid profile, β-carotene was mostly extracted by Hex, Hex:Eth stood out in the extraction of α-carotene, and Eth extracted the highest content of lycopene. It is possible to infer that mixtures of HC and ALC with compositions defined based on Hansen Solubility Parameters (HSPs) demonstrated good ability to extract carotenoid-rich PPFO, maintaining their relatively stable fatty acids composition and free acidity, showing that partial substitution of HC by ALC is technically possible.

Keywords: Elaeis guineensis; ethanol; isopropanol; hydrocarbons; β-carotene; Hansen solubility parameters.

1. Introduction

Palm is the fruit of palm tree (Elaeis guineensis) originated from East Africa (Mba, Dumont, & Ngadi, 2015). The palm oil is the most produced vegetable oil in the world; it is obtained from the mesocarp of the fruit and, before the refining process, is known as crude palm oil (CPO). Its 2018/2019 global production was of approximately 73.58 million metric tons, with Indonesia and Malaysia holding about 84% of the world production of 41.5 and 20.5 million tons of CPO, respectively (USDA, 2019). In the palm fruit processing, after pressing the material, a by-product called palm pressed fiber (PPF), with lipid mass content ranging from 4 to 7% (dry basis), remains in the equipment (Choo et al., 1996). If we consider the proportion of PPF generated in relation to the amount of CPO produced, from 1:1.45 to 1:1.31, reported by Nang, Wafti, and May (2013) and Dal Prá et al. (2016), one can make a projection of the PPF generated and, consequently, of oil (PPFO) that was not extracted from this material. For the period 2018/2019, it can be estimated that at least 50 million tons of PPF were generated, which for the vegetable oil processing industries represents the loss of about 2 million tons of PPFO. PPF is usually burned in a boiler of the company producing palm oil. However, this byproduct is notable for its high content of carotenoids (3800-7000 mg/kg PPFO), vitamin E (tocopherols and tocotrienols, 1900-3000 mg/kg PPFO), phytosterols (4500-8500 mg/kg PPFO) and squalene (1400-1700 mg/kg PPFO) (Choo et al., 1996; Lau, Choo, Ma, & Chuah, 2008; Phoon, Ng, Zakaria, Yim, & Mokhtar, 2018), with different techniques being proposed for the recovery of these compounds such as pressurized liquid and low-pressure solvent extraction (Cardenas-Toro et al., 2014; Dal Prá et al., 2016), ultrasound-assisted extraction (Dal Prá et al., 2017; Tsouko et al., 2018), supercritical fluid extraction (França & Meireles, 2000; Lau, Choo, Ma, & Chuah, 2006; Tai & Brunner, 2019), and sequential adsorption-desorption (Phoon et al., 2018).

Vegetable oils may be obtained by pressing the solid material, solvent extraction or by combining these two methods. According to Anderson (2005), solvent extraction is indicated for oleaginous materials containing up to 20% lipids and, industrially, hexane is the solvent employed because of its high oil solubilization capacity, low loss in the evaporation stage, high stability, low corrosion and low cost (Johnson & Lusas, 1983). However, the use of this solvent has some disadvantages due to its high flammability, high pollutant power and toxicity (Johnson & Lusas, 1983; Oliveira, Oliveira, Aracava, & Rodrigues, 2012), and there is currently considerable interest in the vegetable oils industry to partially or totally replace this solvent (Chang et al., 2018; Khor et al., 2017; Ooi, Ng, & Chemmangattuvalappil, 2018). In this context, some organic solvents have a similar capacity to hexane of vegetable oil extraction, although they are less toxic and with a low risk to human health, such as the heptane solvent (FDA, 2017). Alfonsi et al. (2008) classified various solvents at the preferable, acceptable and undesirable levels regarding work safety, operational use and environmental and regulatory considerations. Thus, the cyclohexane and heptane solvents were considered acceptable, whereas ethanol and isopropanol were considered as preferred, and these alcohols were also widely cited for the extraction of vegetable oils (Bessa, Ferreira, Rodrigues, Batista, & Meirelles, 2017; Sawada, Venâncio, Toda, & Rodrigues, 2014), with outstanding extraction capacity of minor compounds (Capellini, Chiavoloni, Giacomini, & Rodrigues, 2019; Capellini, Giacomini, Cuevas, & Rodrigues, 2017; Navarro, Capellini, Aracava, & Rodrigues, 2016; Scharlack, Aracava, & Rodrigues, 2017). The use of solvent mixtures may result in a synergistic effect for extracting compounds of interest, as reported by Treszczanowicz, Kasprzycka-Guttman, and Treszczanowicz (2001) for the solubility of β-carotene in hydrocarbon and acetone mixtures. Some authors proposed the optimization of mixing using statistical methods, such as response surface methodology or simplex lattice design with axial points, to enhance the extraction of key compounds such as

carotenoids from cantaloupe waste using mixtures of hexane, acetone and ethanol (Benmeziane et al., 2018), and extraction of phenolic compounds from chia seeds using acetone, ethanol and water (Alcântara et al., 2019). Despite the simplicity of statistical methods, the more accurate methodologies with thermodynamic basis have gained visibility in the last few years (Chang et al., 2018; Khor et al., 2017; Sánchez-Camargo et al., 2019). In this context, the Hansen solubility parameters (HSPs) are presented as a useful mathematical tool to estimate the solubility. The three HSPs define a three-dimensional space, known as the Hansen space, where the solute can be visualized as a point surrounded by its solubility sphere in which all solvents and solvent mixtures located within this volume are considered as capable of solubilizing this solute (Hansen, 2004). Thus, it is possible to calculate the solute-solvent distance (Ra) by delimiting from it the potential solvents that will solubilize the solute of interest, allowing the use of solvent mixtures considered less toxic, safe and renewable. According to SánchezCamargo et al. (2019), the use of the HSPs approach has been proposed to the total or partial replacement of petroleum based solvents such as hydrocarbons by bio-based solvents such as ethanol and isopropanol, among others. Thus, the present study proposes the use of mixtures of hexane, heptane or cyclohexane solvents and ethanol or isopropanol with previously defined compositions from the Hansen solubility parameters (HSPs) and solute-solvent distance (Ra) calculation, with the objective of obtaining carotenoid-rich PPFO.

2. Material and Methods 2.1 Material The palm pressed fiber (PPF), kindly donated by a Brazilian palm processing company (Pará, Brazil), with initial humidity of 42 ± 3% (wet basis) was submitted to forced circulation drying (Nova Orgânica, model N035/3) at 40 °C for 24 h according to the methodology

suggested by Cardenas-Toro et al. (2014) up to a maximum moisture content of 6.8 ± 0.3%. The PPF was ground using a knife mill (Marconi, model MA340), subjected to determination of particle size distribution and mean particle size by Tyler sieves (Tyler series, Wheeling, USA) and laser diffraction (Shimadzu, model SALD-201 V, Japan) according to ASAE (1995) and then packed in plastic bags and stored at 4 °C. The solvents used in the extraction experiments were all purity ≥ 98.5%: absolute ethanol (Eth, CAS 64-17-5), isopropanol (IPA, 67-63-0), hexane (Hex, 110-54-3), n-heptane (Hep, 142-82-5) and cyclohexane (CHex, 11082-7), all from Synth (Diadema, Brazil).

2.2. Characterization of pressed palm fiber The PPF was characterized as moisture content (Ac 2-41, AOCS, 2009), lipids (Am 5-04, AOCS, 2009), crude protein (Ba 4f-00, AOCS, 2009), ash (AOAC, 2007) and fibers (Asp, Johansson, Hallmer, & Siljestroem, 1983). The content of non-fibrous carbohydrates was obtained by difference, considering the contents of the different components (ash, lipids, proteins and fibers) on dry basis.

2.3 Characterization of oil extracted from palm pressed fiber The oil of the palm pressed fiber (PPFO) was cold extracted according to the methodology proposed by Neoh, Thang, Zain, and Junaidi (2011), solid:solvent ratio 1:5 (by mass) for 8 h and at room temperature (25 ± 1 ºC). The extract was rotated at 40 °C, vacuum of 5 kPa, to ensure the complete separation of oil and solvent (Heidolph, model Hei-VAP Silver, Germany). The PPFO was characterized by the total content of carotenoids, expressed as β-carotene (725340-7) (Sigma-Aldrich, purity ≥ 97%), by spectrophotometry (Shimadzu, model UV 1650PC, Japan), according to PORIM (1990), and for free fatty acid content (FFA) (IUPAC, 2201, 1979) by titration (Methohm, model 848 Titrino Plus). Calibration curves were constructed with Sigma-Aldrich standards β-carotene (7235-40-7), α-carotene (488-99-5) and lycopene (502-65-

8) to analyze the carotenoid profile adapted from Ansolin (2017). The UPLC-MS/MS (Waters, Acquity UPLCH-Class Xevo® TQ-S, USA) analyses were performed considering electrospray ionization (ESI) in positive mode (ESI+). As the carotenoids studied show similar structures and consequently result in the formation of the same mass/charge (m/z) fragments (444.8 and 119.7 m/z), these were identified by comparing the retention time of the carotenoids. Data were analyzed and treated using MassLynx software (version 4.1, Waters). The PPFO was also subjected to fatty acid profile analysis by gas chromatography (Shimadzu 2010 AF, Japan) of fatty acid methyl esters according to the Ce 1-62 and Ce 2-66 methods of AOCS (2009), using external standards (Supelco, Bellefonte, PA, USA) for identification,

internal

standardization

for

quantification

(methyltridecanoate)

and

chromatographic conditions suggested by Sawada et al. (2014). The calculation of the iodine value was performed as described in the official method Cd 1c-85 (97) of the AOCS (2009).

2.4 Characterization of pure solvents and mixtures The solvents were characterized in terms of water content by Karl Fischer titration (Ca 2e84, AOCS, 2009) and in terms of density and dynamic viscosity (Stabinger Viscosimeter, Anton Paar, model SVM 3000). The dielectric constants for the pure solvents and the solvent mixtures were estimated by Wohlfarth (2014) and Tir, Dutta, and Badjah-Hadj-Ahmed (2012), respectively.

2.5 Calculation of the Hansen Solubility Parameters (HSPs) and solute-solvent distance (Ra) for choosing the best solvent mixtures The total solubility parameter (δT), (MPa)1/2 was calculated according to Hansen (2004), Equation 1, as the sum of non-polar (δD), molecular dipole (δP) and hydrogen bonding (δH) interactions. The calculation of the HSPs for a mixture of solvents can be performed by using

mass fractions (wi) which were added to the mixture in the analysis of the respective parameters, according to Equation 2. (1)

𝛿2𝑇 = 𝛿2𝐷 + 𝛿2𝑃 + 𝛿2𝐻 𝑖=𝑛

(2)

𝛿𝑚𝑖𝑥𝑡𝑢𝑟𝑒 = ∑𝑖 = 1𝛿𝐾𝑖𝑤𝑖 𝐾

Where δK represents: the non-polar interactions according to the dispersion solubility parameter (δD), the molecular dipole with the polar solubility parameter (δP) and the hydrogen bonds according to the hydrogen bonding solubility parameter, (δH); wi is the mass fraction of component i in the mixture, and δKi is the parameter for the pure component i. For the pure solvents these parameters were obtained from Barton (1983), for the β-carotene from Ozel and Gogus (2014) and for the palm oil from Batista, Guirardello, and Krähenbühl (2015). The solute-solvent distance, Ra, (MPa)1/2, can be calculated according to Equation 3. The sub-indices i and j refer to the solute and solvent, respectively. 𝑅𝑎2 = 4(𝛿𝐷𝑖 ― 𝛿𝐷𝑗)2 +(𝛿𝑃𝑖 ― 𝛿𝑃𝑗)2 +(𝛿𝐻𝑖 ― 𝛿𝐻𝑗)2

(3)

The choice of compositions of the mixtures between hydrocarbon solvents (Hex, Hep and CHex) and short chain alcohols (Eth and IPA) was achieved by obtaining Ra values equal to Ra calculated between the β-carotene solute and the pure hydrocarbon solvents, due to their greater ability to solubilize carotenoids.

2.6 Extraction assays The extraction experiments were conducted in batch or in a fixed-bed packed column. All experimental conditions are summarized in Figure 1.

2.6.1 One-stage batch extraction assays The extraction tests were performed in a batch extractor as detailed in Oliveira et al. (2012). Solid-liquid systems were obtained by adding known masses of PPF and solvent in a mass ratio

of 1:7 (solid:solvent) using an analytical balance PW254 (Adam Equipment, UK). By preliminary studies, this was the largest solid:solvent mass ratio that allowed the use of the batch configuration, guaranteeing total immersion of the PPF in the proposed solvents. The extractor was agitated at 300 rpm until the temperature reached 60 ± 2 °C and kept under constant agitation for 5 h, the time interval defined based on the preliminary kinetic extraction experiments. The temperature value was defined based on the boiling temperature of the solvent with the highest vapor pressure (Hex), respecting a safety margin of approximately 10 °C. After this treatment, samples of the extract phase were removed by the valve located in the lower section of the vessel and submitted to analysis of composition (Section 2.7) and the raffinate phase was weighed in a semi-analytical balance for further calculation of solution holdup adhered to the fibers (LH, liquid holdup, kg solution/kg fiber).

2.6.2 Extraction assays on fixed-bed packed column Extraction experiments were performed using the Eth, IPA and Hex solvents and the Hex:Eth and Hex:IPA blends in a fixed-bed packed column, which allowed using a solid:solvent mass ratio of 1:4, at 55 ± 3 °C. It was used a jacketed glass column (FGG, Brazil) (2.6 cm internal diameter, 5.4 cm external diameter and 63 cm in length), peristaltic pumps (Cole Parmer Masterflex, model 77200-60, USA) and a thermostatic bath (Marconi, model MA184, Brazil). The basic configuration of this equipment is shown in Figure 2. Known mass of pre-weighed PPF on semi-analytical scale (Adam, model PGW1502i, UK) was introduced into the column by the top. The solvent content required to ensure the preestablished solid:solvent ratio was weighed on a semi-analytical scale. Subsequently, the pumps were activated to fill the column by the lower section of the equipment, with a flow rate of 20

mL/s. The solvent inlet temperature in the column was monitored throughout the experiment, remaining at about 55 ± 3 °C. The initial extraction time count, of 1 h and 30 min (defined time interval in preliminary experiments of extraction kinetics), occurred at the observation of the liquid phase return to the storage flask.

2.7 Characterization of the extract and raffinate phases Samples from the extract phase were submitted to water content analysis by the official Karl Fischer titration method (Ca 2e-84, AOCS, 2009). The calculation of water transfer to the extract phase (Twater, %) was performed as detailed in Rodrigues, Aracava, and Abreu (2010). The soluble solids content was determined in a forced convection oven (Nova Orgânica, model N035/3) at 100 °C until reaching constant weight. The rest of the extract was rotated and the oil analyzed for FFA content, fatty acid composition, total carotenoid content and carotenoid composition under the same conditions mentioned in Section 2.3. The raffinate phase was extracted from the extractor, in batch or column, weighed on a semi-analytical scale PGW1502i (Adam Equipment, UK) and analyzed for solvent content in a forced convection oven at 100 °C until reaching constant weight and for the residual oil content (Am 5-04, AOCS, 2009, Ankom, model XT10), allowing to calculate the relative extraction yield of PPFO, in percentage, according to Scharlack et al. (2017). The mean values of the results from the extraction experiments were compared by analysis of variance using the Duncan test (1955) at the 95% confidence level, using the SAS® software program (Version 9.3, SAS Institute Inc., USA).

3. Results and Discussion 3.1 Characterization of palm pressed fiber (PPF)

The centesimal composition of PPF, 6.8 ± 0.3 mass% of moisture, can be described as: (values expressed as dry basis): 4.8 ± 0.3 mass% of lipids, 10.34 ± 0.01 mass% of proteins, 3.53 ± 0.05 mass% of ashes, 1.3 ± 0.5 mass% of soluble fibers, 81.3 ± 0.5 mass% of insoluble fibers and -1 ± 1 mass% of non-fibrous carbohydrates. The mean diameter of the PPF particles was 276 ± 11 μm.

3.2 Calculation of composition of mixed solvents Table 1 shows the HSPs and Ra values for the different solvents and solutes. In general, HSPs of the hydrocarbon solvents have values close to the HSP values of palm oil and βcarotene, mainly in relation to the δP and δH parameters. This fact can also be observed by calculating the Ra palm oil and Ra β-carotene, which presented lower values for HC solvents, when compared to Eth and IPA, indicating the higher affinity between non-polar solvents and solutes. Calculations of the HC and ALC composition mixtures resulted in higher IPA contents than Eth contents, since the latter has slightly higher HSP values than the HSPs of the IPA, which allows inferring that the solubility of β-carotene in IPA is slightly higher than the solubility of this solute in Eth. On the other hand, the CHex solvent had the lowest Ra, denoting its greater ability to solubilize β-carotene, when compared to the other HC. For the extraction experiments, the mass composition chosen for the Hep:Eth mixture which presented the Ra β-carotene value of up to 4.6 was 0.81:0.19, respectively. For the CHex:Eth mixture, this mass composition was 0.85:0.15, respecting the Ra β-carotene limit to 2.1.

3.3 Extraction of PPFO with different solvents

Table 2 shows the results of PPFO extraction yields in batch and column. In the batch extractions, Hex and the Hep:IPA mixture had the highest PPFO extraction capacity, with an average PPFO relative yield of 80%, which was confirmed by the lower residual oil contents in PPF. This extraction yield result was higher than that obtained by Gandhi et al. (2003), which obtained soybean oil extraction yield of 72% using the Hep:Eth mixture (52:48, by volume), in the solvent:solid mass ratio of 2:1 and temperature of 70 °C for 4 h. The other solvents and solvent mixtures employed had a statistically lower oil extraction capacity (p < 0.05), of 70 and 73%. For the HC and ALC mixture, the addition of Eth to Hex resulted in a subtle increase in the oil extraction yield when compared to the yield obtained using pure Eth. The evaluation of employing alcoholic solvents in the extraction of rice bran oil (Capellini et al., 2017) and corn germ oil (Navarro et al., 2016), in the solid:solvent ratio of 1:3, at 60 °C, resulted in relative extraction yields of about 80% with the use of IPA, and about 70 to 65% with Eth. In addition, Li et al. (2014) highlighted the higher extraction of oil from rape seed using IPA in comparison with Eth, in Sohxlet type extraction. This increase in the yield of vegetable oil extraction employing IPA in relation to Eth, at 60 °C, was also reported in other studies of the literature (Scharlack et al., 2017), but was not observed in this work. Changing the batch extraction process to column resulted in lower extraction yield values using pure solvents or solvent mixtures. This reduction may be due to the decrease in the amount of solvent relative to PPF and also due to the decrease in the extraction temperature to 55 ± 3 °C. The alcoholic solvents had good oil extraction performance in the column experiments. Moreover, the addition of IPA to Hex promoted greater extraction of PPFO when compared to the value obtained by pure Hex. The chemical and physical properties of the solvents, such as the polarity, expressed by the dielectric constant (Di), density (ρ, g/cm3) and dynamic viscosity (μ, mPa.s), directly influence

the mass transfer steps in the solid-liquid extraction (Toda, Sawada, & Rodrigues, 2016). The values of these properties are shown in Table 2 for the pure solvents and mixtures at the extraction temperatures used for batch (60 °C) and column (55 ºC) experiments. The solvent with the lowest ρ values is Hex, followed by Hep, CHex, IPA and Eth. In relation to μ, among all the pure solvents and solvent mixtures analyzed, IPA has the highest viscosity, followed by Eth, CHex, Hep and lastly, Hex with lower viscosity. As expected, the increase in temperature resulted in a decrease in ρ and μ values for all solvents and solvent mixtures studied. The addition of ALC to Hex and Hep resulted in an increase in the μ and ρ values, however, this behavior was not observed for the mixtures comprised by CHex and ALC, which had their μ values reduced with the addition of ALC, at the same temperature. Thus, it can be inferred that the best performance of the Hex solvent in the extraction of PPFO, in relation to the other pure solvents, is associated with its smaller Di, ρ and μ values, which positively affect the mass transfer steps (Toda et al., 2016). The high extraction yield obtained by using the Hep:IPA mixture may also be related to the increase in the number of carbons of the solvents, relative to Hex and Eth, respectively. This increase may lead to increased solubility of the lipid compounds and, consequently, a higher extraction yield (Capellini et al., 2019, 2017; Scharlack et al., 2017). With regard to the extraction of total soluble solids, the pure Eth enabled the highest extraction, and this effect was observed in the mixture Hex:Eth, in the batch and column experiments. These results are in agreement with previous studies which show that besides lipids, the Eth extracts other more polar compounds, such as proteins and carbohydrates (Navarro et al., 2016; Sawada et al., 2014). The increased ability of Eth to extract polar compounds may be related to Di. The Di values calculated for the ALC were considerably higher than the values obtained for the HC, which

allows to state that Eth and IPA are the most polar solvents. For the solvent mixtures studied, the addition of ALC resulted in increased Di values, but these values still remained low when compared to the pure ALC Di values. The addition of Eth to the Hex, CHex and Hep solvents resulted in a subtle increase to Di values when compared to the addition of IPA to HC. Additionally, the increase in temperature results in a decrease in the Di values, as observed by Bosch et al. (1996). The behavior of the water transfer of the FPP to the extract phase (Twater, %) as a function of the polarity of the employed solvent, expressed as Di, can be observed in Figure 3a for the batch extraction and column experiments. It can be observed in this figure that Twater had an increasing behavior in relation to the increase in Di of the solvents. Thus, the pure HCs presented the lowest Di values, denoting their lower chemical affinity for water and, consequently, the lower Twater values. However, the addition of 15 to 25% by mass of ALC to HC resulted in the increase of Twater, but these values were still lower than the values obtained using the pure ALC, IPA and Eth, which had the highest dielectric constants. Besides the higher polarity of Eth influences the extraction of non-lipid compounds, such as carbohydrates, proteins and water, this property was also associated with higher oil extraction yield in a study regarding the replacement of Hex by Eth in the oil extraction from rapeseed hulls (Mhemdi et al., 2016). According to the authors, the higher polarity of Eth positively impacts the penetration of the solvent into the aleurone cells, increasing the oil extraction yield. Another process variable that has an impact on the extraction yield is the liquid holdup (LH) in the raffinate phase. The LH in solid-liquid extraction processes is important because it has a decisive impact on the volume capacity of the extractor to be used, the number of stages required to perform the extraction and on the recovery stage of the solvent adhered to the

raffinate, therefore a lower LH is desirable considering a lower energy expenditure in the desolventization stage of the defatted solid (Rodrigues & Oliveira, 2010). Figure 3b shows that Eth has the highest LH value, followed by IPA, CHex, Hep and solvent mixtures, whereas Hex had the lowest value. Although Hep and CHex, and their mixtures with Eth and IPA, had low Di values (when compared to ALC), their LH values did not follow this same behavior, possibly due to the physical properties, as shown in Table 2. It can then be inferred that these factors also contributed to obtain lower LH values for Hex and higher values for Eth. The addition of Eth and IPA to Hex resulted in increased LH, but in the case of CHex the addition of alcoholic solvent did not impact this value, probably due to the lower content (in mass) of added ALC. Comparing the LH values for the batch and column experiments, it can be inferred that this latter configuration allows a more effective drainage of the bed of solids, resulting in statistically lower values (p ≤ 0.05). Rodrigues and Oliveira (2010) suggest that solvents with high polarity exert a greater attractive force on the hydrophilic part of the solid resulting in a greater amount of solution adhered in the defatted material. Rittner (1992) investigated the use of Hex in the extraction of soybean oil resulting in a lower LH value when compared to Eth. Additionally, in the extraction of cotton oil with Hex, lower LH was observed when compared to the IPA solvent (Zhang, Rhee, & Koseoglu, 2002). These results are in accordance with the data obtained in the present study.

3.4 Characterization of PPFO obtained with different solvents Table 3 shows the total carotenoids and FFA contents in the PPFO obtained with pure solvents and mixtures, which are compared to the contents obtained for the cold extracted PPFO with Hex, according to Neoh et al. (2011).

For the batch experiments, the use of Hex resulted in a higher content of carotenoids followed by the use of CHex, with the results being statistically equal (p < 0.05) to that obtained by cold extraction (Neoh et al., 2011). In addition, CHex has the lowest Ra value (see Table 1), which denotes, therefore, its greater ability to solubilize β-carotene. Moreover, the physical properties of Hex, such as its lower polarity, μ and ρ, may actually contribute to the greater carotenoid transfer to PPFO. On the other hand, the use of Eth and IPA negatively influences the extraction of carotenoids, which was already expected given the higher Ra values between carotenoids and these solvents (Table 1). Navarro et al. (2016) obtained a higher content of carotenoids in corn germ oil extracted using IPA (373 ± 9 mg β-carotene/g oil) when compared to the value obtained by Eth (287 ± 24 mg β-carotene/g oil) at the solid:liquid ratio of 1:3 (by mass) at 70 °C, however this behavior was not observed in this study. In general, the addition of IPA to Hex and CHex further impaired carotenoid transfer to PPFO than the addition of Eth to these same solvents. In the case of the extraction experiments carried out in a column, the use of IPA and the Hex:Eth mixture resulted in an increase in carotenoid extraction, while Eth recovered the lowest content of this minority, with this worse performance justified by differences between HSP values of Eth and β-carotene (Table 1). In general, the two extraction methods, in batch and column, exhibited the same performance in obtaining carotenoids. The use of solvent mixtures with compositions determined by the calculation of Ra did not result in significant carotenoid transfer to the PPFO for all solvent mixtures employed. The increase of ALC to HC, even in low amounts, was effective in decreasing the solubility between carotenoids and mixtures, but these values, ranging from 1790 ± 230 to 2089 ± 174 mg β-carotene/kg PPFO, obtained for Eth and IPA and their mixtures with Hex, CHex and Hep,

are still relatively high when compared to other crude vegetable oils such as tucumã (1222 ± 35 mg/kg) and buriti (1890 ± 112 mg/kg) (Santos, Alves, & Roca, 2015; Silva et al., 2009). Carotenoid compositions, in terms of β- and α-carotene and lycopene, of the oils extracted with the different solvents in the column experiments and analyzed in UPLC/MS are shown in Table 4. Hex extracted the highest content of β-carotene, followed by the Hex:Eth and Hex:IPA mixtures that did not differ from each other, whereas IPA presented the worst extraction performance of this component. In relation to the extraction of α-carotene, the Hex:Eth mixture showed the highest extraction capacity, followed by pure solvents and Hex:IPA, which exhibited the same performance. The highest extraction of lycopene was done using pure Hex and Eth and their mixtures. Lin and Chen (2003) report higher efficiency in the extraction of carotenoids from tomato juice (solid:solvent ratio of 1:5, mass per volume) from the use of Hex:Eth in the 3:4 ratio (per volume), when compared to the acetone and hexane mixtures (3:5 ratio per volume), ethanol, acetone and hexane (2:1:3 ratio per volume), ethyl acetate: hexane (1:1 ratio per volume) and pure ethyl acetate. Additionally, among 6 different solvent mixtures evaluated, including the Hex:IPA mixture (ratio 3:2, per volume), Taungbodhitham, Jones, Wahlqvist, and Briggs (1998) obtained higher recovery of lycopene, α-carotene and β-carotene with the use of Hex:Eth (ratio 3:4, per volume). These results are in agreement with the data presented in Tables 3 and 4 for column extractions. Choo et al. (1996) investigated the composition of PPFO extracted by Soxhlet with Hex in terms of different carotenoids, and of the 12 different types found, β- and α-carotene and lycopene were present in larger quantities, with values of 30.95, 19.45 and 14.13%, respectively, of a total of 4520-5600 mg/kg. If we estimate the carotenoid composition of the PPFO reported by these authors, considering only the sum of the values obtained by these three major carotenoids, these values can be compared with the data obtained in this study (Table 4).

In general terms, the ratio of the carotenoid types extracted by the pure solvents and solvent mixtures did not differ strongly, as well as the values obtained by Choo et al. (1996). However, higher lycopene content extracted by Eth is observed, possibly due to its greater polarity, which may have facilitated its interaction with the acyclic structure of lycopene and its higher number of double bonds. On the other hand, the solvent with lower polarity, Hex, showed opposite behavior and higher affinity with β-carotene. This behavior is corroborated by study of recovering of astaxanthin from microalgae using Eth and Hex as solvents (Irshad et al., 2019). The authors observed higher extraction yield values for Eth, suggesting better solute-solvent interactions between this carotenoid of polar character and the alcoholic solvent. In addition, Benmeziane et al. (2018) suggested that the combination of polar solvents with Hex improves the extraction of the non-polar carotenoids, such as α- and β-carotene, while pure polar solvent, such as Eth, enhances the extraction of the most polar carotenoids. It should be mentioned that the total carotenoid content extracted by the Hex:Eth mixture was comparable to the pure Hex performance, as can be observed in Table 3, which allows to conclude that, in this case, the calculation of Ra (between solvent mixture and β-carotene solute), which defined the composition of the mixture between Hex:Eth, promoted a higher extraction of total carotenoids in PPF. This result is in agreement with study of SánchezCamargo et al. (2019) where it is possible to see that β-carotene has been studied as target compound in extraction processes from different oleaginous matrices using a great variety of bio-based solvents, employing HSPs theory with high degree of success. Table 3 exhibits the values of FFA in the PPFO obtained in batch and column. Because it is an agroindustrial residue, the PPFO extracted by pure solvents and mixtures have high content of FFA, expressed in oleic acid, and are not in agreement with the FAO (2015) which defines the maximum acid value for CPO at 10.0 mg KOH/g, which is equivalent to approximately 5.0 grams of oleic acid per 100 grams of oil. The FFA values determined in this

work are higher than those reported by Sulihatimarsyila, Lau, Nabilah, and Azreena (2019), 6.1±0.1%, and Lau et al. (2006), 3.94±0.03%, for PPFOs obtained with Hex, and lower than the value reported by Majid, Mohammad, and May (2012), 31.4%. In the batch experiments, of all the solvents studied, CHex stood out for extracting PPFO with lower free acidity, while the FFA contents in the oils obtained with Hep and Hex were similar (Conkerton, Wan, & Richard, 1995). It can be inferred that due to the lower polarity conferred by pure HC and their respective mixtures with ALC, it was possible to obtain PPFO with lower FFA contents when compared to the pure ALC, Eth and IPA, which extracted the highest free acidity, of approximately 19 %. In the column experiments, Eth extracted oil with higher FFA content followed by IPA, Hex and mixtures, which presented statistically similar data. Compared with batch data, the free acidity values presented a slight increase with the use of the Hex and ALC mixtures. As can be seen in Figure 3a and Table 2, Eth also extracted the highest water content and soluble solids content for the extract phase, respectively. Such superior ability of Eth in extracting FFA, water and soluble solids observed in this study is in agreement with several studies in the literature and is related to the increased polarity demonstrated by the ALCs (Johnson & Lusas, 1983; Toda et al., 2016). In terms of fatty acid composition (mass%), the cold extracted PPFO was rich in oleic (32.6 ± 0.4), palmitic (25.3 ± 0.3) and lauric (20.8 ± 0.4) acids, along with minor contents of myristic (7.6 ± 0.1) and linoleic (6.7 ± 0.2) acids, resulting in an iodine value of 39.91 ± 0.09. These results, when compared to the values obtained by Choo et al. (1996) and Neoh et al. (2011), showed that the PPFO obtained in this work has a high content of lauric acid and, consequently, a lower iodine value, which allows to infer about possible palm kernel contamination (Dal Prá et al., 2017; Lau et al., 2006; Majid et al., 2012). The use of pure solvents and solvent mixtures did not result in significant differences in the fatty acid composition of the extracted oils and,

consequently, in the iodine values, which ranged from 34 ± 1, for Hex:Eth, up to 44 ± 2, relative to Hex, both in the batch and column experiments. Regarding the three major fatty acids, oleic acid content ranged from 24 ± 1 up to 33 ± 1 mass%, palmitic acid from 19 ± 1 up to 26 ± 1, and lauric acid content ranged from 19.9 ± 0.8 up to 32 ± 2, considering all assays, batch and column experiments.

4. Conclusions The batch extraction experiments resulted in a high extraction yield of PPFO for all the solvents used, of approximately 70%, however, the Hex and Hep:IPA mixture stood out, with 80% yield. High carotenoid contents were recovered using Hex and CHex. However, in the column experiments, the highest extraction yields were obtained using Eth and the Hex:IPA mixture, of approximately 66%. Hydrocarbon solvents and their mixtures with the short chain alcohols, Eth and IPA, defined based on the solute-solvent distance (Ra) calculation, demonstrated good ability to extract carotenoid-rich PPFO, maintaining their fatty acid composition and free acidity relatively constant. In addition, the low LH values, together with the lower Twater values obtained with solvent mixtures, positively impact the industrial solid-liquid extraction stages, facilitating the subsequent operations of desolventization of the extract and raffinate phases. The proposed mixtures allow the partial substitution of hydrocarbon solvents for short chain alcohols with no significant loss of oil and carotenoid extraction yields, and in the case of the Hex:Eth mixture, it also allows to obtain a total carotenoid content equivalent to the total extracted by pure Hex.

5

Acknowledgments

The authors thank FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo 2014/21252-0, 2017/20840-4, 2018/12713-5), CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico 303797/2016-9) and CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil - Finance Code 001, GL Alvarenga DS grant) for the financial support granted.

6

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Figure Captions

Figure 1. Experimental set-up of the extraction processes.

Figure 2. Scheme of extraction assays on fixed-bed packed column.

Figure 3. a) Water transfer (Twater, %); b) Liquid holdup (LH, kg of solution/kg of inert solid) as function of dielectric constant (Di) of pure and mixed solvents. Batch extraction (empty symbol); Column extraction (full symbol).

Table 1 – Hansen solubility parameters and solute-solvent distance (Ra) between β-carotene and pure and mixed solvents, at 25 °C. Mass fraction of solvent (1) (2) 1

0

1

0

1

0

1

0

1

0

0.7 9

0.2 1

0.7 3

0.2 7

0.8 5

0.1 5

0.8 2

0.1 8

0.8 1

0.1 9

0.7 6

a Barton

0.2 4

Solven t Eth (1)a IPA (1)a Hex (1)a CHex (1)a Hep (1)a Hex (1): Eth (2) Hex (1): IPA (2) CHex (1): Eth (2) CHex (1): IPA (2) Hep (1): Eth (2) Hep (1): IPA (2) Solute βcaroten eb Palm oilc

Ra βcarote ne

δD (MPa)1

δP (MPa)1

δH (MPa)1

δT (MPa)1

/2

/2

/2

/2

15.8

8.8

19.4

26.5

19.7

15.8

6.1

16.4

23.5

16.0

14.9

0

0

14.9

5.3

16.8

0

0.2

16.8

15.3

0

0

15.3

15.1

1.9

4.1

15.7

2.1 4.6

Ra Pal m oil 16. 6 13. 1 7.5 5.3 6.9 5.1

5.3 5.1

15.1

1.7

4.4

15.9

5.3

16.7

1.3

3.1

17.0

2.1

2.9 3.1 16.6

1.1

3.1

17.0

2.1

15.4

1.7

3.7

15.9

4.6

4.6 4.6 15.4

1.5

3.9

16.0

17.4

0.8

1.7

17.5

17.5

3.3

4.1

18.3

4.6

(1983); b Ozel and Gogus (2014); c Batista et al. (2015). Eth: ethanol; IPA: isopropanol;

Hex: hexane; CHex: cyclohexane; Hep: heptane; δD: dispersion solubility parameter; δP: polar

solubility parameter; δH: hydrogen bonding solubility parameter; δT: total solubility parameter; Ra: solute-solvent distance.

35

Table 2 – Relative yield of PPFO extraction (%) in batch and column configurations using pure and mixed solvents. Mass fraction (1)

Dieletric Density Solvent Constant (Di) (ρ, g/cm3)

(2)

Viscosity Relative yield Soluble solids Residual oil (µ, mPa.s) (%)1 content (%)2 content (%)3

Temperature (ºC)

1

0

Eth (1)

21.77 21.34

0.758 0.753 0.674 0.602 5 9 3 3

1

0

IPA (1)

14.86 14.20

0.754 0.749 0.933 0.824 4 4 6 7

1

0

Hex (1)

1.84

1.83

0.631 0.626 0.243 0.230 3 5 9 0

1

0

CHex (1)

1.97

1.96

0.744 0.739 0.569 0.510 6 7 4 1

1

0

Hep (1)

1.87

1.86

0.653 0.648 0.334 0.317 1 6 3 6

Batc Colum Colum Colum Batch Batch h n n n 1.16 ± 1.65 ± 1.50 ± 1.7 ± 70 ± a a ab a ab c 67 ± 2 2 0.02 0.05 0.09 0.1 73 ± ab 1.02 ± 1.48 ± 1.34 ± 1.71 ± abc c ab ab bc 66 ± 2 1 0.04 0.06 0.05 0.04 80 ± 62.4 ± 0.9 ± 1.29 ± 1.06 ± 1.7 ± cde d c ab a bc 4 0.3 0.1 0.06 0.02 0.1 72.3 0.9 ± 1.3 ± ± cde b bc 0.1 0.1 0.3 0.8 ± 1.47 ± 70 ± ef a c 1 0.2 0.08

0.7 9

0.2 1

6.02

5.93

0.651 0.646 0.309 0.295 0 2 0 1

76 ± c 1.09 ± 1.8 ± 1.1 ± 1.85 ± ab a c a ab 62 ± 1 1 0.02 0.1 0.1 0.08

0.7 3

0.2 7

5.35

5.17

0.654 0.649 0.319 0.304 5 6 0 4

70.6 ± c 0.6

0.8 5

0.1 5

4.94

4.87

0.742 0.737 0.559 0.522 2 3 7 4

71 ± c 1

0.8 ±

0.8 2

0.1 8

4.29

4.16

0.741 0.736 0.576 0.538 2 2 1 6

73 ± bc 2

0.67 ±

0.8 1

0.1 9

5.65

0.668 0.664 0.371 0.353 5.56 5 0 0 7

70.3 ± c 0.4

0.7 6

0.2 4

4.99

4.82

0.670 0.666 0.378 0.360 9 3 9 6

80 ± a 1

55

1,2,3

Hex (1):Eth (2) Hex (1):IP A (2) CHex (1):Eth (2) CHex (1):IP A (2) Hep (1):Eth (2) Hep (1):IP A (2)

60

55

60

55

60

66.4 ± 1.02 ± 1.54 ± 1.39 ± 1.61 ± abc bc ab b a 0.4 0.05 0.05 0.03 0.02 ed

0.1

f

1.3 ± b

0.1

1.3 ± b

0.01

0.1

0.98 ±

1.36 ±

bcd

0.02

0.8 ± ef

0.1

ab

0.04

0.96 ± c

0.02

The experimental data are present as average ± standard deviation. 2 Experimentally

determined in extracted phase. 3 Experimentally determined in solid phase. Values in the same column followed by different lowercase letters are significantly different (p < 0.05). Eth: ethanol; IPA: isopropanol; Hex: hexane; CHex: cyclohexane; Hep: heptane.

36

Table 3 – Total carotenoids content (mg β-carotene/ kg PPFO) and free acidity (%, in mass) in the PPFO from batch and column extractions using pure and mixed solvents. Mass fraction of solvent (1) (2) 1 0

Solvent

Carotenoids content (mg β-carotene/ kg PPFO) Batch

Column 1824 ± 41

cdeA

2023 ± 12

aA

1949 ± 30

1831 ± 11

1

0

IPA (1)

2012 ± 116

1

0

Hex (1)

2539 ± 78

1

0

CHex (1)

2410 ± 181

1 0.7 9 0.7 3 0.8 5 0.8 2 0.8 1 0.7 6

0 0.2 1 0.2 7 0.1 5 0.1 8 0.1 9 0.2 4

Hep (1)

2196 ± 217

Hex (1): Eth (2)

2089 ± 174

Hex (1): IPA (2) CHex (1): Eth (2) CHex (1): IPA (2) Hep (1): Eth (2) Hep (1): IPA (2) PPFO from cold extraction*

Batch

deA

Eth (1)

Column

cA

19.2 ± 0.3

bA

19 ± 1

bcB

16.5 ± 0.2

aA

aA bcA

ab

12.7 ± 0.2

abcd

15.8 ± 0.2

eA

1923 ± 32

bA

16.0 ± 0.2

bcA

14.5 ± 0.1

de

bcB

17.3 ± 0.1

bA

dB

15.2 ± 0.2

cA

bc

1875 ± 121

16.32 ± 0.03

e

b

1800 ± 67

16.9 ± 0.1

bcde

16.0 ± 0.5

bc

de

16.5 ± 0.2

2066 ± 238

bc

1858 ± 19

abc

bcA

16 ± 2

c

2012 ± 27

1790 ± 230

aA

19.7 ± 0.1 16.8 ± bcA 0.2

e

bcdeA

2360 ± 152

FFA content (mass %)

a

2360 ± 152

c

15.7 ± 0.6

bc

15.7 ± 0.6

*PPFO (palm pressed fiber oil) obtained according to Neoh et al. (2011). Values in the same column followed by different lowercase letters are significantly different (p < 0.05). Values in the same row followed by different capital letters are significantly different (p < 0.05). FFA: free fatty acids; Eth: ethanol; IPA: isopropanol; Hex: hexane; CHex: cyclohexane; Hep: heptane.

37

Table 4 - Carotenoid content (mg carotenoid/ kg PPFO) in the PPFO from column extractions using pure and mixed solvents. Mass fraction of solvent (1)

(2)

1 1 1 0.7 9 0.7 3

0 0 0 0.2 1 0.2 7

1 1 1 0.7 9 0.7 3

0 0 0 0.2 1 0.2 7

Solvent

Eth (1) IPA (1) Hex (1) Hex (1): Eth (2)

113 ± 8bc

110 ± 10a

101.1 ± 0.4bc

324 ± 18a

Hex (1): IPA (2)

129 ± 8ab

59 ± 4c

83 ± 5d

272 ± 17b

Eth (1) IPA (1) Hex (1)

β-carotene (%) 38.82 31.32 39.74

Hex (1): Eth (2)

34.80

33.98

31.23

100.00

Hex (1): IPA (2)

47.46

21.79

30.75

100.00

47.96

30.14

21.90

100.00

Literature1 1 Choo

Total content β-carotene α-carotene Lycopene (mg βcontent content content carotene + α(mg β(mg α(mg carotene + carotene/ carotene/ kg lycopene/ kg lycopene/ kg kg PPFO) PPFO) PPFO) PPFO) 105 ± 10c 51.3 ± 0.4c 114 ± 1a 271 ± 11b 79 ± 3d 76 ± 5b 97 ± 6c 252 ± 14c a b ab 131 ± 2 89 ± 5 110 ± 4 331 ± 10a

α-carotene (%) 18.94 30.02 26.89

lycopene (%) 42.24 38.66 33.36

Total (%) 100.00 100.00 100.00

et al. (1996). Values in the same column followed by different lowercase letters are

significantly different (p < 0.05). PPFO: palm pressed fiber oil; Eth: ethanol; IPA: isopropanol; Hex: hexane; CHex: cyclohexane; Hep: heptane.

38

Highlights



Palm pressed fiber oil (PPFO) can be obtained using solvent extraction.



Extractions were performed in batch and fixed bed column.



Binary mixtures of hydrocarbons (HC) and alcohols (ALC) were evaluated.



Solvent compositions were defined based on the Hansen Solubility Parameters (HSPs).



Mixtures of HC and ALC enabled obtaining carotenoid-rich PPFO.

39

Graphical abstract

40