Palm oil is a liquid which is extracted from the fleshy mesocarp of the fruits of the palm tree, Elaeis guineensis, which typically contain 45 to 55% oil (Tan and Nehdi, 2012Tan C-P, Nehdi IA. 2012. 13 - The Physicochemical Properties of Palm Oil and Its Components, in: O.-M. Lai et al. (Eds.), Palm Oil, AOCS Press: Urbana, Illinois, USA. pp. 377-391.). According to Phoon et al. (2018)Phoon KY, Ng HS, Zakaria R, Yim HS, Mokhtar MN. 2018. Enrichment of minor components from crude palm oil and palm-pressed mesocarp fibre oil via sequential adsorption-desorption strategy. Indust. Crops Prod. 113, 187-195. https://doi.org/10.1016/j.indcrop.2018.01.039 , crude palm oil contains carotenoids, ca. 500-700 mg·kg−1, mainly in the form of alpha- and beta-carotenes, and ca. 1000-1200 mg·kg−1 tocopherols and tocotrienols (the whole group called tocochromanols). Carotenoids and tocochromanols are interesting valuable bioactive minor compounds. Many studies have reported that carotenes can provide support for the prevention and control of diseases caused by vitamin A deficiency (Strobel et al., 2007Strobel M, Tinz J, Biesalski H-K. 2007. The importance of β-carotene as a source of vitamin A with special regard to pregnant and breastfeeding women. Eur. J. Nutr. 46, 1-20. https://doi.org/10.1007/s00394-007-1001-z ). Alpha-tocopherol, known as vitamin E, and gamma-tocotrienol are strong antioxidants. The combined effects of the properties of carotenes and tocochromanols give palm oil a higher natural oxidative stability compared to many other edible oils. Therefore, palm oil has become the starting material to produce natural carotenes and tocochromanols (Abu-Fayyad and Nazzal, 2017Abu-Fayyad A, Nazzal S. 2017. Extraction of Vitamin E Isomers from Palm Oil: Methodology, Characterization, and in Vitro Anti-Tumor Activity. J. Am. Oil Chem. Soc. 94, 1209-1217. https://doi.org/10.1007/s11746-017-3025-8 ; Ghazali et al., 2022Ghazali NF, Md Hanim K, Pahlawi QA, Lim KM. 2022. Enrichment of carotene from palm oil by organic solvent nanofiltration. J. Am. Oil Chem. Soc. 99, 189-202. https://doi.org/10.1002/aocs.12563 ; Hoe et al., 2020Hoe BC, Chan E-S, Nagasundara Ramanan R, Ooi CW. 2020. Recent development and challenges in extraction of phytonutrients from palm oil. Comprehensive Rev.s Food Sci. Food Safety 19, 4031-4061. https://doi.org/10.1111/1541-4337.12648 ; Iftikhar et al., 2017Iftikhar, Tan H, Zhao Y. 2017. Enrichment of β-carotene from palm oil using supercritical carbon dioxide pretreatment-solvent extraction technique. LWT - Food Sci. Technol. 83, 262-266. https://doi.org/10.1016/j.lwt.2017.05.026 ).
Supercritical extraction has been proven to be a modern separation technique applied in edible oil processing. Supercritical carbon dioxide (SCCO2) is the most commonly studied fluid. However, propane is also an interesting fluid because it is non-toxic with low critical pressure (Pc = 42.5 bar). Because the critical temperature of propane is rather high (Tc = 96.7 oC), this fluid is preferably used at subcritical conditions (Brunner, 1994Brunner G. 1994. Gas Extraction - An Introduction to Fundamentals of Supercritical Fluids and the Application to Separation Processes Steinkopff, Darmstadt, Springer, New York.). It was reported that subcritical propane has been successfully used to extract oil from pequi (Caryocar coriaceum) pulp (Pessoa et al., 2015Pessoa AS, Podestá R, Block JM, Franceschi E, Dariva C, Lanza M. 2015. Extraction of pequi (Caryocar coriaceum) pulp oil using subcritical propane: Determination of process yield and fatty acid profile. J. Supercrit. Fluids 101, 95-103. https://doi.org/10.1016/j.supflu.2015.03.006 ), inajá (Maximiliana maripa) pulp (Turola Barbi et al., 2019Turola Barbi RC, de Souza ARC, Hamerski F, Lopes Teixeira G, Corazza ML, Hoffmann Ribani R. 2019. Subcritical propane extraction of high-quality inajá (Maximiliana maripa) pulp oil. J. Supercrit. Fluids 153, 104576. https://doi.org/10.1016/j.supflu.2019.104576 ), baru (Dipteryx alata vogel) seeds (Fetzer et al., 2018Fetzer DL, Cruz PN, Hamerski F, Corazza ML. 2018. Extraction of baru (Dipteryx alata vogel) seed oil using compressed solvents technology. J. Supercrit. Fluids 137, 23-33. https://doi.org/10.1016/j.supflu.2018.03.004 ), foxtail millet bran (Shi et al., 2015Shi Y, Ma Y, Zhang R, Ma H, Liu B. 2015. Preparation and characterization of foxtail millet bran oil using subcritical propane and supercritical carbon dioxide extraction. J. Food Sci. Technol. 52, 3099-3104. https://doi.org/10.1007/s13197-014-1311-0 ), kiwi fruit seeds (Coelho et al., 2016Coelho R, Kanda LRS, Hamerski F, Masson ML, Corazza ML. 2016. Extraction of Kiwifruit Seed (Actinidia Deliciosa) Oil Using Compressed Propane. J. Food Process Eng. 39, 335-344. https://doi.org/10.1111/jfpe.12225 ), macauba pulp (Trentini et al., 2017Trentini CP, Santos KA, Antonio da Silva E, Garcia VAdS, Cardozo-Filho L, da Silva C. 2017. Oil extraction from macauba pulp using compressed propane. The J. Supercrit. Fluids 126, 72-78. https://doi.org/10.1016/j.supflu.2017.02.018 ), flaxseed (Piva et al., 2018Piva GS, Weschenfelder TA, Franceschi E, Cansian RL, Paroul N, Steffens C. 2018. Extraction and modeling of flaxseed (Linnum usitatissimum) oil using subcritical propane. J. Food Eng. 228, 50-56. https://doi.org/10.1016/j.jfoodeng.2018.02.012 ), pumpkin seeds and peel (Cuco et al., 2019Cuco RP, Massa TB, Postaue N, Cardozo-Filho L, da Silva C, Iwassa IJ. 2019. Oil extraction from structured bed of pumpkin seeds and peel using compressed propane as solvent. J. Supercri. Fluids 152, 104568. https://doi.org/10.1016/j.supflu.2019.104568 ). With the palm fruit (Elaeis guineensis), the subcritical propane extraction of oil using ethanol as cosolvent had been performed in a few studies (da Silva et al., 2018da Silva CM, Zanqui AB, da Silva EA, Gomes STM, Filho LC, Matsushita M. 2018. Extraction of oil from Elaeis spp. using subcritical propane and cosolvent: Experimental and modeling. J. Supercrit. Fluids 133, 401-410. https://doi.org/10.1016/j.supflu.2017.11.006 ; Jesus et al., 2013Jesus AA, Almeida LC, Silva EA, Filho LC, Egues SMS, Franceschi E, Fortuny M, Santos AF, Araujo J, Sousa EMBD, Dariva C. 2013. Extraction of palm oil using propane, ethanol and its mixtures as compressed solvent. J. Supercrit. Fluids 81, 245-253. https://doi.org/10.1016/j.supflu.2013.06.011 ). However, the determination of oil, carotenes, and tocochromanol contents in the pure subcritical propane extract and the residual fibers of palm fruit within a single run has not been reported.
In this context, the study aimed at extracting oil from the palm mesocarp by means of pure subcritical propane and compared with SCCO2 extraction. In addition, samples of extracted oil and the oil of residual fibers were analyzed for their contents in carotenes and tocochromanols to evaluate the efficiency of using the compressed propane to recover these valuable minor compounds.
2. MATERIALS AND METHODS⌅
Palmitic acid (> 99%) and squalene (GC grade) came from Merck (Germany). Monopalmitin (99%), dipalmitin (99%) and tetradecane (99%) were supplied by Sigma (USA). Pyridine (99.8%), hexane (> 95%), acetone (> 99.8%), acetonitrile (HPLC grade) and N-methyl-N-trimethylsilyl-trifluoroacetamide were purchased from Fluka (Switzerland), Lab-Scan (Ireland), Riedel-de Häen (Germany), Prolabo (France), and Macherey-Nagel (Germany), respectively.
Ripe palm fruits (Elaeis guineensis) were from Carotech (Malaysia). The fruits were separated into skin, mesocarp (pulp), and kernel. The yellow part of the mesocarp was investigated in this work. The average particle size of the pulp ready for extraction was about 1 mm x 2 mm x 6 mm (Phan Tai and Brunner, 2019Phan Tai H, Brunner G. 2019. Extraction of Oil and Minor Compounds from Oil Palm Fruit with Supercritical Carbon Dioxide. Processes 7, 107. https://doi.org/10.3390/pr7020107 ).
2.2 Equipment and experimental procedure⌅
A standardized supercritical extraction system developed at the Institute of Thermal Separation Processes, Hamburg University of Technology was used as described in previous research (Phan Tai and Brunner, 2019Phan Tai H, Brunner G. 2019. Extraction of Oil and Minor Compounds from Oil Palm Fruit with Supercritical Carbon Dioxide. Processes 7, 107. https://doi.org/10.3390/pr7020107 ). Fluid, propane or carbon dioxide (99.95% purity) was delivered from the reservoir tank by a Maximator pump (max. 600 bar) to the 100 mL steel extractor cell, which was loaded with 14.5 g of palm mesocarp for each run. A specific flow rate of 35 kg·h−1 of gas per kg of sample was used and the pressure and temperature were monitored. The extracts were collected continuously in 10-mL glass vials, used as sample collectors at atmospheric pressure. Duplicate runs were carried out for each experimental condition with a reproducibility of ± 5%.
2.3. Analytical method⌅
2.3.1. High-performance liquid chromatography (HPLC) analysis⌅
A Gynkotek HPLC system equipped with a RF 1002 Fluorescent detector was used for the analysis. Tocopherols and tocotrienols in the oil samples were separated on a LiChrosorb Diol 5 μm column (250 mm x 4.6 mm). The mobile phase was hexane (96%) and butyl-methyl-ether (4%) at a flow rate of 1300 μL.min-1. The injection volume was 20 μL. External standard curves were used to determine tocochromanol contents in the oil samples.
2.3.2. Gas chromatography (GC) analysis⌅
A capillary gas chromatograph system (Hewlett Packard HP 5890A) was used to analyze monoacylglycerols (MAGs) and diacylglycerols (DAGs). The stationary phase was a J & W Scientific fused silica (DB-5ht) column (30m×0.25mm i.d. with 0.1-µm coating). The carrier gas was nitrogen (2 L.min-1). The oven temperature was programmed as followed: 120 °C, 2 min constant; 10 °C·min-1 to 220 °C; 5 °C·min-1 to 360 °C; 360 °C, 10 min constant. Injection volume was 1 µL at a split ratio of 1:20. For a better peak recording, sample compounds were silylated with N-methyl-N-trimethylsilyl-trifluoroacetamide (MSTFA). For the quantification of MAGs and DAGs, monopalmitin and dipalmitin were used as reference standards, respectively.
2.3.3. Soxhlet extraction⌅
A Soxhlet method was used to determine the oil contents in fresh palm mesocarp and its fibers after extraction. Hexane was used as extraction solvent. The extraction time was 8 hours (Phan Tai and Brunner, 2019Phan Tai H, Brunner G. 2019. Extraction of Oil and Minor Compounds from Oil Palm Fruit with Supercritical Carbon Dioxide. Processes 7, 107. https://doi.org/10.3390/pr7020107 ).
A UV-Vis spectrometer (UV-120-02 from Shimadzu) was used to determine the concentrations of carotenes in the analyzed samples. For each measurement, an amount of 10 to 20 mg oil sample was diluted with a 2-mL mixture of acetone and hexane (30:70 by Vol. %). The absorbance was recorded at the wavelength of 450 nm and compared to the standard curve prepared by the same treatment of a series of known amounts of β-carotene.
2.4. Statistical analysis⌅
Statistical analysis was performed with JMP® version 10 software (SAS, USA). Data were expressed as the mean of triplicate measurements. One-way analysis of variance (ANOVA) and Tukey test (P < 0.05) were carried out to test any significant differences between means.
3. RESULTS AND DISCUSSION⌅
3.1. Characteristics of palm mesocarp⌅
The composition of mesocarp varies with the size and age of the palm fruit. Table 1 presents the average composition of palm mesocarp used as material input for the extraction in this study. The results show that palm mesocarp is a good source to extract oil and valuable minor compounds like carotenes or tocochromanols. The concentrations of these components are in agreement with those reported by Phoon et al. (2018)Phoon KY, Ng HS, Zakaria R, Yim HS, Mokhtar MN. 2018. Enrichment of minor components from crude palm oil and palm-pressed mesocarp fibre oil via sequential adsorption-desorption strategy. Indust. Crops Prod. 113, 187-195. https://doi.org/10.1016/j.indcrop.2018.01.039 . However, the total mono and diacylglycerol contents in the studied palm fruit is rather high compared to 5% reported elsewhere (Tan and Nehdi, 2012Tan C-P, Nehdi IA. 2012. 13 - The Physicochemical Properties of Palm Oil and Its Components, in: O.-M. Lai et al. (Eds.), Palm Oil, AOCS Press: Urbana, Illinois, USA. pp. 377-391.). This can be attributed to the enzymatic hydrolysis of the oil under the influence of an endogenous lipase in the pulp (Doye R. Abigor, 1985Doye R. Abigor FIO, Andy R. Opoku, Anthony U. Osagie. 1985. Partial purification and some properties of the lipase present in oil palm (Elaeis guineensis) mesocarp. J. Sci. Food Agric. 36, 599-606. https://doi.org/10.1002/jsfa.2740360711.) after long transportation and preservation of the palm fruit. The difference may be also due to the analysis method, maturation stage, and environmental growth variation of the palm fruit.
|Total oil||45.1 ± 0.9%|
|Carotenes||450 ± 14 mg·kg−1|
|Tocochromanols||800 ± 40 mg·kg−1|
|Monoacylglycerols||3.0 ± 0.1%|
|Diacylglycerols||7.0 ± 0.2%|
*: Average values of triplicate analyses ± standard deviation.
3.2. Course of extraction of palm oil⌅
The course of a solid extraction of oil can be represented by an overall extraction curve, in which the amount of extract accumulated during the course of the extraction is plotted as a function of time. Figure 1 shows the extraction curves of palm oil with subcritical propane in comparison with SCCO2. According to Brunner (1994)Brunner G. 1994. Gas Extraction - An Introduction to Fundamentals of Supercritical Fluids and the Application to Separation Processes Steinkopff, Darmstadt, Springer, New York., the first part of the overall extraction curve is linear, corresponding to a constant extraction rate. The gradient of this part may represent the equilibrium solubility of the extract in supercritical fluid. However, the straight line of the overall extraction curve could correspond to a constant mass transfer resistance. In the second part, the extraction rate is declining and the graph approaches a limiting value where all the extractible substances are removed from the input material.
The results show that free oil was more soluble in subcritical propane than in SCCO2. However, extraction with SCCO2 gave better total oil yields after 45 minutes when the available oil near the palm surface was depleted. Within the study conditions, palm oil could be recovered by up to 80% after 120 minutes with SCCO2 at 400 bar and 70% with subcritical propane at 50 bar. The difference in oil recovery can be attributed to the structural change in palm fibers during the process. It was proven that SCCO2 can affect the cellulose structure by increasing the accessible surface area of the cellulosic substrates (Kim and Hong, 2001Kim KH, Hong J. 2001. Supercritical CO2 pretreatment of lignocellulose enhances enzymatic cellulose hydrolysis. Biores. Technol. 77, 139-144. https://doi.org/10.1016/S0960-8524(00)00147-4 ; Putrino et al., 2020Putrino FM, Tedesco M, Bodini RB, Oliveira ALd. 2020. Study of supercritical carbon dioxide pretreatment processes on green coconut fiber to enhance enzymatic hydrolysis of cellulose. Biores. Technol. 309, 123387. https://doi.org/10.1016/j.biortech.2020.123387 ). Lau et al. (2006)Lau HLN, Choo YM, Ma AN, Chuah CH. 2006. Characterization and supercritical carbon dioxide extraction of palm oil (Elaeis Guineensis). J. Food Lipids 13, 210-221. https://doi.org/10.1111/j.1745-4522.2006.00046.x reported a palm oil yield of 77.3% obtained with SCCO2 at 300 bar and 80 oC for 8h. In another research, it was shown that flaxseed oil extraction yields using subcritical propane were lower compared to the result from using SCCO2 (Piva et al., 2018Piva GS, Weschenfelder TA, Franceschi E, Cansian RL, Paroul N, Steffens C. 2018. Extraction and modeling of flaxseed (Linnum usitatissimum) oil using subcritical propane. J. Food Eng. 228, 50-56. https://doi.org/10.1016/j.jfoodeng.2018.02.012 ).
3.3. Solubility of palm oil in subcritical propane and SCCO2⌅
The loading of solvent during the extraction can also be obtained from the first part of palm oil extraction curves. This value is commonly considered as apparent solubility and calculated from the extraction when palm oil is easily accessible throughout the fixed bed (at constant extraction rate). In the case of palm oil, SCCO2 at 400 bar only had a loading capacity of 1.7 - 2.7%, while subcritical propane at 50 bar can reach an oil loading of up to 4.5% depending on the extraction condition as described in Figure 2. The same phenomena were also reported by Zanqui et al. (2016)Zanqui AB, da Silva CM, de Morais DR, Santos JM, Ribeiro SAO, Eberlin MN, Cardozo-Filho L, Visentainer JV, Gomes STM, Matsushita M. 2016. Sacha inchi (Plukenetia volubilis L.) oil composition varies with changes in temperature and pressure in subcritical extraction with n-propane. Ind. Crops Prod. 87, 64-70. https://doi.org/10.1016/j.indcrop.2016.04.029 in which the extraction of Sacha inchi (Plukenetia volubilis L.) oil using subcritical propane was faster compared to SCCO2 due to the higher solubility of lipids in propane.
3.4. Extraction of carotenes and tocochromanols⌅
Palm oil is a very good source of carotenes and tocochromanols, which are interesting valuable minor compounds in supercritical fluid extraction. The concentrations of carotenes and tocochromanols in extracted palm oil by compressed propane at 50 bar are presented in Figure 3. It was observed that the concentration of these compounds varied moderately during extraction time with the subcritical propane. Using subcritical propane can co-extract these minor compounds with concentrations in the same range as a normal pressed palm oil. This is in agreement with Trentini et al. (2017)Trentini CP, Santos KA, Antonio da Silva E, Garcia VAdS, Cardozo-Filho L, da Silva C. 2017. Oil extraction from macauba pulp using compressed propane. The J. Supercrit. Fluids 126, 72-78. https://doi.org/10.1016/j.supflu.2017.02.018 regarding extraction from macauba pulp, who assert that propane is more efficient to extract active compounds like tocopherols and carotenoids compared to CO2. In the extraction of oil from perilla, a higher concentration in tocopherols was determined in oil resulting from compressed propane extraction compared to the classical Soxhlet method (Silva et al., 2015Silva C, Zanqui A, Gohara A, Souza A, Filho L, Visentainer J, Chiavelli L, Bittencourt P, da Silva E, Matsushita M. 2015. Compressed n-propane extraction of lipids and bioactive compounds from Perilla (Perilla frutescens). J. Supercrit. Fluids 102. https://doi.org/10.1016/j.supflu.2015.03.016 ).
Palm oil is a complex product consisting of many components as presented in Table 1. Therefore, the concentration in carotenes and tocochromanols of extracted palm oil depends not only on their solubilities in the solvent but also on the solubilities of other compounds like mono, di- or triglycerols at the same time. A decrease in tocochromanol concentration was observed when the temperature was increased from 55 to 65 °C. A rather high temperature may decrease the content in tocochromanols because these compounds are sensitive to temperature. In contrast, it was observed that the concentration of carotenes increased with an increase in temperature. The condition of less solubility of tocochromanols in extracted palm oil can be more favourable for the solubility of other compounds like carotenes. As a result, the concentration in carotenes increased from ca 400 mg·kg−1 to 500 mg·kg−1 when temperature increased from 55 to 65 °C. Zanqui et al. (2016)Zanqui AB, da Silva CM, de Morais DR, Santos JM, Ribeiro SAO, Eberlin MN, Cardozo-Filho L, Visentainer JV, Gomes STM, Matsushita M. 2016. Sacha inchi (Plukenetia volubilis L.) oil composition varies with changes in temperature and pressure in subcritical extraction with n-propane. Ind. Crops Prod. 87, 64-70. https://doi.org/10.1016/j.indcrop.2016.04.029 also showed that temperature can influence the lipid composition of Sacha inchi oil extracted by subcritical propane. The subcritical propane of Maximiliana maripa pulp at 40 °C and 60 bar also provided fast extractions and high yields of oil enriched in beta-carotene (Turola Barbi et al., 2019Turola Barbi RC, de Souza ARC, Hamerski F, Lopes Teixeira G, Corazza ML, Hoffmann Ribani R. 2019. Subcritical propane extraction of high-quality inajá (Maximiliana maripa) pulp oil. J. Supercrit. Fluids 153, 104576. https://doi.org/10.1016/j.supflu.2019.104576 ).
It was reported that a high amount of carotenes and tocochromanols remained in the palm residue from extraction with SCCO2 or screw pressing (Birtigh et al., 1995Birtigh A, Johannsen M, Brunner G, Nair N. 1995. Supercritical-fluid extraction of oil-palm components. J. Supercrit. Fluids 8, 46-50. https://doi.org/10.1016/0896-8446(95)90049-7 ). However, subcritical propane stands out as a good solvent to recover these valuable compounds. As shown in Figure 4, there is a slight difference in tocochromanol and carotene concentrations in the oil extracted from palm mesocarp by subcritical propane and those of oil in the palm residue of extraction. To objectively evaluate the efficiency of recovery of tocochromanols and carotenes, a relative comparison of the concentrations of these compounds in the extracted oil and residue oil was used. Enrichment factor K of a component, as described in a previous study (Phan Tai and Brunner, 2019Phan Tai H, Brunner G. 2019. Extraction of Oil and Minor Compounds from Oil Palm Fruit with Supercritical Carbon Dioxide. Processes 7, 107. https://doi.org/10.3390/pr7020107 ), is defined as the following equation (Eq. 1). As a result, extraction with a higher value of K(X) provides better potential to recover component X.
The results in Table 2 show that carotenes and tocochromanols can be recovered effectively by subcritical propane. The recovery efficiency of these minor compounds by using subcritical propane was better compared to other extraction methods by using SCCO2 or traditional crew pressing. Phan Tai and Brunner (2019)Phan Tai H, Brunner G. 2019. Extraction of Oil and Minor Compounds from Oil Palm Fruit with Supercritical Carbon Dioxide. Processes 7, 107. https://doi.org/10.3390/pr7020107 reported that enrichment factors K(carotenoids) and K(tocochromanols) of palm oil extracted by SCCO2 at 400 bar and temperature of 45-65 °C was only around 0.90-1.19 and 0.54-0.86, respectively. This also agrees with a previous study which confirmed that compressed propane has higher solvating power compared to SCCO2, which results in a reduction in the consumption of solvent, higher efficiency and shorter extraction time (Silva et al., 2015Silva C, Zanqui A, Gohara A, Souza A, Filho L, Visentainer J, Chiavelli L, Bittencourt P, da Silva E, Matsushita M. 2015. Compressed n-propane extraction of lipids and bioactive compounds from Perilla (Perilla frutescens). J. Supercrit. Fluids 102. https://doi.org/10.1016/j.supflu.2015.03.016 ). It was also reported that subcritical propane extraction was a suitable and selective method for the extraction of the foxtail millet bran oil in view of smaller times and lower pressures employed compared to SCCO2 and revealed the possible high content in carotenoids and highest tocopherol content obtained (Shi et al., 2015Shi Y, Ma Y, Zhang R, Ma H, Liu B. 2015. Preparation and characterization of foxtail millet bran oil using subcritical propane and supercritical carbon dioxide extraction. J. Food Sci. Technol. 52, 3099-3104. https://doi.org/10.1007/s13197-014-1311-0 ).
|Temperature||K (carotenes)||K (tocochromanols)|
Moreover, it was reported that the extraction of minor compounds from the palm-pressed fiber is not very practical (Chuang and Brunner, 2006Chuang M-H, Brunner G. 2006. Concentration of minor components in crude palm oil. J. Supercrit. Fluids 37, 151-156. https://doi.org/10.1016/j.supflu.2005.09.004 ). Therefore, the results of this study prove that using subcritical propane as an extraction solvent will bring more benefit because of better recovery of these valuable compounds. The subcritical propane extraction of palm oil, simultaneously recovering its high contents in carotenes and tocochromanols from the palm fruits appears as a promising alternative separation technique for palm oil processing.
Subcritical propane extraction has been proven as an alternative separation technique for palm oil processing. The preliminary study shows that it is possible to extract palm mesocarp directly by subcritical propane without using cosolvent with the aim of recovering valuable minor compounds like carotenes and tocochromanols. Compressed propane at a pressure of 50 bar and flow rate of 35 kg·h−1·kg−1 can be used to recover up to 70% palm oil after 120 minutes. Carotene and tocochromanol concentrations in the extracted oil reached the same levels as in commercial palm oil. Moreover, recovery efficiencies of carotenes and tocochromanols were much higher in the case of extraction with subcritical propane than with SCCO2.