Journal of Food Composition and Analysis 114 (2022) 104752 Contents lists available at ScienceDirect Journal of Food Composition and Analysis journal homepage: www.elsevier.com/locate/jfca Sea buckthorn (Hippophae rhamnoides) oil extracted with hexane, ethanol, diethyl ether and 2-MTHF at different temperatures – An individual assessment★,☆☆,☆ Arnau Vilas-Franquesa a, b, *, Jordi Saldo a, c, Bibiana Juan a a Centre d′ Innovació, Recerca i Transferència en Tecnologia dels Aliments (CIRTTA), XaRTA, TECNIO, MALTA-Consolider, Departament de Ciència Animal i dels Aliments, Facultat de Veterinària, Universitat Autònoma de Barcelona (Cerdanyola del Vallès), Barcelona, Spain b Food Quality and Design Group, Wageningen University and Research, Bornse Weilanden 9, 6708 WG Wageningen, the Netherlands c Instituto Politécnico Nacional (IPN), Centro de Desarrollo de Productos Bióticos (CEPROBI), Yautepec, Morelos, Mexico A R T I C L E I N F O A B S T R A C T Keywords: Sea buckthorn oil (SBO) has been individually extracted using two green solvents (2-methyltetrahydrofuran (2- Sea buckthorn oil MTHF) and ethanol) and two conventional solvents (hexane and diethyl ether) using accelerated solvent Pressurized liquid extraction extraction at four different temperatures (60, 90, 120 and 150 ºC). The efficiency of the extraction was evaluated Green solvents in terms of oil yield by weight difference, the quantification of α-tocopherol and β-carotene by HPLC and the Fatty acid profile α-tocopherol evaluation of fatty acid profile by GC-FID/MS. The results were treated separately so any effect of the temper­ β-carotene ature was clearly seen for each solvent, and the fatty acid profile data was further treated jointly using a principal component analysis, as it is one of the most valued parts of sea buckthorn oil. All solvents revealed different optimal extraction temperature when in terms of oil yield; for ethanol was observed at 90 ºC (21.75%), for hexane was at 60 ºC (23.25%), for 2-MTHF was at 150 ºC (14.65%) and for diethyl ether was at 120 ºC (24.98%). The present work shows the optimal extraction temperature for SBO for each solvent studied depending on aim of the extraction. 1. Introduction the study of solvent-free, microwave-assisted extraction (Périno-Issartier et al., 2011). The use of novel techniques in sea buck­ SBO can be extracted from the pulp and the peel or from the seeds. thorn oil extraction has been principally focusing on the extraction by Both oils have been shown to have potential health benefits, including non-polar techniques or even without the use of solvents. Nevertheless, but not limited to improvements in blood lipid profile, cardioprotective the use of solvents still poses a great advantage, as it is a cheaper properties and other antioxidant benefits (Guo et al., 2017; Olas, 2018). technique compared to the supercritical extraction, it can be combined The most important bioactive components include palmitoleic acid and with other extracting techniques such as microwave or ultrasound β-carotene in the berry oil and linolenic acid and α-tocopherol in the extraction, and the use of a solvent helps achieve great diffusivity and a seed oil (Dulf, 2012). The unique nutritional profile of sea buckthorn oil great oil yield (Hrabovski et al., 2012). Moreover, solvent extraction is makes it very valuable for the food and feed industry to use it as an being adapted to the sustainable needs of the industry, attempting ingredient in the formulation of diverse food products (Vilas-Franquesa vegetable oil extractions with green solvents and more efficient tech­ et al., 2020). niques. Sea buckthorn berry oil has been recently extracted with ethanol Recent works on the extraction of SBO include the study of and 2-MTHF using pressurized liquid extraction technique, achieving ultrasound-assisted extraction (Sanwal et al., 2022; Bhimjiyani et al., greater concentration of β-carotene in the extracted oil when compared 2021), the study of supercritical and subcritical extraction technologies to the oil extracted with hexane as conventional non-green solvent (Dienaite, Barauskiene, & Venskutonis, 2021; Zheng et al., 2017) and (Vilas-Franquesa et al., 2022). Nevertheless, the individual effect of Present address: 2☆☆ Main address (where the work was done): 1☆ Vilas-Franquesa has moved since the work was performed. ★ * Corresponding author at: Centre d′ Innovació, Recerca i Transferència en Tecnologia dels Aliments (CIRTTA), XaRTA, TECNIO, MALTA-Consolider, Departament de Ciència Animal i dels Aliments, Facultat de Veterinària, Universitat Autònoma de Barcelona (Cerdanyola del Vallès), Barcelona, Spain. E-mail address: arnau.vilas@gmail.com (A. Vilas-Franquesa). https://doi.org/10.1016/j.jfca.2022.104752 Received 20 March 2022; Received in revised form 7 July 2022; Accepted 8 July 2022 Available online 19 July 2022 0889-1575/© 2022 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by- nc-nd/4.0/). A. Vilas-Franquesa et al. Journal of Food Composition and Analysis 114 (2022) 104752 green solvents has not been reported. In this line, more data should be or 150 ◦ C. The Soxhlet extraction was performed using a Soxhlet collected to understand the behavior of the individual use of green and apparatus with the same amount of sample for a total of 5 h with hexane conventional solvents, on the extraction of sea buckthorn oil at different as extraction solvent. temperatures. The present experimental research was designed to fill After the extraction was finished, the extracted solution was poured that knowledge gap. into a spherical ball flask. The flask was then immediately attached to a Understanding the individual effect of specific solvents – especially rotavapor for 45 min to allow the solvent to evaporate at 45 ◦ C and 150 green solvents – on the extraction of oil from vegetable matrices is very mbar of pressure. The flask was then allowed to cool and subsequently important for its subsequent application in food industries and the weighed in an analytical balance for the yield. Immediately after, the oil change towards more sustainable extraction processes. Thereupon, the was stored in amber tinted chromatography vials at − 80 ◦ C for further aim of the present work was to understand the nutritional composition analysis. of SBO individually extracted with ethanol and 2-MTHF as green sol­ Ethanol and 2-MTHF dried extracts were further mixed with water vents. Finally, as conventional solvents are still widely used in the re­ (at room temperature) since during the extraction some polar com­ covery of bioactive compounds from vegetable matrices, hexane and pounds were dragged out, possibly derived from the physical charac­ diethyl ether have also been individually used to extract SBO from SB teristics of the used solvents (Vilas-Franquesa et al., 2022). The mixture dried berries, and the nutritional quality of the outcoming oil has also of SBO extracted with ethanol and water resulted in a clear solubiliza­ been investigated. The nutritional quality was assessed by means of tion. The oil was recovered from the walls of the lab flask by dissolving it α-tocopherol and β-carotene concentration as well as the percentage of with hexane. Dissolution was complete and SBO was obtained after saturated, monounsaturated, and polyunsaturated fatty acids (SFA, solvent drying at 45 ºC using a rotary evaporator. The mixture of SBO MUFA and PUFA, respectively). To deeply understand the behavior of extracted with 2-MTHF and water resulted in a fuzzy mixture and each of the solvents used on the extraction yield and recovery of therefore another separation strategy was used. The content of the bioactive compounds from SBO, a pressurized liquid extraction system lab-flask was poured into a centrifugal vial and submitted at 10,000 rpm and different extraction temperatures were used (60, 90, 120 and 150 for 10 min at room temperature. SBO was recovered from the upper ºC). phase using a glass Pasteur pipette. The extraction yield was measured by weight difference after the solvent containing the oil coming from the 2. Experimental design extraction was fully evaporated. 2.1. Solvents and material 2.4. β-carotene and α-tocopherol analysis Hexane, ethanol, diethyl ether and 2-methyltetrahydrofuran were A simultaneous quantification of β-carotene and α-tocopherol was used for the experiment. n-Hexane (with isomers) 99% purity (HPLC adapted from Gimeno et al., (2000) and was performed as previously grade) was purchased from Labbox Labware, S. L., Catalunya, Spain. 2- described (Vilas-Franquesa et al., 2022). DL-α-tocopherol acetate (HPLC Methyltetrahydrofuran (2-MTHF) stabilized with 2,6-di-tert-butyl-4- standard, Merck KGaA, Darmstadt, Germany) was used as an internal methylphenol was purchased from Merck KGaA, Darmstadt, Germany. standard, giving steady recovery values of 70%. α-tocopherol (synthetic, Diethyl Ether, stabilized with 6 ppm of BHT and Ethanol absolute ≥96%, HPLC standard) and β-carotene (synthetic, ≥93%, analytical (99.8%) were purchased from Panreac Química S. A. U., Catalunya, standard) from Merck KGaA (Darmstadt, Germany) were used as stan­ Spain. dard. Calibration curves for both analytes can be observed in the Sup­ Polytetrafluoroethylene (PTFE) O-rings, PEEK seals, cell frites, 20 plementary Material. mm cellulose filters and PTFE-lined silicone septa for the ASE were purchased from Restek Corporation, Pennsylvania, U.S. 2.5. Fatty acid profile 2.2. Sample preparation A rapid extraction methodology developed by Lamba, Modak, & Madras (2017) was adapted to sea buckthorn oil as previously described A sack of sun-dried sea buckthorn berries weighing 15 kg was pur­ (Vilas-Franquesa et al., 2022). Peak identification was performed using chased from a local harvester from Romania. The cultivar is specifically three different techniques; (1) identification with a standard mix of al­ located in the north-east region of Romania. The berries were catego­ kanes, (2) using Kovats retention index and (3) GC-MS identification (GC rized as the subspecies caucasica. Dried sea buckthorn berries were System 7890 A attached to an MS triple-axis detector 5975 C (Agilent grinded down with a Thermomix® TM 21 (Vorwerk, Wuppertal, Ger­ Technologies, California, U. S.)) with the Wiley library and comparison many). The particle size distribution of the powder was measured by with the retention time of bought standards of methylated fatty acids gravimetry using sieves of different mesh sizes. Particle size distribution (Supelco 37 Component FAME Mix, Merck KGaA, Darmstadt, Germany), was quantified twice (by “Centro Nacional de Tecnologia Alimentaria” as previously reported (Vilas-Franquesa et al., 2022). (CNTA, Navarra, Spain) and Office, S.L. (Barcelona, Spain)). Approxi­ mately 8 g of dried and ground sea buckthorn berries were mixed 2.6. Data analysis thoroughly with diatomaceous earth (DE) at a ratio of 4:1. An ASE extraction cell was filled with a cellulose membrane and the mix, in that All statistical analysis was performed with the software R-4.0. As­ order. The cell was closed and inserted in the ASE cell rack. sumptions were checked by first visually interpreting the Q-Q and boxplots from all analysis. Normality was double-checked by the 2.3. Oil extraction and yield Shapiro-Wilk test. One-way ANOVA was performed to each solvent’s results including the final extraction yield, the concentration of the A total of four solvents and four temperatures were tested in the vitamers α-tocopherol and β-carotene, SFA, MUFA and PUFA to under­ present research using ASE methodology, summing up a total of 16 stand differences between temperatures in each single solvent. Further experimental conditions with two independent variables. SBO was analysis involved the use of Tukey’s post hoc tests to understand the extracted from sea buckthorn dried berry powder by using an Acceler­ source of the statistical significant difference. ated Solvent Extractor 200 (Dionex, Thermo Fisher Scientific, California, Sea buckthorn dried berry is a very complex material to work with U.S). The pressure was set at 1500 psi, static time at 10 min, preheating during oil extraction, especially when analyzing the fatty acid content, at 5 min, flushing volume at 30% of the total cell volume, purging time as the berry oil contains high amounts of palmitoleic and palmitic acids at 30 s and one extraction cycle. The temperature was set at 60, 90, 120 and the seed oil contains high amounts of oleic, linoleic and α-linolenic 2 A. Vilas-Franquesa et al. Journal of Food Composition and Analysis 114 (2022) 104752 acids. In the present experimental research, the fatty acid profile was the sample increases as well (Perez et al., 2011) therefore suggesting a analyzed by using the principal component analysis (PCA). The PCA is a better extraction at higher temperatures. Nevertheless, here we show useful technique when analyzing the fatty acid profile in different that at lower extraction temperatures, the best results of α-tocopherol samples, as it allows to discriminate between samples using a two- were achieved. Likewise, the concentration of β-carotene in the extrac­ dimensional graph through a dimension reduction of the variables. In ted SBO was statistically significantly affected by changes in the the PCA analysis, an additional extraction with Soxhlet was run and extracting temperature when using hexane as extraction solvent, F (3, included as reference method. Further analysis involved the use of fatty 20) = 23.055, p < .05 (Table 3). At 60 ◦ C and 90 ◦ C the recovery of acid groups (SFA, MUFA and PUFA) and the individual assessment of β-carotene from SBO was significantly greater when compared to higher each solvent on the extraction of the aforementioned compounds. All oil temperatures. No significant differences were found between the higher extractions and analyses were performed in triplicate. (120 and 150 ºC) nor the lower temperatures (60 and 90 ºC). SBO extracted with hexane also gave significantly different per­ 3. Results and discussion centages of fatty acids depending on the extraction temperature. Sta­ tistically different results were observed in the SFA distribution, F (3, 19) 3.1. Extraction of SBO with hexane = 12.400, at p < .05 and in the MUFA distribution, F (3, 19) = 7.556, at p < .05. The percentage of PUFA in the resulting oil extracted with Hexane has been previously reported as a temperature-dependent hexane was not affected by using different temperatures (Table 1). The solvent. It has been shown to increase oil yield in the extraction of recovery of MUFA and SFA followed an opposite pattern across all ex­ corn and oat oil (Moreau et al., 2003), amaranth seed oil (Kraujalis et al., tractions. Using lower temperatures (60 and 90 ºC) during extraction 2013) and echium seed oil (Castejón et al., 2018). Nevertheless, the resulted in an oil with a significantly greater percentage of SFA yet a present experiment showed that there was no significant effect of the lower percentage of MUFA when compared to the oil extracted at higher temperature on the extraction yield of SBO when using hexane as a temperatures (120 and 150 ºC). Thus, the greater the temperature, the solvent, F (3, 8) = 1.142, p = .389 (Table 1). In that line, the tempera­ greater the concentration of MUFA in the resulting SBO and the lower tures of 90 and 120 ◦ C achieved a higher non-significant extraction yield the concentration of SFA. In contrast, Moreau et al. (2003) showed that when compared to the other two temperatures used, 90 ◦ C being the lower temperatures of extraction (40 ºC) achieved greater percentages of most efficient. free linoleic acid (included in the MUFA group herein) from corn sam­ In contrast, when using extraction temperatures of 60 ◦ C and 90 ◦ C ples when compared to higher temperatures (100 ºC). It should be noted the recovery of α-tocopherol from SBO using hexane was significantly that the lower temperatures in the present experiment are slightly greater when compared to higher temperatures (120 ◦ C and 150 ◦ C, F (3, higher than those used by Moreau et al. (2003) (60 ºC compared to 40 20) = 6.701, p < .05, Table 1). As reported earlier by Moreau et al. ºC). In addition, it could be seen that the results indicate a similar rising (2003), higher temperatures can achieve higher amounts of tocopherols behavior at temperatures of 120 and 150 ºC. using hexane as the extraction solvent. However, the original food ma­ The temperature dependency of hexane reported by other authors in trix may play a role in the extraction of these non-polar compounds. terms of oil yield is not proven when extracting the oil from sea buck­ Moreau et al. (2003) showed that, while the recovery of γ-tocopherol thorn berries. Nevertheless, there is a temperature-dependency for the from corn extracts was higher at higher temperatures, the recovery of extraction of α-tocopherol and β-carotene in the same matrix. This the same compound from oat extracts was lower at higher temperatures. translates into an advantage when using hexane as solvent, since the The same authors explained however that the reported values were very extraction at lower temperatures (60 or 90 ºC) will recover high amounts similar and that increasing the extraction temperature did not yield a of these bioactive compounds in expense of low quantity of energy significant improvement on the recovery of γ-tocopherol. In the present (when compared to the extraction at higher temperatures). This is work, results were significantly different depending on the temperature especially important when the extraction aims at the recovery of one of used when using hexane as extraction solvent. The recovery of these bioactive compounds, such as is the production of oil supplements. α-tocopherol from SBO using hexane was higher at lower extraction Nonetheless, the extraction at 60 and 90 ºC also leads to an greater re­ temperatures (Table 1), making the extraction similar to that observed covery of SFA and lower recovery of MUFA. Whereas the difference does by Moreau et al. (2003) for oat extracts. Different food matrices imply not seem to be particularly great, it is significant and may limit the that tocopherols may be found in different conformations, explaining application of hexane for industrial purposes. the differences of tocopherol extraction at different temperatures (Marquardt et al., 2016). A more linear, saturated conformation would be more likely to be extracted by hexane rather than with other more 3.2. Extraction of SBO with ethanol polar solvents since this conformation would benefit from using a non-polar solvent for the extraction. In fact, hexane extracted more to­ Ethanol has been extensively studied to recover certain bioactive copherols from African breadfruit seed when compared to butanol or compounds from vegetable matrices. For instance, the use of ethanol, or isopropanol extraction, two more polar solvents (Nwabueze and Oko­ a mixture of ethanol and water have been studied on the extraction of oil cha, 2008). In addition, as temperature rises the diffusivity of hexane in from Echium seeds, showing promising results in the extraction yield and nutritional quality of the final oil (Castejón et al., 2018). In the Table 1 Nutritional quality of SBO extracted by ASE using hexane at different temperatures. Dependent variable Temperature (ºC) Yield α-tocopherol β-carotene SFA MUFA PUFA a a a b 60 22.67 ± 0.28 0.934 ± 0.058 1.363 ± 0.060 37.412 ± 1.471 46.073 ± 1.434 15.611 ± 1.033 90 23.56 ± 0.48 0.920a ± 0.045 1.339a ± 0.036 37.180a ± 0.721 46.157b ± 0.878 15.767 ± 0.174 120 23.25 ± 0.18 0.842b ± 0.051 1.131b ± 0.128 35.561b ± 0.461 47.928a ± 0.364 15.572 ± 0.307 150 22.84 ± 0.65 0.843b ± 0.051 1.077b ± 0.022 35.617b ± 1.202 47.717a ± 1.651 15.639 ± 0.454 Yield expressed as g of SBO / 100 g of dried sea buckthorn berries; α-tocopherol and β-carotene content expressed as g / 100 g SBO; SFA, MUFA and PUFA values expressed as percentage of total fatty acids. All values are expressed as mean ± SD Different superscripts show significant differences at p < .05. 3 A. Vilas-Franquesa et al. Journal of Food Composition and Analysis 114 (2022) 104752 present research, the extraction yield was also significantly affected α-tocopherol was non-significantly different. depending on the extraction temperature when extracting SBO with There was also a significant effect of the temperature on the con­ ethanol, F (3, 8) = 4.464, p < .05 (Table 2). The post hoc tests revealed centration of β-carotene in SBO extracted with ethanol, F (3, 20) = that there were significant differences in the extraction yield of ethanol 15.999, p < .05. The oil extracted at 120 ◦ C achieved the greatest re­ at 90 ◦ C when compared to 120 ◦ C or 150 ◦ C using the same solvent, covery values of β-carotene from SBO when compared to the oil being lower in the latter two. The extraction at 90 ◦ C yielded more oil extracted at any other temperature (Table 2). The difference was only than the extraction at 60 ◦ C, although the difference was non-significant. significant when comparing the values obtained extracting the oil at 120 Similarly, extracting corn and oat oil with ethanol at 100 ◦ C also yielded ◦ C against the values from the oil extracted at 60 ◦ C or 150 ◦ C. The more oil than at 40 ◦ C, although this difference was significant (Moreau progressive observable increase in the concentration of β-carotene from et al., 2003), probably derived from the higher difference in tempera­ 60 to 120 ºC dropped dramatically when extracting SBO at 150 ºC. The ture. In addition, results from other authors indicated that the higher the results showed a clear improved concentration of β-carotene when extraction temperature, the higher the oil yield when using ethanol as increasing the temperature except for the extraction at 150 ◦ C, at which the extracting agent (Castejón et al., 2018; Jablonsky et al., 2015). the concentration of β-carotene dropped significantly. This drop may be Nevertheless, the present experiment had the limitation of adding an derived from the possible degradation of the analyte at higher temper­ extra step during ethanol extraction of SBO, therefore possibly atures and short time (Knockaert et al., 2012). compromising the final yield. Consideration should be taken to optimize When analyzing the fatty acid profile, the ASE ethanolic extraction the extraction of water-soluble compounds from SBO extracted with showed differences in the percentage of PUFA across the studied tem­ ethanol to see if this step could have been affecting the oil yield results. peratures, F (3, 19) = 4.467, at p < .05. No significant differences were Temperature significantly affected the concentration of α-tocopherol observed in the distribution of MUFA and SFA across temperatures in the in SBO extracted with ethanol as well, F (3, 20) = 5.708, p < .05. At ethanol-extracted SBO. SBO extracted with ethanol at 150 ºC yielded temperatures of 60 ◦ C and 120 ◦ C, the recovery of α-tocopherol from significantly more PUFA when compared to the oil extracted at 120 ºC SBO was statistically significantly greater than extracting the oil at 90 ◦ C (Table 2). The extraction at 150 ºC resulted in an extracted SBO with (Table 2). High temperatures have not been used until the moment to greater percentage of PUFA when compared to all other temperatures, determine the recovery of α-tocopherol from vegetable oils using which may derive from the decrease in polarity at higher temperatures ethanol. Some authors used lower temperatures (50 and 60 ◦ C) to extract (Lu et al., 2002). However, no differences were observed between other tocopherols from sunflower collets (Baümler et al., 2017), yet no clear temperatures, meaning that the extraction at 120 ºC yielded the oil with difference was observed between both temperatures on the recovery of the lowest percentage of PUFA and the extraction at 150 ºC yielded the tocopherols. The approximate same pattern and same values were higher percentage of the same group of fatty acids. This led to under­ drawn from both extractions, also after increasing the extraction time. standing that extractions using ethanol may lead to greater recovery of The previous year, Baümler et al. (2016) already investigated the dif­ PUFA at lower and higher temperatures than 120 ºC, although more ferences in the recovery of tocopherols from sunflower oil after extrac­ evidence should be brought on the ideal extraction temperature of PUFA tion with hexane and ethanol at two different temperatures (i.e. 50 and from SBO using ethanol as extraction solvent. 60 ºC) and showed a higher recovery of tocopherols when extracting the The extraction with ethanol leads to the recovery of great amounts of oil at 60 ◦ C. Thus, a slight increase in the extraction temperature β-carotene, especially greater when compared to hexane or other sol­ resulted in a higher recovery of tocopherols from the oil when extracting vents, proving it useful for this purpose (Tables 1, 2; Vilas-Franquesa it with ethanol. Nonetheless, different results have been observed in the et al., 2022). Whereas the extraction with ethanol at 120 ºC is not the present study. Higher temperatures (90, 120 and 150 ºC) decreased the most efficient in terms of yield, it is the optimal extraction for β-caro­ concentration of α-tocopherol in the resulting oil when compared to the tene, and this could be interesting for its application in the food sup­ lower temperature used (60 ºC, Table 2). The second temperature plements or nutraceutical industry, where there concentration of applied was 90 ºC, involving a temperature rise of 30 ºC, which was the bioactive compounds in the ingredients is key for their success. In lower temperature jump when comparing the lowest temperature to any addition, ethanol also emerges as a solvent to be used in the extraction of other extraction temperature. The difference of 30 ºC is far greater from SB seed oil as well, as it can extract the highest amount of α-tocopherol what Baümler et al. (2016) studied and therefore it could explain part of at 60 ºC without significantly compromising the yield (Table 2). the differences obtained herein. In general terms, extracting the oil at 60 ◦ C led to a higher recovery of α-tocopherol than extracting at higher temperatures, although some temperatures may lead to non-significant 3.3. Extraction of SBO with diethyl ether differences (Table 2). The extraction at 90 ◦ C resulted in the lowest amount of α-tocopherol, indicating that after the first drop in its con­ Diethyl ether is a petroleum based solvent that has been also occa­ centration, increasing the temperature positively influenced the pres­ sionally used in the extraction of vegetable oils, showing good recovery ence of α-tocopherol. Interestingly, no significant differences were of the bioactive compounds present in the original matrix (Dey and observed on the concentration of α-tocopherol between the tempera­ Rathod, 2013). Diethyl ether was used in the present research because it tures of 150 ◦ C and 60 ◦ C or 120 ◦ C, showing that the presence of has a lower boiling point when compared to hexane, and this could in­ fluence the nutritional quality or the yield of the final oil, as previously Table 2 Nutritional quality of SBO extracted by ASE using ethanol at different temperatures. Dependent variable Temperature (ºC) Yield α-tocopherol β-carotene SFA MUFA PUFA ab a b 60 20.96 ± 0.82 0.945 ± 0.051 1.653 ± 0.054 37.846 ± 0.929 44.263 ± 0.876 12.512ab ± 0.216 90 21.75a ± 0.18 0.897b ± 0.007 1.698ab ± 0.050 37.882 ± 1.357 45.516 ± 1.335 12.414ab ± 0.322 120 20.09b ± 0.62 0.932a ± 0.022 1.768a ± 0.075 37.030 ± 3.053 46.414 ± 2.391 11.573b ± 1.038 150 20.15b ± 0.73 0.931ab ± 0.007 1.543c ± 0.049 37.712 ± 1.908 45.175 ± 2.227 12.907a ± 0.596 Yield expressed as g of SBO / 100 g of dried sea buckthorn berries; α-tocopherol and β-carotene content expressed as g / 100 g SBO; SFA, MUFA and PUFA values expressed as percentage of total fatty acids. All values are expressed as mean ± SD Different superscripts show significant differences at p < .05. 4 A. Vilas-Franquesa et al. Journal of Food Composition and Analysis 114 (2022) 104752 shown (Juhaimi et al., 2019). It can be seen in Table 3 that there was a when compared to all other temperatures (Table 3). The obtained data significant effect of the temperature on the extraction yield of SBO pointed to a maximum at the extraction temperature of 90 ºC, and a extracted with diethyl ether, F (3, 8) = 8.251, p < .05. The post hoc tests subsequent decrease as extraction temperature rose. There were no revealed that there was a significant difference between the extraction statistically significant differences between the percentage of SFA in yield obtained at 120 ◦ C when compared to the extraction yield obtained SBO extracted at 60 and 120 ºC. However, extraction at 150 ºC yielded at 60 and 150 ◦ C, being lower in the latter two. No significant differences an oil with significantly lower amounts of SFA when compared to all were observed in oil yield extracted at 90 ◦ C compared to that extracted other temperatures. Likewise, the percentages of MUFA in SBO extracted at 120 ◦ C, although the latter temperature achieved greater yield. The with diethyl ether also led to one temperature achieving the highest extraction at 150 ◦ C seemed to be the less efficient extraction temper­ values (150 ºC) when compared to all other temperatures, although the ature in terms of yield (Table 3). Literature did not provide enough concentration was not positively associated with temperature. However, evidence on the variation in vegetable oil yield using diethyl ether as the in our previous research the percentages of MUFA in extracted SBO extraction solvent. It seemed reasonable to conclude that the extraction followed a completely opposite pattern when compared to the extraction with diethyl ether had an optimum range of temperature when profile of SFA. In line with SFA concentration, the highest temperature extracting SBO, which was somewhere around 120 ◦ C. was the worst when analyzing the percentage of PUFA in the extracted In addition, there was a significant effect of the temperature on the oil, yielding an oil with the lowest percentage of that fatty acid group. concentration of α-tocopherol in SBO extracted with diethyl ether, F (3, No differences were observed when comparing other temperatures of 20) = 69.689, p < .05. Significant differences were observed in the extraction. PUFA are more prone to be oxidized due to their high degree concentration of α-tocopherol in SBO extracted at 60 and 90 ◦ C when of unsaturation, and high temperatures may help oxidize the molecule compared to the oil extracted at 120 and 150 ◦ C. Thus, the greater the and therefore to lose certain amounts (Fournier et al., 2006), at least extraction temperature, the greater the efficiency in recovering when using diethyl ether as extraction solvent, as it is shown in the α-tocopherol. As temperature rises, the solvent viscosity and density present experiment (Table 3). decrease and solvent diffusivity increases, subsequently yielding greater Diethyl ether could be used for the extraction of both α-tocopherol mass transfer and therefore increased recovery of α-tocopherol (Dey and and β-carotene at the specific temperature of 120 ºC achieving also the Rathod, 2013). There is a clear lack of publications to date studying the best process yield and lower amounts of SFA and high amounts of PUFA. effect of temperature on the extraction of tocopherols using diethyl This along with its boiling point (34.60 ºC) makes this solvent especially ether. The novel investigation with this solvent at different extraction interesting. However, use of diethyl ether would be limited to the cases temperatures brings evidence on the effect that the temperature may in which subsequent formulation would only require the use of this have upon the extraction of valuable compounds. It should be noted that solvent, as it is the solvent achieving lower concentration of both the recovery of α-tocopherol was higher when using extreme tempera­ bioactive compounds in relation to the other solvents (Vilas-Franquesa tures, meaning that it was higher when using 60 ◦ C (low extreme) rather et al., 2022). Nevertheless, in cases where yield is the most important than 90 ◦ C, or using 150 ◦ C (high extreme) rather than 120 ◦ C. parameters this solvent is a good choice. Lastly, it could be used for the Similarly, there was a significant effect of the temperature on the extraction of MUFA (especially in berry oil where palmitoleic acid is concentration of β-carotene in SBO extracted with diethyl ether, F (3, more concentrated) at 150 ºC without compromising the content of 20) = 216.274, p < .05. Significant differences were found between the α-tocopherol. concentration of β-carotene in SBO extracted at 60 and 90 ◦ C when compared to the oil extracted at 120 and 150 ◦ C. The greater the extraction temperature, the greater the efficiency in recovering β-caro­ 3.4. Extraction of SBO with 2-MTHF tene, except when comparing the extraction at 120 ºC against that at 150 ºC, being higher in the former (Table 3). The results of diethyl ether were 2-MTHF is a solvent that is recently gaining interest in the solvent clearly opposed to the overall results since at the highest temperatures extraction industry, as it is a solvent that is produced from biomass and it (120 and 150 ºC) the extraction of β-carotene was proportionally more has been produced for several years (Eldeeb and Akih-Kumgeh, 2018). efficient when compared to the extraction at the same temperatures 2-MTHF is also considered a green solvent and had been performed well using other solvents. However, as already mentioned and as observed in on vegetable oil extractions in the past when compared to conventional the use of other solvents, the extraction at 150 ◦ C led to a drop in solvents (Bourgou et al., 2019; Rebey et al., 2019). In fact, in the present β-carotene concentration when compared to the previous temperature research a significant effect of the temperature on the extraction yield in (120 ◦ C), clearly showing the temperature-dependency of this com­ SBO extracted with 2-MTHF has been observed, F (3, 8) = 75.005, pound (Strati and Oreopoulou, 2011). p < .05 (Table 4). Tukey’s post hoc test revealed statistically significant Diethyl ether was the only solvent yielding significantly different differences in the yield of all extraction temperatures. The greater percentages in all the groups of analyzed fatty acids. Differences were extraction yield was achieved at 150 ◦ C, and in a decreasing order at 120 observed in SFA, F (3, 19) = 15.720, in MUFA, F (3, 19) = 22.520 and in ◦ C, 90 ◦ C and 60 ◦ C. The difference between the latter and the former PUFA, F (3, 19) = 9.350, all of them at p < .05. SFA constituted a greater was more than 2%. The results showed this solvent to be clearly part of the total fatty acids when the extraction was performed at 90 ºC dependent on temperature changes. The extraction of oil was positively associated with temperature. Results from other scientific publications Table 3 Nutritional quality of SBO extracted by ASE using diethyl ether at different temperatures. Dependent variable Temperature (ºC) Yield α-tocopherol β-carotene SFA MUFA PUFA b b c b b 60 24.21 ± 0.50 0.613 ± 0.020 0.267 ± 0.013 36.320 ± 0.699 45.303 ± 0.688 17.181a ± 0.203 90 24.52ab ± 0.20 0.562b ± 0.034 0.244c ± 0.037 37.160a ± 1.590 44.440c ± 1.424 17.356a ± 0.549 120 24.98a ± 0.02 0.787a ± 0.057 0.686a ± 0.025 36.156b ± 0.241 45.776b ± 0.373 17.158a ± 0.094 150 23.92b ± 0.13 0.820a ± 0.027 0.641b ± 0.026 35.283c ± 0.201 47.036a ± 0.310 16.859b ± 0.091 Yield expressed as g of SBO / 100 g of dried sea buckthorn berries; α-tocopherol and β-carotene content expressed as g / 100 g SBO; SFA, MUFA and PUFA values expressed as percentage of total fatty acids. All values are expressed as mean ± SD Different superscripts show significant differences at p < .05. 5 A. Vilas-Franquesa et al. Journal of Food Composition and Analysis 114 (2022) 104752 Table 4 Nutritional quality of SBO extracted by ASE using 2-MTHF at different temperatures. Dependent variable Temperature (ºC) Yield α-tocopherol β-carotene SFA MUFA PUFA 60 11.960d ± 0.16 0.684ab ± 0.660 1.017a ± 0.016 38.919a ± 0.132 45.281 ± 0.585 14.117b ± 0.676 90 12.84c ± 0.15 0.715a ± 0.041 1.014a ± 0.061 37.429bc ± 0.942 44.655 ± 1.384 15.910a ± 0.352 120 13.85b ± 0.19 0.658ab ± 0.070 0.796b ± 0.062 37.881b ± 0.771 45.511 ± 0.928 14.829c ± 0.471 150 14.65a ± 0.37 0.620b ± 0.041 0.706b ± 0.071 37.011c ± 0.753 45.607 ± 0.907 15.722a ± 0.403 Yield expressed as g of SBO / 100 g of dried sea buckthorn berries; α-tocopherol and β-carotene content expressed as g / 100 g SBO; SFA, MUFA and PUFA values expressed as percentage of total fatty acids. All values are expressed as mean ± SD Different superscripts show significant differences at p < .05. used only one temperature, most of them performing extractions with MTHF was obtained at 60 ºC, meaning that higher temperatures could 2-MTHF using a Soxhlet set-up (Bourgou et al., 2019; Rebey et al., 2019; lead to lower extraction of SFA and therefore, lower presence in the oil. Sicaire et al., 2015). Interestingly, 2-MTHF was used to extract limonene In fact, the extraction at the highest temperature (150 ºC) resulted in an from orange peel at different times (30, 60, 90, 120, 150 and 180 min) oil with a lower percentage of SFA. Although the difference was some­ and temperatures (30, 50, 70 and 90 ◦ C) and found an increasing trend times non-significant, the behavior of all the solvents showed a slight in the limonene yield when increasing either the extraction time or decrease in the percentage of SFA at the highest temperature. In addi­ temperature (Ozturk et al., 2019). The limonene recovery yield jumped tion, like what was observed with ethanol, the highest temperature from around 0.5% at 30 ◦ C to almost 1.5% at 70 ◦ C, with a slight yielded significantly higher percentages of PUFA when compared to the decrease when the temperature rose to 90̊ C. The increasing trend in SBO extraction at 120 ºC, but similar amounts when compared to the extraction yield was also observed in the present experiment. extraction at 90 ºC. Therefore, results could indicate a possible drop in The behavior of 2-MTHF was expected to be similar to that of the recovery of PUFA in SBO by polar solvents at some temperature ethanol, according to polarity. However, the behavior of 2-MTHF was around 120 ºC. However, this should be further investigated to add more closer to that of diethyl ether. When investigating the effect of temper­ evidence on the field. It was however clear that the highest extraction ature on the recovery of α-tocopherol, a significant effect of the tem­ temperature did not achieve the poorest extraction of PUFA either using perature on the concentration of α-tocopherol in SBO extracted with 2- ethanol or 2-MTHF as the extraction solvents, suggesting the adequacy MTHF was spotted, F (3, 20) = 3.107, p < .05. Tukey’s post hoc test of the theoretical approach of the decrease in polarity of the most polar highlighted statistically significant differences in the concentration solvents at high temperatures (Lu et al., 2002). extracted at 90 ◦ C when compared to the extraction at 150 ◦ C, being The dependent variable that limits the use of 2-MTHF is the yield, higher in the former (Table 4). The temperature did not negatively affect which is strongly dependent on temperature. The yield increases almost oil yield – it increased – but it negatively affected oil composition, 20% when comparing the extraction at 60 ºC against the extraction at yielding lower amounts of α-tocopherol at higher temperatures when 150 ºC, being higher in the latter (Table 4). This limits the use of 2- compared to lower temperatures. The results were also in line with what MTHF, which gains interest in the recovery of valuable ingredients was observed in the extractions of SBO using hexane, also decreasing the instead of high volumes of product (i.e. nutraceutical, pharmaceutical nutritional quality of the oil as the extraction temperature rose. This industries). The most interesting extraction for this solvent is at 90 ºC, as could derive from the similar technical properties between hexane and it is the best extraction temperature for the recovery of α-tocopherol, 2-MTHF (Sicaire et al., 2015). The recovery of α-tocopherol was lower β-carotene and PUFA and the extraction yield is only 12% lower when when extracting at 60 ºC when compared to 90 ◦ C, but slightly higher compared to the values obtained at 150 ºC (Table 4). Another interesting than in the oil obtained at 120 ◦ C, clearly showing the temperature of application is at 150 ºC, as it gives the best process yield temperature-dependency for the extraction of compounds when using with the greatest recovery of PUFA and great recoveries of α-tocopherol. 2-MTHF (Ozturk et al., 2019). The temperature of 150 ºC could be applied to the extraction of sea Furthermore, there was a significant effect of the temperature on the buckthorn seed oil. concentration of recovering β-carotene in SBO extracted with 2-MTHF, F (3, 20) = 46.086, p < .05. Statistically significant differences were spotted in recovering β-carotene from SBO at 60 and 90 ◦ C when 3.5. PCA of fatty acids in SBO compared to the extraction at 120 and 150 ◦ C, being higher in the former temperatures (Table 4). In the case of β-carotene concentration, the A principal component analysis (PCA) was conducted on the six (6) greater the temperature used in the extraction, the lower the concen­ most relevant fatty acids in sea buckthorn berry and seed oil with no tration of the analyte in the extracted SBO. Although the differences rotation applied (namely palmitic, palmitoleic, stearic, oleic, linoleic were non-significant, the extraction at 120 ◦ C achieved greater con­ and α-linoleic acids). The Kaiser-Meyer-Olkin (KMO) measure verified centrations of β-carotene in SBO when compared to the extraction at 150 the sampling adequacy for the analysis. Bartlett’s test of sphericity ◦ C. These results were in accordance with all other solvents, suggesting indicated that correlations between items were sufficiently large for that the drop in the recovery of β-carotene at 150 ºC was indeed more PCA. An initial analysis was run to obtain eigenvalues for each of the subject to temperature change rather than to solvent choice. It was components in the data. Two of the components showed eigenvalues interesting to note when using 2-MTHF that the oil yield was negatively over Kaiser’s criterion of 1 and in combination explained 85.91% of the associated with the β-carotene concentration. In other words, at higher variance (Table 5). The scree plot confirmed the first two components to temperatures the extraction yield improved (Table 4) in detriment to the be the most relevant for explaining the variance of the statistical model. recovery of β-carotene (Table 4). Therefore, the first two components were retained for the final analysis. Extractions using 2-MTHF yielded significantly different percentages No rotation was applied since the first two principal components showed of SFA, F (3, 19) = 9.514, and PUFA, F (3, 19) = 17.110, both at p < .05. a great fit with the raw data. The items that clustered on the first prin­ No significant differences were observed between the percentages of cipal component were palmitic, palmitoleic, oleic and stearic fatty acids. MUFA in the oil extracted with 2-MTHF when comparing different The items that clustered on the second were linolenic and α-linolenic temperatures. The greater percentage of SFA in the oil extracted with 2- fatty acids. This was interesting, since the dimensions seemed to account for the saturated and mono-unsaturated fatty acids for the first principal 6 A. Vilas-Franquesa et al. Journal of Food Composition and Analysis 114 (2022) 104752 Table 5 The most polar solvent, ethanol, appeared in the main PCA (Fig. 1) as Principal components and their respective eigenvalue and variance explained by a more clearly isolated cluster. The most relevant difference relied on the model. Eigenvalues greater than 1 were used to draw the PCA, according to the extraction of fatty acids from PC2, which was on average higher Kaiser’s criterion. when the oil was extracted using hexane or diethyl ether. Results Dimension Eigenvalue Variance Variance explained (%, however showed a possible slightly higher concentration of poly- explained (%) cumulative) unsaturated fatty acids in SBO extracted with ethanol when compared 1 3.78 63.05 63.05 to the extraction with Soxhlet, as other authors have previously reported 2 1.37 22.87 85.92 (Castejón et al., 2018). Contrarily to what observed by Pieber et al. 3 0.58 9.66 95.58 (2012), pressurized liquid extraction using ethanol led to higher 4 0.15 2.56 98.14 5 0.09 1.50 99.64 amounts of saturated and mono-unsaturated fatty acids (PC1) and lower 6 0.02 0.36 100.00 amounts of poly-unsaturated fatty acids (PC2). Diethyl ether was the solvent that, in all the performed extractions, achieved a higher amount of poly-unsaturated fatty acids in the resulting oil (PC2). Compared to component and the poly-unsaturated fatty acids for the second principal hexane, the extraction with diethyl ether was expected to achieve higher component (Table 6). amounts of poly-unsaturated fatty acids due to the slightly more polar The clustering on PCA was performed on the two main extracted nature of the solvent (Freed et al., 1990). principal components (PC1 and PC2) and the two independent factors Contrarily, temperature did not have a significant effect on the (the solvent used and the temperature). The PCA main graph shows concentration of fatty acids on the resulting oil (Fig. 2). Therefore, the results from individuals in a scattered plot with PC1 in the X-axis and most important factor to consider in the extraction of fatty acids from PC2 in the Y-axis. Individuals are plotted in the same cluster depending SBO is the solvent rather than the temperature when using pressurized on the solvent used during the analysis, to investigate differences be­ liquid extractions. There was a clearly separated cluster from the tween solvents. Fig. 1 shows a clear difference using ASE or using extraction using Soxhlet (Fig. 2). Thus, control samples showed clearly Soxhlet as a technique to extract fatty acids from SBO if we compare the higher amounts of saturated and poly-unsaturated fatty acids presents in groups “Hexane” – extracted using hexane and ASE – against the SBO when compared to ASE. “Control” group – extracted with the same solvent using the Soxhlet technique. According to the results from PCA, the extraction using 3.6. Considerations for the applicability of the results Soxhlet achieved a greater extraction of the components building up PC1, those being oleic, stearic, palmitic and palmitoleic fatty acids, The application of each solvent strongly depends on the ultimate whereas the ASE extraction did not achieve great concentrations of those outcome of the extraction. If the interest remains on obtaining a specific fatty acids. However, ASE extraction did achieve larger concentrations compound from SBO, the choice is the solvent that recovers the most of the polyunsaturated fatty acids (PC2). quantity of the specific compound. For instance, ethanol would be the Looking at the main PCA, it was clear that the oil extracted with solvent of choice for β-carotene or α-tocopherol extraction, and hexane different solvents showed different fatty acid profiles. Specifically, there for MUFA and PUFA extraction, as we showed in our previous work seemed to be a clear difference in the oils obtained by using diethyl (Vilas-Franquesa et al., 2022). If the interest remains in the most effi­ ether, ethanol and hexane. However, the oil from the extractions using cient solvent for yield extraction diethyl ether or hexane are the solvents 2-MTHF did not separate in a new, isolated cluster. Instead, the cluster of choice. Nevertheless, those are petroleum-based solvent and their containing all the individual extractions with 2-MTHF was mixed up production and use is not sustainable. In addition, there are specific with all other clusters from the individual extractions using all other production processes that may need the use of a specific solvent. For solvents (Fig. 1). The solvent 2-MTHF seemed to behave both as the most instance, ethanol is generally used as green solvent for the extraction of polar (ethanol) and the most non-polar solvents (hexane, diethyl ether). polyphenols from vegetable matrices, and the combination of ethanolic Interestingly, the overall average extraction with 2-MTHF resulted in an extracts is not uncommon. Therefore, for this specific purpose, ethanol oil with a greater concentration of poly-unsaturated fatty acids (linoleic could be used for the extraction and recovery of β-carotene and and α-linolenic fatty acids) when compared to the ethanol and hexane α-tocopherol and in that way obtain a product which could be subject to extractions. Although in a non-significant manner, a higher extraction of combination with other ethanolic extracts. However, after understand­ polyunsaturated fatty acids was reported by Sicaire et al. (2015) on ing which solvent is the best for the purpose of the extraction there is the rapeseed oil when using 2-MTHF for the extraction and comparing the need of understanding at which temperature this extraction should be results to other solvents’. The extraction with 2-MTHF achieved, on performed. The present research gives insight on this by providing average, higher concentrations of saturated and mono-unsaturated fatty empirical data of the application of different temperatures when acids when compared to the extractions using hexane. The oil extracted extracting SBO using hexane, diethyl ether, ethanol or 2-MTHF. This with 2-MTHF contained lower amounts of poly-unsaturated fatty acids leads to the understanding of its possible application in the food, nu­ when compared to the extraction using diethyl ether, and similar con­ traceutical or pharmaceutical industries. centrations of saturated and mono-unsaturated fatty acids. 4. Conclusions Table 6 The best yield for the extraction of SBO with ethanol or hexane was Contribution of every variable analyzed (fatty acid) to Dimension 1 and Dimension 2 of the PC model. achieved at 90 ºC, and when using 2-MTHF the best result was achieved at 150 ºC, whereas the best yield for the extraction of SBO using diehtyl Variable Contribution to Dimension Contribution to Dimension analyzed 1 (%) 2 (%) ether was at 120 ºC. Similarly, the best yield was obtained with diethyl ether at 120 ºC. In addition, the extraction of SBO with 2-MTHF at 150 ºC C16:0 23.355 0.004 achieved the lower amounts of SFA and the greatest amounts of PUFA C16:1 25.107 0.522 C18:0 23.714 2.235 when compared to all other extractions with 2-MTHF. Extracting the oil C18:1 25.301 0.588 with ethanol at 90 ºC also achieved good values of PUFA. C18:2 0.683 50.448 The performed PCA on the fatty acid profile revealed that there was C18:3 1.841 46.203 no clustering difference when extracting sea buckthorn oil at different C16:0: Palmitic acid; C16:1: Palmitoleic acid; C18:0: Stearic acid; C18:1: Oleic temperatures, yet differences were clearly spotted when comparing acid; C18:2: Linoleic acid; C18:3: α-Linolenic acid. different solvents. In that issue, diethyl ether showed greater 7 A. Vilas-Franquesa et al. Journal of Food Composition and Analysis 114 (2022) 104752 Fig. 1. Mapping of the samples in two different dimensions. Samples were grouped according to the solvent used during the ASE extraction, and the con­ trol (Soxhlet). Fig. 2. Mapping of the samples in two different dimensions. Samples were grouped according to the temperature used during the ASE extraction, and the Con­ trol (Soxhlet). concentration of PUFA whereas the extraction with ethanol led to the Catalunya”, from which the first author received a predoctoral stu­ highest concentration of MUFA and SFA. dentship grant coded ‘2017 DI 079’. CRediT authorship contribution statement Appendix A. Supporting information Vilas-Franquesa: Investigation, Conceptualization, Methodology, Supplementary data associated with this article can be found in the Data curation, Writing, Editing. Juan and Saldo: Review, Editing, online version at doi:10.1016/j.jfca.2022.104752. Validation. References Declaration of Competing Interest Baümler, E.R., Carrín, M.E., Carelli, A.A., 2016. Extraction of sunflower oil using ethanol as solvent. J. Food Eng. 178, 190–197. https://doi.org/10.1016/j. jfoodeng.2016.01.020. 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