Valorization of argan oil: all you need to know about argan oil from Morocco

This workmakes it possible to study the argan oil which has extracted by several extraction methods (artisanal, mechanical pressing of roasted almonds, mechanical pressing of unroasted almonds, solvent extraction, pulped by a goat), after extraction, a detailed Physico-chemical study was done on this oil to certify its quality, the study of this workmakes it possible to achieve an of icial standard for argan oil and studies the in luence of the extraction method and the origin of production on the chemical composition. The study shows that roasting appears as a parameter in luencing the acidity value of argan oil. Analysis of the peroxide index shows that the samples of argan oil extracted by the artisanal method and that those pulped by goats have a higher peroxide content. The sterol composition as per the data in the literature. They are essentially∆-7-stigmasterols. The main products are schottenol and spinasterol. The compositionof fatty acids and sterols showsno signi icant variation. These results are consistent with those reported in the literature. This shows that the origin and the method of extraction do not in luence the nutritional qualities of argan oil. The results for the tocopherols show that the extraction method (plump by a goat) and roasting can in luence the composition of the tocopherols. On the other hand, the sample obtained by the artisanal method has a lower content of total tocopherols. Roasting decreases the total content of α-tocopherol. After this study, it is urgent to ensure the quality of this oil, so Physico-chemical analyzes were carried out to detect fraud in pure argan oil. Finally, we determined the in luence of the fruit form of the argan tree (spindle-shaped, apiculate, oval, spherical) on the Physico-chemical parameters of argan oil.


INTRODUCTION
The argan tree (Argania Spinosa (L.) Skeels) is an endemic tree of Morocco, where it constitutes the second forest species of the country, after the green oak and just before the thuya. It is a tree that can live up to 200 years. Some 250-year-old subjects could be observed. The argan forest covers about 870 000 ha (Díaz-Barradas et al., 2010) and has more than 20 million trees (Charrouf and Guillaume, 2018). This tree of the Sapotaceae family is particularly resistant to dry and arid conditions in southwestern Morocco. It can indeed withstand temperatures ranging from 3 to 50 • C and be content with de icient rainfall.
The argan tree grows wild and abundant in the arid and semi-arid areas of southwestern Morocco, where it plays an irreplaceable role in the ecological balance and the preservation of biodiversity. Thanks to its powerful root system, it contributes to the maintenance of the soil. It makes it possible to ight against the erosion hydric and windy which threat of deserti ication a good part of the region (Justamante et al., 2017).
The argan tree is also of great economic interest because it is a multipurpose tree. Each part of the tree is usable and is a source of income or food for the user: the wood is used as fuel, the leaves and pulp of the fruit constitute food for goats and camels and the oil extracted from the almond kernel is used in human nutrition and traditional medicine.
The fruits of the Argan tree are green then turn towards the brown at maturity. They look like an olive but are bigger and rounder.
Inside the argan fruit, there is a nut with a tough shell. The shell is represented about a quarter of the weight of the fruit of the argan tree. The nut can contain up to three almonds, and argan oil is extracted from the almonds of the argan fruit. Argan oil plays a signi icant role in the nutrition of indigenous peoples. It is an edible oil extracted from almonds. For the Souss regions, it provides 25% of the fat intake. Its annual production is of the order of 4000 tons, that is 1.6% of the Moroccan consumption in edible oils, and 9% of the national production (Bani-Aameur, 2001). The oleaginous almond represents only 3% of the weight of the fresh fruit (Bani-Aameur, 2001). The extraction of the oil is done in an artisanal way, it results, on the one hand, a loss of 45% of oil in the cake, corresponding to 1,530 tons (Charrouf and Guillaume, 2018), and on the other hand a loss of hygienic and sanitary nature. The rate of oil extraction could be increased, and its quality could be improved by the introduction of appropriate technology that would ensure the extraction of 95% of the existing oil in the kernel (Sinsin et al., 2020).

Artisanal Extraction
The artisanal extraction of argan oil is done in several stages: 1. Purging: the women remove the skin of the fruit with two stones, the separation of the pulp and the nut is done as and when the operation of pulping.
2. Crushing or deshelling: It is done with the same stones as Depulpage, the nut is crushed by crushing it strongly. Sorting is done at the end of the operation.
3. Roasting almonds: It is made in earthenware containers on a softwood ire.
4. Grinding almonds: It is made in a cut stone wheel. The result is a brown dough.
5. Mixing and pressing: The paste obtained is kneaded by hand in a bowl. It is supplemented with lukewarm water in a small quantity until a smooth paste is obtained, which is then vigorously kneaded and then manually pressed until the oil is obtained.
6. Bottling: The artisanal oil is usually put in recycled bottles and very often poorly cleaned.

Extraction By Mechanical Pressing
The extraction of argan oil is carried out from the almonds of the argan fruit by several (Charrouf and Guillaume, 1999;Waroux and Lambin, 2013). In most cases, the extraction yield has been improved compared to the artisanal method.
All operations were mechanized except the crushing which has remained traditional. A detailed technical study of this process is described in the literature (Sinsin et al., 2020). A machine of local manufacture carries out the pulping operation. It allows you to tear the fruit pulp and separate it from the nuts via a blower. The work done on the tearing of the pulp gives a yield of 70-95%.
On the other hand, the work done by the wind tunnel is negligible and needs to be improved. For a Kg of raw fruit, it takes on average 4 minutes. The roaster operates with butane gas. It allows for roasting 6 Kg to 10 Kg of almonds at a time.
It takes 20 to 30 minutes to roast 6 to 10 kg of almonds. A screw press type KOMET D85 carries out the pressing. It can produce 6 to 8 litres of oil per hour. The oil obtained by mechanical pressing is heavily loaded with solid material (remaining cake). It requires decantation of 4 to 10 days before iltration on a ilter press. The low of the latter is 17 litres/hour.
Thanks to the mechanical extraction one can obtain two types of oil: 1. Food oil, nutty lavour, obtained by mechanical pressing of roasted almonds.
2. Virgin oil, or cosmetic oil intended for cosmetic purposes, obtained from unroasted almonds.
So the mechanical pressing reduces the time, and the roughness of the work also allows to obtain a better quality oil and with good performance (Guillaume and Charrouf, 2016).
The argan oil thus produced does not require the addition of water for extraction (the oil can be stored longer).

Previous Studies on Aragn Oil
The work summarizes all the studies that have been done on argan oil: 1. Study of the chemical composition of argan oil according to its extraction method and its origin of production 2. Multi analyzes for adulteration research of pure argan oil by other edible oils.
3. The in luence of the diversity of the morphological characters of the argan fruit on the chemical composition of argan oil, fruit pulp and oilcake could give new life to the argan tree.
4. Studying the effect of storage on the chemical composition of argan oil 5. The study of the roasting effect of almonds on the chemical composition of argan oil would help produce a better quality organoleptic oil.

Preparation of different samples of argan oil and olive oil
Argan oil was prepared by extraction, by the mechanical pressing method and by artisanal extraction in the cooperative of Tidzi (province of Essaouira, southern Morocco) according to the methods already described: extraction by mechanical pressing (almonds roasted (Taarji et al., 2018).

Determination Of Composition And Nature In Total Sterols
Operating Mode Weigh 2.5 g of argan oil and put into a 20 ml lask. 25 ml of a solution of potassium hydroxide (1N of ethanol) is added. The lask is heated under re lux for 30 minutes until the solution becomes clear; afterwards, 25 ml of distilled water are added to stop the reaction.
The extraction of the unsaponi iable is carried out using 75 ml of hexane or petroleum ether. The organic phase is subjected to a series of washing with 15 ml of a mixture (water/ethanol 95 • ) (90/10) in a separatory funnel.
The hexane phase is transferred from the top of the ampoule into a 100ml lask. After evaporation of the solvent using a rotary evaporator, the unsaponi iable material is recovered.
The unsaponi iable agent, diluted with 300 µl of hexane or petroleum ether, is iltered on a silica column (25cm × 4mm). The HPLC device is equipped with a 205 nm-254 nm UV detector. The eluent is an isooctane/isopropanol (99/1) mixture whose low rate is 1.2 ml/min. The duration of the analysis is 15 min, the sterol fraction recovered according to standard NF 12228 May 1999, is evaporated to dryness.
The sterols are converted to silylated derivatives (TMS) using a mixture of pyridine, hexamethyldisilazane (HMDS) and trimethylchlorosilane (TMCS), The pyridine is evaporated to dryness, and the silylated derivative is diluted with 60 µl of heptane or hexane. The TMS sterols are analyzed by gas chromatography (GC) on an apolar column (Chroma pack) (30m × 0.32mm, DI: 0.25µm, phase: CPSIL8CB). The Hewlett Packard brand and series 6890 GC chromatograph is equipped with an FID detector (T • : 300 • C). The carrier gas is nitrogen, and its low rate is 1 ml/min (PE: 8.6 bar). The analysis is performed in temperature programming (200 • C up to 270 • C with a speed of 10 • C/min and an isotherm at 270 • C for 35 min) (Honfo et al., 2014).
The silylation reaction of sterols is shown in Figure 1

Operating Mode
The test sample of argan oil 1g is supplemented with 0.5 ml of methanolic KOH for HPLC (minimum 98%) and 10 ml of methanol in a 100 ml lask. The mixture is re luxed for 15 minutes until the solution is clear. Then 1 ml of heptane is added to the reaction mixture after cooling.
The heptanic phase containing the methyl esters is transferred to a test tube. Then a solution of sodium carbonate Na 2 CO 3 is added, this neutralizes all free acids by giving sodium salts with a release of carbon dioxide.
The methyl esters, which are in the organic phase, are removed using a 2 ml cone pipette and placed in The methyl esters undergo a series of washing20ml are taken from the esters, which are placed in a tube of the nominal capacity of 2 ml and then illed with heptane.
The fatty acid methyl esters are analyzed by GC gas chromatography.
The HP Hewlett Packard 6890 GC Series GC chromatograph is equipped with a divider (T: 240 • C) and an FID (T: 260 • C) injector. The carrier gas is nitrogen (PE: 12.4 bar). The analysis is carried out in temperature programming (140 • C to 200 • C with a speed of 10 • C / min and an isotherm at 200 • C for 40 min) on a capillary column (polyethene glycol) (30 m × 0,32 mm, DI: 0.25 µm) (Baer et al., 2010).
The reaction of the methyl esters of the triglyceride fatty acids is as follows (Figure 2) Tocopherol Analysis

Operating Mode
In a 25 ml volumetric lask, 2g of argan oil is introduced, and then we illed the lask with 2,2,4trimethyl pentane. The test sample is added to 2, 2, 4-trimethyl pentane up to the mark, then mixed thoroughly.

Triglyceride Analysis
Operating Mode 0,15 g of argan oil is placed in a beaker after adding 0,5 ml of hexane and 15 ml of a hexane/diethyl ether mixture (87/13), This solution is poured into a supelco brand cartridge with 0.5 g of silica gel previously activated with hexane. The triglyceride fraction is thus separated from the diglycerides and monoglycerides. It is recovered in a 100 ml lask. It is subjected to analysis after evaporation of the solvent and dilution with 1.5 ml of acetone.
The triglycerides are analyzed by HPLC on a reversephase C18 column (250 mm × 4.6 mm, Φ silica 5 µm), according to IUPAC Method No. 2.0324. The HPLC apparatus is equipped with an HP refractometric detector 1047A,during the analysis time (90 min). The elution is made by the mixture (acetonitrile / acetone) (v / v) with a low rate of 0.5 ml / min (Álamo et al., 2004).

In luence of Origin and Extraction Method on Argan Oil Physico-Chemical Characteristics and Composition
As part of the development of argan oil, several studies were made on argan oil, starting by a comparative study of the different physicochemical parameters of argan oil according to its mode of extraction and its origin of production. To carry out this work, 21 samples of argan fruits located in different geographic locations of Morocco were selected. They were extracted in different ways (by mechanical pressing, artisanal, and from fruit removed by goats, extraction by the solvent) to realize a standard of argan oil from Morocco for the irst time.

Figure 2: The reaction of methyl esters of triglyceride fatty acids
The study of physicochemical characteristics shows that all acid values of argan oils are lower than 1.40% (Charrouf and Guillaume, 2008). This result shows that argan oil is characterized by low acidity compared to other vegetable oils (olive ≤ 2%).
The study shows that roasting appears as a parameter in luencing the acidity value of argan oil. Indeed, the acidity value is higher in argan oil samples prepared from unroasted almonds. More than that the argan oil sample from Tamanar, (a village south of Morocco) lot has a higher acid value than the samples. This result suggests that geographical origin can in luence acidity values (Hilali et al., 2005).
The results concerning the unsaponi iable rate show that argan oil is characterized by a low unsaponi iable rate (≤ 0.81%), but unsaponi iable of olive oil is (Olive ≤ 1.50%).
The extraction technology of argan oil can in luence the unsaponi iable rate of argan oil. Indeed, the unsaponi iable rate of the sample prepared by hexane is lower (0.34 to 0.56%) than those prepared by mechanical or artisanal press (0.6% to 0.81%).
The results of the saponi ication index of argan oil were found to be between 180.0 and 199.0 (virgin olive oil varies between 184 and 196).
Analysis of the saponi ication index shows that the sample of argan oil extracted by hexane or extracted by the artisanal method have a saponi ication index lower than that of the samples extracted by mechanical pressing. Still, the study the argan oil shows that torrefaction and depulping by the goat in luence the increase of this parameter (Hilali et al., 2005).
The results of the peroxide index on the 21 samples of argan oil are lower (≤ 6 meq O 2 / kg) than those required for virgin olive oil (≤ 20 meq O 2 / kg).
The analysis of the peroxide value shows that the samples of the argan oil extracted by the artisanal method and which those de lated by the goats have a higher peroxide content compared to the other samples. The determination of the peroxide value appears to be a critical measure for assessing the quality of argan oil.
The refractive index was determined at 20 • C. This index varies between 1.4644 and 1.4705.
The speci ic extinction has been determined at 270 nm in general, the values found are higher than that of olive oil; they vary between 0.228 and 0.426.
Speci ic extinction and refractive index give no precise information on the origin and method of extraction of argan oil.
The fatty acid analysis shows that argan oil contains 80% unsaturated fatty acids. It is oleic-linoleic and contains between 29% and 35% of essential fatty acids: linoleic acid (29 to 34%) (Vitamin F). Its oleic acid content makes this oil particularly interesting in the regulation of cholesterol.
Sterol analysis shows that the total sterol levels of argan oil range from 130 to 233 mg / 100g of fat (Charrouf and Guillaume, 2008). .
The sterol composition is under the data of the literature. These are essentially ∆-7-stigmasterols. The major products in argan oil are schottenol (47.75%) (or ∆-7-stigmasterol) and spinasterol (36.21%). Schottenol and spinasterol are rarely found in vegetable oils and are characteristic of argan oil. Argan oil does not contain β-sitosterol (∆-5-stigmasterol), Schottenol and spinasterol, which are very rare in vegetable oils, maybe a parameter in the detection of adulteration of this oil. Two minority sterols were identi ied based on their GC / MS mass spectrum and compared with literature data. It is stigmatist-8.22-diene and stigmasta-7,24-28-diene (or ∆-7avenasterol); their proportion varies between 2.6% and 6.9%.
The results of the composition of fatty acids and sterols show that the origin and the method of extraction do not in luence the nutritional qualities of argan oil.
The results for tocopherols show that the extraction method and roasting can in luence the composition of tocopherols (Harhar et al., 2011). On the other hand, the sample obtained by the artisanal method has a lower content of total tocopherols. Roasting decreases the total α-tocopherol content.
The result of determining the percentage of palmitic acid at position-2 in triglycerides is low and varies between 0.16 and 0.43%.
The results of triglycerides and palmitic acid at the 2-position of triglyceride give no speci ic information on the geographical origin and the extraction process of the fruit of the argan tree.
The determination of the wax content of certain fats can be used in particular to differentiate press oils from extraction oils.
The analysis of the wax content can give ideas on the extraction process, which allows the introduction of an exogenous wax, or by the use of almonds stored under poor conditions.
Determination of the wax content shows that the sample extracted from roasted almonds has a higher percentage of waxes than the sample extracted from unroasted kernels.
These results show that roasting can increase the percentage of waxes in argan oil.
The study of the concentration of benzo-α-pyrene suggests that roasting does not produce signi icant amounts of benzo-α-pyrene, this work has shown that the argan oil extracted by mechanical pressing is the best and the results from this work contributed to the development of a national standard for argan oil.

Study of the Chemical Composition of Aragn Oil According to its Shape of the Aragn Fruit
In the perspective of domestication of the argan tree with economically interesting trees, a comparison between the oils produced from the different forms of the fruit of the argan tree has been launched.
Regarding the quality indices, no signi icant in luence of all the parameters has been shown apart from the acidity, the peroxide index and the extinctions E232 and E270 of the oil of the fusiform form which has shown maximum values (Gharby et al., 2012).
Regarding the quality criteria, the shape of the fruit does not in luence the percentages for triglycerides and tocopherols. For the latter, their content in oils of the apiculate and oval forms is of the order of 770 mg/kg, whereas the other two do not exceed 626 mg/kg (Mcgown, 2006). Given the nutritional value of tocopherols and the difference of 150 mg/kg between forms. The shape of the fruits slightly in luences the fatty acid and sterol composition. Indeed the results clearly show that tree selection based on fruit shape could allow the natural production of argan oil rich in linoleic acid and schotenol from spherical fruits and an oil rich in oleic acid from fusiform fruits. These results are to be taken into account for the domestication of the argan tree (Gharby et al., 2012).
The mode of extraction in luenced the phospholipid content regardless of geographical origin. This criterion recorded the highest values in the food press oil, followed by the oils produced by traditional methods. For cosmetic press oil, the phospholipid content is lower. This demonstrates the link with roasting. The same result was observed for beta carotene.
Regarding the oxidative stability, evaluated by Rancimat, it seems more in luenced by the extraction methods than by the three geographical origins studied. Indeed, the fastest oxidation was observed for oils produced from unroasted kernels, followed by those produced by traditional methods and that prepared by mechanical pressing of roasted kernels (Gharby et al., 2013). The stability of the latter is twice that of the irst. Regarding the shape of the fruit, it does not in luence the stability of the oil because the induction time of all the oils extracted from the different forms is between 18 and 21 hours.
The stability results obtained by Rancimat were con irmed by the stability study at 60 • C. Indeed, the edible oil obtained by mechanical pressing of roasted almonds is more stable to oxidation for 35 days (Gharby et al., 2013).

Multi Analyzes for Adulteration Research of Pure Aragan Oil by Other Edible Oils
After establishing Moroccan argan oil standards, there is an urgent need to ensure the quality of argan oil. So, to detect argan oil fraud with other edible oils such as soybean, rapeseed, sun lower, apricot, hazelnut, olive, sesame, and peanut oils is a real analytical challenge. These oils have, in fact, physicochemical characteristics and a very close fatty acid composition which greatly hinder their detection when they are mixed. The analysis of fatty acids makes it possible to demonstrate a falsi ication of argan oil by soybean oil and rapeseed oil from a level of 1% based on the percentage of the acid linolenic (C18: 3) that does not exceed 0.1% in pure argan oil (Hilali et al., 2005). On the other hand, olive oil, hazelnut oil and sesame oil can only be detected at a rate of 5%. The result of the fatty acid composition does not make it possible to demonstrate a falsi ication of argan oil by sun lower oil, apricot oil and peanut oil.
The determination of the sterol composition prompted us to take the percentage of campestral as a marker of adulteration. The latter does not exceed 0.4% in pure argan oil (Hilali et al., 2007). The result of the sterol composition shows that the detection threshold of edible oils having a percentage greater than 10% of campesterol such as soybean, rapeseed, sun lower, sesame and peanut oils in argan oil is 1% against oils with a percentage of campesterol less than 10% the threshold of detection of adulteration is 2% for apricot oil and 5% in the case of olive oil and hazelnut (Hilali et al., 2007).

Study of the Storage Effect on the Physico-Chemical Composition of Argan Oil
The quality of argan oil lead to making the following recommendations; 1. The duration of the drying should be limited to 2 -3 weeks.
2. Fruits and nuts can be kept for 24 months without affecting the quality of the oil; it is recommended to store nuts rather than whole fruits to save space in the warehouse.
3. The storage conditions of the kernels, after suficient drying, do not affect the quality of the oil.
4. Roasting increases the stability of argan oil in addition to its signi icant in luence on organoleptic properties (Guillaume et al., 2019).

CONCLUSION
Great efforts have been made to develop argan oil by improving its extraction technology and the creation of argan oil extraction good quality cooperatives and achieve the preservation of the argan tree because argan oil is very important in nutrition. Argan oil contains 80% unsaturated fatty acids and contains 38% of essential fatty acids: linoleic acid (38%) (Vitamin F), while the percentage of linoleic acid in the oil of the olive is 10.83%. The total sterol content of the argan oil is 154 mg / 100g fat. The major products in argan oil are schottenol (47.75%) (or ∆-7stigmasterol) and spinasterol (36.21%). Schottenol and spinasterol are rarely found in vegetable oils and are characteristic of argan oil. Argan oil is richer in tocopherol (717 mg / kg) than olive oil (320 mg / kg). Argan oil is rich in γ-tocopherol (80 to 90%).
The study of this work shows that extraction technology can in luence the Physico-chemical parameters of argan oil. Our study demonstrated the high quality of argan and olive oil extracted by mechanical pressing.