The Variation Effect of Solvents on the Physicochemical Properties Baobab (Ophelussitularius) Seeds Oil

Description of the Study Area

Kordofan state is one of the central state of Sudan, it occupies the center part although trends to be a little western, between longitude 16, 30 - 30,9ο’ North 32, 35 - 40,36ο’East, it bordered to the north by Northern state, from the north-east by Khartoum state, from the east by White Nile state, from the west by Darfur state and from south by South Sudan. Kordofan state occupies a land area of 240,974 km2. The climate of Kordofan is hot and semi-arid with mean annual rainfall varying from 300 mm in the north to over 900 mm in the south, rainfall is concentrated in a single short season which increases in reliability and length from May to October. The region depends on rain fed agriculture. Kordofan lands are known to be agricultural, and the most important product Arabic gum, peanuts, sesame, Baobab, hibiscus and it is at the forefront in the export of watermelon, cotton, millet and corn [5].

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Sample Collection

Matured and fresh fruits of Baobab were harvested from (El- Nuhud city), Sudan, which located in Kordofan state, Sudan. The city located in the western part of Kordofan state. Sampling was collected randomly without consideration of tree fruit amount, fruit size or tree height characterize 3-7 trees in each source from each Baobab tree.

Sample Preparation

Fruit shell was manually cracked using hammer to extracted fruits, seeds were soaked in water for about one hour, washed by hand to remove residual of pulp and fiber, and they were diffused on the drying trays mantled with an absorbent (paper towels).

Left overnight on the laboratory bench to lost moisture gained during seeds washing. Seeds were put on the dryer at 70οC for 1 hour to reached constant moisture content, then packed in polyethylene bag. Dried seeds were crushed and milled into powder using the electrical crusher.

Solvent Extraction

Extraction was carried out by soaking the powder of baobab seeds for 48 hr in an enclosed glass jar with two solvents (n-hexane and ethanol), with ratio Baobab seed powder weight to solvent Volume 1:5. Leaching was done by solid extraction method, solvents were separated from the extract oil with the rotary evaporator at 40°C.

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Oil Separation

Some chemical procedures require a quick and effective separation of substances through evaporation. The Rotary Evaporator is a tool which puts the separable substance under vacuum and heats evenly through a spinning motion, causing one component to evaporate and leaving the first component behind.

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Determination of Density (ρ)

The density of the oil was determined by the dry pycnometer filed with prepared sample in such a manner to prevent trap of air bubbles after removing the cap of the side arm.

The stop per was inserted in pycnometer immersed immediately in water bath 30.0±0.2 and hold for 30 minutes. Any oil came off the capillary opening for the pycnometer stopper was wiped out carefully. The bottle removed from the bath, cleaned and dried thoroughly.

The cap of the side arm removed and quickly the bottle weighed ensuring the temperature did not failed below 25°C [6].

( ) ( ) $$ \rho \left(\frac {g}{m l}\right) = \frac {W 2 - W 1 (g)}{V (m l)} $$

Where, W2 bottle weight with oil, W1 weight of empty bottle and V volume of oil.

Determination of Refractive Index

The refractive index of oil was determined by method of AOAC [6]. The refract meter was first adjusted at 1.3330 at 25οC with pure distilled water as a blank reading. A drop of the oil was placed in the instrument and telescope was adjusted so that the cross hairs were distinct and in focus. The adjustment of the knob was rotated until the lower part of the field was dark and the upper part was light and a clear definite boundary appeared. The coarse adjustment knob was moved first and then the fine adjustment knob until the boundary line coincided with the intersection of the cross hair in the telescope; the instrument was read when temperature is stable. Refractive index value read directly from refract meter.

Determination of Oil Content

Lipid was determined according to the method of AOAC [6] using Soxhlet apparatus follows: An empty clean and dry exhaustion flask was weighed. About 2 gram of sample was weighed and placed in a clean extraction thimble and covered with cotton wool. The thimble was placed in an extractor.

Extraction was carried out for eight hours with petroleum ether. The heat was regulated to obtain at least fifteen siphoning per hour. The residual ether was dried by evaporation. The flask was placed in an oven at 105°C till it dried completely and then cooled in a desiccators and weighed.

$$Oil\% = \frac{Wo(g)}{Ws(g)} \times 100$$

Where Wo oil weight and Ws seeds sample weight.

**Determination of Ash Content (AC)**

Ash content of the sample was determined according to the method of AOAC [6], 2 g of sample were placed in a clean dry pre-weighed crucible, and then the crucible with its content ignited in a muffle furnace at about 550oC for 3 hours or more until light grey ash was obtained. The crucible was removed from the furnace to desiccators to cool and then weighed. The crucible was reignited in the furnace and allowed to cooling until a constant weight was obtained.

$$AC\% = \frac{[W1(g) - W2(g)]}{Ws(g)} \times 100$$

Where, W1 weight of pot with ash, W2 weight of empty pot and Ws, sample weight.

**Determination of Saponification Value (SV)**

Determining of saponification value method by AOAC [6], a 2 g of the oil was weighed in a 25 ml conical flask to which 5 ml of 0.5 ml alcohol and 20 ml of 0.5 M alcoholic KOH solution were added.

Also 5 ml of 0.5 alcoholic KOH solution were added for the blank and both were refluxed for an hour, after cooling. The contents of the flasks were titrated against 0.5 M HCl using phenolphthalein as indicator. The difference in titer between that of the blank and the sample solution is equivalent to the amount of the fatty acid present.

$$SV = \frac{56.1 \times N(HCl)(M) \times [v0 - v1(ml)]}{Ws(g)} \times 100$$

Where, V0, V1, are the volume of hydrogen chloride required by blank and sample, respectively, N is the concentration of hydrogen chloride and Ws, sample weight.

**Determination of Peroxide Value (PV)**

The method described by AOAC [6], 5 g of sample was delivered into conical flask with stopper. About 25 ml of solvent (15 ml acetic acid+10 ml chloroform) were added and gently shake to dissolve the sample completely. The air inside flask gently replace with nitrogen to remove remaining oxygen. One ml of saturated potassium iodide was added and immediately seals the flask and gently shakes it for one minute. The flask left at room temperature 15 to 20oC in dark room. 30 ml of pure water were added, and the flask sealed and stirred. Titration with 0.01mol/L sodium thiosulphate was performed to measure peroxide value.

$$PV = \frac{[T(ml)*M]*100}{Ws(g)}$$

Where T, Titration of stander, M Molarity of stander and Ws, sample weight.

**Determination of Acid Value (AV)**

About 5 of cooled oil sample accurately was weighed in a 250 ml conical flask and 50 ml added to 100 ml of freshly neutralized hot ethyl alcohol and about one ml of phenolphthalein indicator solution. The mixture was boiled for about five minutes and titrated while hot against standard sodium hydroxide shaking vigorously during the titration, determined by standard methods [6]. The oil mixed thoroughly before weighing. The weight of the oil taken for the estimation and the strength of the alkali used for titration shall be such that the volume of alkali required for the titration does not exceed 10 ml.

$$AV = \frac{[56.1 \times T(ml)*M]}{Ws(g)}$$

$$FFA = \frac{AV}{2}$$

Where, T Titration of stander, M Molarity of stander and Ws, sample weight.

Physicochemical Properties of Baobab Oil

The study was conducted in order to found out the nutritional content of Baobab seed and oil varied with two different types of solvent (n-hexane and ethanol). The proximate analysis was determined in percentage and the values presented on Table 2.

The moisture test important to determine whether seeds were ready for use, moisture content of the seed was determined to be 23.70 % which much higher than that found to be 5.02% and 4.80% as obtained by Ajayi IA, et al. [8] and Murray SS, et al. [9] respectively.

Ash analysis measured the amount of minerals present, ash value found 2.99 % lower when compared with literature that obtained by Ajayi IA, et al. [8], which are 7.50% and 7.61% respectively, but closer to 3.45% [4, 10].

The protein content is 13.48%, which is lower than 20.13% and 36.60% determined by Ajayi IA, et al. [8] and Murray SS, et al. [9] respectively. Crude fibre obtained is lower than that obtained by Ajayi IA, et al. [8] and higher than value obtained by Nkafamiya I, et al. [11] which found 49.72% and 6.71% respectively. The high seed protein content is a reflection of high amino acid content within the seed tissue.

Baobab seed oil content is 13.26% found within the range obtained by Osman MA [12] and Ajayi IA, et al. [8] which are 12.25 and 33.00% respectively for the same plant.

Baobab seed contains high oil content indicating that it is a promising source of oils.

The obtained yield was agreeable with a literature stating that Baobab seed contains 22-45% oil, this value is represented in terms of lipid or fat content.

The Carbohydrate content was found to be 46.57 % which within the range obtained by Murray SS, et al. [9] and Proll J, et al. [13] which are 11.2% and 56.75% respectively.

The results of physicochemical properties of the Baobab seeds oil shown in table 3, The physical characters were studied to different aspects as physical state density were 0.89 and 0.88 g/cm3, viscosity were 62.80 and 64.58 mm2/s, refractive index were 1.4510 and 1.3730, for oil extracted by hexane and ethanol respectively.

While, the literature had reported that Baobab oil density value was ranged from 0.1950 to 1.0240 g/cm3, this is agree to the obtained value [14].

Refractive index is the ratio of light in a vacuum to its velocity in specific medium. RI is can be used as objective method for evaluation rancidity in edible oils and fats.

RI gained were within normal range of vegetables oils. Oil viscosity were much higher than obtained value 32.53 mm2/s. RI for Baobab seeds oil was closed to that reported by Ibrahim AMA, et al. [4] 1.4666 it was acceptable within values of literature studies.

The saponification values measured were 338.49 and 406 mgKOH/g respectively for Baobab oils extracted with hexane and ethanol. This fluent variation noted between the obtained values of extracted oils can be referred to the physicochemical properties of the solvents used in process. Baobab oil gained had much higher than saponification value reported in literature which ranged 133-200 mgKOH/g of oil according to Nkafamiya I, et al. [11]. This refers to oil be also be used in soap making since its saponification value falls within the range of these oils the term “Unsaponifiable Matter” in oils or fats.

Peroxide value is used as a measure the extent to which rancidity reactions has occurred during storage. A high peroxide value for any oil shows the fact that the oil has less resistance to lipolytic hydrolysis and oxidation while a low peroxide value shows otherwise. The peroxide values obtained were 1.42 and 1.72 mEq/kg for oil extracted with n-hexane and ethanol respectively these values were lower than that reported by Proll J, et al. [13] which is 6.6 meq O2/ kg. PV amounts were lower than that found by Erwa YI, et al. [15] and Ibrahim AMA, et al. [4] which is 6.6 and 3.22meq O2/kg. It is within the range of 0-10 mEq/kg stipulated for freshly prepared oil, oils PV below 10 meq/kg are considered fresh.

The peroxide indicates the rancidity process, whereby the higher the peroxide value is higher oxidation level and the worsening of lipids, it was increased with the storage. The low value of peroxide is an indication of low level of acidity of the oil and also suggests the high level of antioxidant, decomposition of peroxides which results in the formation of aldehydes and higher acidity. Theoretically, oil that shows a high amount of peroxide value is more prone to undergo rancidity that affects the total quality of the oil [4]. The Acid values are used to measure the extent to which glycerides in the oil has been decomposed by lipase and other physical factors such as light and heat. The acid values found in this study 1.96 and 2.90 mgKOH/g for oil extracted by hexane and ethanol respectively, hexane value were within range of recommended for cooking oil which is 0.00- 3.00 mgKOH/g [16].

The experiments showed that extracted Baobab oil varied in quantity and purity based on the type of solvent used, that affected in oil physicochemical properties (Table 3).

The overall results of this analysis show that Baobab seed is contain valuable amount of oil, energy, protein and minerals. The obtained results in this study were acceptable and similar to previous studies. The obtained results in this study were acceptable and similar to previous studies. Comparing the obtained properties oil extracted using n-hexane is better than ethanol, because ethanol contained gummy substance dissolved, which resulted in deviation of properties from stander.