EVALUATION OF PERCENTAGE OIL YIELD AND PHYSICOCHEMICAL PROPERTIES OF EXTRACTED OILS FROM DIFFERENT PEANUT SPECIES (ARACHIS HYPOGAEA) GROWN IN INDIA

EVALUATION OF PERCENTAGE OIL YIELD AND PHYSICOCHEMICAL PROPERTIES OF EXTRACTED OILS FROM DIFFERENT PEANUT SPECIES (ARACHIS HYPOGAEA) GROWN IN INDIA

Shashikant Pardeshi

86-Main Brijvihar colony, Nr. Vaishali Nagar, Annapurna Road, Indore - 452009, Madhya Pradesh, India.

ABSTRACT: In the present study, four different groundnut varieties such as RS-1 (Rs-1), TAG-3a (Tg-3a), TAG-51 (Tg-51), and TAG-24 (Tg-24) were grown under different geographical places in India. Physicochemical properties of collected groundnut seeds and their extracted oils were determined for their nutritional assay. It was found that the seeds contained in the range of extracted oil, the specific gravity, viscosities, impurities, refractive index and color of the extracted groundnut seed oil were in the range of 39.98-41.9 (±0.4837) 0.9154-0.9164 (± 0.000), 91.56-91.64 (± 0.0365), 0.03-0.05 (± 0.0085), 1.4633-1.4639 (± 0.000) and 1.24-2.2 (± 0.4313) yellow units respectively. AV (mg KOH/g oil), IV (g I2/100 g oil), SV (mg KOH/ g oil), ester value and unsaponifiable matter content (%) of the extracted oil from groundnut seeds were in the range of 2.33-3.38 (± 0.4837), 91.37-93.65 (± 0.9468), 191.0-193.99 (±1.3588), 187.67-191.67 (± 1.9574) and 0.52-0.63 % (± 0.0466) respectively. This study is empirical and on the basis of finding it revealed that groundnut seed oil could be a valuable source of edible oil.

Keywords: Groundnut varieties, oil yield, Physical and Chemical properties

INTRODUCTION: Peanut (Arachis hypogaea L.) is an herbaceous plant, which is an important source of edible oil for millions of people living in the tropics ¹. Groundnut, (Arachis hypogaea L.) also known as peanut or earthnut is a native to a region in eastern South America ². Groundnut/peanut (Arachis hypogaea) is a legume that is widely grown as a food crop. The genus Arachis, a member of the family Leguminosae, is among the major oilseeds in the world. China, India and the USA are the main producers of groundnuts to the rest of the world ³.

Groundnut is now grown worldwide in the tropical and temperate zones primarily as an oilseed crop ⁴. In 2003, the US food and drug administration reported that scientific evidence suggests that eating 1.5 ounces (43 g) per day of most nuts including peanuts, as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease ⁵.

India is the largest producer of groundnut in the world. Around 88% of the groundnut area and production in India is concentrated in five states: Andhra Pradesh, Gujarat, Karnataka, Tamil Nadu, and Maharashtra. Nearly 83% of the total area is under rainy-season groundnut, and the other 17% is cultivated during the post rainy season. During 1995-98, groundnut was grown in India over 7.47 Mha with a total production of 8.02 Mt ⁶. India possesses varying climatic conditions results in cultivation of a wide range oil bearing crops trees and nuts. Peanuts make an important contribution to the diet in many countries. Peanut seeds are a good source of protein, lipid and fatty acids for human nutrition ^{7, 1}. Recently, it has been associated with metabolic benefits in the context of counteracting metabolic dysfunction associated with the increasing prevalence of obesity and metabolic syndrome ⁸. The fat content in groundnut has been largely studied. In general, Groundnut seed contains 44-56% oil and 22-30% protein on a dry seed basis and is a rich source of minerals such as phosphorus, calcium, magnesium and potassium and vitamins like E, K and B group ⁹. The nutritive value of food is high as the groundnut is affordable and serves as a good source of oil and protein ¹⁰. The oil content of groundnut differs in quantity, the relative proportion of fatty acids, geographical location, seasons, and growing conditions ¹¹. Vegetable oils are in high demand due to diseases associated with fat from animal origin. The groundnut cake has several uses in feed and infant food formulations ¹². ¹³ have reported changes in the chemical composition as a result of processing.

However, little information on the effect of traditional processing on peanuts quality was reported. The chemical properties of oils are amongst the most important properties that determine the quality and help to describe the present condition of oils. It constitutes one of the essential components of a balanced diet as a good source of energy. The study indicated that Peanut oil may have a higher shelf life, nutritional value and industrial applications. Vegetable oil had made an important contribution to the diet in many countries. The aim of this study is to investigate and evaluate the physical and chemical composition of Groundnut seed varieties of RS-1 (Rs-1), TAG-3a (Tg-3a), TAG-51 (Tg-51) and TAG-24 (Tg-24) which are having different geographical places such as Rajasthan, Karnataka and Maharashtra.

In this study, the groundnut seeds of different places were assessed and analyzed for a yield of extracted oil and the extracted oils were analyzed for physical and chemical parameters, such as refractive index, specific gravity, viscosity, iodine value, acid value, saponification value and unsaponifiable matter etc.

MATERIALS AND METHODS:

Procurement of Materials: Proximate, physical and chemical analysis of seeds and extracted oil were based on four peanut varieties namely RS-1 (Rs-1), TAG-3a (Tg-3a), TAG-51 (Tg-51) and TAG-24 (Tg-24) have been used for cultivation in arid zone as well as irrigated regions of Rajasthan, Karnataka, and Maharashtra then used for extraction of oil which was provided by oil mills association, Jalgaon (Maharashtra). The seeds and pod shells were separated manually. For analysis, mature and healthy seeds were stored in the grinded form in glass containers.

Methods:

Extraction of oil of Collected Seeds: The groundnut oilseed were purchased from the local market. The groundnut seeds were separated from the shaft by handpicking method. The seeds were freed of the dirt and were collected into a separate pre-cleaned beaker. From each sample, 500 g were crushed and weighed using a commercial grinder and fed to a soxhlet extractor and hexane was used as the extraction solvent, equipped with thimble and fitted with a 2 L round-bottomed flask.

The extraction was carried out for a period of 8 h. At the end of the extraction period, the solvent was recovered by using a rotary evaporator and residual oil was dried at 75° C for 1 h. The extract was transferred to desiccators and then stored in airtight containers until needed for further analysis ¹⁴. The amount of oil extracted was determined using the following equation

Oil content (%) = weight of oil extracted/weight of seed×100

Determination of Physical and Chemical Properties of Extracted Oil: The extracted oil was immediately analyzed for chemical properties, such as iodine, acid and saponification value, ester value and unsaponifiable matter while specific gravity, viscosity, refractive index, impurities and color were examined for physical properties. The refractive indices of the oil at room temperature were determined with Abbe / Butyro Refractometer and the specific gravity measurement (also carried out at room temperature), using a specific gravity bottle. The state and color of the oil were noted, using the Lovibond tintometer at room temperature. Viscosity measurement with Hakke viscometer (rheoVT550) at room temperature and yield were determined, using the method described by the association of official chemists (AOAC). Results are expressed as the means of three separate determinations.

Determination of Physical Properties of Extracted Oil:

Determination of Color: The method determines the color of oils by comparison with Lovibond glasses of known color characteristics. The color is expressed as the sum of the yellow and red slides used to match the color of the oil in a cell of the specified size in the Lovibond Tintometer. Clean the glass cell of the desired size with carbon tetrachloride and allow it to dry. Fill it with oil and place the cell in position in the tintometer. Match the color with sliding red, yellow and blue colors. Reports the color of the oil in terms of Lovibond units as follows ¹⁵.

Color reading = (a Y + 5 b R) --------------------------- (ii)

Where, a= sum total of the various yellow slides (Y) used, b = sum total of the various red (R) slides used

Determination of the Refractive Index at 40 °C: The refractive index was measured, as this figure can help determine the level of unsaturated of the fatty acids in oils, a nutritive quality of interest for this study ¹⁶. Measurement of the refractive index of the sample is done by means of a suitable Butyro refractometer at 40 °C, a refractometer was used to measure the refractive index of extracted oils.

Distilled water which has refractive index 1.3330 at 20 °C and 1.3306 at 40 °C, the usual temperature of taking readings Make sure the sample is completely dry, circulate a stream of water through the instrument. Adjust the temperature of the refractometer to the desired temperature. Ensure that the prisms are clean and dry. Place a few drops of the sample on the prism. close the prisms and allow standing for 1-2 min. Adjust the instrument and lighting to obtain the most distinct reading possible and determining the refractive index or butyro-refractometer number ¹⁵.

Determination of Specific Gravity: The specific gravity of extracted oil was recorded as a general measure of oil density compared to the density of water ¹⁶. This is useful for physically comparing and identifying oils. The specific gravity was determined using the specific gravity bottle method. The following formula was used to calculate the specific gravity of extracted oils ¹⁵.

Specific gravity = (weight of bottle + oil) - (weight of bottle) / (weight of water)---------(iii)

Impurities: The level of impurities (mesocarp fibers, insoluble materials, phosphatides, trace metals, and oxidation products) was measured in each oil, as high levels of these substances are typically prohibited in the regulated production of edible oils ¹⁸. Two grams (2 g) of oil was weighed into a 500 ml flask and mixed with 20 ml of a 1:1 solvent (petroleum ether and diethyl ether). The contents were vigorously shaken, covered, and allowed to stand for 24 h. The mixture was filtered through a weighed 11 cm qualitative filter paper. The paper was then washed with 10 ml of the 1:1 solvent and placed in an oven at 103 ºC for 1 h. The dried paper was then weighed. The impurity (%) of oil was calculated with the following formula ¹⁷.

Impurities (%) = (w₂- w₁) / w₃ ------------------- (iv)

w₂ = Weight of paper before filtering, w₁ = Weight of paper after filtering, w₃ = Weight of initial sample.

Determination of Viscosity: The viscosity of extracted oil was measured as an additional proxy for fat unsaturation, as prior studies have described an inverse relationship between viscosity and fatty acid unsaturation in oils ¹⁹. Viscosity was determined at room temperature 25 °C, using a Hakke viscometer (rheo VT550). The results of the physical properties of the selected oils examined are shown in Table 1.

Determination of Chemical Properties of Extracted Oil:

Determination of Acid Value: The acid value, an indirect measurement of free fatty acid levels, was recorded to test the oils’ freshness and likeliness to develop taste and odor defects ^{20, 16}. The acid value is determined by directly the oil in an alcoholic medium against standard potassium hydroxide/sodium hydroxide solution. Mix the oil or melted fat thoroughly before weighing. Weigh accurately about 5 to 10 g of cooled oil sample in a 250 ml conical flask and 50 ml to 100 ml of freshly neutralized hot ethyl alcohol and about one ml of phenolphthalein indicator solution.

Boil the mixture for about five minutes and titrate while hot against standard alkali solution shaking vigorously during the titration ¹⁷.

Acid value = (56.1) (V) (N) / W ------------------------ (v)

Where V = Volume in ml of standard sodium hydroxide solution used, N = Normality of the standard sodium hydroxide solution and W = Weight in g of the sample.

TABLE 1: PHYSICAL PROPERTIES OF DIFFERENT GROUNDNUT EXTRACTED SEED OILS

Values are mean ± SD, SD-standard deviation, CV-coefficient of variance, SEM-standard mean error, RI-Refractive index

Determination of Iodine Value (Wij’s Method): The iodine value of such oil was measured, as this value is also useful for determining the unsaturation level of the fatty acids in oil ²⁰. The iodine value of an oil/fat is the number of grams of iodine absorbed by 100 g of the oil/fat, when determined by using Wijs solution.

The oil/fat sample taken in carbon tetrachloride is treated with a known excess of iodine monochloride is treated with glacial acetic acid Wijs solution) the excess of iodine monochloride is treated with potassium iodide and the liberated iodine estimated by titration with sodium thiosulphate solution. The iodine value is a measure of the amount of unsaturation (number of double bonds) in a fat ²¹.

Iodine value = 12.69 (B- S) N / W --------------------------- (vi)

Where B = volume in ml of standard sodium thiosulphate solution required for the blank,

S = volume in ml of standard sodium thiosulphate solution required for the sample, N = normality of standard sodium thiosulphate solution, W = weight in g of the sample.

Determination of Saponification Value: The saponification value is the number of mg of potassium hydroxide required to saponify 1 g of oil/fat. The saponification value of such oil was measured to explore the potential industrial uses for the oils, as this parameter reveals oil’s suitability to be made into soap ²². Two grams (2 g) of oil was dissolved in 25 ml of alcoholic potassium hydroxide. The mixture was refluxed for 45 min and then cooled. 1 ml of phenolphthalein indicator was added. The solution was titrated using 0.5 M HCL.

A blank determination was conducted. The oil sample is saponified by refluxing with a known excess of alcoholic potassium hydroxide solution. The alkali required for saponification is determined by titration of the excess potassium hydroxide with standard hydrochloric acid ²¹.

Saponification value = 56.1 (B- S) N / W ----------------- (vii)

Where, B = Volume in ml of standard hydrochloric acid required for the blank, S = Volume in ml of standard hydrochloric acid required for the sample, N = Normality of the standard hydrochloric acid, W = Weight in gm of the oil fat taken for the test.

Determination of Ester Value: The ester value is the ‘mg’ of KOH required to react with glycerol/ glycerin after saponifying 1 g of oil sample. Ester value is calculated by the following relation

Ester Value = Saponification Value – Acid Value

Determination of Unsaponifiable Matter: The Unsaponifable matter was determined using the neutralized liquid after titration for the determination of the saponification value. The neutralized liquid was transferred quantitatively into a separating funnel using 50 ml of water for washing the flask. Add to the flask 50 ml of petroleum ether, shake vigorously and allow the layers to separate. Transfer the lower soap layer into another separating funnel and repeat the ether extraction for another 3 times using 50 ml portions of petroleum ether. Wash the combined ether extract three times with 25 ml portions of aqueous alcohol followed by washing with 25 ml portions of distilled water to ensure ether extract is free of alkali (washing is no longer alkaline to phenol-phthalein) Transfer ether solution to 250 ml beaker, rinse separator with ether, add rinsing to the main solution. Evaporate to about 5 ml and transfer quantitatively using several portions of ether to Erlenmeyer flask previously dried and weighed. Evaporate ether. When all ether has been removed add 2-3 ml acetone and while heating on steam or water bath completely removes the solvent under a gentle air. To remove last traces of ether, dry at 100 °C for 30 min till constant weight is obtained dissolve residue in 50 ml of warm ethanol which has been neutralized to a phenolphthalein endpoint. Titrate with 0.02 N NaOH ²¹.

Weight in g of the free fatty acids in the extract as oleic acid = (0.282) (V) (N)

Where, V = Volume in ml of standard sodium hydroxide solution, N = Normality of standard sodium hydroxide solution

Unsaponifiable matter = 100 (A- B) / W   ---------------- (viii)

Where,

A = Weight in g of the residue, B = Weight in g of the free fatty acids in the extract

W = Weight in g of the sample.

The results of the chemical properties of the selected oils examined are shown in Table 2.

TABLE 2: CHEMICAL PROPERTIES OF DIFFERENT GROUNDNUT EXTRACTED SEED OILS

Values are mean ± SD, SD-standard deviation, SEM-standard mean error, CV-coefficient variance, AV-Acid value, IV-Iodine value, SV-Saponification value, EV-Ester value

FIG. 1: ACCURACY OF DESCRIPTIVE STATISTICS OF DIFFERENT VARIETIES OF GROUNDNUT GROWN IN DIFFERENT PARTS OF INDIA

Statistical Analysis: The statistical parameter like standard deviation and coefficient of variance standard mean error were calculated for physical and chemical parameters. All the experiment was carried out in triplicate and the results are presented as the mean ± SD, CV ± SEM. Accuracy and descriptive Statistics of different groundnut varieties from different parts of India as shown in Fig. 1.

RESULTS AND DISCUSSION: Results of the physical characteristics of the different varieties of groundnut seed extracted oil was investigated in Table 1, the oil yield ranges from 39.98-41.9 and the color in yellow units ranges from 1.24 to 2.2 on Lovibond tintometer.

The specific gravity ranges from 0.9154 to 0.9164 for all the varieties of groundnut. The value of the viscosity of the various extracted oils ranges from 91.56 to 91.64. The refractive index analysis shows that the values between 1.4633 and 1.4639, the refractive index increases as the double bond increases.

Others could be attributed to the presence of some impurities and other components of the crude oil mixture range from 0.03-0.05%. Result of the chemical characteristics of the different varieties of groundnut seed extracted oil were investigated in Table 2. Results obtained from this work indicate that the acid value of the oils as determined ranges from 2.33 -3.38 mg KOH/g oil. The saponification values of the various oils were found to be in ranges from 191.0 to 193.99. The iodine values show an increase in the average degree of unsaturation of the oil, ranges from 91.37 to 93.65. Unsaponifiable matter in the range from 0.52-0.63, ester value ranges from 187.67-191.67. As a result of their agreement with standard, all the oils could be classified as non-drying oils; since their iodine values are lower than 100 (gI2/100 g sample).

CONCLUSION: The physicochemical properties of different varieties of groundnut seed oils have been analyzed and compared; all the oils gave good yields and were pale yellow in color. From the physicochemical characterization, all the oils have a very low degree of unsaturation and could be classified as non-drying oils. The percentage oil content of most of the seeds selected from different varieties of groundnut, show them as high oil yielding. Groundnut characteristically contained a high level of oil and this makes it is a potential source of edible oil.

Though, the saponification value is high, a property adequate for the soap making industry, a low iodine value in the nut is the suitability for cooking. Most of the values obtained complied with the standard specified as per the food product and standards regulations 2011 of Food safety and standard act 2006, under the food safety and standards authority of India (FSSAI).

The oil is of good quality and could be recommended as suitable for cooking usage especially; all the oils show a good tendency to be used as unrefined. It is concluded that all the groundnut varieties are revealed that groundnut seed oil can be a valuable source of edible oil.

ACKNOWLEDGEMENT: I would like to thanks to Jalgaon oil mills association for providing different groundnut varieties for this research study.

CONFLICTS OF INTEREST: Nil

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    How to cite this article:

    Pardeshi S: Evaluation of percentage oil yield and physicochemical properties of extracted oils from different peanut species (Arachis hypogaea) grown in India. Int J Life Sci & Rev 2019; 5(11): 155-61. doi: 10.13040/IJPSR.0975-8232.IJLSR.5(11).155-61.

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