Fatty acids and chemical composition of peanut (Arachis hypogaea L.)

INTRODUCTION

Peanut (Arachis hypogaea L.) is an important oil, food and feed crop of the world. Peanut seeds (Kernels), the most important product of peanut is a rich and a good source of nutrition and provide a several health benefits. The kernels contain 40-55% oil, 20-35% protein and 10 - 20% carbohydrates. They provide 567 kcal of energy from 100g of kernels (Jambunathan, 1991). Fageria et al. (1997) reported that groundnut seeds contain high oil (45%), 26-28% protein, 20% carbohydrates and 5% fiber. The seeds have high nutritive value for human consumption and for animal feed as well as, the green leaf is also used to hay for livestock (Abdalla et al., 2009). Anyasor et al. (2009) found that the fatty acids composition of different varieties of peanut oils (%) were as follows: palmitic 10.10-11.85%, stearic 2.67-3.70% oleic 41.67-44.20%, linoleic 38.50-41.89%, linolenic 0.12-0.15 arachidic 1.18-1.76%. The previous literature reported that the oils contain total saturated fatty acids 16.32-29.39%, and the total unsaturated fatty acids from 66.94-83.32%. Ayoola et al., (2010) indicated that the iodine value of peanut oil ranged from 105.7-110.7, saponification value 170-190 and acids value 1.79-2.52.

Eshun et al. (2013) determined the chemical composition of different varieties of peanut seeds. They reported that moisture 2.13-3.99, protein 17.62-22.80, fat content 38.10 to 48.79%, ash 2.4-2.9, carbohydrates 11.50-13.60 and fiber 12.69-15.55%. The physical and chemical properties were as follow: Refractive indea 1.460-1.461, colour pale yellow, iodine value 105.1-108.9, and saponification value 144-208.9. Anyasor et al. (2009) cleared that peanut seeds contain 4.7% moisture, 41.2% oil, 25.8% fiber, 1.7% ash, 16.3% protein and 11.05% carbohydrate. Therefore, this study was carried out to evaluate the fatty acids and the chemical composition of three varieties of peanut as affected by storage time.

MATERIALS AND METHODS

The raw peanut seeds of the three varieties were obtained from Wady El-Melouk Farm at Ismaillia during 2017-2018 season.

The raw peanut seeds of the different varieties i.e (Balady, NC and Greogly varieties) were cleared and stored at room temperature for 0, 3, 6, 9, and 12 months for further analysis.

Proximate Analysis: The proximate analysis of raw peanut in term of moisture fat, protein, fiber, ash and total carbohydrate were determined by NIRA 1650-D-Foss at the Central Laboratory, Fac. Agric., A-Azhar Univ.

Oil Extraction: Samples were crushed using an electric grinder and the oils were extracted according to Folch et al. (1957).

The physical and chemical properties of oil samples of the three varieties were determined according to the AOAC. (2010).

Determination of fatty acid profile: fatty acids were methylated by methylating agent according to Farag et al. (1992). The fatty acid methyl esters (FAME) were dissolved in M-Hexane and chromatographic separation was performed using Thermogas chromatograph instrument equipped with FID using 30m long x 0-32 i.d column. Oven temperature was programmed from 150°C for 1 min then elevated to 230°C with the rate of 3°C/min.

RESULTS AND DISCUSSIONS

The results presented in table (1) showed the chemical composition of the three varieties of peanut under this study at the different storage time from 0, 3, 6, 9 and 12 months.

 Results indicated that fat content was increased with increasing the storage time from 0 month to 9 months. A slight decrease was observed in 12 months. the NC variety gave the highest values at the different storage time from 0,3,6,9and12 month, the fat contents were 42.98, 43.60, 43.81, 44.50, and 44.30%, respectively.

Also, Carbohydrates content were increased with the storage time. The NC variety gave the lowest values, but Balady variety had the highest value at the different storage time. However, values of moisture, protein, ash and crude fiber were decreased with increasing the storage time from 0 to 12 months (Table, 1).

These results are in harmony with those reported by Jambunatham (1991), Fageria et al. (1997), Anyasor et al. (2009), and Eshun et al. (2013). The physical and chemical properties of peanut seed oils of Balady, NC and Gerogly varieties as affected by storage time are shown in Table 2, 3, and 4 values of refractive index were increased with increasing the storage time at 0, 3, 6, and 9 months. However, the values were decreased in 12 months. On the other hand, results obtained of acid value, iodine value and saponification value were increased with increasing the storage time from 0, 3, 6, 9 and12 month. It could be concluded that the physical and chemical properties were affected by the storage time. these results are in agreement with those obtained by Cifuentes and Cruz (2017), and Elrasheid et al. (2017) who reported that the chemical properties of peanut oil were: saponification value was 168-188 (mg/KOH/g oil) iodine value 86.3-88.11 (g I2/100g oil) and free fatty acids were 0.71-0.80 (mg/KOH/g oil)

Result presented in Table 5, 6, and 7 showed the effect of storage time (0, 3, 6, 9, and 12 month) on fatty acid methyl ester composition of peanut oils of the three varieties under study.

 The major detected fatty acids in Balady, NC, and Gerogly peanut oils were palmitic acid C16:0, oleic acid C18:1and linoleic acid C18:2.

Results indicated that values obtained C12:0, C14:0, C15:0, C16:0, C16:1, C18:0, C20:0, C22:0, and C24:0 were decreased with increasing the storage time for all the three oils on the other hand the values of C18:1, C18:2, and C18:3 were increased with increasing the storage time. The saturated and unsaturated fatty acids were affected by the storage time.

Results indicated that as decreasing the total saturated fatty acids from 0 to 12 month, the total of unsaturated fatty acids were increased for the three different peanut oils.

Conclusion

It could be concluded that the chemical composition, physical and chemical properties and the fatty acid composition of peanut were affected by the storage time. The NC peanut seed variety had the highest values as compared with Balady and Gerogly peanut seed varieties.

REFERENCES

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Jambunathan, R., 1991. Groundnut quality characteristics. in: Uses of Tropical Grain Legumes. Proceedings of a Consultants Meeting ICRISAT, Patancheru, India. pp. 267-275.