Evaluation of nutritional quality of groundnut (Arachis Hypogaea L.) from Ghana.

Abstract

Groundnut is the most important legume in Ghana. The crop is grown in all the agroecologies in the country; from the dry savannah regions to the moist forest areas. Several food preparations incorporate groundnut to improve the protein level, taste and flavour. Despite the importance of the crop, the chemical compositions of the varieties grown by farmers have not been analyzed according to their nutritional quality. Oil, fatty acids, protein, oleic/linoleic (O/L) acid ratio, iodine value and free soluble sugars were studied in 20 groundnut varieties grown in Ghana to determine their nutritional quality and to inform endusers which variety to choose for maximum benefit. Results indicated a significant difference (p<0.05) in oil content among the varieties. Oil content ranged from 33.60 to 54.95%. Mean oil content of the subspecies hypogaea (49.7%) was higher than in subspecies fastigiata (47.3%). The major fatty acids were oleic and linoleic which accounted for 77.89% of the total fatty acids. The subspecies hypogaea had significantly higher (p<0.01) content of oleic acid (55.9%) than the subspecies fastigiata (43.3%). The sum of three fatty acids oleic, linoleic and palmitic acid constitute 89.35% of the total fatty acids of the seeds. The mean O/L ratio ranged from 1.14 to 3.66; the mean for subspecies hypogaea was 2.59 as compared to 1.28 for subspecies fastigiata. There was high correlation between oleic and O/L acid ratio (r2=0.983) and negative correlation between oleic acid and linoleic acid (r2=-0.996). The iodine value ranged from 85.77 to 98.43% and total soluble sugars from 9.20 to 13.30%. Protein of defatted portion ranged from 39.65 to 53.45%. Subspecies fastigiata had higher mean protein content than subspecies hypogaea. Generally, there were significant variations in the parameters measured in the groundnut varieties. Five varieties with O/L ratio more than 2.0 were identified and their oils would be further tested for their stability.

Keywords: Groundnut, oil, oleic, linoleic, protein

AJFAND Vol. 8 (2) 2008 pp. 134-150