Fatty acid, amino acid composition and effects of soaking temperatures on physicochemical qualities of Hibiscus cannabinus seed extract

Abstract

Kenaf is a multipurpose herbaceous plant of economic significance. This study analysed the effects of different soaking temperatures of kenaf seed on the physicochemical qualities of the extracts. Kenaf seed extracts were extracted separately from kenaf seed soaked at temperatures of 25, 35, 45, 55 and 65 ˚C at their respective optimum soaking time of 10.27, 7.00, 5.00, 3.50 and 2.67 h. The extraction yield, proximate composition, anti-nutritional factors, colour profile and thermal stability of the extracts obtained at the different soaking temperatures and time were analysed and compared. Also, the fatty acids and amino acids compositions of kenaf seed meal and the extract were determined and compared. The extraction yield of the extracts significantly increased as the soaking temperatures of the seed increase from 25-65 ˚C. The different soaking temperatures had no significant effects on the proximate composition of the extracts except for the ash content which decreased as the soaking temperature of the seed increases. However, the soaking temperatures significantly affected the colour profile of the extracts. Soaking of kenaf seed significantly reduced the trypsin inhibitor activity, tannic and phytic acid of the extracts. This study also found that both the kenaf seed oil and kenaf seed extract oil were rich source of hexadecenoic acid (26.71 and 26.11 %), 9-octadecenoic acid (33.80 and 40.41 %) and 9,12-octadecadienic acid (30.59 and 28.62 %), respectively. Additionally, the total essential amino acids of the kenaf seed (462.80 mg/g) and freeze-dried kenaf seed extract (487.44 mg/g) were not significantly different. Soaking of kenaf seed at 25, 45 and 65 ˚C and their respective optimum soaking time of 10.27, 5.00 and 2.67 h are recommended for the extraction of kenaf seed extract.