Biochemical characterisation of the soluble proteins, protein isolates and hydrolysates from oil palm (Elaeis guineensis) kernel

Oil palm kernel proteins have been less well characterised than other seed proteins. Hence, this study characterised the extractable proteins, protein isolate and hydrolysates of defatted oil palm kernel meal to provide information regarding the biochemical properties of oil palm kernel proteins affected by two harvest seasons (2010 and 2011). The defatted oil palm kernel meal and the protein isolate contained 54.8% and 75.6% protein, respectively. The polypeptide molecular mass ranges of the defatted oil palm kernel meal, the protein isolate and the protein hydrolysates were 19–50, 15–50 and 7–12 kDa, respectively. The alkali-soluble glutelin fraction (60%) was the major soluble portion of the oil palm kernel meal, followed by albumin (25%) and globulin (5.7%). The oil palm kernel protein isolate and hydrolysates showed significantly better amino acid profiles than the extractable soluble fractions, meeting all the essential amino acid requirements for infants, preschool children, adolescents and adults. Threonine was not detected in the defatted oil palm kernel meal nor in any of the extractable fractions, while serine was the least abundant detectable amino acid in the protein isolate and hydrolysates. Both the protein isolate and the hydrolysates were rich in cysteine, methionine, valine and lysine. Globulin and albumin were most sensitive to seasonal variations in amino acid composition and protein content. In conclusion, oil palm kernel protein isolate and hydrolysates generated from the defatted oil palm kernel meal can potentially be utilised in the food and health-based industries due to their good amino acid compositions and high protein contents.