Preparation of Protein Isolate from Neem Seed: Biochemical Evaluation, Antinutrients and In Vitro Digestibility Study

Neem protein isolate (NPI) was prepared from neem seed cake (NSC) resulting in five fold increase of crude protein content, amounting to 82%. The recovery of protein was highest (49%) when the NSC was solubilised at pH 12 for 2h and precipitated at pH 4. Crude fibre, nitrogen free extract and total ash contents were significantly (P<0.05) reduced substantially in the isolate compared to the NSC. The NPI has a balanced amino acid composition with high levels of methionine and arginine. A significant decrease of anti-nutritional factors such as oxalate (87.50%), phytic acid (70.50%), tannin (72.73%), cyanide (50.98%) and azadirachtin content (79.06%) was found in the isolate, implying that the isolation process was effective in the removal of toxic components. A significant (P<0.05) increase in the in vitro protein digestibility (90.4) was also obtained for the protein isolate, suggesting that the NPI as a promising feed ingredient.