Optimization of Hexametaphosphate‐Assisted Extraction of Flaxseed Proteins Using Response Surface Methodology

Total proteins of defatted low‐mucilage flaxseed meals were isolated by extraction with aqueous sodium hexametaphosphate (SHMP). A composite central rotatable design was used to study effects of pH (X 1 ), meal‐to‐solvent ratio (X 2 ) and concentration of SHMP (X 3 ) on nitrogen extractability (Y 1 ) and protein recovery (Y 2 ). Using RSM, quadratic polynomial equations were obtained for Y 1 and Y 2 by multiple regression analysis. All three variables significantly affected nitrogen solubility and protein extractability. The pH was the most effective factor and meal‐to‐solvent ratio was least. Verification experiments confirmed validity of predicted models. Stationary points for response surfaces were characterized as maxima and they were Y 1 =77.6% at X 1 = 8.90, X 2 = 1:33.6 and X 3 =2.75% and Y 2 =57.5% at X 1 =9.00, X 2 =1:33.3 and X 3 =2.85%, for nitrogen extractability and protein recovery, respectively.