Isolation and characterization of undenatured chlorogenic acid free sunflower (Helianthus annuus) proteins.

A method for obtaining sunflower protein (SFP) isolate, nondenatured and free of chlorogenic acid (CGA), has been developed. During the isolating procedure, the extent of CGA removal and protein denaturation was monitored. The defatted flour contained 2.5% CGA as the main phenolic compound. Phenolic compounds were removed by aqueous methanol (80%) extraction, before protein extraction at alkaline pH and diafiltration. Differential scanning calorimetry and solubility tests indicated that no denaturation of the proteins had occurred. The resulting protein products were biochemically characterized, and the presence of protein-CGA complexes was investigated. SFPs of the studied variety were found to be composed of two main protein fractions: 2S albumins and 11S globulins. In contrast to what has been previously reported, CGA was found to elute as free CGA, not covalently associated to any protein fraction.