Low-molecular-weight proteins from sunflower (Helianthus annuus L.) seed: effect of acidic butanol treatment on the physicochemical properties

Abstract

Sunflower seed proteins are not fully utilized as a food because they interact with chlorogenic acid (CGA) leading to development of an unfavourable colour. Low mol. wt. (LMW) proteins tend to be more closely associated with CGA. Washing with acidic butanol removes CGA from LMW proteins, but may alter their physicochemical properties. Effect of acidic butanol treatment (ABT) on LMW proteins was studied. LMW proteins were isolated from butanol treated and untreated sunflower seed flour and their properties compared. Sedimentation coeff. (1.8 S) was not affected by ABT. Gel filtration on Sephadex G-75 revealed 4 protein peaks. ABT increased the proportion of the 2nd peak from 35 to 53%. Mol. wt. of the proteins was not affected by ABT, as demonstrated by SDS-PAGE. Secondary structures of the native and ABT samples were (%): 19 and 27 alpha-helix; 40 and 38 beta-structure; and 41 and 35 aperiodic, respectively. Fluorescence emission max. showed a red shift from 330 nm, indicating structural alterations in the proteins due to ABT.