The influence of kosmotropic and chaotropic salts on the functional properties of Mucuna pruriens protein isolate

Abstract

The influence of chaotropic and kosmotropic salts on Mucuna pruriens protein isolates was investigated. Protein solubility profile indicated that solubility was minimal at the isoelectric point of the protein isolate (4.0) while the solubility was maximal at pH 10.0 in all salt solutions. Chaotropes (I −, ClO 4 − and SCN −) exhibit better protein solubility than the kosmotropes (SO 4 2−, Cl − and Br −). Increase in protein solubility follows the Hofmeister series: NaSO 4 < NaCl < NaBr < NaI < NaClO 4 < NaSCN. Maximal water absorption capacity was recorded at low concentration of all the salts (0.1 M). The water absorption capacity reduced as the concentration of the salts was increased to 2.0 M. Kosmotropic salts exhibited better water absorption capacity than chaotropic salts. Both foaming capacity and stability were better in chaotropic salts compared with kosmotopic salts. Maximal foam capacities and stability were observed in protein solutions at 0.1 M concentration. However the foam capacity and stability decreased as the concentration was increased further to 2.0 M. The result indicates that emulsion activity index (EAI) and emulsion stability index (ESI) was reduced as the concentration of salts in each protein solution was increased. Protein solutions which contained NaSCN exhibited the highest emulsifying properties while those in Na 2SO 4 recorded the lowest emulsifying properties. In addition, chaotropic salts had better emulsifying properties compared with kosmotropic salts. Increase in emulsifying activity follows the Hofmeister series. The least gelation concentration increased as the concentration of the salts increased. However chaotropic salts exhibited better gelation properties than kosmotropic salts.