Purification of pectin from apple pomace juice by using sodium caseinate and characterisation of their binding by isothermal titration calorimetry

The binding of sodium caseinate to pectin using Isothermal Titration Calorimetry (ITC) under different pH values (2, 3, 3.5), and comparison of two purification processes (sodium caseinate or ethanol), based on the physicochemical characteristics of purified pectin was evaluated. The results indicated that ITC titration confirmed the existence of interactions between caseinates and pectin at pH 3 and 3.5. The interaction depicts two interdependent steps, one attributed to an electrostatic interaction and another related to a co-acervation mechanism. The chemical characteristics of pectins are strongly dependent on the purification process. Under some extraction conditions, ethanol is not specific to the recovery of pectin since it causes the precipitation of other compounds together with this polysaccharide. However, compared to the caseinate, it allows total precipitation of pectins extracted, but caseinates have the advantage of being more specific for the charged polymers.