Evaluation of casein protein transport through surface functionized membranes using irreversible thermodynamics and concentration polarisation model

Abstract

Casein is an important protein in the raw milk and many approaches have been established to separate casein to make cheese. This study mainly deals with the analysis of casein protein (19 kDa, pI 4.6) transport characteristics through ultrafiltration (UF) membranes. Polysulfone (PS) based polymer membranes are used and modified with polyethylene imine (PEI), polydiallyl dimethyl ammonium chloride (PDDA) and polyacrylic acid (PAA). The fabricated membranes are characterized by contact angle and Fourier transforms infrared (FTIR) spectroscopy. The UF process was conducted with a dead-end filtration unit and the volumetric flux and transmission values are recorded and that varies with pressure and pH. The experimental results are explained using the concentration polarization and irreversible thermodynamics model. The characteristics of the transport of casein are determined from the values of the parameters such as the solute concentration near the surface of the membrane [Cm], the solute permeability [Pm], mass transfer coefficient [k], and the reflection coefficient [σ]. From the results, it is concluded that the casein transport through the UF membrane was controlled by convection with decrease in casein rejection. Although, this model predicts the transmission behavior as a function of flux and supports the experimental results for both membranes.