Improvement of a sustainable hybrid technology for caseins isoelectric precipitation (electrodialysis with bipolar membrane/ultrafiltration) by mitigation of scaling on cation-exchange membrane

Abstract

Abstract Electroacidification of milk by electrodialysis with bipolar membranes (EDBM) can be performed to produce isoelectric precipitated casein. In spite of advantages of EDBM, a problem of fouling hampers the industrial application of this technology. There are two types of fouling occurring during milk electroacidification such as protein fouling inside the EDBM stack and scaling on cation-exchange membrane (CEM). Recent studies demonstrated that protein fouling can be avoided by coupling an EDBM module with an ultrafiltration (UF) module. The present study aims the mitigation of scaling on the CEM. In order to attain this goal, two approaches were tested: 1) addition of KCl in the milk reservoir and 2) use of a UF membrane allowing higher permeate flux and consequently higher flow rates of solutions in the EDBM stack. Results of this study demonstrate the reasonableness of both approaches resulting in the significant decrease of CEM scaling (more than 30%). Industrial Relevance Caseins are the major milk proteins largely produced in the world (around 330 000 t per year) and widely applied in the food and pharmaceuticals industries. There are several relevant features of proposed method (electrodialysis with bipolar membranes coupled with ultrafiltration (EDBM-UF)) for the casein production such as 1) absence of the hazardous reagents; 2) high purity of caseins due to the demineralization during EDBM; 3) no waste generation; 4) the base stream from EDBM module (co-product) can be used for the formation of caseinates. The present work demonstrates the significant decrease of scaling on the cation-exchange membrane (more than 30%), which is the major problem of the EDBM-UF process. Indeed, during milk acidification, there is a liberation of minerals (Ca 2 + and Mg 2 + ), which form the membrane deposit. This deposit negatively affects the process performance and leads to the membrane replacement. The cost of ion-exchange membranes in ED module comprises a major part of the total cost of EDBM-UF process. Thus, control and prevention of the membrane deposit will allow to increase a lifetime of ion-exchange membranes and to decrease a price of EDBM-UF treatment.