In order to quantitatively estimate the effects of membrane fouling and osmotic pressure on the performance of membrane separation systems, a concentration polarization equation and a membrane transport equation based on nonequilibrium thermodynamics were applied to membrane processes for liquid foods, and new mathematical models were proposed. These models were then applied to several membrane processes in the food industry, including an ultrafiltration process for cheese whey fractionation, a reverse osmosis process for fruit juice concentration, and a nanofiltration process for oligosaccharide purification. The efficiency of the membrane processes could be precisely expressed by the new models, and the validity of the models was demonstrated. Thus, some membrane processes in the food industry can be optimized by using these models, and their feasibility evaluation is described.
