Pressure Driven Membrane Technology for Food and Biotechnology Industry

The increase in energy costs and the demands for products with greater nutritional value and of processing procedures less toxic to the environment are attractive factors for transferring membrane processing to food industry and biotechnology applications. Sugar production is one of the most energy-intensive applications in the food industry, therefore membrane separation processes find many applications, nevertheless some limitation exist for application of membrane processes in the sugar industry. This study focused on Food applications of membrane processes. A critical summary of a wide experimental investigation is reported. In this work, separation performances of commercial polyamide NF membranes are investigated in a wide range of compositions in the feed side at temperatures from 30 to 50°C; aqueous solutions containing monosaccharides, disaccharides, and mixtures of them are studied, and the role of the electrolytes on their rejection is investigated. All the results obtained, have been organized in three main sections: (i) Hydraulic permeability, (ii) experimental investigation as it is, and (iii) Intrinsic membrane performances. Differently from literature, where typically aqueous solutions containing monosaccharides and oligosaccharides are used at low concentrations, at room temperature and only experimental data as it is are reported, a key point of this study is the critical evaluation based on intrinsic membrane performances. The data processing discussed allows to introduce a revised Donnan Steric Pore & Dielectric Exclusion model. The revised model provides useful elements to understand which kind of interactions (complex formation or dehydration) can affect sugars rejections in presence of strong electrolytes, however dehydration effects caused by temperature and electrolyte are the most evident. The revised model is able to predict with good confidence both the temperature effect on membrane performances and rejections in multicomponent mixtures, ranging from laboratory to process/industrial scale.