Trim size: 170mm x 244mm Datta c01.tex V3 - 04/02/2015 1:55 P.M. Page 1 1 Crossflow Microfiltration in the Dairy Industry Peggy M. Tomasula and Laetitia M. Bonnaillie Dairy and Functional Foods Research Unit, United States Department of Agriculture/Agricultural Research Service/Eastern Regional Research Center, USA 1.1 Introduction 1.1.1 Membrane Types Since their introduction in the 1960s, pressure driven, crossfow or tangential fltration membrane technologies have become important in the food processing industries. The dairy industry currently uses crossfow membrane technologies for applications such as fractionation of the casein and whey proteins, whey protein concentration, demineralization of whey, removal of somatic cells and bacteria from milk, and milk concentration to save transport costs (Pouliot, 2008; Gésan-Guiziou, 2010). Mem- branes are also used alone or with the evaporation step in the manufacture of milk powders, and are increasingly being used in the development of new dairy-based bev- erages, fermented milk beverages and yogurt products. They are also fnding a place in clean-in-place (CIP) processes to recover cleaning agents or to recover water used in processing (Alvarez et al., 2007; Luo et al., 2012). Four types of membranes are used by the dairy industry: reverse osmosis (RO), nanofltration (NF), ultrafltration (UF) and microfltration (MF). The oper- ating parameters for crossfow fltration membranes are shown in Figure 1.1. The pressure-driven feed, with fow rate, Q F , fows through the membrane channel parallel to the surface of the membrane. The applied pressure, P F , must overcome the osmotic pressure, π F , of the feed solution (Cheryan, 1998). The crossfow velocity (CFV), the velocity of the feed as it fows parallel to the membrane through the channel, has a sweeping effect that minimizes build-up of the feed particles on the membrane surface. Some of the feed stream containing the smaller molecules fows through the walls of the membrane leaving as the permeate, with fow rate, Q P , and pressure P P .Q P is often reported as the permeate fux, J, defned as the volume of permeate per unit membrane surface area per time. P P has a gauge pressure reading of 0.0 if the stream Emerging Dairy Processing Technologies: Opportunities for the Dairy Industry, First Edition. Edited by Nivedita Datta and Peggy M. Tomasula. © 2015 John Wiley & Sons, Ltd. Published 2015 by John Wiley & Sons, Ltd. COPYRIGHTED MATERIAL