Membrane Technologies Applied to Cheese Milk
Antonio Trani, Pasqua Loizzo, Angela Cassone and Michele Faccia
Department of Soil, Plant and Food Sciences, University of Bari, Bari, Italy
The term membrane technology is used to indicate separation processes that are based on cross-flow filtration of a liquid throughout a semipermeable septum. The introduction of membrane technologies in the food sector at industrial level dates about 60 years, and started after the development of anisotropic membranes. The first application in the dairy industry was introduced in the early 1970s, and regarded treatment of acid whey by reverse osmosis. Successively, continuous evolution has occurred and brought a number of innovations that also regard milk (Cuperus and Smolders, 1991). Classically, these technologies are classified into four types, according to the pore size of the membranes: micro-, ultra- and nano-filtration (MF, UF, NF), and reverse osmosis (RO). The transport mechanisms of MF and UF are mainly dependent on convective phenomena, whereas diffusion is the basic mechanism of NF and RO (Pizzichini et al., 2009). MF membranes have the largest pore size, ranging from 0.1 to 20 p, and are used to separate particles with a molecular weight higher than 200,000 Da, at low-pressure conditions (<2 bar). UF selectively separates macromolecules within the molecular weight range of 1,000 to 200,000 Da, at moderate pressure (1-10 bar). NF is a particular form or reverse osmosis in which the pore size has increased to about 200 Da, and is classically used to separate sugars, whereas only water and some ionized minerals can pass the RO membranes. The operating pressure of NF and RO is significantly higher than UF, and can also reach 80 bar in RO.
Milk can be successfully fractionated by these membranes since constituents have a broad size distribution (from > 10 p to < 1 nm): a scheme is given in Figure 2.1.З.1.
Currently, membrane treatments in the dairy field can be found in a number of operations, applied both to milk and whey, ranging from concentration to debacterization and fractionation of groups of compounds. Furthermore, they can be used for other purposes such as recycling brines and processing waters, and physical sterilization of solutions to be used as governing liquid. This chapter only deals with applications to milk and whey in connection with the cheese-making process.
Advances in Dairy Products, First Edition.
Edited by Francesco Conto, Matteo A. Del Nobile, Michele Faccia, Angelo V. Zambrini, and Amalia Conte.
© 2018 John Wiley & Sons Ltd. Published 2018 by John Wiley & Sons Ltd.
Figure 18.104.22.168 Passed and rejected milk constituents based on membrane pore size.