(326a) Critical Length of Diffusion during Sequential Separation of Whey Proteins Using Radial Chromatography

The sequential separation of whey proteins is often effected by radial chromatography Two major categories of proteins are casein and whey proteins. Casein is a colloid and whey is soluble. In the cheese industry, two types of precipitation techniques are most commonly used to separate the total milk proteins separated into caseins and whey proteins, i.e., rennet precipitation and acid precipitation. The cheese industry produces large amounts of whey, much of which is used to make whey protein concentrate Commercial-scale fractionation of different whey proteins has been hampered by the lack of an economical fractionation technology. It would be desirable, therefore, to provide a method for the continuous and sequential separation of various proteins from whey in a simple one or two step separation process. Sepragen Corp. San Jose, CA, USA, provides a process for the sequential separation of at least five different proteins from whey and incorporating these separated whey proteins into pharmaceutical and food formulations. The process of the invention is directed to the continuous, sequential separation of whey proteins by chromatography, comprising adsorbing the proteins in liquid whey on a suitable separation medium packed in a chromatographic column and sequentially eluting immunoglobulin (e.g, IgG), .beta.-lactoglobulin (.beta.-Lg), .alpha.-lactalbumin (.alpha.-La), bovine serum albumin (BSA), and lactoferrin (L-Fe) fractions with buffers at suitable pH and ionic strength. Even though both axial and radial flow chromatography may be utilized, a horizontal flow column is particularly suitable. The liquid whey is selected from the group consisting of pasteurized sweet whey, pasteurized acid whey, non-pasteurized acid whey, and whey protein concentrate. The spatio-temporal concentration in the radial flow chromatographic column is discussed. The finite speed of diffusion was taken into account. The generalized Fick's law of diffusion was combined with the Navier Stokes equations for radial flow to obtain the governing equation. The governing equation was written in dimensionless variables. Peclect number (mass) was a important parameter. The solution was derived by solving for the governing equation analytically. The steady state and transient state solutions were obtained separately. The critical distance was calculated as

Rcrit > 1.916sqrt( Dtr/Pem)

The design of the radial flow chromatography column greater than the Rcrit will not result in any further separation. This is the critical length of diffusion.