An empirical mathematical model of retentate composition in ultrafiltration of dairy products

Abstract

SUMMARY. Analysis of retentates of milk or whey, ultrafiltered and diafiltered by a pilot batch process with DDS Lab module equipment or (whey only) ultrafiltered by an industrial continuous process showed that nitrogen and ionic contents could not be described mathematically by the use of any value of the retention coefficient K. Analytical data suggested a new concept called segregation for nitrogen and ions in which each of these components consists of a completely permeable fraction and a totally retained fraction that do not exchange. A segregation coefficient Y is then defined as the ratio of the totally retained fraction to the total concentration of the species in the product fed to the equipment. However, this concept does not apply to lactose, where the classic retention concept (K) is retained. The two models are equivalent when K = Y = 0 or K = Y = 1. A first mathematical expression of this model was elaborated for batch ultrafiltration and/or constant volume diafiltration. Another set of equations was established for industrial conditions. These empirical models predict the retentate and permeate composition at any time during processing as well as after drying. The fit of analytical data with computed values was generally fair, with K being 01-0-4 in the pilot plant, and 0-1 in the factory. The nitrogen Y value was ~ 0-95 for milk, and 0-85 for whey. In whey, the calcium Y value varied greatly from 0 -06-0 -71 depending on the pH, citrate content and heat treatment; in milk it was fairly constant at 0-5 at pH 67-5 -8.Ultrafiltration (UF) and diafiltration (DF) of milk and/or whey yield retentates with various lactose: protein: ash ratios. It is of value to be able to monitor the process to a given composition of the retentate. This needs a model accommodating various raw materials, pretreatments and processing conditions.Mathematical descriptions of the behaviour of the individual components during UF and DF do exist, but they have usually been derived theoretically, or from small laboratory equipment, and do not apply satisfactorily to pilot or industrial processes. In addition, often they do not describe both UF and DF.The aim of this work was to establish an empirical model to describe the retentate composition during UF and DF of milk and whey, and to test this model under a variety of conditions. available at https:/www.cambridge.org/core/terms. https://doi

Production of Functional Whey Protein Concentrate by Monitoring the Process of Ultrafilteration

“…The increase in protein content and decrease in lactose and ash content during diafiltration could be attributed to the addition of water to the UF retentate, which aids in reducing the viscosity and, thereby more of lactose, minerals and low molecular weight compounds pass along with the permeate (Derham and Chanton, 1986;Vuillemand et.al., 1989). As the diafiltration aids in dilution of retentate, more and more of salts and lactose permeate through the membrane resulting in exponential increase in protein content.…”