SUMMARY. Casein phosphopeptides (CPP) were produced by tryptic hydrolysis of sodium caseinate and further purified by precipitation and chromatography on QAE-Sephadex A-25. Their physico-chemical properties were compared with the properties of an enzymically dephosphorylated equivalent preparation (DPP). Binding of Ca 2+ to the peptides was measured using a Ca selective electrode and was found to increase with pH and to show 1/1 stoicheiometry Ca/P org in CPP at pH 6 -5 a.nd 7-6. Klotz plots indicated equivalent binding sites at these two pH values, but some heterogeneity was seen at pH 3-5. In contrast, DPP did not bind significant amounts of Ca 2+ . CPP effectively inhibited the formation of insoluble calcium phosphates at different Ca/P ratios. The effective CPP concentration was 10 mg/1 and complete stability of calcium phosphate solutions was obtained at about 100 mg/1. This stabilizing effect was dependent on the presence of organic P.

SUMMARY. Tryptic phosphopeptides were obtained from whole bovine casein by chromatography on the anion exchange resin QAE-Sephadex A 25. Salt gradient clution of the column allowed separation of non-phosphorylated peptidcs from phosphorylated species. The preparations obtained contained at least seven distinct phosphopeptides of which the following casein fragments were identified: a sl (43-58):2P, a sl (59-79): 5P, a s2 (46-70): 4P, /?(1-28):4P, /?(2-28):4P, and /?(33-48): IP. Fast protein liquid chromatography (FPLC) on Mono Q HR 5/5 resin showed that the phosphopeptides were eluted in the same order as from the QAESephadex resin. However, on the analytical column HR 5/5 the fragments a sl (59-79): 5P and /?(2-28): 4P, having the same net charge under the conditions of chromatography, co-eluted, whereas they were at least partly separated on the preparative column HR 16/10. Following enzymic dephosphorylation, the peptides eluted at lower salt strength in the gradient. FPLC on Mono Q resin thus permitted dephosphorylation to be monitored and intermediates between the parent species and the fully dephosphorylated peptide to be identified.

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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