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A combined membrane process has been used to fractionate skim milk. Microfiltration and ultrafiltration were employed to obtain concentrates with different protein/lactose ratios depending on the volume concentration ratio to produce protein enriched yoghurt. Nanofiltration has been used for lactose recovery from the ultrafiltration permeate with partial demineralization, while the permeate water of NF can be reused or recycled. Feed, permeate, concentrates and yoghurt have been physicochemical characterized and compared with commercial products. The obtained yoghurts have a smooth aroma and an agreeable taste, the protein content increased up to 50 % and the lactose content decreased approximately 50 % in comparison with commercial yoghurts, while calcium and iron were also increased, leading to a product with special characteristics and high commercial value. Lactose powder has been obtained by lyophilization; the product has good solubility and has 90% purity which can be used in different food preparations or for other applications.

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The purpose of this study was to evaluate the use of ultrafiltration and discontinuous diafiltration (DD) to obtain a protein concentrate from Atriplex lampa saltbush, improving its palatability by decreasing the salt content (mainly sodium and potassium chloride). The experimental work was done using a Pellicon  cassette (25 units) system equipped with polyethersulfone organic membranes with a molecular weight cut-off value of 10 kD. The characteristic of the membranes and the feed material, the parameters and operational conditions were studied in the pretreatment of the sample as well as in the ultrafiltration process to obtain a maximum performance. The product obtained contained 85% protein on aa dry weight basis and a marked decrease in salt content, from 40% in fresh leaves to 2.5% after processing by DD, which is in agreement with the average conductivity values observed, from 18.1 mS cm −1 in the initial aqueous alkaline extract to a final value of 3.5 mS cm −1 . Measurements of normalized water permeability were determined after each wash cycle in order to verify the flow recovery through the membrane. Analysis of amino acids from the protein concentrate with a chemical score of 85.13 was calculated using a Food Agricultural Organization reference pattern (sulfur amino acids as limiting amino acids). Nitrogen retention was evaluated by means of a biological test and the following values were obtained: net protein utilization = 63.00 ± 4.00, true digestibility = 79.00 ± 5.21, and biological value = 79.80. The presence of oxalic acid, nitrates, saponins, phenolic compounds and condensate tannins is not significant. The results indicate that the concentrate obtained has a high content of lysine, making these products particularly useful as a complement for cereal flour, which is deficient in this amino acid. The determined values suggest that the product can be used in balanced animal feed formulation.

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