The effect of surfactant on the isolation of protein products from chromium-containing solid tannery waste. Influence on the process and on the chemical, physical and functional properties of the resultant gelatin

Protein products can be isolated from chrome shavings using two processes t hat had been demonstrated to be economically attractive. Surfactant is used during the extraction of the protein products to avoid foam formation. Foa m would make the manipulation of the mixtures difficult, disturbing the sep aration of the protein products from the residual chrome cakes, and could i nactivate the enzyme. The influence of surfactant on the gelatin isolated f rom chrome shavings was studied. First, the need for surfactant during the extraction process in the one-step and the two-step processes was studied i n the laboratory. Then, the two-step process was carried out with and witho ut surfactant in pilot plant scale experiments to evaluate the foam formati on during the first step. The physical and chemical analyses of the gelatin extracted showed good repeatability of the process, with no significant di fferences between the gelatins isolated with and without the use of surfact ant. Finally, functional properties of the gelatin extracted in the pilot p lant experiments were determined and compared, to evaluate the influence of surfactant on each of them. These experiments showed that surfactant is no t always necessary, and it will depend on the equipment used when the proce ss is carried out industrially. The use of surfactant should be avoided whe n possible, and when used its influence on foaming and emulsification prope rties should be expected.