Cristalização em leito vibrado: uso de soro de queijo purificado na separação de lactose

Abstract

Crystallization is a unit operation widely used in the chemical and food industries for production of high purity compounds, even in presence of other substances in solution. The aim of this work was to study the operation of isothermal crystallization in den se phase, of alpha-lactose monohydrate in whey, a byproduct of the dairy industry. Initially, to obtain drivers initial parameters were performed a central composite design, using commercial lactose monohydrate for prepare the solutions and seeds, cylindrical-conical vibrated bed crystallizer and operating temperature of 50.0°C. This has enabled a study of significant variables in the operation, construction of prediction models, analysis of response surfaces and selection of an optimal operation point within the experimental range adopted and associated responses, which were the mass percentage increase and Sauter mean diameter. To evaluate the reduction in the average diameter of the crystallization products against seeds, obtained in the first planning, we propose a second, with similar process conditions, but with seeds produced by cooling to 7°C for 24 h, to remove the effect of microparticles adhered on the surface of commercial lactose crystals, which probably influencing the crystallization. The average size of the crystals in the process increased from 5.61 ± 0.050 × 10-6 m (seeds) to 8.06 ± 0.22 × 10-6 m, with average mass percentage increase of 119%. For operation with whey, an initial study was conducted to reduce the amount of fats and proteins. The coagulant used was of organic origin, based on tannin. Using a concentration of 2.0 × 10-3 L Tanfloc.L-1of whey, was obtained a removal of 40.3% of protein and 90% fat. The crystallization of lactose using cheese whey concentrated and purified was performed under similar conditions to the optimization performed in the central composite design with seeds obtained by cooling. The responses indicated growth of seeds added, even in the presence of interferents and possible crystallization inhibitors. The growth rate was also evaluated for the step. Using concentrated and purified whey cheese too, was performed a analysis in situ of crystallization operation, with evaluation of population and crystal habit during the procedure, in conventional agitation and vibration units, where it was found interfering action from the beginning of the crystallization step and intense effect of secondary nucleation in high degrees of agitation, especially in a conventional unit.