Remoção do colesterol e fracionamento do oleo de manteiga com dioxido de carbono supercritico




Growing consumer search for low fat food has led to an increased demand for skim milk and subsequent surplus of butter, a by-product in skim milk production. At the same time butter has been loosing markets for low cholesterol, low fat products such as margerine. One way to solve this problem is form new products from milk fat. With the fractionation of the butter oil , it is possible to produce milk fat with unique and specific physical and chemical properties. These fraction can be used to manufacture a more spready butter at the refrigerator temperature or more stable butter at room temperature for the bakery industry. Cholesterol removal makes these products still more atractive to consumers. The objective of this thesis is to obtain information that permit the understanding and evaluation of the potential of supercritical extraction as a viable technology for the removal of cholesterol and fractionation of triglycerides in butter oil. In this work, we report on the solubilities of cholesterol and butter oil in supercritical ?CO IND. 2? and the selectivities of cholesterol in relation to triglycerides in butter oil, at 40, 55 and 70°C, and pressures ranging from 100 to 360 bar. The solubility data was obtained using an experimental apparatus for extraction at high pressures that permits the independent control of temperature and pressure. The compositions of cholesterol and triglycerides in the fraction collected with varying accumulated ?CO IND.2? volume were also determined. Due to the low selectivity of cholesterol in relation to triglycerides in butter oil with the simple extraction using supercritical ?CO IND.2?, an adsorption stage utilizing alumina was coupled to this process. With this combined supercritical extraction / adsorption on alumina process it was possible to simultaneously fractionate the butter oil and remove 97% of the cholesterol. The adsorption process with alumina did not cause alteration in the compositions of triglycerides in the fraction obtained. Finely, a thermodynamic model that describes the phase equilibria involved in the fractionation of the butter oil was developed. To apply this model, a procedure that represents the more than 1300 triglycerides of the butter oil, by only 14 families, with properties estirnated using experimental data and correlations available in the literature, was implemented. The thermodynamic model employed the Peng-Robinson volumetric equation of state. Using this model, it was possible to correlate literature data for triglyceride composition in the supercritical phase tha is in equilibrium with the liquid phase of the system butter oil ?CO IND.2. The adjusted model was subsequently used to predict the mole fraction of triglycerides in the oil fraction extracted with experiments realized in this work. With the exception of triglycerides of higher molecular weigh, the model predicts the mole fraction of the triglycerides in the supercritical phase in a satisfactory manner. It is hoped that this work may contribute to the development of large scale processes for the removal of cholesterol and fractionation of butter oil with supercritical fIuids


termodinamica colesterol gordura do leite