Aplicação de processos com membranas no tratamento do resíduo da desodorização do óleo de soja para a recuperação de compostos bioativos

Abstract

In soybean oil refining, most bioactive compounds are concentrated in intermediate by-products and waste streams. In particular, deodorized soybean oil distillate (DDOS), obtained during the oil deodorization stage, is a rich source of commercially valuable substances, including fatty acids, phytosterols, tocopherols, squalene and glycerides. Squalene is a hydrocarbon with diverse applications, including in the preparation of cosmetics, as it is moisturizing and antioxidant, and in the biosynthesis of cholesterol. Originally, it was obtained for commercial purposes, mainly from the liver oil of some deep-water sharks. However, due to environmental concerns, including the protection of marine life, the extraction of squalene from plant sources is of great interest. In this context, this work aims to recover and concentrate bioactive compounds from DDOS, specifically squalene, using the polymer membrane filtration process. Initially, the DDOS was characterized in terms of density, acidity index, saponification index and amount of soaps. Microfiltration tests were then carried out with a 0.22 µm polystersulfone polymer membrane (PES), characterized in terms of hydraulic permeability, in a bench-scale frontal filtration module. In the first stage, the influence of saponification as a pre-treatment was evaluated, using different concentrations of KOH (0, 10 and 20%) at two operating pressures (0.5 and 1.0 bar). In the second stage, a combined centrifugation and microfiltration process was used, using the best concentration of KOH (20%), at the same operating pressures mentioned above. The performance of the process was evaluated in terms of permeate flow, selectivity of the membrane in relation to squalane and removal of the amount of soaps. From the results, it was observed that for the same concentration of KOH in the pre-treatment, increasing the pressure caused a reduction in retention, indicating the permeation of undesirable compounds through the membrane. On the other hand, for the same pressure, increasing the concentration of KOH led to an increase in the concentration of squalane in the permeate, probably due to the greater production of saponifiable materials which favor the formation of a phase that is retained by the membrane, leading to the concentration of unsaponifiables, such as squalane, in the permeate. The results obtained showed that the membrane used is selective to squalane and, in the best condition used (20% KOH and 1.0 bar pressure with a combined centrifugation process), there was a concentration of the compound in the permeate of 174.03 mg 100 g sample-1, which is thirteen times higher than in the concentrate. It was also observed that centrifugation was efficient in removing soaps, reducing their concentration in the centrifuged phase that was fed into the membrane. In the fouling evaluation, a 59.8% reduction in water flow through the membrane was observed after the cleaning cycle applied, indicating that fouling had occurred. The results indicate the potential for using membrane processes as an alternative for obtaining squalene, combining separation processes such as centrifugation for greater process efficiency.