Liposomes as vehicles for vitamins E and C: An alternative to fortify orange juice and offer vitamin C protection after heat treatment

Soy phosphatidylcholine-based liposomes were studied as vitamin transporters to be incorporated in orange juice, which is later subjected to pasteurization. These systems allowed the incorporation of vitamins E and C. Stearic acid and calcium stearate were incorporated into liposomes as an alternative to lipid bilayer stabilizers. Calcium ions and essential fatty acids are contained in calcium stearate and soy phosphatidylcholine, respectively, conferring extra nutritional value. Liposomes prepared by the dehydration-rehydration method were tested in a food model system to avoid interference caused by orange juice components. The oxidative stability was analyzed by the thiobarbituric acid method before and after the pasteurization process. Size was analyzed by light scattering also before and after pasteurization, and shape was analyzed by transmission electron microscopy. Percentage encapsulation efficiency (EE%) of vitamins C and E was determined by a centrifugation process. Also. EE% of vitamin C was measured against dialysis for 72 h. Liposomes had a protective effect on antioxidant activity of vitamins before and after pasteurization; even considering that vitamin C is thermolabile. Besides, EE% by centrifugation showed a high encapsulation of vitamins E and C. And the results of dialysis of vitamin C, demonstrated that it was retained by all the systems. Formulations that included stearic acid were the most efficient encapsulating with a 38%. The results showed a relationship between oxidative stability and aggregation, along with changes in size and morphology: peroxidation increases with aggregation. Addition of stearic acid favors oxidative stability and EE% due to a bilayer stabilizing effect. It is important to note that the combination of liposomal formulations and vitamins with orange juice did not change its organoleptic characteristics, and showed microbiological stability after pasteurization and storage at 4 degrees C for 37 days. (C) 2011 Elsevier Ltd. All rights reserved.