SOLID LIPID MICROPARTICLES LOADED WITH ASCORBIC ACID: STABILITY BY THERMAL CYCLIZATION

Ascorbic acid (AA) is an essential nutrient used in food industries as antioxidant. It presents some limitations, such as oxidative and reactive features, that can be minimized using the microencapsulation technology. The aim of this work was to study the stability by thermal cyclization of solid lipid microparticles (SLMs) loaded with AA. SLMs were prepared by spray chilling technique and were composed of fully hydrogenated palm oil (FHPO) and palm oil (PO) as wall materials. The proportions of FHPO:PO were varied in different formulations: F1 (80:20), F2 (70:30) and F3 (60:40), respectively. The ratio of wall material and AA was set at 80:20 (w/w). In order to study the stability by thermal cyclization, SLMs were submitted to storage in stress condition at two alternating temperatures (30 and 45°C) for 48h each. The particles were characterized by thermal behavior using DSC, polymorphism, AA retention levels and AA retention kinetic modeling. The analyses were performed on days 0, 7, 15, 30 and 45 of storage. At the end of the 45th days, SLMs presented satisfactory AA retention values, equivalent to 76.39, 74.25 to 83.07%, respectively to F1, F2 and F3. These values were influenced by increases in the PO concentration in each formulation. The results indicate that all the SLMs had controlled release and followed the Higuchi kinetic model (R2= 0.9025, 0.9145 and 0.8950, respectively to F1, F2 and F3). The melting peaks remained stable throughout the storage period therefore there was no significant statistical difference (p≤0.05) among them. Polymorphic analysis revealed β and β' crystals. The β' crystals type was predominant in all the formulations studied. Thus, it is possible to conclude that AA was successfully encapsulated in the structure of the SLMs.