Microencapsulação de óleo essencial de limão (Citrus aurantifolia): emulsões e estudo das propriedades físicos-químicas

Abstract

Lime essential oil (Citrus aurantifolia) is a product widely used by the food, cosmetics and pharmaceutical industry due of its remarkable chemical and sensory properties. After extracted, the lime essential oil is very susceptible to degradations and volatilizations. Thus, it is necessary to promote processes to reduce undesirable reactions. The microencapsulation process is widely recommended and used to preserve bioactive compounds for long periods. The objective of this work is to study the microencapsulation process of lemon essential oil through the spray drying process, using several biopolymers as a wall material. In the first article we studied the stability of lemon essential oil emulsions added of Arabic Gum (AG) and Whey Protein isolate (WPI). It was proposed a purely randomized design, varying the concentration of essential oil (5, 7,5 and 10%) and the composition of the wall material (AG, WPI and AG / WPI). The emulsions were homogenized using assisted ultrasound (240W / 2min). PH, conductivity, zeta potential, droplet size, rheology (viscosity and shear stress), optical microscopy and cream index were evaluated. No phase separation was observed during the first 4 hours of storage. In all treatments there was no significant variation of pH and conductivity values. Higher zeta potential values were found for treatments with WPI and higher oil concentration due to the characteristics and functional groups present in the biopolymer and in the lime essential oil. All droplet sizes presented values lower than 2μm. It is concluded that the whey proteins had more stable emulsions, this wall material being the basis for the production of the microparticles of lemon essential oil. The second article shows the study of the physicochemical properties of lemon essential oil microparticles using whey protein concentrated (CWP) and maltodextrins of dextrose equivalent (DE) values of 5, 10 and 20. The emulsions were homogenized by of ultrasound-assisted with power of 240W, for 2 min. After homogenization, the emulsions were spray dried at 170øC, with emulsion feed flow of 0.7 L / hr. Rheology, optical microscopy and droplet size analyzes were performed for the emulsions; and major composition and antioxidant activity of crude and encapsulated oil, moisture, water activity, surface oil content, total oil content, encapsulation efficiency, oil retention, particle size, scanning electron microscopy and x-ray diffraction. Emulsions with maltodextrins of higher DE values presented lower viscosity. The degree of hydrolyzation of the maltodextrin chains increased the moisture and water activity of microparticles. Surface structure of the microparticles showed no cracking. DRX showed the amorphous structure of the microparticles, ideal for microencapsulation processes. DE 20 presented better results of efficiency and antioxidant activity. DE of maltodextrins may interfere with the physicochemical properties of microparticles of lemon essential oil. In summary, the biopolymers used may be an alternative for the production of emulsions and microparticles of lemon essential oil.