Physical and Thermal Properties of Oregano (Origanum vulgare L.) Essential Oil Microparticles

• Published in: Journal of food process engineering Vol. 38; no. 1; pp. 1 - 10
• Main Authors: Toledo Hijo, Ariel Antonio Campos, da Costa, Joyce Maria Gomes, Silva, Eric Keven, Azevedo, Viviane Machado, Yoshida, Maria Irene, Borges, Soraia Vilela
• Format: Magazine Article
• Language: English
• Published: Blackwell Publishing Ltd 01-02-2015
• Subjects: Differential scanning calorimetry; Hygroscopicity; Microparticles; Moisture content; Oregano; Origanum; Sorption; Spray drying; Thermal properties
• ISSN: 0145-8876; 1745-4530
• DOI: 10.1111/jfpe.12120

In this study, the physical and thermal properties of essential oil microparticles of oregano (Origanum vulgare L.) dried via spray drying were examined. The product was characterized by morphology, mean diameter, particle size distribution, moisture sorption curve, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The process promoted the formation of spherical capsules with high polydispersity. The isotherm exhibited type II behavior (sigmoidal curve), and the best fit was obtained by the Guggenheim–Anderson–de Boer (GAB) model (E = 6.748%). The DSC analysis showed that the increase equilibrium moisture content reduced the Tg value of the microparticles (164.47–91.29C). The samples stored at low humidity resulted in more thermally stable particles, and the samples with equilibrium moisture content of 4.74% showed higher thermal stability.
Practical Applications
The applications of essential oils with relevant antioxidant activities, such as oregano essential oil, as a food additive is limited in the conventional form, due to their fast degradation triggered by temperature, light, presence of oxygen and humidity, among others. The encapsulation technique by spray drying has been successfully used to overcome this drawback. However, the spray‐dried products may present some technological problems, such as high hygroscopicity and low resistance when subjected to high temperatures. The evaluation of microparticle stability is a relevant and important issue when desiring to ensure their quality and application. Studies of the functional properties such as hygroscopicity, sorption behavior and thermal resistance determine the ideal conditions for the storage of this type of product.