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The goal of this work was to select the best combination of encapsulants for the microencapsulation of oregano essential oil by spray dryer with the addition of Arabic gum (AG), modified starch (MS) and maltodextrin (MA). The simplex-centroid method was used to obtain an optimal objective function with three variables. Analytical methods for carvacrol quantification, water activity, moisture content, wettability, solubility, encapsulation efficiency (ME) and oil retention (RT) were used to evaluate the best combination of encapsulants. The use of AG as a single wall material increased ME up to 93%. Carvacrol is the major phenolic compound existent in the oregano essential oil. Carvacrol exhibits a maximum concentration of 57.8% in the microparticle with the use of 62.5% AG and 37.5% MA. A greater RT (77.39%) was obtained when 74.5% AG; MS 12.7% and 12.7% MA were applied, and ME (93%) was improved with 100% of gum.

Many studies on the cinnamon essential oil has attracted the attention of researchers because of their antimicrobial and antifungal properties. The objective of this study was to evaluate the influence of different wall material on the physicochemical characteristics of microencapsulated cinnamon essential oil. Microcapsules produced with combinations of wall materials (gum arabic, whey protein isolate and maltodextrin) were evaluated with regard to moisture, solubility, hygroscopicity, bulk density, tapped bulk density and microscopic analysis. The encapsulation efficiency was based on cinnamaldehyde retention in relation to the content of the pure oil. The results showed that blends of gum arabic and maltodextrin obtained better retention of cinnamaldehyde (50%). The presence of maltodextrin together with whey protein isolate favored the formation of more spherical particles. Transmission electron microscopy images clearly showed the oil dispersed in the wall materials. Thermogravimetric curves showed higher thermal stability for microcapsules with whey protein isolated. Based on the physicochemical characteristics analyzed, the best wall material for the process of microencapsulation essential oils of cinnamon was the combination of gum arabic and maltodextrin. PRACTICAL APPLICATIONSThis paper aims to add knowledge about the microencapsulation process of essential oils, promoting greater stability to oils.

Summary Response surface methodology (RSM) was employed to investigate variations in powder characteristics with respect to spray drying operating parameters including both feed rates (L min−1) and inlet temperatures (°C). Inlet temperatures around 180 °C provided the lowest values for moisture. Powder recovery was significantly affected (P < 0.10) by inlet air temperature and feed rate, where a raise in inlet temperature and feed rate resulted in higher powder recovery. No significant difference (P > 0.05) was observed for water activity, solubility and hygroscopicity between treatments. Regarding oil retention, the results showed a significant (P < 0.05) interaction between the two studied factors. A tendency for higher values of oil retention was observed when using combinations of high inlet temperatures/low feed rates and low inlet temperatures/high feed rates. Particle size distribution averaged 2.0, 8.1 and 18.3 μm for D10, D50 and D90, respectively. The morphology of particles showed no cracks in most capsules. The results indicate that high temperature (185 °C) and moderated feed rate (0.63 L min−1) are the best spray drying conditions.

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