Microencapsulation of Citrus limon essential oil by complex coacervation and release behavior of terpenic and derived volatile compounds

Abstract

Citrus limon essential oil (CEO) is used as food ingredient due to its pleasant aroma and characteristic taste, as well as beneficial health effects. In this study, it was hypothesized that complex coacervation can be used to develop microcapsules able to protect CEO from oxidation reactions while allowing to modulate the terpenic compounds release along digestion. For this, gelatin (G) and carrageenan (C), two oppositely charged polymers, were used to encapsulate CEO recovered from lemon peel by steam distillation. The higher encapsulation yield (93 %) and efficiency (95 %) were obtained when using 1.4 g G, 0.2 g C, and 0.6 mL CEO, defined by a Box-Behnken design and a response surface methodology. The microcapsules had low crystallinity and water activity (aw = 0.2), 0.3 % moisture, 9.9 % hygroscopicity, and 41.7 % water solubility at 20 °C. The G/C microencapsulation did not prevent the early release of monoterpenic compounds and the later release of the less volatile sesquiterpenic compounds. The pleasant aroma of CEO can be perceived 8 months after its microencapsulation. At different pH, approaching gastrointestinal conditions, a fast CEO release from the microcapsules at the first 25 min was observed, allowing to infer its bioavailability. Therefore, G/C microcapsules can safeguard essential oils composition, potentiating their exploitation as functional food ingredients.