75 Evaluating the in vitro release of essential oils from microparticles in simulated swine gastric and intestinal fluids and the essential oil stability in microparticles during feed pelleting process

Abstract

Abstract Essential oils are defined as plant-derived natural bioactive compounds with positive effects on animal growth and health due to their antimicrobial and antioxidative properties. However, essential oils are very volatile, can evaporate rapidly and be rapidly absorbed in the upper gastrointestinal tract. In addition, due to their labile nature, the stability of essential oils during feed processing is often questionable, leading to variable final concentrations in feeds. Micro-encapsulation has become one of the most popular methods to deliver essential oils into the lower gut. The objective of the present study was double: 1) to validate and demonstrate the slow release of essential oils, such as thymol, micro-encapsulated in combination with organic acids in a matrix of triglycerides, in simulated swine gastric and intestinal fluids and 2) to evaluate the essential oil stability in the microparticles during feed pelleting process. In the in vitro release experiments, the microparticles were incubated in simulated gastric fluids for 2 hours and then the samples were incubated in simulated intestinal fluids for 0, 1, 2, 3, 4, 6, 8, 10, and 24 hours at 39°C. In the pelleting experiment, a wheat-corn basal diet with 2 kg of micro-encapsulated product was formulated and pelleted. The thymol content in the samples was analyzed by gas chromatography with flame-ionization detection. The results showed that 27.65% thymol was released in simulated gastric fluids and the rest of thymol was progressively released in intestinal fluids until completion, which was achieved by 24 hours. The thymol concentration was not significantly different between the mash feeds and pelleted feeds (P > 0.05). In conclusion, the micro-encapsulated organic acid and essential oil product was able to maintain the stability of thymol under a commercial pelleting process and allow a slow and progressive release of its active ingredients as thymol in simulated digestive fluids.