Inhibitory effect of thymol via different modes of delivery on growth of Escherichia coli DH5α

Although thymol is a natural antimicrobial with broad-range activities, it is not suitable to be added directly into the food formulation (a delivery mode known as instant addition), due to its strong aroma and high concentration requirement for microbial inhibition. Recent studies have shown that lower concentrations can achieve the same inhibitory effect as instant addition if antimicrobials are added in a time-release manner. However, the effect of combined mode (i.e., instant addition plus time release) has not been studied. The objective of this work is to compare the effects of thymol via three delivery modes (instant addition, time release, and combined mode) on microbial inhibition of Escherichia coli DH5α. The results showed that via time-release and combined mode, the minimum inhibitory concentrations of thymol were lowered by 25% and 50% respectively, as compared to instant addition. Implications of the results for the design of controlled release packaging are discussed.