Stability of Citral Sustained-release Preparation and Its Inhibitory Effect on Aspergillus flavus

To provide data support for the development of green, efficient and safe sustained-release bacteriostatic agent of citral, the stability of the two kinds of sustained-release preparation of citral liposome (CL) and citral liposome-chitosan (CL-CS) and the bacteriostatic effect and mechanism of Aspergillus flavus were investigated. Under the condition of different temperature and pH, the appearance, particle size, Zeta potential and retention rate were studied to explore the storage stability. The instantaneous bacteriostasis rate and long-term bacteriostasis rate of citral sustained-release were determined by spore counting method. The bacteriostatic mechanism of citral sustained-release preparations was revealed according to the changes of cell permeability. The results showed that the two citral sustained-release preparations had uniform nano-sized particle sizes. After chitosan modification, the Zeta potential of the system changed from −16.63±1.67 to 35.72±3.29. After 28 days of storage at 4 ℃, the change of particle size and Zeta potential was small, and the retention rate was higher, CL-CS was more stable than CL. At pH4~6, the two sustained-release preparations were more stable, and the particle sizes of CL and CL-CS were about 150 and 200 nm. The instantaneous inhibitory EC50 of CL and CL-CS against Aspergillus flavus within 48 h were 77.88 and 68.20 mg·L−1, respectively. After 48 h of culture, the inhibitory rates of CL and CL-CS were 67.69% and 82.89%, respectively, while citral was only 30.26%. The results showed that CL-CS had good bacteriostatic effect and long-term bacteriostatic effect. The extracellular conductivity and nucleic acid content of Aspergillus flavus both increased after treatment with the two kinds of sustained release preparations, indicating that the permeability of cell membrane increased and the action time was shorter than that of free citral. In conclusion, the two kinds of sustained-release preparations have good stability. They inhibited the growth of Aspergillus flavus by the change of cell permeability and the leak of insoluble substance. The properties of CL-CS was better than CL, and it would have the potential to be developed as plant source mildew inhibitor.