Response surface optimization of microcapsule preparation of tobacco (Nicotiana tabacum L.) extract

Tobacco extract has good insecticidal activity. In order to improve the stability of tobacco extract, microcapsules were prepared by complex coacervation with tobacco extract as the core material and gelatin and gum arabic as the wall material. The preparation method of microcapsules was optimized by the response surface method with the embedding rate as the evaluation index. The surface morphology, the particle size measurement, the infrared spectrum analysis, the thermal stability analysis and the indoor virulence determination of microcapsules were carried out. The results showed the highest embedding rate of 58.93% was obtained when the following conditions were used: emulsifier mass fraction 4%, gelatin mass fraction 2.05%, gum arabic mass fraction 3%, wall core mass ratio 1.34 : 1.00 and complex coacervation reaction time of 36 min. The actual embedding rate of microcapsules under these conditions was 58.42% ± 0.12%, which was close to the theoretical value. The microcapsules prepared by this model exhibted smooth surface, good capsule genicity with the particle size distribution of 4.72-17.05 μm and median diameter of 8.63 μm.Infrared characteristic peaks of tobacco extracts were preserved at 877.55 cm⁻¹ and 2 922.13 cm⁻¹. Microencapsulation can improve the thermal stability of tobacco extract. Indoor virulence test showed that the LC₅₀ value of tobacco extract microcapsules was 20.19 mg/mL, which was equivalent to the virulence level of the tobacco extract, indicating that microencapsulation didn’t reduce the insecticidal effect of tobacco extracts. To conclude, the present study can provide a reference for the optimization of tobacco extract microcapsules preparation process.