Abstract: Ultrasonic technology was used to microencapsulate nisin in this study. Single-factor and orthogonal array experiments were carried out to optimize the process parameters based on encapsulation efficiency and particle size. The prepared microcapsules were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR). Subsequently, the microcapsules were applied to ready-to-eat mustard to extend its shelf-life. The results showed that the optimal process conditions were as follows: nisin-to-pectin mass ratio 1:1, ultrasonic power 800 W, and ultrasonication 20 min. Under these conditions, the encapsulation rate of the microcapsules was 76.23%, and the average particle size was 94.67 μm. Free nisin was firmly adsorbed onto the “eggshell” structure formed by pectin through hydrogen bonds, resulting in a three-dimensional reticular amorphous structure and forming a slow-release system. The application of microcapsules to ready-to-eat mustard greens effectively delayed acidification and significantly inhibited microbial growth (P < 0.05), extending the shelf-life from 5 to 12 days. These findings open up a new technological pathway for the microencapsulation of nisin and offer innovative insights for the storage of ready-to-eat mustard greens.

Key words: mustard greens; nisin; microencapsulation; ultrasonic technology; shelf-life