Enzyme-sensitive soybean protein isolate/cinnamaldehyde antibacterial microcapsules triggered by blueberry proteases

Abstract

In this study, enzyme-sensitive microcapsules using soybean protein isolate as the wall material, and cinnamaldehyde as an antimicrobial core material, were prepared by vacuum freeze-drying. The results showed that a 4% solution of soybean protein isolate with cinnamaldehyde added at a 4:1 (w/w) ratio provided an effective microcapsule formulation, with an embedding rate of 62.63 ± 0.95% and a particle size of 347.00 ± 31.18 nm. After lyze-drying, SPI-CA microcapsules showed uneven morphology, sag and agglomeration, but the microcapsules had small particle size and good dispersion stability. The 4%SPI/CA-4:1 microcapsules provided protection for cinnamaldehyde for 12 days. The release of cinnamaldehyde was slow from the 6th day, and the cumulative release was 79.08 ± 3.0% after 12 days. In addition, infrared spectroscopy, XRD and DSC prove that the hydration of soybean protein isolate, electrostatic repulsion charges, and the creation of cinnamaldehyde essential oil nanodroplets resulted in stable microcapsules. The microcapsules produced were successful in providing the controlled release of its antibacterial substance when exposed to natural protease concentrations triggered by fungal growth on blueberries. The release of cinnamaldehyde from SPia-Ca microcapsules was triggered by protease, which was secreted from blueberry by microbial contamination. The developed microcapsule has wide applications, and the results of this study provide new ideas for future food preservation technology development.