Enhanced storage stability, controlled release, and antibacterial activity of cinnamaldehyde via nano-encapsulation in soy protein isolate and ε-polylysine hydrochloride

Cinnamaldehyde (CA), a plant-derived antioxidant and antibacterial agent, is limited in fruits and vegetables preservation due to its instability and volatility. To address these challenges, this study developed a soy protein isolate (SPI)/ε-polylysine hydrochloride (ε-PLH) composite nanocarrier for CA encapsulation. Systematic optimization identified ε-PLH and CA concentrations as pivotal factors. Under optimal conditions, the SPI/ε-PLH/CA nanocomplexes (SEC) achieved 78.91 % encapsulation efficiency, and 0.390 mg/mg protein loading. The interactions between CA and SPI involved hydrogen bonding and hydrophobic interactions, concurrent with the formation of Schiff bases. Additionally, electrostatic interactions between ε-PLH and SPI facilitated the formation of protective polyelectrolyte shells. Encapsulation improved CA stability, and the retention rates of CA within SEC was 1.80-fold and 1.73-fold higher than those of free CA after storage 30 d at 4 °C and 25 °C, respectively. Additionally, the nanocomplexes exhibited pH-responsive release properties, with a higher release constant ( k ) under acidic conditions (68.26) compared to neutral (53.54) and basic (53.00) buffers. Furthermore, the antibacterial activity of CA within SEC was 1.84 and 2.27 times greater than those of free CA against Escherichia coli and Bacillus cereus at pH 6.0 respectively. These findings provide an effective strategy for enhancing antibacterial performance of CA with pH-release properties. • A soy protein isolate/ε-polylysine hydrochloride core-shell nanocarrier was fabricated for encapsulating of cinnamaldehyde. • The nanocarrier significantly improved cinnamaldehyde's stability and enabled pH-responsive release. • The nanocarrier markedly enhanced cinnamaldehyde’s antimicrobial activity against Escherichia coli and Bacillus cereus .