Antimicrobial film based on poly(lactic acid) and natural halloysite nanotubes for controlled cinnamaldehyde release

Using nanocarriers to load antimicrobial agent instead of direct incorporating into film matrix could avoid burst release. Halloysite nanotubes (HNTs) are natural clays with a unique tubular structure; therefore in many studies it served as carriers to achieve a controlled release of active agents. However, when HNTs biocomposites were loaded into packaging film, the antimicrobial activity was reduced too seriously to preserve the packaged food. This study aimed to improving preservation properties of the fabricated films from two perspectives: enlarging the loading capacity of the carrier, and increasing the concentration of HNTs biocomposites. Brunauer, Emmett, Teller's test (BET) and thermogravimetric analysis (TGA) were conducted to evaluate the performance of acid treated nanocomposites. Results showed that acid treatment expanded the lumen of HNTs, increasing the loading capacity of cinnamaldehyde (Cin) from 14.6 wt% to 25.0 wt%. Active packaging films were then fabricated by incorporating Cin loaded HNTs into poly(lactic acid) matrix, and it revealed bionanocomposites at 30 wt% achieved the optimum film, considering the mechanical performance and controlled release of Cin. Cumulative release rate of the films were further verified by the fumigant antimicrobial activity. This study demonstrates a solution for improving the antimicrobial properties of packaging film without comprising mechanical strength.