Optimization of heat-sealing properties for antimicrobial soybean protein isolate film incorporating diatomite/thymol complex and its application on blueberry packaging

Abstract

Heat-sealing parameters of the as-prepared antimicrobial soybean protein isolate (SPI) film incorporating diatomite/thymol complex (S/D/T film) were optimized using single factor experiment and response surface methodology, and further used to seal the films into packaging bags to preserve blueberries at 25 °C and 70 % relative humidity. The S/D/T film had a maximum sealing strength of 2.41 N/15 mm at the optimized sealing conditions of 139.5 °C, 2.5 s and 0.48 MPa due to the strong physical intermolecular interaction induced upon heat-sealing areas as confirmed by FT-IR and SEM. Moreover, the S/D/T film could effectively delay the deterioration in blueberry quality during 5 days of storage, exhibiting better fresh-keeping effect than other groups. Additionally, all films were completely biodegraded in soil within 8 days. In summary, the developed antimicrobial protein films with improved heat-sealing ability and excellent biodegradability can provide a promising alternative to nondegradable synthetic materials in active packaging.