Preparation of grafted starch by IPDI coupling and its antibacterial properties

Antibacterial acetate grafted starch (AGS) was synthesized by isophorone diisocyanate (IPDI) coupling acetate esterified starch (AST) and the antimicrobial agent polyhexamethyleneguanidine hydrochloride (PHMG), and the antimicrobial properties of AGS were evaluated. The process parameters of AGS were: IPDI reacted with PHMG at 120 °C for 1 h, then, reacted with starch at 60 °C for 3 h. The grafting yield of PHMG and starch reached 28.43%. The Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance (1H NMR) showed that the binding of IPDI to PHMG was successfully grafted on the AS. The antibacterial effect of AGS was investigated. AGS produced inhibition zones and confirmed its significant inhibitory effect on Escherichia coli and Staphylococcus aureus, as the grafting yield increased, the inhibition effect on bacteria became stronger. When the grafting yield was 28.43%, the inhibition rate of AGS was 90.24% for Escherichia coli. and 94.45% for Staphylococcus aureus. The experiments of water washing showed that after AGS was washed 10 times with water, the inhibition rate of AGS to E. coli. only reduced 3.04% and that of S. aureus 2.95%, indicating that the combination of PHMG and starch was stable and the inhibition effect was long-lasting, AGS has huge potential to be developed into antibacterial material.

Characterization of ginger starch-based edible films incorporated with coconut shell liquid smoke by ultrasound treatment and application for ground beef

The aim of the present study was to investigate the structural and physicochemical properties of ultrasound-treated ginger starch-based edible films incorporated with coconut shell liquid smoke (CSLS), and determine the inhibitory effect of the films against Escherichia coli O157:H7 in ground beef during the storage at 4 °C. Ultrasound-treated CSLS-ginger starch films presented a better mechanical, barrier, thermal, and antibacterial properties. The antibacterial effect of CSLS against E. coli, S. aureus, E. coli O157:H7, Listeria monocytogenes, Salmonella Enteritidis, and B. cereus increased significantly with ultrasound treatment. The CSLS-films showed antibacterial activity against E. coli O157:H7 without negatively affecting the sensory attributes of ground beef. The films containing 15% CSLS reduced E. coli O157:H7 populations by 1.33 log cfu/g in ground beef during the 12-day-storage. The CSLS-starch films effectively inhibited lipid oxidation in the ground beef samples during the refrigerated storage. These results indicated that ultrasound-treated CSLS-ginger starch film has the application potential as a novel antimicrobial active packaging for proteinous foods.

Development of poly(vinyl alcohol)/starch/ethyl lauroyl arginate blend films with enhanced antimicrobial and physical properties for active packaging

Active packaging films have emerged as alternatives to replace petroleum-based packaging materials. In this work, poly(vinyl alcohol) (PVA)/starch/ethyl lauroyl arginate (LAE) films possessing enhanced properties were prepared. Scanning electron microscopy (SEM) showed that PVA and starch were compatible, the concentrations of LAE greatly affected the structural integrity. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction showed that the inclusion of LAE did not significantly affect the intermolecular interactions and crystal structures of the polymer matrix. With an increase of the LAE content, the tensile strength (TS) was slightly decreased due to the altered microstructures, the elongation at break (EB) significantly increased ascribed to the synergistic effect of acetic acid, glycerol and LAE. The values of TS and EB were 17.25 MPa and 586.08%, respectively when LAE was 10%. Active films showed good barrier properties from UV while retaining the transmittance in the visible light region. The films containing 1% of LAE exhibited antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), the inhibition zone of bacterial growth gradually expanded with increasing LAE content. This study demonstrates the potential of using LAE as the antibacterial agent for synthesizing natural-based polymeric films for active packaging applications.