Pectin-nanolignin composite films with water resistance, UV resistance, and antibacterial activity

In this work, pectin-lignin nanoparticle (LNP) composite films were prepared, the physical, antioxidant and antibacterial properties of the films systematically evaluated. The LNP were compatible with the pectin matrix, and the tensile strength (TS) and water contact angle (WCA) of the pectin-based films were enhanced by 164% and 56% at the optimum LNP loading of 3.0% (w/w). The results of dynamic WCA demonstrate the hydrophobic stability of pectin-LNP composite films. Even trace amounts of LNP (1.0%, w/w) were found to significantly improve the mechanical properties (TS improved 67.33%), hydrophobicity (WCA improved 48.83), and water barrier properties (the water vapor permeability decreased by 25.30%) of the pectin-based films. The tight entanglement and strong positive interaction between pectin and LNP promote the formation of dense structures, which is beneficial to the film properties. In addition, all pectin-LNP composite films almost completely shield the UVB (320-275 nm) and UVC (275-200 nm) spectrum, along with most of the UVA (400–320 nm) spectrum, which demonstrates their strong anti-ultraviolet performance. In terms of bioactivity, the addition of LNP significantly enhanced the DPPH radical scavenging ability (maximum boost is 6.33 times) and antibacterial ability (maximum inhibition rate was 78.79 for S.aureus and 47.80% for E.coli) of the pectin film. These results suggest that the pectin-LNP composite film are promising active packaging materials for food preservation/packaging applications.