Antibacterial porous xanthan-based films containing flavoring agents evaluated by near infrared chemical imaging technique

Xanthan gum (XG) is a widely applied natural polysaccharide in food industry as thickening agent. Nowadays, one of the major problems is that some food products are found to be contaminated by pathogenic bacteria such as Escherichia coli and Staphylococcus aureus reducing so, their shelf life. This research aims to demonstrate the antibacterial activity of some biodegradable formulation XG-lignin hydrogel films and their potential application as carriers for controlled release of flavoring compounds. The XG-lignin films containing an aspen wood lignin type showed a high antibacterial activity against Salmonella Typhymurium ATCC 14028, E. coli ATCC 25922 and Listeria monocytogenes ATCC 25922 bacteria compared with those containing softwood lignin, or lignin from annual plants. Surface morphology indicated a homogeneous distribution of both components within the hydrogel network and the generation of a porous structure after swelling and lyophilization. Additionally, near infrared chemical imaging technique was used as nondestructive method to observe the spatial distribution of the polymeric components and vanillin into the hydrogel films as well as its release profile. The vanillin release rate dependence on the lignin type was also evidenced, a retarded release of vanillin being observed. These results give an important insight into the use of XG, lignin, and vanillin for the development of new edible films for active packaging materials.