Development of polyethylene films for food packaging activated with a foodgrade antilisterial bacteriocin

Food packaging can be defined ‘‘functional packaging’’when a material and/or an accessory are used to improve the generic food protection of traditional food packaging. In the active packaging there is an interaction between package and food, implying a gas modification of headspace and/or a release of antimicrobial, antioxidant or other substances that improve food quality. Therefore, the final purposes of functional packaging are long time protection and safety of food as well as increase of appreciationand satisfaction of the consumers. Research on active packaging is already aiming the development of films capable to exercise an antimicrobial effect on food and drinks. In this study the antimicrobial effect of active polyethylene films was evaluated against Listeria monocytogenes. The film was made active by using the anti-listerial bacteriocin 32Y by Lactobacillus curvatus with three different procedures: soaking, coating and incorporation. While the soaking and coating treatments led to anti-listerial activity, no growth inhibition of the indicator strain Listeria monocytogenes OH was observed when the bacteriocin was incorporated in the polyethylene film. The antimicrobialactivity of the soaked and coated films was also tested in experiments of food packaging involving pork steak and ground beef contaminated by Listeria monocytogenes OH at roughly 103 cfu per cm2 and gram, respectively.The results of the challenge tests showed the highest antimicrobial activity after 24 hours at 4°C, with a decrease of about 1 Log of the Listeria monocytogenes population. Finally, experiments of migration of the coated bacteriocin in water were also performed resulting in a slow release of the antimicrobial substance.