Influence of Surface Corona Discharge Process on Functional and Antioxidant Properties of Bio-Active Coating Applied onto PLA Films

Abstract

PLA (polylactic acid) is one of the three major biopolymers available on the market for food packaging, which is both bio-based and biodegradable. However, its performance as a barrier to gases remains too weak to be used for most types of food, particularly oxygen-sensitive foods. A surface treatment, such as coating, is a potential route for improving the barrier properties and/or providing bioactive properties such as antioxidants. Gelatin-based coating is a biodegradable and food-contact-friendly solution for improving PLA properties. The initial adhesion of gelatin to the film is successful, both over time and during production, however, the coating often delaminates. Corona processing (cold air plasma) is a new tool that requires low energy and no solvents or chemicals. It has been recently applied to the food industry to modify surface properties and has the potential to significantly improve gelatin crosslinking. The effect of this process on the functional properties of the coating, and the integrity of the incorporated active compounds were investigated. Two coatings have been studied, a control fish gelatin-glycerol, and an active one containing gallic acid (GA) as a natural antioxidant. Three powers of the corona process were applied on wet coatings. In the test conditions, there were no improvements in the gelatin crosslinking, but the corona did not cause any structural changes. However, when the corona and gallic acid were combined, the oxygen permeability was significantly reduced, while free radical scavenging, reduction, and chelating properties remained unaffected or slightly improved.

Effect of Corona Treatment Method to Carvacrol Nanocoating Process for Carvacrol/Halloysite-Nanotube/Low-Density-Polyethylene Active Packaging Films Development

“…In addition, FTIR measurament shown that tr-LDPE_CV film adsorbes higher amounts of CV molecules than un-LDPE_CV because of corona treatment activation. This result is in accordance with previous reports [41][42][43]59,60]. On the other hand un-LDPE/10HNT_CV and un-LDPE/10CV@HNT_CV active films adsorbed equal CV amounts with tr-LDPE/10HNT_CV and tr-LDPE/10CV@HNT_CV active films because of the additional active sites of pure HNT and CV@HNT nanohybrid.…”

“…The development of such antibacterial coatings implies the use of novel surface treatment methods such as chemical surface treatment, UV treatment, corona treatment, and plasma treatment [40]. Among them, Corona treatment can activate polymeric surfaces for adhesion of a variety of functional coatings and it could be potentially explored further in terms of creating special antimicrobial coatings based on natural extract and EOs [41][42][43].…”