Propolis and chitosan as antimicrobial and polyphenols retainer for the development of paper based active packaging materials

The research investigates the potential combination of propolis and chitosan to develop a completely bio-based active food packaging material. Propolis glycolic extract was used as antioxidant and antimicrobial, due to its polyphenols content. Two commercial chitosans with different molecular weights were comparatively used as antimicrobial, wet strength additive substitute and polyphenols retainer. The effects of the addition of carboxymethyl- (CMC) or microfibrillated cellulose (MFC) and two pH values in paper production were investigated for polyphenols retention and paper strength. Chitosan, in replacement of the most commonly used wet strength resin (PAAE), increased polyphenols retention more than 10 times. Paper sheets produced with the highest molecular weight chitosan, at pH 7 and with MFC addition showed the best wet strength (7.4 ± 0.5 Nm/g) and wet resistance (13.3 ± 1.2%). Paper antimicrobial activity was confirmed on thinly sliced raw veal meat, where a decrease of intentionally inoculated L. innocua of around 1 log cycle was achieved in 48 h at 4 °C.