Simultaneously flame-retardant and antibacterial films from κ-carrageenan/carboxylated cellulose nanofibril/phytic acid for the preservation of cooked pork

Abstract

Conventional polysaccharide films are flammable and susceptible to bacterial growth, decreasing the potential in practical applications such as bio-based and active food packaging. In this study, the nontoxic naturally occurring compound phytic acid (PA) was introduced to a blended film of κ-carrageenan (κC) and carboxylated cellulose nanofibrils (CCNF) to overcome these disadvantages. Compared with the κC-CCNF-PA0 film, the κC-CCNF-PA24 film possessed improved elongation at break (41%), water vapor permeability (3.46 g m−1 Pa−1 s−1 × 10−8) and oxygen permeability (1.50 cm3 mm−2 Pa−1 day−1 × 10−12). Thermogravimetric analysis, limiting oxygen index and actual flame-burning behaviors revealed good flame retardancy of the prepared films with the increase in PA. When the PA content reached 18% and 9%, the antibacterial rate against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) reached 100%, respectively. The cooked pork samples packaged by κC-CCNF-PA24 exhibited lower values of malondialdehyde (0.61 mg kg−1) and total viable count (8 CFU g−1) compared with those by κC-CCNF-PA0 film (0.99 mg kg−1, 447 CFU g−1). On the basis of these results, we believe that the sustainable and clean strategy provides an opportunity to improve and functionalize very brittle and flammable polysaccharide-based films.