Esculin and ferric citrate-incorporated sturgeon skin gelatine as an antioxidant film for food packaging to prevent Enterococcus faecalis contamination

Abstract

Herein, a sturgeon skin gelatine film combined with esculin and ferric citrate was developed as an edible food packaging material to prevent Enterococcus faecalis (E. faecalis) contamination. E. faecalis is able to hydrolyse esculin in the film, and then the hydrolysed product, esculetin, combines with ferric citrate to form a brown-black phenol iron complex. This phenomenon can be observed easily after 48 h of contamination under visible light, and it can be determined under 365 nm ultraviolet light with high sensitivity. With the addition of esculin and ferric citrate, the film showed better mechanical properties and water vapour permeability than those of the unmodified gelatine. When an increased amount of esculin was added, an increase in thermal stability, antioxidant activity, and antioxidant stability of the film was observed. These physicochemical characteristics are beneficial for developing a packaging material for food storage that mitigates foodborne illness caused by E. faecalis.