Effects Of Antibacterial Film Containing Gallnut Water Extract On Fish Preservation

Gallnut water extract was prepared by water extraction,its physic-chemical properties were determined.Antimicrobial film was prepared by adding gallnut aqueous extract into KGM-EC film,and physic-chemical properties of the films were characterized.The antibacterial film was used to package fish fillets stored at 4°C,the storage stability of fish fillets were measured.The results are following:(1)The water extraction rate of Chinese gallnut was 65.3 ± 0.1%.Total phenolic content in this extract was 67.8 ± 0.1%.It showed strong inhibition on Escherichia coli and Staphylococcus aureus.Moreover,it also had a strong anti-oxidation.(2)Chinese gallnut extract,chitosan,and lysozyme solutions were used to coat fish fillets.The coated fish fillets had better indexes compared with uncoated groups.Fish fillets coated with Chinese gallnut extract had lower TVB-N and TBA values,compared with fish fillets coated chitosan and lysozyme.Fish fillets coated with lysozyme had lowest total number of colonies,but no obvious difference was showed between fish fillets coated Chinese gall extract and fish fillets coated lysozyme.Gallic extract was suggested for fish preservation.(3)Tensile strength(TS) of KGM/EC composite film increased with the increase of gallnut aqueous extract concentration,until the concentration reached 15%.With the content of gallnut water extract increasing from 0% to 20%,elongation at break(EAB)and water vapor permeability(WVP)were significantly increased and decreased(p<0.05),respectively.Moreover,oxygen barrier properties were enhanced significantly(p<0.05).KGM/EC films incorporated with 20% gallnut water extract were used to fish fillet packaging,the values of pH,TVB-N,and total numbers of colonies of fish fillet had significantly difference,respectively,compared with fish fillets and fish fillets packaged with films without gallnut during storage(p<0.05).Considering the total numbers of colonies as a reference index,KGM/EC composite film containing 20% gallnut water extract can prolong the shelf life of fish fillets stored at 4°C for 3 days,compared with fish fillet without film packaging.