Preparation And Properties Of Acetylated Cellulose-Nanofibrils-Starch-Nisin Antibacteral Film

Biomass material such as cellulose and starch that are widely available in nature have gained extensive attention across various fields.However,poor mechanical properties and inferior water-resistance of starch-based materials largely limit their applications.Cellulose nanofibers(CNF)possess excellent mechanical properties,light weight,biodegradability and many other favorable characteristics and can be used to improve mechanical properties of starch-based materials.Nevertheless,the water-resistance of CNF is also poor.Acetylation modification can render excellent hydrophobicity for CNF and thus enhance the application performances of starch-CNF-based composites.In this study,acetylated cellulose nanofibers(ACNF)was employed as a reinforcing phase to prepare ACNF-starch film with good mechanical properties and hydrophobicity.At the same time,antimicrobial peptide-Nisin was introduced into the as-prepared ACNF-starch film to prepare biomass-based antimicrobial film.This paper will provide theoretical and practical references for the application of biomaterials in food industry.The main methods and results are as follows;(1)CNF was prepared by chemical purification and mechanical treatment,which possessed geometric dimension of dozens of microns in length and tens of nanometers in diameter.Moreover,cellulose content of the prepared CNF was up to 90.10%.ACNF with different degree of substitution(DS)was prepared through adjusting the preparing conditions and the amount of acetic anhydride.And the influences of preparing conditions and the amount of acetic anhydride on the DS of prepared CNF were studied.The results showed that in the heterogeneous system,DS increased nonlinearly with the increase of acetic anhydride amount,but the Tmax and crystallinity decreased.After modification,ACNF still has the basic structure of cellulose ? and high crystallinity.In the homogeneous system,the DS increases linearly with the increase of acetic anhydride amount,and Tmax was barely affected.However,after modification,the crystal structure of ACNF changed from cellulose ? to cellulose ?,and the crystallinity decreased simutaneously.(2)The ACNF with higher crystallinity prepared by heterogeneous modified was selected as an enhancement phase for the starch film.The effect of DS of ACNF on the properties of starch film was studied.Results showed that the introduction of ACNF significantly improved the hydrophobicity mechanical strength,thermal stability of the starch film,however,the transmittance were decreased.Increasing the DS of ACNF can also improve the hydrophobicity of the composite film.Results indicated that the starch composite film prepared by ACNF2 with low DS(0.27)had the best tensilestrength,water resistance and transmission among the prepared samples.(3)Nisin in the ranging amount of 0%,5%,10%,15% were introduced into ACNF2-starch film to study the properties of Nisin antibacterial film.With the increase of Nisin content,the antibacterial effects against Escherichia coli and Staphylococcus aureus were enhanced,and furthermore Nisin showed more obvious effect against Staphylococcus aureus.However,the tensile strength,thermal stability and transmittance of composite film decreased with the increase of Nisin content,and elongation at break,water vapor barrier were improved.