Chitosan starch based packaging film enhanced with empty fruit bunch cellulose nanofiber

Abstract

Starch-based biopolymers exhibit low mechanical properties. Based on recent studies, it has been shown that the incorporation of nano fillers, such as cellulose nanofiber (CNF), into a polymer matrix can greatly improve its mechanical properties. Interestingly, the incorporation of CNF into antimicrobial packaging enhances the results of antimicrobial efficacy towards food shelf life. Cellulose nanofiber (CNF) from oil palm empty fruit bunch was prepared, through pretreatment, to remove non-cellulosic content and then underwent an hydrolysis process involving strong acid. Starch-based nanocomposite film was formed by the incorporation of 2, 4, 6, 8 and 10% CNF, per weight of starch, into the film matrix. The nanocomposite film appeared translucent and easy to handle however, the film became more opaque as the percentage of CNF was increased. The surface morphology of the film was observed using field emission scanning electron microscopy to analyze the effect of CNF addition on the film surface. Mechanical properties such as tensile strength, percentage of elongation and Young’s Modulus were determined using a tensile test machine. Tensile strength of the starch-based film without CNF (as a control) was 3.1 MPa which increased to 4.68MPa with the addition of 2% CNF. However, the strength was gradually decreased with the addition of more than 2% CNF. Optimum Young’s Modulus was also detected at 2% CNF incorporation. The percentage of elongation gradually decreased from 1.79% to 0.89% for film with 0% to 10% CNF loading, respectively. Influence of CNF addition in antimicrobial film with regard to its antimicrobial properties and food shelf life were also studied. Antimicrobial composite film was prepared by blending 1 to 9 ratio of chitosan per weight of starch while antimicrobial nanocomposite film was prepared by adding 2% of CNF and the control film was formed using starch only. The antimicrobial test showed that starch/chitosan with CNF gave 30% better bacterial inhibition towards Gram-positive bacteria Bacillus subtilis compared to the starch/chitosan control film. However, in Gram-negative bacteria Escherichia coli starch/chitosan with CNF composite packaging gave rise to a similar inhibition zone as the control starch/chitosan packaging. Results showed that nano-reinforced starch/chitosan packaging was able to retain moisture in a tomato 7 days longer than the control starch and starch/chitosan composites which gradually changed the tomato’s colour which highlighted the slow ripening process and lessened mould infection. In conclusion, the addition of CNF to a starch-based matrix has shown a significant impact on the mechanical properties of the formed film as well as water barrier properties. It also embarked the potential of CNF as a filler for antimicrobial packaging as it enhances the results on antimicrobial properties and food shelf life.