Investigation of the efficacy of a ZnO-starch nanocomposite packaging to prolong the shelf life of fragaria ananassa (strawberries)

Nanomaterials have been used recently in food packaging as antibacterial coatings because

of their desirable antibacterial and antifungal properties. The use of antimicrobial packaging

is to deter the growth of microorganisms responsible for spoilage or diseases in packaged

foods, therefore prolonging their shelf life. In this study, potato peel starch and ZnO-starch

nanocomposite paper (ZnO-starch NC paper) were developed and evaluated for

antibacterial activity against Escherichia coli, Bacillus subtilis, Staphylococcus aureus,

Pseudomonas aeruginosa, and antifungal activity against the Botrytis cinerea fungi. The

ZnO nanoparticles (ZnO NPs) were synthesized using the hydrothermal method whilst the

ZnO-starch NCs were synthesized by adding the potato starch to the ZnO NPs. The

synthesized ZnO nanomaterials and potato starch were characterized using X-ray

diffractometry (XRD) and UV-Vis spectrophotometry (UV-Vis). The analysis showed that

the nanomaterials were purely synthesized without the presence of impurities. The ZnO starch NC paper was made by coating Whatman filter paper (size 3) with the ZnO-starch

NC. The antibacterial/antifungal activity of the ZnO-starch NC paper showed that the

nanomaterials were effective against the Gram-positive bacteria S. aureus and B.

subtilis but not against the Gram-negative E. coli and P. aeruginosa. The ZnO-starch NC

paper was used to package inoculated strawberries in plastic containers for 10 days at 4°C

and 27°C, respectively. Quality assays on the incubated strawberries showed that the

percentage weight loss and bacterial counts of the fruits packaged with the ZnO-starch NC

paper at 4°C were lower than those packaged without the ZnO-starch NC paper. The fruits

incubated with the NPs were seen to be more acceptable in appearance and sensory value

than their respective controls. In conclusion, the ZnO-starch NC paper was able to prolong

the shelf life of strawberries for longer at lower temperatures. Hence, this nanomaterial

could be used to explore nano-packaging for prolonging the shelf life of fruits.