Fabrication of polylactic acid/chitosan/cellulose nanocrystal incorporated with essential oil for Harumanis mango postharvest application

‘Harumanis’ mango is the leading commercial cultivar on north Peninsular Malaysia, which also refer as “king of mangoes” in Malaysia and have the maximum consumer demand. The major challenges face by Harumanis mango’s farmer is mango postharvest diseases. The application Polylactic acid and Chitosan biopolymer as packaging during postharvest could provide an eco-friendly alternative to those conventional approaches. However, due to higher costs, poor mechanical strength, poor water and gas barrier and poor antioxidant antimicrobial activity of the films, biopolymer packaging is still relatively limited. The purpose of adding nanofillers (cellulose nano crystals) and essential oils to films is to improve their properties. The ability of essential oils to retain and additives to prevent water and gas transfer between product and environment produce a layer that allows for the control of chemical barriers and serves as an additional barrier to improve the overall quality and stability of fruit. Hence, the aim of this research is to incorporate Cellulose nanocrystal (CNC) and Coleus aromaticus essential oil (CAEO) and their constituents into a new packing material of poly-lactic acid (PLA)/ Chitosan (Cs) and to examine the effect of CNC and CAEO on the properties of PLA/Cs films as fruit packaging. The films are fabricated via solvent casting technique. The obtained films' antimicrobial, antioxidant, microstructural, and mechanical properties were studied. Mechanical properties studies showed the incorporation of CNC indicated higher Tensile strength (TS) value by incorporation of 2% of CNC. However, the PLA/Chitosan-CNC films at 3% and 4% CNC concentration exhibited a decreased TS value. PLA/Cs films were improved with the addition of a small amount of CNC. On the other hand, when the CAEO was added, it improves the elongation breaks which reflect on its flexibility properties. Scanning electron microscopy (SEM) analysis revealed that SEM analysis showed that the surface of PLA/Cs films smoother when 1% and 2 % of CNC and start to produce bubbles and crack on 3 % and 4 %. The surface of films became rougher when CAEO was incorporated into the film. Antioxidant activity of biopolymer film significantly increased (p< 0.05) with increasing CAEO. In-vitro and in-vivo tests were used to evaluate the inhibitory effect of the film against isolated fungi from mango (Curvularia sp.) by comparing the film with different concentration of essential oil with the treatment of control. Disk diffusion was used to evaluate mycelial growth inhibition, which the film incorporated with 1.2 wt% CAEO showed the best result. For in-vivo with wounded mango, the disease incidence was successfully reduced by the film incorporated with 1.2 wt% CAEO. All FTIR spectra of PLA/Cs/CNC and CAEO blends displayed the characteristic bands of PLA-based materials. TEM analysis shows the presence of CAEO, and homogeneity of oil droplets was detected in the PLA/Cs/CNC matrix. The results indicate the biopolymer film incorporated with CAEO could be used as active packaging in fruit industry and be a promising alternative to current control treatment that used for controlling postharvest disease on Harumanis mango.