Isolation and the Use of Fungal-derived Chitosan as a Substrate-Free Edible Coating to Extend the Postharvest Shelf Life of Guava

Guava (Psidium guajava) is a nutrient-rich tropical fruit with a very short postharvest shelf life due to its thin skin, high respiration rate and susceptibility to microbial spoilage. Chitosan is an edible film and a preservative, which can be developed from the fungal source and it benefiting the shelf life of perishable foods and vegetables.

The fungal species were isolated and identified by standard methods. Acid and alkali treatments were used to extract the chitosan from the chosen fungal isolates. FTIR and XRD were used to characterize the isolated chitosan. The surface of the guava fruit was coated with the fungal-based chitosan (1% and 2%). Various physiological properties such as weight loss, ripening and shelf life were evaluated at regular intervals. The DPPH assay and the Agar well diffusion method were used to assess antibacterial and antioxidant properties.

Fungal isolates were selected, namely Fusarium oxysporum and Aspergillus fumigatus, based on morphological stability for the biomass yield for chitosan extraction. The yields of the chitosan for A. fumigatus (0.685 g/100 ml) and F. oxysorum (0.850 g/100 ml), respectively. Fruits that have been treated with 2% fungal-based chitosan exhibited a lower weight loss (3.2%), slow ripening and longer shelf life (9 days) and retained higher antioxidant activity (68.2%), than 1% and control group. 2% chitosan of A. fumigatus showed high antibacterial activity. The current study focusing on developing a fungal derived chitosan, which can be used as a suitable sustainable, non-toxic and safe alternative preservative to prolong the shelf life of guava.