Effect of chitosan coating on maintenance of aril quality, microbial population and PPO activity of pomegranate (Punica granatum L. cv. Tarom) at cold storage temperature.

Background: Chitosan edible coating was used in an attempt to extend the storage life of pomegranate arils during 12 days at 4 °C. Prior to storage, treated arils were dipped in 0.25, 0.5 and 1% (w/v) chitosan aqueous solutions and 1% (v/v) acetic acid for 1 min, while control arils were dipped in distilled water with 1% (v/v) acetic acid.

Results: Chitosan coating inhibited bacterial and fungal growth on the surface of arils. The water content of arils coated with 0.5 and 1% chitosan was maintained during 12 days of storage. Chitosan reduced the increase in total soluble solids (TSS) and titratable acidity (TA) of arils during storage. The lowest TSS and TA were detected in arils coated with 0.5 and 1% chitosan, which maintained the highest TSS/TA ratio after 12 days of storage. In contrast, application of chitosan delayed the decrease in total phenolics, total anthocyanins and antioxidant capacity during storage. The results also showed that chitosan coating suppressed the monophenolase activity of polyphenol oxidase (PPO) with pyrogallol substrate and the diphenolase activity of PPO with dopamine hydrochloride substrate, but the diphenolase activity of PPO with pyrocatechol substrate increased during storage.

Conclusion: The results suggest that chitosan coating has the potential to extend the storage life of pomegranate arils by reducing the microbial population on their surface.