Effect of zinc oxide nanoparticles concentrations in methylcellulose edible coatings on shelf life of pomegranate aril sacs (‘Wonderful’)

This study aimed to investigate the effect of methylcellulose-based coatings functionalized with zinc oxide nanoparticles to improve the shelf life of pomegranate aril sacs. Fresh pomegranate aril sacs were dipped into six formulations of methylcellulose coatings functionalized with ZnONP at 0, 0.1, 0.25, 0.5 and 1%. Distilled water was used as a control. Aril sacs were packed in punnets and stored at 4°C for 24 days. At three-day intervals, weight loss, respiration, titratable acidity (TA), total soluble solids (TSS) and antioxidant capacity were investigated. The results showed that the treatments were significantly (p<0.05) different from the control (untreated samples). The treatment containing 0.25% ZnONP was the most effective at delaying respiration rate and maintaining the TA and TSS. All the ZnONP treatments showed promising results on storage stability of pomegranate aril sacs. At the end of the trials, treated fruit (14.89-19.61%) showed a lower weight loss than the control (21.53%). Respiration rate was also markedly lower in treated fruits (1.71 to 1.94 mL CO2 kg^-1 h^-1) compared to the control (2.78 mL CO2 kg^-1 h^-1), suggesting the ability of the treatments to control the physiology of the aril sacs. Treated samples were more acidic (1.18-1.22%) and sweeter (17.4-17.6 °Brix) compared to the TA (1.09%) and TSS (17.08 °Brix) of the control. This suggests that the treated samples exhibit better sensorial attributes than the control. Although considered effective, MC+ ZnONPs coatings require further investigation to understand the mode of action and optimise the concentration of ZnONPs in the methylcellulose matrix.