Effects of chitosan coating enriched with thyme essential oil and packaging methods on a postharvest quality of Persian walnut under cold storage

This study evaluated the effects of edible coatings and different packaging methods on the shelf-life and quality of walnut kernels. It focused on the coatings with chitosan (1%) and thyme essential oil (TEO) at concentra- tions of 500 and 1,000 μl L–1 (CT , CT ) or with chitosan alone (CT). The effects of the coatings was assessed 500 1,000 for different packaging methods (LP, loose packaging; PP, packaging in polypropylene bags; and AP, active packa- ging) as contrasted to control walnuts (C). Walnuts were stored for 120 days in darkness, with relative humidity of 55%, at 4°C. The results showed that the L* index and moisture content of the samples in the chitosan with 500 and 1,000 μl L–1 thyme essential oil in active packaging were maximum, whereas peroxide and conjugated diene values were minimum. The lowest rate of mold growth was observed for the chitosan samples with 500 μl L–1 thyme es- sential oil in active packaging. The best overall acceptability score was related to the samples with chitosan alone and the chitosan with 500 μl L–1 thyme essential oil in active packaging. The chitosan alone and the chitosan with 500 μl L–1 thyme essential oil in active packaging are recommended for storage of kernels at 4°C.