Abstract
There are high levels of damage imposed on persimmon fruit postharvest, especially after storing it in cold storage, which causes chilling injury (CI). To reduce this stress on the fruit, the conventional way is to use chemical treatments. Since there is a limitation in the use of chemical materials, it is necessary to apply non-harmful treatments to decrease chilling injury and maintain the quality of persimmon in cold storage. The aim of this study is to investigate the effects of chitosan-loaded phenylalanine nanoparticles (Cs-Phe NPs) (2.5 and 5 mM) on physiochemical and quality factors of persimmon (Diospyros kaki) during 45 days of storage at 4 °C (38 °F) and evaluate the impact of Cs-Phe NPs on the preserving quality in order to reduce the chilling injury of this fruit. The experiment was conducted using a completely randomized design with three replications. Treatments were applied at 15, 30, and 45 days after storage at 4 °C with ≥90% relative humidity. The size of Cs-Phe NPs was less than 100 nm, approximately. The results showed that application of 5 mM of Cs-Phe NPs delayed the negative effects of chilling stress and enhanced antioxidant capacity, firmness, and total soluble solids of persimmon fruit. Lower H2O2 and malonaldehyde (MDA) accumulation along with higher soluble tannin and total carotenoid accumulation in persimmon fruit treated with 5 mM Cs-Phe NPs was also observed. Fruit coated using Cs-Phe NPs in both concentrations (2.5 and 5 mM) showed the highest antioxidant enzyme activity for superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) and the lowest for polyphenol oxidase (PPO) and chilling injury during storage. According to our results, 5 mM of Cs-Phe NPs could be considered as the best treatment under chilling-stress conditions.
Highlights
Cold storage is an effective postharvest technology to maintain the quality and to extend the marketing span of most horticultural crops
Signals at 3448 and 1601 cm−1 are related to stretching vibration –OH and –NH2, respectively, and the signal in 1076 cm−1 is attributed to stretching vibration C–O–C
The peak in areas 2963 and 1625 cm−1 is related to C–H and C=C, respectively, which indicates the presence of a benzene ring [38]
Summary
Cold storage is an effective postharvest technology to maintain the quality and to extend the marketing span of most horticultural crops. The major symptoms of chilling injury in persimmon fruit are flesh softening and gelling, external browning, loss of fruit flavor, compacted flesh areas, and internal browning, depending on the cultivar [1,2]. Various methods such as modified atmospheres packaging and controlled atmospheres (CA) storage [3,4], application of hot water [5], hot air [6], 1-methylcyclopropene (1-MCP) [7], short-term high. The presence of hydroxyl and amine groups in the structure of chitosan allows it to be synthesized in nano size and combined with other materials [12,15]. Chitosan nanoparticles have more advantages than conventional chitosan, as in nano shape the surface-to-volume ratio were increased in comparison with the conventional type, which gradually occurs with decreasing particle size, increases the activity of the particles, and increases their effectiveness [16,17]
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