Polysaccharide-based edible coatings are served as an attractive preservation method for postharvest maintenance of most fruits. The current study examined the effect of carboxymethylcellulose (CMC)- and pectin (Pec)-based edible coatings on titratable acidity (TA), firmness; vitamin C (vit C); total soluble solids (TSS); pH; total phenolics; anthocyanin and flavonoid contents; total antioxidant capacity (based on 1,1-Diphenyl-2-picryl-hydrazyl hydrate (DPPH)); the activities of peroxidase (POD), polyphenol oxidase (PPO) and polygalacturonase (PG) enzymes; and weight loss during cold storage. The results showed that each coating and their combinations caused positive effects in all measured parameters except weight loss. The applied coatings preserved firmness and improved total phenols, anthocyanin and flavonoid contents, antioxidant capacity and POD activity. In addition, TSS decreased and pH values remained more or less stable with the coating application. The coatings delayed TA and vitamin C loss, and decreased enzymatic activities such as PPO and PG. It could be stated that CMC at 1% and Pec at 1.5% separately demonstrated the best results for most of the measured parameters; and 0.5% Pec + 1.5% CMC could be considered as the best combination. In conclusion, application of CMC, Pec, or their combinations would be considered as an interesting approach to improve postharvest quality characteristics of plum fruit.

Exploiting safer methods for fruit preservation such as application of edible coatings can improve shelf life, valuable characteristics, and antioxidative capacity. The current study aimed to investigate the effect of a pectin-based edible coating on antioxidative capacity of plum fruit during shelf life (19 ± 2 ℃ and 65% relative humidity for eight days). To do this, three solutions (0.5, 1, and 1.5%) of pectin, plasticized by glycerol (0.3% w/v), were applied on plum fruit and compared to a control treated with only distilled water. Ascorbic acid, total phenolics, anthocyanin and flavonoid contents, total antioxidative capacity based on 1,1-diphenyl-2-picryl-hydrazyl hydrate method, peroxidase (as an antioxidant enzyme), and polyphenol oxidase (as an oxidant enzyme) activities were recorded during this period. The results demonstrated that pectin-based edible coating was significantly effective on maintaining ascorbic acid, anthocyanin and flavonoid contents, and antioxidative capacity in plum fruits (P ≤ 0.01). The activities of enzymes were significantly affected by the coatings; peroxidase activity increased and polyphenol oxidase activity decreased (P ≤ 0.01). All pectin concentrations significantly caused higher ascorbic acid and anthocyanin contents, antioxidative capacity, and peroxidase activity but a lower polyphenol oxidase activity than the control; however, just 1 and 1.5% concentrations were effective in terms of total phenolic compounds and flavonoid content, respectively, and the other concentrations acted the same as the control. In general, the coating constituted from 1.5% pectin showed the best results for most measured parameters. Considering the influences of pectin-based edible coating on antioxidative characteristics of plum fruits, its application can be potentially regarded as a favorable method to enhance nutritional value of fruits.

Salinity substantially affects plant growth and crop productivity worldwide. Plants adopt several biochemical mechanisms including regulation of antioxidant biosynthesis to protect themselves against the toxic effects induced by the stress. One-year-old pistachio rootstock exhibiting different degrees of salinity tolerance were subjected to sodium chloride induced stress to identify genetic diversity among cultivated pistachio rootstock for their antioxidant responses, and to determine the correlation of these enzymes to salinity stress. Leaves and roots were harvested following NaCl-induced stress. The results showed that a higher concentration of NaCl treatment induced oxidative stress in the leaf tissue and to a lesser extent in the roots. Both tissues showed an increase in ascorbate peroxidase, superoxide dismutase, catalase, glutathione reductase, peroxidase, and malondialdehyde. Responses of antioxidant enzymes were cultivar dependent, as well as temporal and dependent on the salinity level. Linear and quadratic regression model analysis revealed significant correlation of enzyme activities to salinity treatment in both tissues. The variation in salinity tolerance reflected their capabilities in orchestrating antioxidant enzymes at the roots and harmonized across the cell membranes of the leaves. This study provides a better understanding of root and leaf coordination in regulating the antioxidant enzymes to NaCl induced oxidative stress.

This study investigated the carboxymethylcellulose (CMC)-based edible coating effects on some quality parameters and enzyme activities of plum fruits ( Prunus domestica L. cv. Golden drop) during their shelf life. Three concentrations of CMC (0.5%, 1%, and 1.5%), plasticized with glycerol (0.3% w/v), were applied to plum fruits plus a control treated with only distilled water. The results demonstrate that the CMC-based edible coating was significantly effective in maintaining firmness and titratable acidity (TA); vitamin C, anthocyanin, and flavonoid content; and the antioxidant capacity of plum fruits. Enzymatic activity was affected significantly by the coating. Peroxidase (POD) activity increased, and polyphenol oxidase (PPO) and polygalacturonase (PG) decreased. In general, the formulation consisting of 1% CMC showed the best results in most of the measured parameters. Taking into account the positive effects on qualitative and biochemical characteristics of CMC-based edible coatings on plums, their application can be a potentially promising method to enhance the shelf-life of this fruit.