Suppression on postharvest juice sac granulation and cell wall modification by chitosan treatment in harvested pummelo (Citrus grandis L. Osbeck) stored at room temperature.

Deposition of both lignin and cellulose accompanied by juice sac granulation is widespread in harvested citrus fruit. Hence, measures to suppress postharvest granulation of 'Majiayou' pummelo is of great importance. The fruit was treated with 1.5% chitosan and then stored at room temperature (20 ± 2 °C) for 150 d. As compared to the control fruits, chitosan coating significantly suppressed granulation index and maintained good quality. Chitosan coating inhibited lignification by suppressing the activities and expression levels of lignin synthesis-related enzymes (PAL, CAD and POD). By contrast, chitosan treatment enhanced the activities and expression levels of cell wall degrading enzymes, including PME, PG, Cx, XTH and ß-Gal, which might contribute to the decrease in cellulose. In a nutshell, chitosan coating can effectively suppress juice sac granulation and fruit senescence of pummelo fruits, and play a crucial role in maintaining the cell wall modification.

Comprehensive Evaluation of the Postharvest Antioxidant Capacity of Majiayou Pomelo Harvested at Different Maturities Based on PCA.

Majiayou pomelo (Citrus grandis L. Osbeck, MP) is a famous local red pulp pomelo from the Jiangxi province in China that is rich in natural active substances. In order to investigate the postharvest antioxidant capacities of MP pulp and determine the optimal harvesting time, fruits that were harvested at three different maturities (185, 200, and 215 days after full bloom) were observed for 180 days of preservation at ambient temperature. An abundance of ascorbic acid and lycopene in the MP pulp was found during storage, and in Harvest I, these substances were significantly higher than in Harvest II and Harvest III fruit (p < 0.05). The activity of ascorbate peroxidase (APX), peroxidase (POD), and catalases (CAT) in Harvest I and Harvest II were far higher after 90 days. The radical scavenging ability of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, superoxide anion radical (O2-•), and hydroxyl radical (•OH) in Harvest I and Harvest II were higher. There was a significantly positive correlation (p < 0.01) between the antioxidant components (ascorbic acid, lycopene, carotenoids, total phenols, and total flavonoids), enzyme activity, and radical scavenging ability. The comprehensive scores determined by principal component analysis (PCA) in Harvest I and II were higher than those in Harvest III. Therefore, the optimal harvesting period of MP for each year is determined to be early November. The study provides a theoretical basis for the maintenance of the postharvest fruit value and the regulation of fruit functional components.

Preservation of Xinyu Tangerines with an Edible Coating Using Ficus hirta Vahl. Fruits Extract-Incorporated Chitosan.

Xinyu tangerine is a citrus fruit that has enjoyed great popularity in China for its fewer dregs and abundant nutrients. However, it is considered an easily perishable fruit that is vulnerable to various pathogenic fungal infections, especially by Penicillium italicum, which reduces its storage life and commercial value. Normally, to reduce the losses caused by fungal deterioration of harvested fruit, polysaccharide-based edible coating, containing natural antimicrobial agents (e.g. plant extracts), have been applied. In current study, we evaluated the effects of Ficus hirta Vahl. fruits extract (FFE)⁻incorporated chitosan (CS) edible coating on Xinyu tangerines during cold storage at 5 °C. The results showed FFE has efficacy as an antifungal against P. italicum in a dose-dependent manner in vivo, with an EC50 value of 12.543 mg·mL-¹. It was found that the edible coating of FFE⁻CS exhibited a higher reduction of total soluble solid (TSS), titrable acid (TA), and ascorbic acid (AsA) content by reducing the fruit decay rate, weight loss, respiration rate, and malondialdehyde (MDA) content during cold storage at 5 °C. Moreover, the activities of protective enzyme such as superoxide dismutase (SOD), peroxidase (POD), and phenylalanine ammonia-lyase (PAL), which have been linked with reactive oxygen species (ROS) and the phenylpropanoid pathway, were higher in the FFE⁻CS-coated fruits. On the basis of these study results, the FFE⁻CS edible coating could reduce postharvest loss and enhance the storability of Xinyu tangerines due to the in vivo antifungal activity of FFE.