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Quality and biochemical changes of navel orange (Citrus sinensis L., Osbeck) fruits in response to cinnamaldehyde-chitosan coating were studied during 120 day of storage at 10 ± 1 °C and 80–90% RH. The results showed that the coating significantly reduced the decay rate and weight loss of the navel orange fruits, delay the decrease of the content of total soluble solids (TSS), titratable acidity (TA) and vitamin C (Vc), effectively inhibited the content of MDA. Furthermore, the coatings maintaining enhanced the activity of SOD, CAT, POD and PPO, delay the senescence of fruits. The high performance liquid chromatography analysis showed that coating treatment inhibited the decrease of total sugar content of fruits and slowed down the decline of total organic acids by slowing down the degradation of sucrose, fructose and citric acid content. Compared with chitosan coating, cinnamaldehyde- chitosan coating could significantly reduce the decay rate and had no adverse effects on fruit quality. Meanwhile, it could improve CAT, SOD and POD activity, induce the activity of PPO to increase, and improve the disease resistance of navel orange fruits. This study suggests that cinnamaldehyde-chitosan coating can extend the storage time and maintain quality of citrus fruit.

The current work aimed to evaluate the efficacy of four coating formulations&mdash, chitosan coating (CH), 0.5% cinnamaldehyde + chitosan (0.5% CI&ndash, CH), 1.0% cinnamaldehyde + chitosan (1.0% CI&ndash, CH), and 1.5% cinnamaldehyde + chitosan (1.5% CI&ndash, CH)&mdash, on fresh mandarin fruit cv. Ponkan quality maintenance (weight loss, decay rate, total soluble solids, titratable acidity, vitamin C, color index, malondialdehyde, and antioxidant activity) over 100 days of storage at 20 &deg, C. Compared to the control, chitosan treatment effectively reduced the decay and weight loss rates of mandarin fruit cv. Ponkan during storage at room temperature, delayed the decline of nutritional quality in fruits, increased the antioxidant capacity, and inhibited the accumulation of malondialdehyde (MDA). In comparison to chitosan coating, 1.5% CI&ndash, CH did not improve the fruit storage effect, but inhibited the normal color change of fruits and increased the accumulation of MDA. Both 0.5% CI&ndash, CH and 1.0% CI&ndash, CH effectively reduced the rate of fruit decay, improved the quality of fruits after harvest, and delayed fruit aging. Our study suggests that 0.5% CI&ndash, CH might be good formulations for maintaining the quality of mandarin fruit cv. Ponkan during room-temperature storage.

In citrus fruit, citric acid is the predominant organic acid which influence fruit taste, flavor and quality. The effect of hot air treatment (HAT 40°C, 48 h) and 1.0% chitosan coating on the change of organic acids and the related gene expression of citric acid synthesis and degradation in ponkan (Citrus reticulata Blanco) fruit during cold storage have been studied. The results showed that citric acid was the main organic acid in fruit, the trend change of citric acid content was consistent with total organic acids and titratable acidity (TA) content, which decreased with the prolongation of storage time, hot air treatment significantly promoted but chitosan coating treatment significantly delayed citric acid degradation in Ponkan fruit. Hot air treatment could induced CitAco2/3, CitIDH2/3, CitGAD4, CitACLs, CitPEPCKs and CitFBPases expression during fruit storage period, but had no significant effect on CitGSs expression, The enhanced expression of degradation-related genes was closely related to the degradation of citric acid. The expressions of CitAco3, CitGAD4 CitACLα2/β, CitPEPCKs and CitFBPases were inhibited, which leading to the degradation rate of citric acid was slowed by chitosan coating during storage. These results showed that the degradation of citric acid in fruit was regulated by ATP citrate lyase (ACL) pathway and γ-aminobutyric acid (GABA) pathway.

Fruit color is one important traits that largely determine the quality of navel orange fruits. The goal of this work was to evaluate the influence of ventilating warehouse (VW), mechanical refrigeration warehouse (MRW) and mountain evaporative cooling ventilating warehouse (MECW) storage on the quality and peel color in navel orange. The weight loss rate, decay rate, total soluble solids (TSS), titratable acidity (TA) and vitamin C (Vc) content of fruit were measured. The color index of the skin was determined by a chromameter, and the carotenoids from the skin were determined by high performance liquid chromatography. During storage, the weight loss rate and rot rate of navel orange fruit gradually increased, and TSS, TA and Vc gradually degraded. The weight loss rate and decay rate of fruits stored in MRW and MECW were lower than those of fruits stored in VW, and the contents of TSS, TA and VC were higher than those of fruits stored in VW. However, the color change of VW and MECW fruits was better than that of MRW fruits. The chlorophyll content of VW and MECW fruits was significantly lower than that of MRW fruits, and the carotenoid content of VW and MECW fruits was significantly higher than that of MRW fruits in the late storage period. Our study suggests that MECW had the best storage effect among the three storage methods, which provided a theoretical basis for the practical application of MECW in citrus fruit storage.