International Journal of Aquaculture, 2025, Vol.15, No.4, 208-220 http://www.aquapublisher.com/index.php/ija 216 7 Progress in Storage and Storage Technology after Harvest 7.1 The impact of storage environment on quality changes The water content of fresh water chestnuts is as high as 75%, and it still maintains a high respiratory strength and metabolic activity after harvesting, and is very prone to water loss, wilting, browning and rot. The storage environment has an important impact on the quality changes of water chestnuts. Low temperature can effectively inhibit the respiration and bacterial reproduction of water chestnuts, which is the key to prolonging the shelf life. Studies have shown that under conditions of 0 ℃~4 ℃, water chestnuts can be stored for about 4~6 weeks without changing their quality; while obvious germination and rot occurred in only about 2 weeks at room temperature of 25 ℃ (Baehaki et al., 2019). Therefore, most of the cold storage refrigerated water chestnut raw materials are used. However, it is necessary to note that water chestnuts are not resistant to freezing. If they are below -1 ℃, they will become transparent and water-stained. The skin of the water chestnut is not dry enough to have a leather layer of 0.5 mm~1 mm, which has a certain ability to prevent water loss. However, long-term storage will still cause weight loss. The relative humidity should be maintained at 85%~90%. Too low humidity will accelerate the evaporation of water and cause wilting; too high humidity will easily breed mold. Generally, open water trays are placed in cold storage or humidifiers are used to maintain a high humidity environment. In addition, moderate drying of the surface before storage can reduce moisture transpiration during storage (Luengwilai et al., 2014). Using air conditioning (CA) storage technology can further inhibit the respiration of water chestnuts and delay browning. Some studies have tried to reduce oxygen concentration, increase carbon dioxide or add inert gases in storage environments. As Japanese scholars have found that placing water chestnuts in an environment of 5% O2+5% CO2+90% N2 can significantly slow down their browning and corruption. The latest research has introduced rare gases: filling low-concentration xenon (Xe) and krypton (Kr) gases into the packaging, and it was found that these two inert gases can effectively inhibit the enzymatic browning of peeled water chestnuts and at least double the storage period. 7.2 Fresh preservation and disease prevention plan In order to further extend the storage period of water chestnuts and prevent storage diseases, a series of preservation treatment technologies have been developed in recent years: water chestnuts are prone to browning due to phenolic oxidation after harvesting. To address this problem, chemical and physical methods can be used to inhibit PPO enzyme activity. Commonly used chemical treatments such as coating 0.1% sodium sulfite or citric acid on the surface of water chestnuts can effectively prevent browning for 2~3 weeks, but sulfite may have residual problems. In physical methods, high concentration of carbon dioxide atmosphere can significantly inhibit browning. To reduce water dispersion and bacterial infection, a edible film can be applied to its surface. Commonly used coating materials include polysaccharides such as sodium alginate and chitosan (Zhang et al., 2021). The most common storage period is soft rot and mildew caused by fungi. For example, mold and rot during storage caused by Penicillium and Rhizobium. In this regard, water chestnuts can be subjected to preventive sterilization after harvesting. Based on food safety, the surface of water chestnuts can be cleaned and disinfected with low concentration of hypochlorous acid or peracetic acid solution. Ozone fumigation or ultraviolet irradiation can also be used to kill attached bacterial spores. The ozone concentration is 5 ppm~10 ppm and the action is 30 minutes, which can effectively reduce the occurrence of mold and rot in the later stage. Since the deterioration of the quality of water chestnuts after harvest involves many factors and the effect of a single measure is limited, it has tended to comprehensive preservation technology in recent years. For example, a study combined 2% acetic acid+low dose ozone+ice-temperature refrigeration, and found that freshly cut water chestnuts remained in good color and qualified microbial indicators after 10 days of storage under this combination. Comprehensive treatment achieves the dual purpose of extending shelf life and controlling disease through the synergistic effect of multiple targets.
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