Haocool
Green plums, also known as Chinese green plums, are rich in organic acids, including citric acid, malic acid and tannic acid. They are known for their distinctive sour taste and high acidity. However, green plums are difficult to store at room temperature. After just 24 hours, some of their organic acids may begin to deteriorate or decrease.
To better preserve their acidity and nutritional value, controlled-atmosphere (CA) cold storage can help extend the storage life of green plums and maintain their quality. This guide explains the storage methods and temperature requirements for green plum cold storage.
Green Plum Cold Storage Methods and Temperature Requirements
1. Harvesting
For better storage quality, green plums should preferably be harvested on sunny or cloudy days. Harvesting during rainy weather should be avoided to reduce the risk of excess moisture accumulating on or in the fruit, which may increase the likelihood of decay during storage.
2. Sorting and Grading
After harvesting, green plums should be sorted and graded according to size and quality.
Fruit affected by pests or diseases, as well as deformed, damaged, undersized or cracked fruit, should be removed before storage. This helps reduce the risk of spoilage spreading to healthy fruit during the storage period.
3. Pre-Cooling
Pre-cooling is an important step in green plum preservation. Its main purpose is to reduce the fruit’s respiration rate by removing field heat as soon as possible.
Freshly harvested green plums may still be relatively warm. Without proper pre-cooling, they may turn yellow, develop mold spots or deteriorate more rapidly.
Forced-air cooling is a recommended option for removing field heat efficiently. The pre-cooling process should be planned according to the product condition and required cooling performance, and the pre-cooling period should not exceed 48 hours.
4. Cold Storage
Atmosphere control equipment for controlled-atmosphere (CA) storage
The recommended temperature for controlled-atmosphere storage of green plums is approximately 0°C. The temperature should remain stable, with a target operating range of around ±1°C. Temperature fluctuations should generally not exceed 2°C.
Excessive temperature fluctuations may increase the risk of mold growth and fruit decay.
Relative humidity is also important because it affects moisture retention, fruit quality and flavor. The recommended relative humidity for green plum cold storage is approximately 95%.
If the humidity inside the storage room is insufficient, a suitable humidifier, such as a conventional humidifier or a microwave air humidifier, can be used to help maintain stable humidity levels.
For controlled-atmosphere storage, the recommended atmospheric conditions are:
- Oxygen (O₂): 2–3%
- Carbon dioxide (CO₂): 3–5%
Under these storage conditions, green plums may be preserved for approximately two months. The method is intended to help retain fruit acidity and nutritional value, with a reported marketable fruit rate of up to approximately 90%, depending on the fruit quality, handling procedures and storage conditions.