Apple air-conditioning storage technology

Apple storage under controlled atmospheric conditions must be carefully managed based on the specific characteristics of each variety. The apples should be harvested at the right time, free from pests and mechanical damage, and cooled down to their optimal temperature as quickly as possible. While atmosphere storage is typically combined with mechanical refrigeration, effective results can also be achieved in crypts or ventilated rooms where temperature is well regulated. This method requires specialized equipment and gas control systems to maintain a specific gas composition, with strict monitoring of oxygen (O₂) and carbon dioxide (CO₂) levels throughout the storage period. Common techniques include cold storage, plastic film covers, sealed plastic bags, and silicone windows. 1. **Cold Storage with Gas Control** Air-conditioned storage relies on a well-sealed cold room equipped with devices for adjusting and measuring gas composition, temperature, and humidity. This system is easy to manage and ensures stable environmental conditions, significantly improving storage quality compared to regular cold storage. It allows for precise regulation of O₂ and CO₂ levels, which is crucial for maintaining apple freshness over long periods. 2. **Plastic Film Covers** Large plastic film covers are used in cold or ventilated rooms to create a simple controlled environment. These covers are made of 0.1–0.2 mm thick polyvinyl chloride (PVC) and can hold between 2.5 to 10 tons of apples. The process involves laying the film at the bottom of the storage area, placing a mat such as bricks or sleepers, and then arranging pre-cooled apple boxes inside. The cover is then sealed tightly, with the edges rolled and buried in a ditch or pressed with bricks to ensure an airtight seal. Gas adjustment in these accounts can be done through two methods: **spontaneous respiration** or **rapid hypoxia**. In spontaneous mode, the fruit's own respiration lowers O₂ and increases CO₂ naturally. In rapid hypoxia, some air is removed using a pump, and nitrogen is introduced to quickly reduce oxygen levels. After several cycles, the desired gas balance is achieved. Regular sampling is necessary to check O₂ and CO₂ levels, and adjustments are made accordingly. If O₂ becomes too low or CO₂ too high, air is added or slaked lime is used to absorb excess CO₂. Typically, 0.5–1 kg of slaked lime is used per 100 kg of apples. 3. **Silicone Window Storage** This method involves attaching a silicone rubber window to the plastic film cover, allowing controlled gas exchange. The silicone window has better permeability for both O₂ and CO₂ than standard plastic, enabling the film to self-regulate gas composition. The size of the window is determined experimentally based on the quantity of apples and the required gas ratio. 4. **Plastic Bag Storage** Small-scale storage uses polyethylene bags with a thickness of 0.06–0.08 mm. Apples are placed in baskets or boxes and sealed in the bags, which act as individual storage units. The bag’s permeability and the apples’ respiration help maintain a balanced internal gas environment. However, it’s important to regularly monitor O₂ and CO₂ levels. If the oxygen level drops too low or CO₂ rises too high, the bag should be opened for ventilation to restore balance. This method is ideal for small quantities and offers flexibility in storage management.

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