Harvest and Post Harvest Processes for Cold Storage of Apples
Cold storage of apples there are issues to be considered during and after the harvest until the apple comes to the Cold Storage. It has to go through some processing. Apples are harvested before they reach eating ripeness, during the period defined as tree ripeness or harvest ripeness. Apples harvested too early are of poor quality due to a lack of flavor and aroma. It is recommended to separate very large and small fruits and to store medium-sized fruits specific to the variety. Very large fruits stored in cold storage have a shorter storage life, and very small fruits have low economic value. Before storing apples, it is necessary to classify them according to color, size, and maturity, and separate damaged, injured, bruised defective and diseased fruits.
Cold Storage of Apples Conditions
The cooling rate of apple fruit affects product quality, but its importance varies with variety, harvest maturity, nutritional status of the fruit, and storage history. It is very important to quickly cool apple varieties that mature in the early part of the harvest season (summer varieties) since they will soften more quickly than those that mature in the latter part of the harvest season. Summer apples tend to soften more quickly in the later stages of maturity than in the early stages within the species. The effects of slow cooling become greater as the storage length increases. Therefore, inadequate investment of resources at harvest to ensure rapid fruit cooling may not be apparent until late in the storage period when fruit may not meet minimum firmness standards for marketing. For example, a 1-day delay at 21 °C (70 °F) before cooling results in a 7- to 10-day loss of storage life for an apple.
Optimum Conditions
Apple producers have learned that apple fruit responds dramatically to both temperature and atmosphere modification. Rapid temperature drop and proper maintenance of low temperatures near the cultivar’s freezing point can yield good results for a medium quality crop after 4 to 7 months of storage and in some cases longer storage. However, modern commercial cold stores can be made more suitable with the CA system for the long-term storage of apples.
Regular Conditions
The recommended conditions for commercial cold storage of apples are -1 °C to 4 °C (30 to 39 °F) and 90 to 95% RH, depending on the variety. The acceptable duration of cold room storage has become shorter over the last several years as quality standards in the market have increased.
Apple Storage Conditions at a Glance
| Item | Value |
|---|---|
| Storage temperature | –1 to 4 °C depending on the variety; –1.1 to 0 °C for Golden |
| Humidity | 90–95 % |
| Storage life in a regular cold room | 3–4 months for Golden; 4–7 months for a medium-quality crop cooled quickly |
| Storage life in controlled atmosphere | 8–10 months for Golden |
| Cooling delay | Each day at 21 °C before cooling costs 7–10 days of storage life |
Values from the product data of our cold room calculator, based on USDA Agriculture Handbook 66, UC Davis, FAO and GCCA sources.
Regular Cold Storage or Controlled Atmosphere?
In a controlled atmosphere (CA) cold store oxygen is lowered, carbon dioxide is held at a set level, ethylene is absorbed and nitrogen is supplied by a generator, so the fruit ages more slowly without chemicals. The storage time of apples, pears, grapes, pomegranates and kiwis rises 2–3 times. CA rooms need gas-tight doors, panel joints, floors and ceilings, so they are planned as CA rooms from the start.
Planning an Apple Cold Store
- Fast cooling: plan the refrigeration for the daily harvest intake; forced-air pre-cooling removes the field heat quickly.
- Separate rooms: varieties with different storage temperatures, and fruit for early and late sale, do better in separate rooms.
- Our project: in Bukhara, Uzbekistan we built a fruit cold storage with 10 cm panels, sliding doors and a central refrigeration system with Bitzer compressors and an air-cooled condenser.
Frequently Asked Questions
What temperature should apples be stored at?
Between –1 and 4 °C, depending on the variety, at 90–95 % humidity. Most varieties keep best close to their freezing point.
How long can apples be kept in cold storage?
Golden apples keep 3–4 months in a regular cold room and 8–10 months in controlled atmosphere.
Why do apples need to be cooled quickly?
Apples soften while they are warm: one day at 21 °C before cooling costs 7–10 days of storage life, and the loss shows only late in storage.
