Apple cold storage is indispensable for the preservation of apples until the harvested apples are shipped to the market and delivered to the final consumer. These warehouses can be ordinary warehouses, cold storages or atmosphere controlled cold storages.
The storage period of apples, the storage time of the fruit, the nutritional status of the tree varies according to the season and variety. Many apple varieties can be stored for a long time at -1 to 0°C and 85-90% relative humidity. The temperature in commercial warehouses is 0-2°C. Apples freeze at -2°C. Golden and Starking should be stored at 0°C and 90% relative humidity, and Granny Smith should be stored at +3°C.

Apple Harvest

The criteria to be considered in determining the harvest time in apples are the number of days from full flowering to maturity, the firmness of the fruit flesh, the color of the fruit skin, the breaking of the fruit from the branch and the starch level. Golden Delicious and Starspur Golden Delicious varieties can be stored for 5 months, Starking Delicious and Starkrimson Delicious varieties for 7 months, and Granny Smith varieties for 9 months with just-in-time harvesting and proper storage conditions. In general, summer apples should be picked when they reach full maturity on the tree, both in terms of picking and eating. In this case, summer apples will be of high quality. There is a long time interval between tree death and eating death in winter apples depending on the variety characteristics. If the harvested apple is to be eaten immediately, it is necessary to wait for eating. If it will not be consumed immediately and will be stored, it can be harvested when they reach tree maturity (they easily break from the branch).

Apple Storage

Ethylene Production and Sensitivity

The apple is classified as a climacteric fruit whose respiration increases during ripening. This increase is associated with increases in internal concentrations of carbon dioxide and ethylene, respiration and autocatalytic ethylene production. Endogenous ethylene production can vary greatly between cultivars. In general, early harvest varieties have high ethylene production rates and mature quickly, while late harvest varieties have low ethylene production rates and mature slowly. Apple ripening is promoted by exposure to ethylene. Preventing or slowing ethylene production by interfering with ethylene synthesis is a strategy to increase fruit storability. This is achieved mainly by the use of low storage temperatures and the application of atmosphere-controlled storage technologies.

Respiration Rates

Generally, early harvest varieties have high respiration rates while late harvest varieties have low respiration rates. The respiration rate of the fruit is directly affected by temperature, and the airway temperature is suppressed by storage temperatures below 10°C. The lowest temperatures for storage should be above freezing and above temperatures where chills injuries will develop.

Cooling Conditions

The cooling rate of apples affects the maintenance of quality, but its importance varies with variety, harvest maturity, nutritional status of the fruit and storage date. Rapid cooling of apple varieties ripening in the first half of the harvest season (summer varieties) is very important because they soften faster than those ripening later in the harvest season. In one variety, apples tend to soften faster in the later stages than in the earlier stages. Slow cooling effects increase with increasing storage length. Therefore, insufficient investment of resources at harvest to ensure rapid cooling of fruit may not be apparent until late in storage, when fruit may not meet minimum hardness standards for marketing. For example, a delay of 1 day at 21°C before cooling results in a hypothetical loss of storage life of 7-10 days. Maximizing the quality care of fruit requires attention to temperature not only immediately after harvest and during storage, but also during packaging, transportation and retail display. The confluence of these events is described as the "cold chain", emphasizing the importance of maintaining links from harvest to consumer.

Conclusion

Optimum Storage Conditions

Apple producers are well aware that apples respond significantly to both temperature and atmosphere modification. Consideration and proper application of rapid and pre-chilling can provide a medium quality product for apples with 3 to 6 months of storage and in some cases longer. However, modern commercial warehouses combine temperature management with atmosphere control for long-term storage of apples. A well-designed cold store, recommended conditions for commercial storage of apples should be observed at -1°C to 4°C and 90-95% humidity depending on the variety. As the quality standards in the market have increased, the acceptable storage time has been shortened. Also, as the available period for sale of stored fruit decreases, short-term atmosphere controlled storage is becoming more common.

Controlled Atmosphere Assessments

Apples are products that are usually stored under controlled atmosphere conditions, but gas composition and storage temperature conditions vary according to variety, volume, and equipment available for monitoring and controlling the atmosphere. Interactions occur between oxygen, carbon dioxide, and temperature. For example, low storage temperatures increase susceptibility to low oxygen level damage. Also, when very low oxygen levels are used, carbon dioxide levels must be reduced to prevent oxygen damage. For all your questions about your apple cold storage projects that you plan to store apples, you can call us without hesitation and get information from our expert teams.