Sleeping Apples

portrait photo of Kenneth

Kenneth R. Ridings, P.E.

Sleeping Apples

Have you ever wondered how you can buy apples in the store in wintertime when you know apples ripen in the summer? How can that be? Well, shortly after they are picked in the summer months they are put to sleep. They hibernate until the grocery stores need them in other months of the year and they are brought out of hibernation. How are they put to sleep and how do they wake up? Through a process known as Controlled Atmosphere (CA) Storage.

Like humans, apples need oxygen to breathe. Unlike humans, apples can live, albeit in a sleepy state, with reduced levels of oxygen. Shortly after picking, apples are placed in bins and stored in large sealed, windowless, and unlit storage rooms where the air is refrigerated to slightly above freezing and most of the oxygen is removed. Air temperature, carbon dioxide, oxygen and humidity levels are controlled in the room in order to slow the ripening process. In other words, the “atmosphere” of the room is “controlled”, thus the name Controlled Atmosphere (CA) Storage. Slight deviations in any of these conditions could damage the fruit. 

Uniform conditions throughout the room are accomplished by stacking and positioning the crates in a manner that allows air to circulate around and in between the bins. Also important is the electrical and mechanical equipment that monitors and controls the air conditions and circulation in the room. 

EDT is often called to investigate damaged fruit in CA rooms and asked to determine what caused the damage. One of the first things to look at is which, if any, of the atmosphere conditions varied from their intended setpoint, and if so, then determine if equipment or facility operation caused the variation. For example, if room temperature was 5 degrees above set-point, things to look at include the refrigeration system, temperature monitoring and control system, placement of bins, quantity of apples, and traffic in and out of the room.

Now you no longer need to wonder how there can be ripe apples in grocery stores in the wintertime!

About the Author

Kenneth R. Ridings, P.E. is a consulting engineer with our Oakland Office. Mr. Ridings provides consultation services in the areas of infrastructure utilities, machinery and equipment investigations, scope of damage and value of loss estimates, business interruption timeline schedules, construction monitoring and timeline scheduling, project management, fire causation, and water damage investigations. You may contact Ken for your forensic engineering needs at or (925) 674-8010.

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