In this week’s post, I’m tackling one of the most common questions we get about our fruits and sharing with you all about how we store apples and pears. Stemilt harvests apples and pears in the fall months, but packs and ships them to your stores most months out of the year. How can that be? It’s made possible by controlled atmosphere storage technology and lots of research on understanding each apple and pear variety we grow.
Controlled atmosphere (CA) storage helps agriculture producers like us extend the seasonality of our fruits. The history of CA storage in fruit dates back nearly 100 years and came about after concerns surrounding food shortages in England during World War I. In 1917, two researchers in England, Franklin Kidd and Cyril West, were recruited by the government to study ways to improve fruit storage. Through a decade of research, Kidd and West found that fruit ripening could be halted in storage by increasing carbon dioxide and lowering oxygen levels. They also found refrigeration to be an important component to fruit storage as cold temperatures were found to reduce fruit respiration.
The first commercial CA storage facilities made their way to the United States in the 1940s. My grandfather and Stemilt founder, Tom Mathison, built Stemilt’s first CA storage rooms in 1964.
Apples and pears are ideal fruits to be stored because they contain stored carbohydrates. This is not the case for fruits like cherries, peaches, or nectarines. Apples and pears convert starches in their flesh to sugars by taking in oxygen and giving off carbon dioxide. CA rooms are set up so that we can regulate temperature, natural gases (oxygen, carbon dioxide, and nitrogen), and humidity levels using computer control. Temperatures in the rooms are kept between 32-36 degrees Fahrenheit and humidity is maintained at 95 percent.
Bins of apples or pears with the right storage characteristics are placed into CA rooms immediately after harvest. Once full of bins, the room is sealed and oxygen levels are reduced by infusing nitrogen gas into the room. Oxygen goes from the 21 percent found in the air we breathe to 1-2 percent. Low oxygen levels significantly slow the respiratory process, or starch-to-sugar conversion, in apples or pears while they are kept in sealed CA rooms. Each piece of fruit is essentially in a resting state, respiring very little, and all the while maintaining its crisp texture.
Using information kept about fruit quality from tests we run during harvest, Stemilt creates a schedule to open CA rooms and begin packing the fruit inside. In the fall and early winter, the fruit that is packed comes out of regular refrigerated storage. By this time of year, apples and pears from CA rooms are the ones being packed by us fresh daily. Once we open the room and take bins of fruit out of controlled atmosphere, the apples or pears begin respiring again. The fruit is awake and the starch-to-sugar conversion starts again.
Fruit that is reserved for long-term CA storage actually has great qualities at harvest time. It is picked when mature, but has high starch levels that result in high sugar levels and great flavors when the fruit makes it to store shelves in the winter, spring, and even summer months. We follow storage protocol for any of the apples and pears we put into CA storage, and even have a R&D department that researches best practices for each variety of apple or pear we grow, as well as how to maintain fruit quality during storage.
The technology we use to store apples and pears has certainly evolved over the years, and will improve in the future, but continues to be all about providing you with crisp, flavorful fruit and a consistent eating experience no matter what time of year it is.