You harvest apples in the fall. They are no longer really fresh and crunchy on the fruit bowl within a week. Even in the refrigerator or a cold shed you won’t keep them fresh all winter long – let alone until next fall. Even if you keep mold in check, mealiness seems inevitable. How is it possible that you can always buy juicy apples, even from your own country?
First the question why apples actually become mealy. That lies in the cells that make up the apple. A newly picked apple contains those cells full of moisturewhich makes them sturdy, and they are firmly attached to each other with a kind of adhesive: pectin. As soon as you bite into the apple, the tissue bursts and the juice flows into your mouth. That combination gives that delicious mouthfeel of a fresh apple.
But the apple continues to ripen even after picking. Starch is converted into sugars, making the apple sweeter. But things happen other things too. The cell walls become less firm, and the pectin that sticks the cell walls together is broken off. The apple also dries out slowly, causing each cell to shrink a little. Now you’re essentially biting into a loose collection of limp bags instead of a solid, coherent structure. These loose cells remain intact in your mouth for longer, which is a problem during chewing dry and mealy mouthfeel gives.
For the secret of fresh apples all year round, we naturally call the Betuwe. That’s where One Frio is located, one of the larger fruit storage companies in the Netherlands. “Apples go straight from the orchard to the refrigerator,” says Gian Piels of One Frio. “Sometimes at the cultivation company itself, sometimes at corporations. But you also have specialized storage companies, like us.”
Pears are kept colder
One Frio stores apples in large crates in cold rooms measuring 6.5 by 8 by 13 meters: large enough for a few hundred tons of apples. “These are the same crates in which the apples are harvested,” says Piels. “They drive out of the orchard in fruit trains and then go straight to the refrigeration facility in a truck.”
Apples should be stored at 1 to 3 degrees Celsius, depending on the variety. Pears even at 0.7 degrees below zero. “After picking, we let the fruit rest in the refrigerator for a few days,” says Piels. “And then we start with a CA regime: controlled atmosphere.”
The most important element of this is ULO: ultra low oxygen. An apple is a living product, even after picking. All kinds of processes take place there: ‘normal’ combustion, but also maturation. “All these processes require oxygen. So if you keep the oxygen concentration very low, below 1 percent, they virtually come to a standstill. You don’t want to stop them completely, because then the tissue will die.”
This storage method was developed in the 1980s, Piels knows, and is still being refined. “A lot of research is being done into for example in Wageningen“, he says. “There are now very precise ‘recipes’ for storage for each variety.” In addition to temperature and oxygen, there are more buttons you can turn. For example, the levels of carbon dioxide and ethylenea gas that plants (and also apples) produce and that drives growth and ripening. Piels: “We are already working on this, and a lot of research has been done, but the biggest benefit is in ultra-low oxygen.”
