Apple ripeness determined by several factors

Emma Johnson demonstrates how using an iodine solution on the white flesh of apples can help indicate ripeness.
Photo courtesy of Practical Farmers of Iowa

by Deborah Jeanne Sergeant

Knowing if your apple crop is ripe is very important for your farm’s profits. That’s certainly true at Buffalo Ridge Orchard,

where co-owner Emma Johnson determines when it’s time to harvest the Central City, Iowa, farm’s crop. Johnson spoke on apple ripeness in a recent virtual on-farm workshop hosted by Practical Farmers of Iowa.

Buffalo Ridge Orchard grows 4,500 apple trees and 300 pear trees. It’s not always easy to tell when the fruit is ready to pick, though. The farm’s 50 apple varieties ripen at different times and even those that coincide in one year may not do so another year. Factors such as frost, temperature, available sunlight and rainfall affect the varieties differently.

Initially, tasting the fruit told Johnson that the fruit was good to go; however, that model is difficult to scale up once the farm grew to its current capacity and diversity.

“At a point, we were testing 20 varieties,” Johnson said. “Our palate isn’t refined enough to know if something is right. If it’s a tart apple, you can err on the side of something too starchy and tart and not suitable to storage.”

This year’s bloom was late, so the farm anticipated a late season. Even the number of apples on a tree can influence harvest timing.

“If you have a few apples on a tree, it will ripen sooner than one that is loaded,” Johnson said. “If you’ve over-thinned, it can make difference.”

The color of the skin can indicate ripeness, but that should not be the only indicator that it’s time to harvest.

“We want to make sure we test and realize when they’re at peak ripeness,” Johnson said.

She tests pressure with a Wagner pressure gauge. She peels the side with less color and the side with more color if the apple has a color difference.

“I would test an apple that I thought looked a little under-ripe and one I think is overripe,” she said. “You’d be surprised at the number of times they’re closer together than you think.” The goal is to find apples as close to peak ripeness as possible.

“If our goal is to store these apples for a year in controlled storage, we’d have a much different strategy,” Johnson said. “We have walk-in coolers and do something with Smart Fresh but not much else. We want a nice, crunchy apple that tastes good.”

Apple pressure should be around 15 on the pressure gauge for many varieties, but a MacIntosh at 12 is a softer type; a crisp apple like Empire should be at 14.

“The pressure will tell you how crisp and crunchy that apple will be,” Johnson said. “If you let it hang until it has less pressure, as long as it doesn’t drop, it will not be as crisp.”

Johnson cuts the apple in half crosswise, to look inside. “If the seeds are black, not white, that can indicate they’re close,” she said.

While wearing gloves and safety goggles, she sprays the inside flesh with a 10% iodine solution and waits a few minutes. “You can take a shallow cookie sheet or pan and dip the apples, but you use a lot more iodine that way,” Johnson said.

Since apples ripen from the inside out, it’s vital to know what’s happening from the core outward, and to not rely only on the “skin deep” beauty of peel color. After two minutes, iodine causes the apple’s flesh to appear stained blue-black if starch is present. Those apples aren’t ripe yet. White-fleshed apples are ripe. (Carefully dispose of any fruit tested with iodine, as it’s poisonous.)

Johnson also recommends using the starch scale available from Cornell University, which is available at https://tinyurl.com/y682223h, since it includes many varieties.

Testing apples in a variety of ways allows Johnson to ensure her farm’s resources of time and labor are used effectively for harvest.

“Testing allows us to make a plan,” Johnson said. “You’d be amazed in four days how much can change.”

Each week, the farm harvests the apples that are ready and then records the timeline to give an approximate idea for next year. During harvest season, she walks the harvest to test what apples appear ready.

“If you pick a gold too late, you’re not going to get the storage life, but you don’t want to err on having them taste like a potato,” Johnson said. That’s why testing is vital.

“The pressure test and starch test will help you get the right timing on that,” she said. “You could pick an apple a month early, but it’s not storing as well and it won’t be as sweet. You want plenty of sugar and plenty of integrity with that apple.”

2020-11-04T15:02:29-05:00November 4, 2020|Grower East, Grower Midwest|0 Comments

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