by Tamara Scully
The optimal time for picking fruit involves the convergences of ripeness, storage ability, market demand and the whims of Mother Nature. If any of these are ignored, rotten apples just might be the end result.
Fruit ripening involves ethylene, which triggers genes in the cells of the fruit. These genes turn on proteins, which in turn cause ripening to occur. One of the problems with apples is that this system isn’t equally developed in all varieties.
The ripening response isn’t uniformly expressed in all apples. Rapidly rising ethylene levels cause fruit to soften quickly after picking. To store apples long-term, they must be picked prior to this occurrence. In some varieties, the ethylene response is much quicker than in others.
“Some varieties work better than others,” Dr. Christopher S. Walsh, Professor of Pomology, University of Maryland, said. “Growers can’t measure ethylene,” as it requires expensive, sophisticated equipment, leaving growers without a reliable standard to uniformly assess apple fruit maturity.
Ethylene forms in the core and moves outward. As ethylene levels rise, they are believed to cause other physiological changes in the fruit. These changes are visible, or are more easily measured. They include: fruit size; surface color and ground color; starch pattern index; seed color; flesh firmness; and soluble solids (Brix).
Dr. Walsh, along with Penn State Extension Educator Tara Baugher, have been performing apple maturity assessments from August through October. These assessments are an attempt to quantify the changes seen in the various attributes of the apples leading up to harvest, and to assist growers in picking at the correct times.
The right time for picking isn’t going to be the same for everyone. Not only will ripeness vary by region, it will vary by elevation, sunlight received, rainfall amounts and type of training system. And, the degree of ripeness needed at picking will vary by market.
Supermarkets need to handle fruit for several weeks, Dr. Walsh said, with the rule of thumb being three weeks from harvest to sale.
If fruit for this market is picked too ripe, it will lose quality by the time the customer takes it home. Combine that with the commercial grading system — which depends on color — as well as a blemish-free appearance, and it’s not a given that customers will be biting into a flavorful apple from the supermarket, no matter where it originates.
The supermarkets are demanding more selection, too.
“It used to be that supermarkets only wanted two or three varieties,” he said.
Today, the demand for apples has moved beyond Red and Golden Delicious or McIntosh. But the sought-after varieties are often competing for shelf space with the end of the late peach season, leaving growers with excess fruit left on the trees, but too ripe to put into long-term storage.
Another complicating factor is the many strains of certain cultivars, such as Fuji. Some can be picked before they are ripe, and they taste and eat great, Dr. Walsh said. Others can stay on the tree for a month past ripeness and be perfect for eating.
The wholesale market demand for fresh early season apples occurs in the spring, but growers who tried to pick ripe to direct market, or to sell to regional supermarkets, don’t have a surplus that can last in storage this long. Galas picked tree-ripe should be sold by October or November, Dr. Walsh said.
The proper cold storage temperature varies by apple variety. While Honeycrisp are notorious for cold injury at the relatively high storage temperature of 37 degrees Fahrenheit, most apples do well at 32 degrees, as long as they don’t freeze. Soft scald or soggy breakdown are conditions which occur when there is chilling damage.
Disorders such as bitter pit can be augmented if apples are harvested early. This has been a problem for Honeycrisp apples. Superficial scald is a browning disorder also associated with early harvest dates of some apple varieties. Late harvesting can cause deterioration in storage, too, and pre-dispose certain varieties to a variety of storage disorders.
The rule of thumb for apples is FILO, or “first in, last out,” Dr. Walsh said. The early maturing apples, if picked before they are too ripe, have the best prospects for long-term storage.
The U-Pick market has its own concerns. Lately there’s been some chatter in certain circles that many apple growers aren’t concerning themselves with optimal picking times, particularly for this group of customers.
One grower, who needs to remain anonymous, admits to pre-harvesting some varieties for cold storage before opening for PYO sales each season. While this may not be ideal, it is the only way he has been able to ensure he has these high-demand apples to sell to his other sales outlets.
Other strictly PYO growers are known to be “picked out” by the beginning of October, even though their orchards have late-season apples which are nowhere ready to be picked for immediate consumption. Unable or unwilling to control PYO crowds, some growers simply allow a free-for-all in the orchard, with all varieties being up for grabs, no matter how far from ripe they may be.
The pressure to have whatever in-demand variety a customer wants, no matter whether it is ready to be harvested or not, has also caused some growers to be less than particular about ripeness.
The result of this type of harvest can be a bad reputation that inadvertently can spread to all growers. If apples coming from local orchards don’t taste flavorful, customers can readily find non-local apples year-round at the supermarket. The edge local growers have over apples shipped in from elsewhere is the tree-ripened flavor and eating quality.
Finding the right time to harvest any given apple variety has become too complicated for many traditional picking methodologies. Color, firmness, Brix and traditional harvest dates aren’t as reliable as indicators of ripeness as growers need them to be.
Market channel demands, climate change and weather extremes, new cultivars and the type of orchard training system used are some of the factors which impact a grower’s decision on when to pick any given apple variety. In order for growers to maintain their reputation for fresh, flavorful apples, all season long, Apple Maturity Assessments — such as the one provided by Dr. Walsh — should be, too.