Left: Soft scald on Honeycrisp. Right: Honeycrisp with soggy breakdown.
Honeycrisp is a challenging apple to grow, and the challenges don’t stop when the fruit is in the bin, notes Dr. Jim Mattheis, postharvest physiologist with the U.S. Department of Agriculture in Wenatchee, Washington, who is researching strategies for storing the variety long term.
Honeycrisp is prone to a number of disorders, including soft scald, soggy breakdown, internal breakdown, and bitter pit, and can turn greasy when ripe. Research in Michigan and New York has shown that DPA (diphenylamine), which is used to prevent scald on other apple varieties, is not effective on Honeycrisp, Mattheis reported.
When storing the fruit long term, and trying to minimize postharvest disorders, it’s important not to compromise the aroma and acidity or other quality attributes of the apple, he noted.
Researchers believe that low storage temperatures might induce soft scald and soggy breakdown, and that a delay in cooling can reduce the risk of such disorders developing. In experiments in the eastern United States, holding fruit at between 50 and 68°F for seven days before cold storage, reduced the incidence of soft scald and soggy breakdown, Mattheis said. The higher temperature seems to have little negative impact on the firmness of the fruit after storage, but a downside is that it can result in more bitter pit and greasiness. Growers need to do all they can to manage bitter pit in the field because the industry might not have the luxury with this variety of being able to cool the fruit as fast as possible at the packing house, Mattheis said.
In experiments in Washington State last season, Mattheis tested the effect of delayed cooling on Honeycrisp stored for four or eight months. None of the fruit had much starch left at harvest—with starch readings ranging from 5.3 to 5.9—and there was a definite transition in the background color from green to yellow before the apples were put in storage.
Some fruit was held at 33°F for the entire storage period, some was held at 40°F the whole time, and some was held at 40°F for ten days, and then 33°F for the rest of the storage period. Some of the fruit was put in CA (controlled atmosphere) storage, and some in air. Some were treated the day after delivery from the orchard with MCP (1-methylcyclopropene) and some were not treated. After storage, the fruit was held at room temperature for a week before being evaluated.
The fruit held at 33°F for the whole period had the most soft scald, and fruit held at 40°F for the whole period had the least. However, in lots that were highly susceptible to scald, holding the fruit at 40°F was not sufficient to prevent the disorder, he said. The fruit lot that had the most soft scald had the lowest firmness (12 pounds) at harvest. The effect of CA or MCP on soft scald varied by fruit lot, but those treatments did not seem to make scald worse, Mattheis reported.
In every case, there was less soggy breakdown than soft scald. Fruit that had soft scald had soggy breakdown as well. Only the fruit from one orchard, which had a light crop load and large fruit, developed a large amount of bitter pit.
After four months of storage, there was no difference in the firmness of apples put into the various treatments. After eight months, and a week at room temperature, there was still no difference in the outer firmness, but the inner flesh of fruit held at 40°F for the whole storage period was significantly softer than fruit in the delayed-cooling treatment. MCP had a beneficial effect on firmness in some cases but not in others.
The condition of the fruit in the trial was variable, both at harvest and after storage. The better treatments overall were typically CA or MCP with the temperature held at 40°F for ten days followed by 33°F, but they weren’t great, Mattheis said.
"They were okay, but they weren’t the Honeycrisp that you’ve come to expect, when you pick them with these kinds of maturity parameters."
This is something to consider when deciding how long to store Honeycrisp apples, he added. Some of the inherent qualities of the apple might not be preservable for as long as eight months.
Delaying the cold treatment is definitely a good thing, he concluded, but continued high temperature is not. Both CA and MCP slowed the loss of acid, the loss of firmness, and reduced decay in some lots, Mattheis said.
Fruit as mature as those he tested would be good to pack and ship immediately, Mattheis said. For successful long-term storage, the fruit should have a lower starch conversion score and be less mature at harvest, just as with other varieties. The fact that the apple doesn’t soften as rapidly as other varieties allows it to be stored at higher temperatures in order to manage storage disorders.
Trying to develop long-term storage protocols for Honeycrisp is difficult, he noted, because some of the Honeycrisp plantings in Washington are not yet mature. "It’s hard to predict which types of management are going to give you the best long-term storage potential."
An online gallery of Honeycrisp apples with various maladies, compiled by Jon Clements, extension tree fruit specialist at the University of Massachusetts, can be found at www.fruitadvisor.info/honey crisp/honeycrisp. html. Dr. David Rosenberger of Cornell University in New York supplied many of the pictures.