Above: Honeycrisp is sensitive to chilling disorders such as soggy breakdown. Center top: Radial browning is another common storage problem for Honeycrisp. Center middle: Soft scald can develop if Honeycrisp are subjected to cold storage temperatures right after harvest. Center bottom: An example of bitter pit in Honeycrisp. Growers might be able to identify Honeycrisp apples prone to bitter pit before harvest by exposing fruit samples to a hot-water treatment and cutting them the next day for evaluation.
Honeycrisp is a dream apple, with a crispness and unique flavor that has sent retail sales soaring. But the apple is a nightmare for packers because it’s prone to the kinds of disorders that are made to order for postharvest research.
As researchers and industry gain more experience with the relatively new variety, storage and handling recommendations are emerging to help improve fruit quality and length of storage. A panel of Washington fruit packers, together with a scientist and consultant, assembled during statewide horticultural talks last December to share their experiences in storing the fickle variety.
“Honeycrisp issues start with knowing when to pick it, to managing bitter pit and greasiness, and end with knowing how to store a variety that’s highly decay-susceptible,” said Dr. Jim Mattheis, U.S. Department of Agriculture postharvest physiologist. “I’ve seen postharvest things on Honeycrisp that I’ve never seen on any other apple. Honeycrisp provides us with real challenges in figuring out how to use the tools we have so that growers and packers can be successful producing and delivering high-quality fruit.”
When picked early (green background color with starch less than 4), Honeycrisp has good storability but might not develop the intense flavor that the variety is famous for, Mattheis said. Conversely, late harvest, with yellow background and starch at 6, can result in greasiness, and the fruit is at highest risk for chilling disorders and development of off flavors. The variety is highly sensitive to chilling—cooling fruit at 32° to 34°F significantly increases chilling disorder risk. Honeycrisp also appears to be sensitive to carbon dioxide injury when stored at rates of less than 1.5 percent oxygen and more than 1 percent carbon dioxide.
To reduce incidence of storage disorders, Mattheis recommends controlled atmosphere rates above 2 percent oxygen and less than 1 percent carbon dioxide. He has also found benefits from applications of SmartFresh (methylcyclopropene), including reduced greasiness, loss of acidity, color change, development of off flavors, and radial internal browning.
Harold Ostenson, who recently retired from Washington’s Stemilt Growers, Inc., to start his own organic production consulting business, encouraged growers and packers to segregate Honeycrisp by its storage potential.
“Segregation starts in the orchard with horticultural practices that lead to high fruit quality,” he said. Practices like planting in cool sites, using a strong rootstock, pruning in early June to overcome alternate bearing, following a low nitrogen/ high calcium program, and clipping stems at harvest all help produce high-quality fruit.
Hot water bath. He recommends identifying—before harvest—blocks that are prone to bitter pit. An easy way to detect potential bitter pit is to collect fruit samples, expose them to a 110°F hot water bath for 30 minutes, and then cut fruit the next day for evaluation. “If bitter pit is going to occur, it’ll show up the next day,” Ostenson said, adding that it’s better to identify bitter pit potential before fruit is in the box.
Fruit acidity. Fruit acidity levels can also be a tip regarding the block’s storage potential. He’s found from years of analyzing data that fruit with higher acidity stores better.
Fruit tissue samples. Sampling fruit tissue three weeks before harvest is another segregation technique. Ostenson pays close attention to the nitrogen-to-calcium ratio and the magnesium/potassium-to-calcium ratio, using the levels to help decide which fruit has long-term storage potential. He looks for nitrogen to calcium ratios to be 10 or below, and magnesium plus potassium to calcium ratios to be around 28, for an accumulated ratio of zero or less. (The accumulated ratio is the N:Ca and Mg+K:Ca ratios added together with the ratio being the amount above 38. For example, a nitrogen:calcium ratio of 14, plus the magnesium-potassium/ calcium ratio of 31 added together is 45. The accumulated ratio would be 7 because 45 minus 38 is 7.) Ostenson believes that the higher the accumulated ratio, the more likely the block will have bitter pit, soggy breakdown, or other storage issues.
Keep records. “By keeping track of records annually, one can see the numbers increase and decrease with the current crop load,” he said, adding that the data can help indicate if orchards are biennial bearing. “The importance of all this at the warehouse level is to determine the packing order of grower lots, packing the worse lots first.”
Andy Birley of Borton and Sons, Inc., a grower-shipper in Yakima, Washington, described Borton’s experiences with Honeycrisp storage. When the company first began packing Honeycrisp in 2003, bitter pit was the biggest concern. But they soon found that storing fruit in regular storage at 35 to 37°F to combat bitter pit created even worse problems.
“We had multiple years of chilling injury that resulted in severe, severe losses from packouts and delivery problems,” Birley said. “Loads looked good when they left our dock but on arrival fruit had chilling injury problems.”
To counter chilling injury, Birley said they began raising holding temperatures of fruit just in from the orchard. Now, they hold fruit at 50°F for a minimum of seven days, a practice that has dramatically reduced soft scald and other chilling disorders. After at least seven days, temperatures are brought down two degrees each day until a final temperature of 36° is reached.
While there is a trade off between bitter pit and chilling injury, he said the amount of bitter pit is now minimal compared with soft scald. The higher temperatures also help bring out bitter pit within the first week, a better time than when fruit is being packed.
Birley said that they were encouraged by the success they had in a six-room controlled atmosphere experiment last year using SmartFresh and a fungicide drench at harvest to control greasiness. Atmosphere levels in the rooms were 3.5 percent oxygen and 0.5 percent carbon dioxide. “We believe we’ll be able to continue to lengthen the storage season each year for Honeycrisp and still deliver a good, quality product to the consumer.”
Sean Gilbert of Gilbert Orchards in Yakima Valley said they use industry metrics to evaluate storage potential of fruit. They evaluate titratable acidity, aiming for levels of 0.5 gram per milliliter or higher and good flavor to help identify fruit with storage potential. “If fruit doesn’t have the flavor intensity that we want, we may choose not to store the fruit,” he said.
“It’s a balance of controlling temperatures, atmosphere, high fan speed, and using SmartFresh,” he said, referring to their Honeycrisp storage regime. Early harvested fruit is held at 50°F in regular air storage, but by the last pick, he said that regular storage temperatures are dropped to 40°F.