Honeycore has drawbacks in long-term storage

A little honeycore makes Fuji apples taste better, but you can have too much of a good thing.

By Geraldine Warner

Whether you call it watercore or honeycore, and consider it a disorder or an attribute, one thing's for sure: it's more difficult to store affected apples successfully long term.

During the Columbia Basin Tree Fruit Day in Quincy, Washington, orchardist Jim Baird reported on a trip to Japan, where the watercore Washington growers dread is considered a virtue in an apple and is called "honeycore."

Baird suggested Washington producers might be doing themselves a disservice by labeling the condition "watercore," and urged the industry to adopt Japan's more mouth-watering terminology.

Dr. Jim Mattheis, plant physiologist with the U.S. Department of Agriculture in Wenatchee, Washington, followed Baird's suggestion during his presentation at the same meeting, but pointed out that Fuji apples with severe honeycore do not hold up well in long-term, low-oxygen storage.

Slow start

Mattheis recalled that the 1997 growing season got off to a slow start with a late bloom, which is a concern with a variety that usually needs 180 to 190 days between bloom and maturity. In north central Washington, the postbloom period was relatively cool and wet, which not only increases the risk of fireblight, but can lead to increased problems with postharvest decay, he explained. Some of the decay-causing pathogens can get into the fruit any time from bloom onward, ready to infect the fruit as it starts to ripen.

Some positive aspects of the 1997 season were that there were no blistering hot periods, so there was not much sunburn, and the lack of intense stress on the trees during the summer led to high soluble solids and titratable acid levels, judging by samples tested by Washington's Apple Maturity Program. In fact, both sugar and acid levels were higher than they have been for the past four years, which bodes well for storage performance, assuming other conditions are appropriate, Mattheis said.

One of the less desirable aspects of the 1997 season was early cold weather in late September and early October, which led to the early onset of honeycore. This happened about 140 days after full bloom when samples showed that the apples were not yet mature enough to be harvested. The honeycore became a predominant concern, whereas in other years growers focused more on the change in background color, red color development, and starch loss when deciding when to pick the fruit.

"When we get that early honeycore, you have to look at that first, and see how everything else is fitting into that, so you don't end up with a situation where the fruit looks as good as it's going to look, but has watercore and not much starch left, because that's difficult to put into long-term storage," Mattheis noted.

In his tests, Mattheis has had good results storing low to moderate honeycore in low-oxygen atmospheres, but advanced maturity decreases the chances of successfully holding fruit in controlled atmosphere (CA) storage. He said there had been reports of problems with some fruit coming out of storage that appear to be related to maturity and honeycore at harvest.

Red color development was fairly good overall in 1997 compared with some other years, he said, and the change in background color progressed in a more orderly way than in 1996, when many people delayed harvest until November because of the green background color.

Mattheis said as more supplies of Fuji become available, buyers are becoming more selective and don't want fruit with a green background color. He said it also appears that fruit with a green background doesn't develop the good eating qualities associated with Fuji.

The background color of fruit from older trees seems to change more readily and earlier in the maturation process, so growers don't have to wait until most of the starch is gone before seeing the background change, he said. However, if the trees have too much wood and too much shade, it will affect the ability of the fruit to develop red pigments, and the fruit will accumulate less sugar and acid, because the resources of the tree go into growing the tree rather than the wood.

Staining

For the past several years, Mattheis has been studying the brown skin staining that sometimes mars Fuji. Some orchards are more prone to the disorder and have it to a degree every year. Some had less staining in 1997; some had more. It usually shows up after two months in storage.

A warehouse in north central Washington has reported seeing a fair amount of staining this year in fruit that was packed early in November, when the packing line was available, and then held for three to four weeks until the company was ready to ship it. The fruit had to be repacked.

Internal breakdown

While it is recommended that Red and Golden Delicious apples be brought down to CA conditions as quickly as possible after they are placed in the storage room, this may not be the best tactic for Fuji, Mattheis said.

One of the main benefits of rapid CA is that it helps maintain firmness, but Fuji apples don't soften very quickly, he said. Fuji is a dense apple and does not respire as well as some other varieties. If the apples are suddenly exposed to a low-oxygen atmosphere, the internal concentrations of oxygen may not be enough for the fruit to survive, and carbon dioxide may build up inside the fruit, which can lead to internal browning. This also applies to Braeburn.

"We can get away with not being in a big hurry as far as pull-down of CA," he said. "You're much better off to put them into storage, and let the fruit acclimate to being off the tree and in a cold room, before you impose CA on them."

Researchers in New Zealand have found that Braeburn apples treated with the antioxidant DPA (diphenylamine) are less likely to develop internal browning in storage. USDA researchers in Washington State have found this works with Fuji as well as Braeburn.

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Honeycore has drawbacks in long-term storage

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