Challenges with Managing Honeycrisp
The Honeycrisp apple has had a huge impact on the apple industry in the Northeast and beyond. From a consumer perspective, the variety offers a unique eating experience as a result of its excellent, crisp texture and flavor. The willingness of consumers to pay premium prices for Honeycrisp has sustained the profitability for many growers, and yet if it wasn't such a great eating experience it would probably rate as the world's most disastrous apple ever bred!
In addition to its many orchard management challenges, Honeycrisp is difficult to store, and susceptible to several storage disorders (Figure 1) which can result in significant economic losses for growers and packers. The most serious of these disorders is bitter pit, which is associated with high ratios of nitrogen, potassium or magnesium to calcium. The variety is also susceptible to the chilling disorders, soft scald and soggy breakdown. These disorders can occur together or separately, and soggy breakdown is especially disconcerting as it often cannot be seen from the outside of the fruit.
Figure 1. Physiological disorders of Honeycrisp apples. A. Bitter pit, B. Soft scald, C. Wrinkly skin, D. Soggy breakdown, E. Carbon dioxide (CO2) injury, F. Lenticel blotch, G. Senescent breakdown, H. Vascular browning
In an ideal world, we would be able to predict the risk of bitter pit and soft scald development at or shortly after harvest, and make appropriate marketing decisions based on when fruit should be sold. Our current work, funded by the New York Apple Research and Development Program, the New York Farm Viability Institute, the State Horticultural Association of Pennsylvania and Federal Multi-State funding has the objective of developing such prediction methods.
For bitter pit, our focus is on mineral relationships, while for soft scald and soggy breakdown, the focus is on ethanol, an alcohol that may accumulate in the fruit before injury develops. The work on prediction methods is in progress, but in this article our aim is to describe the patterns of disorder development and document the effects of conditioning on increasing the risk of bitter pit development. Our Honeycrisp storage disorder research team was led by Christopher Watkins, Director, Cornell Cooperative Extension and Professor of Post-harvest Physiology, who kindly granted permission to reprint these results originally reported in the Summer, 2016 issue of the New York Fruit Quarterly.
Honeycrisp - To Condition or Not Condition?
Conditioning reduces risk of low temperature storage disorders but increases risk of bitter pit development. Conditioning may be avoidable depending on the orchard block and marketing plan.
Soft scald and soggy breakdown are associated with low storage temperatures, typically 32 to 33°F. In early studies at Cornell a conditioning period of 7 days at 50°F dramatically reduced development of these disorders (Watkins and Rosenberger, 1999), and subsequently the benefit of this treatment was confirmed by colleagues in other growing regions (Watkins et al., 2004). For most apple varieties, delayed cooling of fruit would normally be avoided because of loss of quality, but the unique texture of Honeycrisp with its limited cell wall breakdown made this treatment acceptable. While conditioning greatly alleviated the risk of soft scald, however, it increased bitter pit incidence. An example is shown in Table 1, in which fruit were stored at 33°F or 36°F with and without conditioning. Clearly, the lower the storage temperature, the lower the bitter pit risk, but the higher the soft scald incidence.
Table 1. Soft scald and soggy breakdown incidence in Honeycrisp apples stored at 33°F or 36°F with or without a conditioning treatment of 50°F for 7 days (modified from Watkins et al., 2004). Means with different letters indicate that disorder incidence is significantly different at P=0.05.
|Temperature (°F)||Conditioning||Soft scald and soggy breakdown (%)||Bitter pit (%)|
Understanding the effects of temperature and conditioning in fruit from multiple orchards in several regions can provide insight for growers and storage operators to ensure that the best management decisions can be made. In this report, we outline our findings on the patterns of soft scald and bitter pit development during storage and the critical balance between advantages and disadvantages of conditioning.
Patterns of disorder development
Fruit were harvested in 2013 from 6 Hudson Valley, 12 Western New York and 4 South-central Pennsylvania orchard blocks, transported to the Cornell postharvest laboratory at Ithaca and stored at 38°F without conditioning. Bitter pit and soft scald incidences were assessed visually on stored fruit at monthly intervals for 4 months. The results are shown in Figure 2 and illustrate:
- Bitter pit usually developed in the first month of storage. This means that it is not progressive in storage and that losses around this time will be the maximum achieved, and therefore a good time to assess losses from bitter pit.
- Soft scald developed after 1 to 2 months of storage. (Soggy breakdown incidence was negligible.) Note that there was no soft scald in fruit from Pennsylvania and incidence was negligible in fruit from the Hudson Valley. In Western New York, the maximum incidence was 12%, and incidence in fruit from most orchard blocks was considerably less. The disorder can however be progressive in that it may continue to develop with increasing storage periods, although maximum incidence generally is present by months 3 or 4.
Figure 2. Bitter pit (top three graphs) and soft scald incidence (lower graphs) in 4 Pennsylvania, 6 Hudson Valley and 6 Western New York Honeycrisp orchard blocks during storage in air at 38°F.
Effects of conditioning
In 2014, fruit were harvested from 3 Hudson Valley, 2 Western New York, 3 Champlain and 2 Pennsylvania orchard blocks. Fruit were either untreated or conditioned at 50°F before storage at 38°F for 20 weeks plus 7 days at 68°F.
Bitter pit incidence in untreated fruit ranged from 4 to 42%, and in conditioned fruit from 8 to 67% (Table 2). Conditioning increased bitter pit incidence in every orchard, with increases ranging from 33% to 78% and averaging 63%. The degree of increase was not necessarily related to bitter pit levels in untreated fruit since orchard blocks with less bitter pit overall had lower losses as a result of conditioning. This is illustrated by plotting bitter pit in fruit with and without conditioning against orchard block (Figure 3).
Table 2. Bitter pit (%) in Honeycrisp apples stored at 38°F with or without a conditioning treatment of 50°F for 7 days, and the percentage increase in bitter pit associated with conditioning.
|Growing region and orchard number||38°F||Conditioning + 38°F||% Increase over no conditioning|
Figure 3. Bitter pit incidence in Honeycrisp apples from 10 orchard blocks, either untreated or conditioned at 50°F before storage in air at 38°F for 20 weeks.
Soft scald incidence in fruit from all orchard blocks was generally low (<4%), although a 9% loss occurred in one Hudson Valley block (Table 3). Losses were on balance minor compared with those caused by bitter pit development. Senescent breakdown (Figure 1) was detected in fruit from several orchard blocks, most notably in fruit from one Pennsylvania and one Hudson Valley orchard (Table 4). However, surprisingly, for a disorder we associate with riper fruit, there was no increased incidence as a result of conditioning. Wrinkly skin (Figure 1) was found only in fruit from Pennsylvania--38% and 2% in orchard 1 and 2, respectively, and incidence was not affected by conditioning.
Table 3. Soft scald (%) in Honeycrisp apples stored at 38°F with or without a conditioning treatment of 50°F for 7 days.
|Orchard block||38°F||Conditioning @ 50°F + 38°F|
Table 4. Senescent breakdown (%) in Honeycrisp apples stored at 38°F with or without a conditioning treatment of 50°F for 7 days.
|Orchard block||38°F||Conditioning @ 50°F + 38°F|
In 2015, we increased the number of treatments to include conditioning followed by storage at 33°F as well as 38°F on fruit from several orchards and regions. Bitter pit incidence was affected more by storage temperature and conditioning than by growing region (Table 5). The lowest bitter pit incidence occurred at 33°F, but conditioning followed by storage at 33°F increased incidence to levels close to that at 38°F. Conditioning followed by storage at 38°F resulted in an average of 90% more bitter pit compared with 38°F alone.
Soft scald was negligible at 38°F, irrespective of conditioning, but incidence in fruit stored at 33°F was very high in fruit from Western New York (Table 5). Across all orchards, conditioning of fruit followed by storage at 33°F reduced soft scald to less than 4%. However, in two of three orchards, soft scald incidence was 18% and 29%, compared with 64% in the third, and conditioning reduced incidence to 2%, 0% and 9%, respectively. Soggy breakdown incidence was low overall.
Incidence of the wrinkly skin disorder was highest in Pennsylvania and Champlain fruit at 33°F and unaffected by conditioning. However, skin wrinkling was markedly reduced by storage at 38°F irrespective of conditioning. Vascular browning (Figure 1) incidence was highest in Champlain-grown fruit, but also low at 38°F compared with storage at 33°F. Senescent breakdown incidence was highest in fruit grown in Western New York and was not affected by storage temperature or conditioning (Table 5).
Table 5. Bitter pit, soft scald, soggy breakdown, skin wrinkling, vascular browning and senescent breakdown in Honeycrisp apples stored at 33°F or 38°F with and without conditioning at 50°F for 7 days. Means presented are the averages of 4 orchard blocks from Pennsylvania and 3 orchard blocks in each of the Hudson Valley, Western New York and Champlain regions.
|Region||33°F||Conditioning at 50°F + 33°F||38°F||Conditioning at 50°F + 38°F|
|Bitter pit (%)|
|Soft scald (%)|
|Soggy breakdown (%)|
|Wrinkly skin (%)|
|Vascular browning (%)|
|Senescent breakdown (%)|
Implications for Storage Operators and Growers
The standard recommendation for storage of Honeycrisp apples based on work at Cornell University and elsewhere is air storage at 38°F after 7 days of conditioning at 50°F. With few exceptions, such as extremely late harvest, this treatment prevents development of soft scald and soggy breakdown. Storing fruit at temperatures lower than 38°F after conditioning can sometimes be safe, and can reduce bitter pit incidence, but the risk of soft scald and soggy breakdown increases. Also, we find little evidence that indicates any advantages in terms of quality (firmness, soluble solids concentrations, acidity) of using temperatures lower than 38°F.
There are several take-away messages from this research:
- Check fruit for bitter pit after the first month of storage.
Most bitter pit develops within the first month of storage, while soft scald develops between one and two months of storage.
- Reduce the potential for bitter pit by storing fruit without conditioning, and reduce the potential for soft scald development by storing fruit at 38°F.
Bitter pit levels are reduced if fruit are not conditioned, and the risk of soft scald development is low if storage is at 38°F. In general, even when soft scald occurs, losses are less overall than those associated with bitter pit. With few exceptions, soft scald development was low in fruit from most regions. (Important caveats are that multiple harvests of fruit within regions were not tested; also risk of injury may change over time.)
Manage bitter pit in the orchard to minimize losses after harvest
Risk of bitter pit development, both with and without conditioning, must be managed in the orchard. It is rare to find an orchard with absence of bitter pit, and conditioning increased incidence by an average of 63% in one of our studies. The overall goal must be bitter pit reduction in the orchard to minimize losses after harvest.
The implications of these studies are that fruit should be managed differently based on the risk of bitter pit versus soft scald. For example, fruit with high bitter pit risk should be stored without conditioning, but marketed earlier than conditioned fruit. Growers and storage operators should consider the following strategies, recognizing that Honeycrisp is an apple with variable behavior from season to season.
- If risk of bitter pit is high, based on either high levels of preharvest bitter pit, or mineral analyses (to be reported separately), do not condition fruit. Store at 38°F or even lower, if you know that fruit will be marketed less than 6 weeks from harvest. To avoid significant retail losses, fruit with high bitter pit risk should not be marketed before most bitter pit has been expressed.
- Fruit with low bitter pit risk should be conditioned and stored at 38°F if storage periods are uncertain. This is the ideal, but we recognize that in many cases, conditioning may not be necessary at all. Note that if fruit are going into controlled atmosphere storage, however, a conditioning period is important not for soft scald control, but for control of CO2 injury.
- Temperatures lower than 38°F may be safe for short term periods, but beyond 1 to 2 months the risk of soft scald, soggy breakdown and other low temperature injuries can increase markedly.
In conclusion, losses of Honeycrisp fruit after harvest can be very high, and this is sustainable only if returns in the marketplace also remain high. Putting losses into dollar terms, an example exists from Western New York. In 2015, we paid $700 for a bin of fruit from each orchard at Sun Orchard Fruit Company, or ignoring existing losses for bitter pit in orchard run fruit, close to $35 a bushel. If fruit had been stored at 38°F without conditioning the loss of fruit per bin as a result of bitter pit was $83 and $150 per bin for orchards 1 and 2, respectively, and with conditioning, $228 and $330 per bin for orchards 1 and 2, respectively.
The expense of the conditioning treatment can therefore result in serious financial losses. On the other hand, if the fruit had been stored at 33°F without conditioning and marketed within a month of harvest, losses due to bitter pit would have been $19 and $20 per bin for orchards 1 and 2, respectively. Management of Honeycrisp fruit therefore must take into account presumed risk of bitter pit on a block by block basis, and the trade-off with conditioning and storage time required for orderly marketing.
Yosef Al Shoffe is a post-doctoral associate working on postharvest biology projects in the Watkins laboratory. Tara Baugher is a Penn State Extension Educator whose applied research and outreach focus on tree fruit production and specialty crop innovations. Jackie Nock is a research support specialist on postharvest storage in the Watkins laboratory. Chris Watkins is a research and extension professor who leads Cornell University's program on postharvest biology of fruit and vegetables, as well as being the Director of Cornell Cooperative Extension and the Herman M. Cohn Professor of Horticulture.
We thank the many growers and storage operators in New York and Pennsylvania who generously provided fruit for these experiments, and to Lee Showalter and Leighton Rice, Rice Fruit Company, for organizing delivery of PA-grown fruit to Ithaca. We also thank Jim Eve, Craig Kahlke and Michael Fargione for identification of orchardists in Western New York and the Hudson Valley and Tom Jarvinen, Kristi Kraft and Erin Dugan for their valuable contributions as Penn State Extension program assistants.
This work was supported in part by the New York Apple Research and Development Program, the New York Farm Viability Institute and the State Horticultural Association of Pennsylvania. The work was also supported by the USDA National Institute of Food and Agriculture, Hatch Project 2013-14-483, Improving Quality and Reducing Losses in Specialty Fruit Crops through Storage Technologies (NE-1336).
Any opinions, findings, conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the National Institute of Food and Agriculture (NIFA) or the United States Department of Agriculture (USDA).
Watkins, C.B., Rosenberger, D.A. 1999. Cornell Fruit Handling and Storage Newsletter. 12pp.
Watkins, C.B., Nock, J.F. 2003. Postharvest treatments to decrease soggy breakdown and soft scald disorders of Honeycrisp apples. New York Fruit Quarterly 11 (3): 33-35.
Watkins, C.B., Nock, J.F., Weis, S.A., Jayanty, S., Beaudry, R.M. 2004. Storage temperature, diphenylamine, and pre-storage delay effects on soft scald, soggy breakdown, and bitter pit of 'Honeycrisp' apples. Postharvest Biology and Technology 32: 213-221.