Shelf-life and Marketing Window Extension in Sweet Cherries in NY

Final Report for ONE10-119

Project Type: Partnership
Funds awarded in 2010: $14,880.00
Projected End Date: 12/31/2011
Region: Northeast
State: New York
Project Leader:
Craig Kahlke
Cornell Cooperative Extension - Lake Ontario Fruit Program
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Project Information

Summary:

Six sweet cherry growers participated in the study, and stored a total of 1,375 pounds of fruit in modified atmosphere packaging bags (MAPs) and corresponding un-bagged controls. The varieties tested, based on previous years’ promising results included Sam, Hudson, Emperor Francis, and Hardy Giant. Growers and the project leader (PL) rated texture and flavor on cherries coming out of MAPs at 4, 5, and 6 weeks (if necessary), along with corresponding controls. Overall ratings were given based on these 2 main factors, and growers were asked if they would market the fruit. Most of the varieties in the MAPs were rated by the growers as of acceptable quality at 4 weeks, with some extending to 5 and 6 weeks, with nearly all controls rated as unacceptable or fair even at 4 weeks. Stem color, loss, and hold were also rated and considered as additional key factors to marketability. Three of the six growers in this study indicated they would extend the season on sweet cherries by storing part of their crop in MAPs and marketing them at a later date.

From these results, we would recommend hydro-cooling with cold water (32-40 F)for 10-20 minutes with chlorine at a concentration of 70-100 ppm with a pH under 7.0. The use of a fungicide such as Scholar is also recommended, but not necessary. The MAPs work very well (5-6 weeks) for Hudson, Sam, Schmidt, 19, and Emperor Francis. Caution for large-fruited varieties that soften when over-mature, like Hardy Giant. If harvested at correct maturity, this variety stores well (4-5 weeks). Other white -fleshed cultivars like Rainier and Honey are prone to bruising, and may need some air left in the MAPs to reduce damage. Regina and Lapins are not recommended, as are any cherries that are large and soft. Some may have a sensitivity to high CO2 levels, and may develop a tin-like or off flavor. Caution on Hedelfigen, Sweetheart, and Royalton. They have stored well for some, and not well for others. More testing is needed for Vic, Oxhearts, Black Gold, Van, and Columbian.

It is recommended that all varieties tried for the first time with individual growers be tested on a small scale first.

Introduction:

Sweet cherries (Prunus avium L.) are one of a handful of fruits that have generated excitement in recent years due at least in part to their reported health benefits. Cherries contain several key phytochemicals such as the powerful antioxidant anthocyanins and vitamin C . These and other phytonutrients contained in sweet cherries have anti-inflammatory properties that have been shown to relieve arthritis and gout . These are just a few of the reasons cherries seem to be increasing in popularity on the public’s radar. In smaller commercial-growing regions in NY, consumption of sweet cherries and other fresh produce will hopefully continue to rise as the “buy local” movement strengthens. Supplying local and regional supermarket chains, farmer’s markets, along with pick-your-own enterprises, will generate what farmers hope will be increased sales.

Unfortunately, sweet cherries have a relatively high respiration rate and are therefore a very perishable commodity with a short shelf life of 7-14 days in conventional cold storage. In addition, the local sweet cherry season may only be 3 weeks long.

However, past work by Dr. Olga Padilla-Zakour and Mr. Herb Cooley, researchers at the Department of Food Science at the New York State Agricultural Experiment Station (NYSAES) at Geneva have shown the use of MAP designed specifically for sweet cherries, along with proper harvest timing and use of rapid cooling, can increase shelf life an additional 2-4 weeks beyond conventional storage. Research over the previous 2 seasons by the PL has confirmed this.

Project Objectives:

Six sweet cherry growers named as cooperators on this project ended up choosing 1-4 varieties that have shown promise with previous MAP testing or that have not been tested before. For five of the growers, each used their standard pre-harvest practices followed by their usual method of harvest, cooling (statically- overnight). Each variety was placed in the MAP liners and sealed, alongside un-bagged controls. CO2 and O2 concentrations inside the liners were all checked at 12-15 days. Evaluations were done at roughly 4 weeks after packing, and also at approximately 5 and 6 weeks if the quality was acceptable from previous evaluations. Evaluations were performed that consisted of a grower and/or PL ratings on appearance, stem data, flavor, and texture, as outlined in the methods section and in the addendum in the original submitted proposal. The remaining 3 growers did as above, except they compared static cooling with hydro-cooling, on 1 of their varieties.

Cooperators

Click linked name(s) to expand
  • Jim Bittner
  • Alan Buhr
  • Herb Cooley
  • Gary Craft
  • Roger Lamont
  • Dr. Olga Padilla-Zakour
  • Kent Schwab
  • Guinevere Smith

Research

Materials and methods:

Growers harvested sweet cherries by hand at acceptable maturity. For most cases, the fruit were cooled overnight statically in a grower’s cooler at temperatures between 32-39 F. Cherries were culled by the grower’s crew, graded, and packed the following day. Small cherries, cherries with defects such as cracking or splitting, and debris such as leaves were removed prior to packing. The cherries were then weighed and packed into MAPs or put loose in cardboard boxes (controls) by the PL. In most cases, 3 replicates of 20 pounds of sweet cherries went into MAPs, and ten pounds of un-bagged controls went loose into cardboard boxes. In some cases, 10 pounds of cherries were put into the smaller 10 pound MAP liners. The MAPs were either Lifespan L204 20-pound or L212 10-pound bags designed for sweet cherry storage (courtesy of Chris King, Amcor,Australia). The air was pushed out of the MAPs after packing, and special twist ties were put on. All fruit were then put back in the grower’s coolers. A technician from the NYSAES measured CO2 and O2 concentrations in the MAPs 12-15 days after the packing of cherries in liners. All atmospheres were within recommended levels. Evaluations began at 4 weeks after packing, at +/- 3 days due to scheduling and logistics.

At 4 weeks post-packing, Evaluations began visually, looking at the fruit through the clear MAPs, and noting condition. A sample data sheet is attached. Control fruit were also examined visually to start. Notes were made of stem color/loss, approximate percentage of rots, splits, or pits, and if the cherries appeared to be dehydrated or drying out. Then 1 replicate MAP was opened, and 20 fruit were taken randomly from all portions of the liner. The numbers of rots, pits, and splits were recorded. In addition, stem color, and percentage of stems missing were noted. No stems lost were a 5 rating, 20% loss was a 4, all the way down to a 0, which meant 100% loss. Remaining fruit with stems were pulled with increasing force and rated on stem hold. A 3 was strong, 2 intermediate, and a 1 rating was considered weak stem hold. The same evaluations were done, pulling 10 fruit from 1 un-bagged replicate control, and 10 fruit from the second control replicate.

Following this analysis the grower and/or PL tasted a handful of cherries, and rated the flavor and texture on a scale of 1-7. A 7 rating represents excellent, or like fresh- picked, a 4 rating is the minimum acceptable for sale, and a 1 rating is the poorest possible. These 2 categories were averaged and an overall Marketing rating was given. The four overall categories were Unacceptable, Fair, Acceptable, and Fresh. Unacceptable – could not sell these cherries (too many rots, pits, brown stems, etc.). Fair – if I had no other cherries, and I culled out the rots, pitted cherries, etc., I may sell some. Acceptable – they are not going to be confused with fresh picks (a few rots, perhaps stem color not bright green), but the flavor/texture is acceptable. Fresh – these cherries are nearly indistinguishable from fresh-picked cherries (very few culls- green stems, very few missing stems, no off-flavors, very good flavor/texture).

If the 4 week MAPs were Acceptable or Fresh, the other 2 replicates remained sealed until the following week, and the evaluations were repeated. If the 4 week MAP was Fair or Unacceptable, the experiment was terminated. Un-bagged controls were kept for comparison purposes for the duration of the experiments. If the 5 week evaluations were Acceptable or Fresh, the last replicated remained sealed another week, and final evaluations were then done at 6 weeks. If the 5 week MAP was Fair or Unacceptable, the experiment was terminated.

If a grower chose a variety for comparison of hydro-cooling versus static cooling, the following methods were used: Growers harvested sweet cherries by hand at acceptable maturity. One-half of the fruit used for the experiments were then cooled overnight statically in a grower’s cooler at temperatures between 32-39 F. Cherries were culled by the grower’s crew, graded, and packed the following day. Small cherries, cherries with defects such as cracking or splitting, and debris such as leaves were removed prior to packing. The cherries were than weighed and packed into MAPs or put loose in cardboard boxes by the PL. For the hydro-cooled portion, the same variety was harvested from the same block one day after the statically-cooled fruit were harvested. On the same day of harvest, fruit was hydro-cooled for 2 growers (2 varieties) in a stainless steel tub with chlorinated (50-100 ppm, pH < 7) cold water (~ 35 F) for 10-20 minutes. In addition, one grower used Scholar fungicide at a rate of 4 liquid ounces of Scholar per 100 gallons of water in the tub. The third grower (3rd variety) hydro-cooled with a cascading hydro-cooler with chlorinated (50-100 ppm, pH < 7) cold water (~ 35 F) for 10-15 minutes. In addition, the grower used Scholar fungicide at a rate of 4 liquid ounces of Scholar per 100 gallons of water in the hydro-cooler. Sweet cherries were packed as described above, but with 3 MAP replicates per hydro-cooled treatment, plus 3 MAP replicates per statically-cooled treatment. There were 2 replicates each of un-bagged controls for the hydro-cooled and statically-cooled fruit. Evaluations were done as described earlier.

Research results and discussion:

Nearly all accomplishments/milestones outlined in the proposal were met with few exceptions. The MAP liners and fungicide/disinfecting chemicals were ordered/received in April and May. Initial grower consultations/farm visits were in late May or June. The proposal stated that 6 of the 8 sweet cherry growers who initially agreed to be cooperators would end up participating. This turned out exactly correct -2 of the 8 partners were not able to participate in the study. One grower could not participate because the two varieties we had lined up to test received heavy rain-cracking prior to harvest and could not be harvested. Another grower could not participate due to a family emergency that rendered the farm short-handed. The proposal stated that each farm would choose 1-3 varieties to test that have shown promise with previous MAP testing or that have not been tested before. This was true, but one grower tried four varieties. Evaluations were to be done at 4 weeks, and also at approximately 5 and 6 weeks after packing if the quality was acceptable from previous observations. The 4, 5, and 6 week observations did not vary more than 3 days on either side, due to scheduling/logistics for the PL. The proposal stated the evaluations would be +/- 2 days. Harvest, sorting/grading, cooling, and packing occurred from late June though early July, depending on the varieties tested and the optimal harvest date based on local growing conditions. Harvest and sorting/grading was performed by grower personnel. Cooling and packing was performed by the PL in nearly all cases (one variety on 1 farm was packed by a grower, under the PL’s direction). A technician from the Department of Food Science at the NYSAES measured CO2 and O2 concentrations in the MAPs 12-15 days after the packing of cherries in liners. All atmospheres were within recommended levels. The PL, growers, technician, and key personnel (when growers were unavailable) performed assessments from late July though late August.

While all basic accomplishments/milestones were met, there were some interesting things learned. Budbreak, full bloom, and harvest dates were nearly record-early, and harvest ended up being 1-2 weeks ahead of normal. The growing season was characterized by timely rains, and development of near record degree-growing days due to the earliness of budbreak. However, there was no real period of extreme heat, drought, rainy, or severe weather. With a few exceptions, most tree fruit growers in Western NY agreed that 2010 was one of the best growing seasons on record. Untimely rains just prior to anticipated harvest did cause some significant rain-cracking in a few cases. Fruit size and quality of sweet cherries at harvest were good to excellent. Fruit for this study were harvested at proper maturity, were free from brown rot, and properly cooled prior to harvest, with one exception, which is noted in the detailed data. Thus, it could be argued that this year represents a “best case scenario” for sweet cherries quality-wise, as they were packed into MAPs.

See table 1 for a summary of each variety/location tested. Nearly all of the varieties tested compared closely in storage life, taste, texture, stem color, stem hold, and stem loss across the different farms. There were a few exceptions. As predicted, sweet cherry quality and marketability were better in hydro-cooled fruit as compared to statically cooled fruit in most cases. The addition of a fungicide in 2 of the hydro-cooling treatments reduced the number of rots as compared to statically-cooled treatments with no fungicide. For the promising Sam variety, the MAP cherries were still saleable at 6 weeks for 1 grower, and at 5 weeks for another. The 3rd grower had unusual pitting in the MAP fruit at 4 weeks that could not be explained. Fruit was unacceptable at 4 weeks. It should be noted that the MAP manufacturer indicates that pitting is not caused by the liners, it is primarily caused by impact damage below the epidermis. Perhaps rough handling at harvest was a factor. Hudson was another promising variety that was tested at 4 farms in 2010. In 1 farm, the fruit were still saleable at 6 weeks, and the other 3 were saleable at 5 weeks. In Emperor Francis, one farm had saleable fruit at 6 weeks, and the other was good at 5 weeks. Three varieties (19, Summit, and Honey) that were not previously tested were included in the study. 19 showed excellent promise, and storage up to 5 weeks. It is interesting to note that the hydro-cooled 19’s had noticeably firmer fruit than the static treatment. However, the hydro-cooled treatment had burned stem tips, probably indicating exposure to chlorine too long or at too high a concentration. Summit had some temperature issues at harvest and packing that could have caused an unacceptable number of rots. Honey bruised too easily and lost too many stems, even though the flavor was still good. A pattern is emerging here- firmer cherries seem to do better in MAPs than larger, softer cherries. In addition, some cultivars like Regina have a sensitivity to the high levels of CO2 in the liners, and develop an off-flavor, and therefore are not recommended for MAP use.

Research conclusions:

It is my hope that in a few years time, a significant percentage of growers state-wide will use MAP in a portion of their crop to increase availability of local produce, and to give consumers who want to “buy local”, an extended season to do so.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary

Education/outreach description:

Presentations of this research by the PL took place at a regional fruit meeting, the Lake Ontario Fruit Program’s Winter Fruit Schools in Wallington and Albion, NY on January 18 and 19, 2011. A pdf of the presentation is available for upload after this section. Over 250 growers and other industry personnel attended this 2 day event. Plans to write a follow –up article in the New York Fruit Quality will disseminate the results to a larger audience. Each year, I will advertise the option of using MAPs for the sweet cherry season and market extension in local newsletters. I will continue to order liners for growers and instruct them in their use. I will continue to push rapid-cooling methods such as hydro-cooling for improved quality.

Project Outcomes

Project outcomes:

A complete economic analysis was not performed. The cost of the MAPs are approximately 50 cents each. In a survey of over a dozen sweet cherry growers in 2009, all indicated this was affordable. Each liner can hold 10-20 pounds of fruit. Even if 30% of fruit is culled after 4-6 weeks, this is fruit that is in demand after all fresh cherry supplies are exhausted. One grower sells her MAP sweet cherry fruit at Farmer’s Markets, and can get a premium for the fruit. Another grower puts about 20,000 pounds of a certain variety in MAPs each year, and sells them from 2-5 weeks after harvest. Many growers have indicated that they cannot sell all of their fresh supply of certain varieties in time before spoilage occurs. This would be a viable option for growers with the right varieties.

Farmer Adoption

With positive growers’ experiences and feedback, along with other industry people (extension, postharvest and storage personnel) promoting the use of MAP, I theorize that a minimum of 2 large sweet cherry growers will rely on MAP to store and profitably market a significant (5-10%) portion of their crop well into mid to late August, when sweet cherries in the state are weeks past the latest sites being picked clean. I had proposed previously that a minimum of 1 grower will adapt a rapid cooling method plus a disinfectant for their entire sweet cherry crop. I already have 2 growers committed to do this, with two more thinking seriously about it. I feel that on a regular basis, at least 10 sweet cherry growers in New York will use MAPs in at least 100 pounds of sweet cherries each, and continue to test its viability in new varieties.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

As mentioned previously in this report, new varieties and those cultivars that have not been previously tested need to be tried, at least on a small scale to start. The ease of use and fact that cherries can be visually evaluated quickly will enable farmers to try their varieties under their own conditions. I plan on getting valuable feedback from these growers, and add their information to my growing database of sweet cherries tested in MAPs.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.