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

View the project final report

• 2010 annual report

Commodities

• Fruits: cherries, general tree fruits

Practices

• Education and Training: extension, on-farm/ranch research, participatory research
• Farm Business Management: value added

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 (Kim et al., 2005). These and other phytonutrients contained in sweet cherries have anti-inflammatory properties that have been shown to relieve arthritis and gout (Wang, 1999). 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

Previous research has shown promise for shelf-life and marketing window extension for some varieties of sweet cherries when using modified atmosphere packaging (MAP) in concert with pre-harvest sprays, harvest at optimal maturity, proper cooling, and grading/sorting prior to packing in MAP liners. Eight sweet cherry growers will choose 1-3 varieties that have shown promise with previous MAP testing or that have not been tested before. For 5 of the growers, each will use their standard pre-harvest practices followed by their usual method of harvest, cooling (statically- overnight). Each variety will be placed in the MAP liners and sealed, alongside un-bagged controls. CO2 and O2concentrations inside the liners will be checked at 10-15 days. Evaluations will be done at 28 days (d), also at 35 and 42 d if the quality is acceptable from previous evaluations. Evaluations will consist of grower and project leader ratings on appearance, stem data, flavor, and texture, as outlined in the methods section and in the addendum. The remaining 3 growers will do as above, except they will compare static cooling with hydro-cooling, a rapid cooling method. On at least 1 of their varieties we will compare hydro-cooling with static cooling. Presentations of this research, along with positive growers’ experiences and feedback, along with other industry personnel (extension, postharvest and storage personnel) promoting the use of MAP, will disseminate my results to a wide audience. It is my feeling 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.

Flow Chart & Description of Methods for Proposed MAP Project in Sweet Cherries
2010 Season

Stem, taste, and appearance ratings will be combined into one of four marketability ratings; unacceptable, fair, acceptable, and fresh. An unacceptable rating indicates that the flavor and/or texture of the cherries is such that they should not be sold in the marketplace, and that the average consumer who likes and buys sweet cherries on a regular basis would not buy them again after tasting them, or simply that the grower would not be comfortable putting his or her name behind that product. A fair rating indicates borderline or barely acceptable flavor and/or texture. With the fair rating, there is something about the cherries (slightly off-flavor, too many pits, stems turning brown, stems falling off or missing, etc.) that the grower would hesitate in putting the cherries on the market. With the acceptable rating the grower would sell the product, but with some reservations, perhaps being that the flavor is good but the consumer will be able to tell that the cherries aren’t fresh- perhaps stems turning brown, some increased pitting, lower texture/taste, etc. A fresh rating indicates the cherries would be virtually indistinguishable from just-picked, fresh cherries. There may be the occasional rot or pit or lost/loose/lighter green stem, but overall taste and appearance make the grower confident they could sell the cherries and have consumers return for repeat sales.

Static Cooling treatment (5 growers)
?
Harvest (Day 1 or D-1) to cooler overnight, cooler temperature will be recorded ? D-2 sort/grade defects, small size , pack 3 minimum replicates into MAP liners, plus minimum 2 equal lots of controls, un-bagged (loose in a cardboard container or plastic cherry lug) ? all will be packed together(same section of cooler to avoid differences in microclimate) in grower’s cooler for the duration ? CO2 and O2 measured in MAP bags (without removal of seal) 1 time between D-12 & D-17 ? Storage until D-30 (+/- 2 days), then Evaluation 1, (see description below) ? If necessary, Evaluation 2 at D-37 (+/- 2d) ? If necessary, Evaluation 3 at D-44 (+/- 2d)

Hydro-cooling treatment (3 growers, at least 1 variety/grower)
?
Harvest (Day 1 or D-1), and hydro-cooling the same day – either using cascading hydro-cooling (1-2 growers) or batch hydro-cooling (1-2 growers); all hydro-cooling will be with a disinfectant, either Scholar fungicide (preferred) or sodium hypochlorite with pH adjustment? drying of cherries overnight in cooler ? packing on D-2, rest as above with static cooling treatments

Evaluations - Appearance (general condition observed without opening bags)- if the grower determines there are an unacceptable number or rots, pits, cherries without stems, or fruit with brown stems, i.e. he would not be comfortable marketing these cherries – the experiment will end at evaluation 1, provided other replicates are nearly the same condition- if there is a difference between replicates, it will be recorded- if the other replicates look acceptable to the grower, one will be evaluated at this time, and the other will be left in MAPs until evaluation 2. If the evaluation 2 MAP fruit are still acceptable, the last replicate will be left for evaluation 3.

After noting appearance, open 1 liner- take a random sample of 20 cherries (including un-bagged controls)
A) Take stem color data , B) Take stem loss data,
C) Take another random sample of 10 with stems still on
(MAP & controls) then take stem hold data
D) Take another random sample of 10 cherries (MAP & controls) grower and another person taste 5 cherries each, then give ratings on flavor and texture
Evaluation 2, if necessary, same as above, 7 days (+/- 2 days) after Evaluation 1
Evaluation 3, if necessary, same as above, 7 days (+/- 2 days) after Evaluation 2

Stem Loss Stem Hold Flavor & Texture Marketability
Rated 1-5, 1 = 100% loss, 5 = no loss
Rated 1-3, 1= stem weak and easy to pull off, 3= stem strong & difficult to pull off Each Rated 1-7, 1= completely unacceptable, 4 minimum for sales, 7= excellent- like fresh-picked
Flavor & Texture are Average to give a Taste rating Unacceptable, Fair, Acceptable, or Fresh

All data taken into account, with grower impressions being paramount