Cherry Warehouse Survey Report, 1988
This report presents the results of the second year of a study to examine cherry handling practices to improve the quality of Pacific Northwest cherries. The Cherry Warehouse Survey was funded by the Tree Fruit Research Commission as part of its overall cherry funding program. The assistance of the United States Department of Agriculture-Agricultural Research Service in Yakima and Wenatchee and the Hops Inspection Laboratory of the Washington State Department of Agriculture in providing storage and laboratory space is acknowledged.
The goals and objectives of the survey are to:
Describe the relationships between fruit quality parameters
Determine how postharvest practices affect cherry quality
Determine "best practices" for handling cherries.
Cherries were sampled from 19 packing lines in the three major cherry growing districts. Due to increased funding by the Tree Fruit Research Commission, the number of cherries sampled rose from 9,840 in 1987 to 19,500 cherries in 1988. Four technicians were employed to survey the warehouses and evaluate fruit quality in 1988. The number of individual grower lots sampled (both bin and box) rose from 164 in 1987 to 325 grower lots in 1988. In 1988, efforts were made to sample only Bing fruits. The number of grower lots sampled in each packing house rose dramatically and ranged from 10 lots to 25 lots. The percentage of fruit sampled from each of the three districts remained about the same in 1988 as in 1987.
Technicians sampled fruits from the same lot from both the bin and the box, then stored them for 2 weeks at 40 ºF. After storage, fruit was held an additional 24 hours at 70 ºF. This would simulate a transit period under moderately adverse conditions. Additional fruit from the bin was examined in the warehouse for cracks and decay at the time of sampling.
Following the storage period, fruit were individually examined for size, color, firmness, brightness (luster), and stem color. Damage was also determined by rating each cherry for pitting, bruising, brown discoloration, cracks and decay. Soluble solids were determined for the first time this year by mashing 30 cherries from each bin and box sample and reading the soluble solids on a refractometer. Size and color were determined through the use of Wilbur-Ellis cherry cards. All other quality attributes were determined subjectively.
In previous years, data differed significantly among technicians due to the subjective nature of the tests, especially in firmness, pitting and bruising. In order to remove any biases from the data, this year all the technicians met and rated the same group of cherries. All data gathered by each technician were then corrected mathematically so that each district's fruit quality could be compared without prejudice.
In addition to collecting samples from each line, the technicians obtained information about line configuration, number of drops, fruit temperature and water temperature.
A major effort was made in 1988 to compare the quality of fruit treated with gibberellic acid (GA) with that of untreated fruit. This provided interesting information with regard to the use of GA in each district and the volume of fruit treated with GA statewide. In 1987, 28% of the fruit sampled had been treated with GA; in 1988, 37% of the fruit sampled had been treated. If this survey of 325 grower lots of fruit is indicative of fruit as a whole, GA use in 1988 rose significantly over use in 1987 (Figure 1).
When comparing this information on a district basis, in 1987, 21% of the fruit treated with GA came from the Lower Yakima Valley, 16% from Yakima and 63% from Wenatchee. In 1988, only 7% of the treated fruit came from the Lower Valley and 10% from Yakima, while fully 83% of the GA-treated cherries came from Wenatchee. Recognize that approximately the same proportion of lots was sampled from each district each year.
We compared GA-treated cherries with untreated fruit as they arrived at the warehouse. After being held for 2 weeks at warm temperatures, GA-treated cherries were larger (by almost one size), slightly darker, significantly firmer, and brighter. GA-treated fruit were 0.7% higher in soluble solids than nontreated fruit (18.1% for GA treated compared with 17.4% for untreated). GA-treated cherries had less pitting but more bruising and speckled stems than untreated. These findings are consistent with last year's survey results.
In summary, GA-treated cherries are of superior quality to those not treated, and the application of GA by a wider number of growers can positively influence cherry quality on a statewide basis.
Cherries sampled from the bin prior to dumping in 19 warehouses had the following quality attributes (Figure 2):
Size: In 1988, fully 73% of fruit was 61/64 or larger. In 1987 this figure was 69%.
Color: In 1988, 98% of fruit sampled was mahogany or darker. In 1987 this figure was 97%.
Firmness: In 1988, 92% of fruit was firm-ripe or firm (firm is fruit with the greatest firmness in the study). In 1987 only 67% of fruit was this firm.
Luster: In 1988, cherries were brighter than in 1987 (98 vs 93%, respectively).
Stem Color: In 1988, cherries had slightly fewer brown stems than in 1987 (0.8 vs 2.5%, respectively).
Cherry damage in 1988 was compared with that of 1987 as follows:
Pitting: According to this survey, pitting was the most severe problem in 1988. Pitting rose from 23% moderately to severely pitted fruit in 1987 to 26% moderate to severe pitting in 1988.
Bruising: In 1988, 15% of fruit arriving at the packing house was moderately to severely bruised as compared with 20% in 1987.
Brown discoloration: In 1988, brown discoloration was reduced to 5%, from 16% in 1987.
The survey reminded us that certain quality attributes are related. However, correlations only explained small percentages of the variability in these quality indices.
Larger fruit is firmer, has less brown discoloration and is less pitted than smaller fruit of commercial maturity.
Very small fruit has more pitting and bruising and is softer than larger commercially harvested fruit.
Fruit with cracks is highly susceptible to decay.
Rain early in 1988 caused cracking in a number of orchards in the Lower Yakima and Yakima valleys. While the worst orchards were not picked, many orchards attempted to salvage part of the crop through selective picking, field sorting and warehouse sorting. Crops in later maturing orchards were not seriously affected.
Cracking was examined in the warehouse as fruits were sampled, and significant decay developed in cracked or rain-softened fruit. The survey showed a 10% increase in cracked cherries and an 8% increase in decay for samples in the whole state over 1987. If these data were re-analyzed to include only the earlier district this figure would be much higher. Cracking and decay were closely correlated.
Washington did not experience the very hot temperatures in 1988 that it did in 1987. Cherries respond to both extremes of growing season temperatures. Other studies have shown that any time the temperatures reach above 100°F for an extended period, fruit quality suffers. Keeping track of orchard temperatures can indicate fruit stress.
Good temperature management is critical to preserving cherry quality. Cold fruit retains its sweetness, has less decay and shrivel, and cold temperatures help retain color. Cold fruit are firmer than warm fruit regardless of how long the fruit has been stored. In fact, more quality is lost in one hour at 70°F than in 24 hours at 32°F!
Great progress has been made by a number of warehouses over the last few years to reduce fruit temperature. In 1988, two additional warehouses began Hydrocooling fruit upon receipt over those in 1987. This means that 85% of the sheds surveyed hydrocool fruit upon receipt.
An additional three warehouses added a second hydrocooler in their packing line just before the box filler. Now two-thirds of the warehouses surveyed employ a second hydrocooler. The effect of the second hydrocooler was reflected in the temperature of fruit leaving certain sheds in 1988 (Figure 3). One shed experienced a drop in fruit temperature at the box filler from 58°F in 1987 to 41°F in 1988--or 17 degrees! Another shed went from 65°F to 41°F--a drop of 24 degrees. A third went from 51°F in 1987 to 43°F in 1988.
A shed which did not install a second hydrocooler was able to achieve a 4 to 5 degree drop in its average fruit temperature by tightening its fruit handling procedures.
Fruit being boxed in sheds without a second hydrocooler averaged 49°F while fruit being boxed in sheds with a second hydrocooler averaged 41°F, a difference of 8°F, which is very significant to fruit quality.
Unfortunately, two sheds are still boxing fruit which is above 53°F. Fruit sorted in the shed with the coldest temperatures averaged 34°F at the box filler.
Fumigation and Fruit QualityIn certain years much of Washington's finest cherries are sent to Japan. These are large, firm, GA?treated fruits which, in order to be allowed into Japan, are fumigated with methyl bromide before shipment. We chose three warehouses which run both fumigated and nonfumigated fruit to run comparison tests. The data are from a total of 25 lots of fumigated fruit in comparison with 30 lots of nonfumigated fruit.By comparing fumigated and nonfumigated fruit from the same warehouse we determined that in these tests fumigated fruits were significantly softer, less bright, and had browner stems than fruits which were not fumigated. Fumigated fruits had more pitting, more bruising and more brown discoloration. A shortcoming of this test is that the fumigated fruit might not have come from the same orchard as the nonfumigated fruit. It is possible that we are looking at fruit of different inherent quality.
The results of the 1988 Warehouse Survey reinforce the desirability of using GA wherever possible since it improves fruit quality. The survey also pointed out that small fruits are inferior to larger fruits. Perhaps the industry should consider raising the minimum size. Firm fruits are superior to soft fruits; growers should continue their efforts to improve cherry firmness.
The survey also showed that some warehouse managers are making a significant investment in equipment and in modifying their practices to lower temperature of fruit at the end of the packing line. Temperature management is the key to preserving cherry quality. Since fruit does not have reserve carbohydrates (similar to starch in apples), rapid respiration burns up sugars, decreases firmness, increases shrivel and decay, and turns fruit darker. Respiration can be lowered by using low temperatures immediately after harvest. It is critical that growers cover fruit in the bin while in the orchard and deliver fruit to the warehouse promptly. Warehouse personnel must lower fruit temperature rapidly to well below 40°F before shipping it. Time and temperature are keys to the retention of quality in cherry fruit.
Dr. Eugene Kupferman and Postharvest Specialist and Robert C. Ebel, Research Technician
WSU Tree Fruit Research and Extension Center
1100 N. Western Ave., Wenatchee, WA 98801
Post Harvest Pomology Newsletter, 7(1): 4-7