Anjou Pear Quality: Postharvest Practices
This is the second part of a summary report of research activities for 1991, 1992, and interim report for the 1993 crop. Please consult "Anjou Pear Quality: 1. Fruit Quality" for survey design and results.
This section describes packinghouse practices encountered regularly when our technicians visited each packinghouse. It is not meant to be a guide of best practices.
Most Anjou pears handled in northcentral Washington are packed immediately after harvest and stored as packed fruit. Pears harvested in the mid-Columbia region are usually packed on demand and may be presized prior to storage in bins. In the Yakima Valley, some fruit is packed prior to storage; other fruit is stored loose in bins.
Temperatures on the Packingline
A comparison between the temperatures obtained over the three years of this study did not indicate any change in practices (Table 1). Fruit temperature rose an average of 2 degrees after dumping and an additional 6 degrees during drying in 1993.
Table 1. Average temperatures of fruit, water, and dryer air during the 1991-93 packing seasons.
|Fruit at dump||39.5||36.6||40.5|
|Fruit at riser||42.1||38.3||43.0|
|Fruit before dryer||44.7||39.8||45.3|
|Fruit at dryer||49.0||42.2||50.3|
|Fruit at tub||49.3||45.7||50.0|
It is useful to examine the range of temperatures encountered this season (Table 2). Note the range in final (at tub) temperatures. Fruit packed at 65°F will remain at that temperature for a long time, thus shortening its storage or shelf life.
Table 2. Range in temperatures for fruit, water, and dryer air obtained for 1993.
|Fruit at dumper||40.5||32.1-48.7|
|Water in dumper||41.4||36.7-57.6|
|Fruit at riser||43.0||35.2-52.5|
Fruit before dryer
|Fruit after dryer||50.3||37.5-69.3|
|Fruit in tub||50.0||39.2-64.9|
Chemical use was restricted to very few chemicals and was fairly uniform among those packers surveyed.
Drenching. Only four of the 21 packinghouses drenched any pears at all; each drenched with TBZ. One reported use of Captan on certain lots. One drenched with ethoxyquin. No one reported the use of calcium.
Presize. Four packinghouses presized Anjou pears. In the presize, sodium silicate was used by two packers; lignin sulfonate or sodium sulfate was used by the others. Flotation materials and fungicides (SOPP or chlorine) were used in flumes as well as in the dump tank. One packer applied ethoxyquin in the bin filler with TBZ. Another reported the use of wax, ethoxyquin, and TBZ as a line spray at presize.
Packingline. In the dump tank on the packingline, over half (52%) of the packinglines used lignin sulfonate, one-third used sodium silicate, and 10 percent used sodium sulfate. SOPP was used by 67% of the packers; chlorine, by 24%.
The conductivity of the dump tank mixtures was measured to determine levels used (Table 3). Conductivity is a measure of the amount of salts in the water, which may be related to skin marking. Levels of conductivity varied greatly in packinghouses whether they used similar or different chemical mixtures. At this time, we do not have recommendations for levels.
Table 3. Conductivity levels in Anjou dump tanks, 1993.
|Lignin sulfonate + SOPP||5,675|
|Sodium silicate + SOPP (1 line)||8,560|
|Sodium Silicate + Chlorine||13,360|
As line sprays, the vast majority applied TBZ (86%); one packer applied chlorine. Wax was applied by half of the packers. Almost two-thirds of the packers (62%) sprayed on a fruit cleaning compound. Ethoxyquin was applied as a line spray by 19% of the packers. Semperfresh was used on some lots by 20% of the packers.
Paper wrap chemicals included ethoxyquin (62%), copper (48%), or oil (10%). Plain wrap was not widely used.
It would be in the best interest of this industry to develop methods of handling pears which would allow for an extension of the packing season without detriment to the pears. A side benefit of a longer packing season would allow for a diversification of pear packages which may appeal to a larger number of consumers.
The number and effectiveness of chemical treatments will continue to decrease due to fungal resistance and prohibitions against chemicals being present in packinghouse waste water. Sanitation programs and the development of alternative methods, including chemicals, would be prudent.
Finally, I remain concerned about the temperature of the pears after packing. Pears must be cooled immediately after packing and it takes a long time to cool pears that have been packed warm. Further work is planned to develop an understanding of the effect of packing temperature on fruit quality.
Dr. Eugene Kupferman, Postharvest Specialist
WSU Tree Fruit Research and Extension Center
1100 N. Western Ave., Wenatchee, WA 98801
Tree Fruit Postharvest Journal 5(1):11-13