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WSU-TFREC/Postharvest Information Network/Anjou Pear Quality:  Fruit Quality



Anjou Pear Quality:  Fruit Quality


Background

The goal of this project is to determine the effects of warehouse practices on packed Anjou quality to improve fruit quality and reduce cullage. This project was funded by the Washington Tree Fruit Research Commission and the Winter Pear Control Committee. This is a summary of research activities for 1991, 1992, and an interim report for the 1993 crop. Note that the data for 1993 are incomplete, as the packing season and the project have not yet been completed.

Cullage due to postharvest problems can appear at the time of packing, after storage, or in the marketplace. It reduces grower returns and can endanger the reputation of the industry when fruit of poor quality appears in the market. Postharvest cullage was studied by Dave Burkhart whose report is considered in Part III in this series.

The largest volume of winter pears for fresh consumption in the USA is grown and shipped from packinghouses in Washington and Oregon. During the period 1989-1991, the largest volume of Anjou pears was shipped from the Wenatchee district (43%), followed by the mid-Columbia district (39%), the Yakima district (14%), and the Medford district (4%). The 1993 crop is the largest Anjou crop in history.

Anjou pears are stored in both regular and controlled atmosphere (CA) storage and marketed from September through July. They are sold throughout the USA and in an expanding number of export markets. For example, in marketing the 1991 crop, large volumes were sold in Sweden, Canada, Mexico, Saudi Arabia, and Taiwan.

Storage and packing practices vary between warehouses and districts. Most packinghouses pack fruit as soon after harvest as possible, store it in boxes, and ship from this inventory. Other packers store fruit in bins, either field run or presized, and pack on demand

This study used repeated visits to the major pear packinghouses in northcentral Washington and the mid-Columbia region of Oregon during the packing season to develop a picture of similarities and differences in fruit handling practices among packinghouses.


Study Methodology

Fruit was sampled on a weekly basis from packinghouses throughout Washington and the mid-Columbia region of Oregon as it was being packed. Temperature and chemical treatment information was obtained by technicians, and at each visit a commercially packed box of fruit was purchased off the line.

The pears were brought back to the lab and analyzed for quality including firmness, soluble solids, starch content, and acidity. To estimate shelf life, additional pears were allowed to remain at 70°F for seven days and examined. Firmness was measured on two sides of each fruit using an Effegi tester mounted in a drill press stand using a pear tip.

To estimate the latent diseases and disorders within the remaining pears from each lot each week, the fruit was placed in a commercial CA storage room. A subsample was removed in March or April and again in June for analysis of external and internal defects as well as quality.


Sampling Frequency

Twenty-three packinglines were sampled during this project. The number of times each packinghouse was visited ranged from twice to 13 times per season depending upon their size and length of packing season.

Most packers completed packing by mid-December, and only those warehouses that stored fruit in bins packed after that date (Figure 1). There is a strong belief in the industry that Anjous must be packed as soon as possible after harvest or belt burning and scuffing will be too severe. How then do packers who continue to pack into April (May) deliver a good product? What are they doing to eliminate scuffing and belt burn?


Fruit Quality

Firmness. Firmness at the time of packing averaged 15 lbs. after data from all lots and years were combined (Figure 2). Fruit firmness at packing was highest in fruit packed from the 1991 crop out of CA storage from mid-November to December.

The loss in firmness over a seven-day ripening period at 70°F of Anjou pears sampled at time of packing varied from year to year (Figure 3).

The ability of Anjou pears to ripen varied from year to year. Fruit sampled after CA storages were opened in 1991 remained firmer than during the other two years (Figure 4).

Fruit Ripening. Consumers have complained about lack of uniformity in ripening Anjou pears purchased during the early part of the season. In our samples, only those fruit sampled off the packinglines after about November 1 softened sufficiently (Table 1 and Figure 5) as to be considered of eating maturity after one week at 70°F. In this project pears were not selected off the packingline as to whether they were being packed for immediate shipment or storage.


Table 1

Table 1. Average firmness of Anjou pears by week following seven days at 70°F.

Week
starting
19911992 1993Average
Sept. 6  15.6 15.6
Sept 13  13.8 13.8
Sept 20  12.414.613.5
Sept 27  11.715.912.5
Oct 4  10.513.411.2
Oct 11  9.512.711.0
Oct 18  7.311.19.3
Oct 25 5.78.98.67.9
Nov 1 4.36.79.76.7
Nov 8 3.86.87.36.0
Nov 15 8.17.25.27.7
Nov 22 10.14.96.99.1
Nov 29 6.85.05.55.9
Dec 6 10.1 56.7f
Dec 13 8.83.87.37.7
Dec 20 10.1  10.1
Dec 27     
Jan 3  4.16.15.4h
Jan 10  3.84.44.2i
Jan 17 11.1 6.87.9
Jan 24 10.9  10.9
Jan 31 6.84.1 5.5

Softening of Pears Packed in the Early Season

It has been the policy of the industry to select pears of advanced maturity to ship early in the season in the belief that these lower firmness pears are thought to soften without a storage (chilling) period. To determine whether fruit firmness at time of packing would be a good indication of the ability of pears to soften (using only fruit sampled in September and October), firmness at time of sampling was compared with firmness after the seven-day ripening test (Figure 6). Firmness at time of packing appears to have little relation to the ability of pears to soften. There must be other factors; therefore more investigation of pear ripening is needed. Tests should be undertaken to determine whether early season pears should be treated (with ethylene?) prior to shipment to induce uniformity of ripening. We plan to pursue this further next season.


Fruit Soluble Solids

At the time Anjous were packed, the soluble solids levels in the pears did not vary greatly over the seasons (Figure 7). The average soluble solids level was 13.1% over the three years.


Fruit Acidity

At time of packing, the acid levels in Anjou pears averaged 0.373% over the three years (Figure 8).


Fruit Quality after Storage

A box of pears was purchased at time of sampling and brought to the laboratory where it was divided into thirds. In the first third, fruit quality was examined at time of sampling, and the rest of the pears were placed in CA storage. The second third was examined in March; the final third, in the beginning of June.

The spreadsheet gives the firmness, starch rating, percent extractable juice, soluble solids, and acidity for fruit sampled from the 1992 crop (Table 2). It is interesting to note the averages for softening after warm room testing.

Fruit stored until June had a firmness of only 2.5 lbs. after ripening, while the same lot of fruit stored in April softened to 4.1 lbs. after ripening. At time of packing, the fruit from the same lot was 9.8 lbs. after ripening. Thus, Anjous purchased in September may need far longer to soften to an acceptable level, while those purchased in June may need far less time. The differences in soluble solids were not as great; however, acidity of the fruit dropped from 0.45 to 0.26 during storage. It did not change as dramatically during ripening. This indicates a loss in flavor and firmness over time in storage. There was also an increase over time in extractable juice.


Table 2

Table 2. Summary of quality attributes of the 1991 and 1992 Anjou pear crops at time of sampling and after storage in CA.

Test Date Firmness (lbs) Soluble Solids (%) Acidity (%) Ext. Juice (%)
OOS*S+7*OOS S+7OOSS+7S+7
1991 Initial 15.27.612.813.8 .297.31660.3
1992 Initial 15.29.813.213.9 .451.452n/a
1991 Middle 14.03.612.813.7 .240.24846.5
1992 Middle 13.64.113.214.6 .410.38236.8
1991 Late 12.73.612.413.4 .229.26063.2
1992 Late 12.32.513.414.0 .261.27147.3
*OOS is out of storage (time of sampling); S+7 is after 7 days at 70F.


Conclusion

The first part of this report addresses the quality of pears packed in Washington and northern Oregon in 1991-1993. Most packers have completed packing by the end of December each year.

Fruit firmness was highest in fruit packed out of CA storage and the average firmness at time of packing was 15 lbs. Unfortunately, in most years consumers purchasing fruit packed prior to the beginning of November would have a difficult time getting these fruits to soften to below 6 lbs. Thus, the industry must find a method to treat early season marketed pears so that they will soften or convince the consumer to enjoy crisp pears. Pears capable of softening were thought to be those harvested at advanced maturity (low firmness), but in this study the relationship of firmness at time of packing and ability to soften appeared very tenuous. We plan to explore this relationship more fully next season.

The author acknowledges the contributions of Ken Miller, Agricultural Research Technologist; Lori Kutch and Casey Parish, Technicians; and Dave Burkhart, Consultant.

Dr. Eugene Kupferman, Postharvest Specialist

WSU Tree Fruit Research and Extension Center
1100 N. Western Ave., Wenatchee, WA 98801
Kupfer@wsu.edu

Tree Fruit Postharvest Journal 5(1):3-10
April 1994

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