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WSU-TFREC/Postharvest Information Network/Packing Golden Delicious Apples in Washington State



Packing Golden Delicious Apples in Washington State


Sampling

Sampling of Golden Delicious began in November 1990 at the request of and with funding provided by the Washington Apple Commission. Funding from the Tree Fruit Research Commission covered the cost of sampling Golden Delicious in subsequent years. Sampling continued through the end of May 1993.

Packinghouses from each of the major growing districts were selected (Table 1).

Table 1. Distribution of packinghouses for Golden Delicious included in this study.

Location 1990 Crop 1991 Crop 1992 Crop
Wenatchee
8
7 8
North Central Washington 4 5 6
Yakima 7 5 6
Total 19 17 20
Total samples (season) 129 183 188

Fruit Firmness

The retention of harvest season firmness is an important component of Golden Delicious quality. Several observations can be made about the firmness of Golden Delicious over the three years of the study (Table 2). The firmness in Golden Delicious was generally less than the firmness of Red Delicious both at time of packing and after being held at 70°F for 7 days. The range of firmness (standard deviation) was much larger than in Red Delicious.

Table 2. Seasonal average firmness of Golden Delicious at time of packing and after 7 days at 70 ºF.

  Regular storage CA storage
Crop Time of
packing
After 7 days
@70 ºF
Time of
packing
After 7 days
@70 ºF
1990*
13.3 (3.0)
12.8 (2.5) 14.5 (1.4) 14.0 (1.5)
1991 14.0 (1.8) 12.6 (1.7) 14.9 (1.5) 14.3 (1.5)
1992 13.3 (2.0) 12.2 (1.8) 14.1 (1.5) 13.5 (1.6)
* Only 5 samples were obtained from regular storage in 1990

Figure 1 plots the average firmness by week for all samples tested at time of packing. Note the rise in firmness about the time CA rooms are opened in December of each year. Golden Delicious for the 1991 crop was firmer than from the other years.

These data illustrate the lack of firmness for the fruit harvested in 1992 as compared with 1991. Immediately upon opening CA rooms in December of 1992, Golden Delicious firmness rose.

Goldens packed from September through December 1992 lost firmness very rapidly in warm room tests (Figure 2). After warm room tests of regular storage fruit, Goldens picked in 1992 averaged 1.1 lbs. less firm than those from the 1991 crop. CA stored Goldens from the 1992 crop averaged 13.5 lbs. after warm room testing, slightly lower than fruit sampled in the two previous years.


Shelf Life

As seen in Red Delicious, the loss in firmness following the ripening treatment (7 days at 70°F) was greatest in the early season as compared with fruit stored in CA (Figure 3). However, it is not possible to predict firmness loss by week in storage due to the strong effect of type of storage and fruit maturity.


Short-term CA

There is a positive effect on the firmness of fruit stored in CA for a short period of time as compared with that stored in regular storage (Table 3). When Golden Delicious apples are placed in CA, the loss in firmness is less than in regular storage, even when apples are packed within only 30 to 60 days of harvest.

It is clear that in seasons of marginal fruit firmness it is important to put the fruit into CA regardless of the intended length of storage (Figure 3 and Table 3) as this fruit remains firmer than if it were in regular storage.

Table 3. Comparison of the firmness of Golden Delicious apples stored in regular storage with those stored in "Special CA" within 90 days of harvest.

Crop year Regular storage "Special CA" Difference
1991 14.8 15.7 0.9
1992 12.0 13.8 1.8

Soluble solids

The levels of soluble solids during the 1992 season were approximately equivalent to that found in previous years in spite of low firmness levels (Figure 4). The general pattern to soluble solids throughout the marketing season appears variable. CA fruit averaged 12.7% (0.8 St. Dev.) in 1990, 12.8% (0.8 St. Dev.) in 1991 and 13.2% (0.8 St. Dev.) in 1992 (St. Dev. = standard deviation). Over the term of the study, the soluble solids content of Golden Delicious averaged 13.0% (0.8). The level was the same whether the fruit were stored in CA or in regular storage.


Acidity

The level of acids in Golden Delicious was higher in 1992 than in the previous two years (Figure 5) in spite of lower firmness levels. This is another demonstration of how unusual fruit characteristics were in 1992-1993. Over the course of the study the acidity of Goldens averaged 0.411% (0.094). Goldens stored in CA (0.400% [0.089]) were less acidic than those stored in regular storage (0.449% [0. 103]). This is the reverse of what I would have expected. Research trials using paired samples have showed that Goldens stored in CA have higher acidity than those stored in regular storage for the same period.


Fruit Firmness as Affected by Temperature

The greatest rise in fruit temperature occurs in the dump tank due to the ability of water to heat the fruit more rapidly than air. Tabulated below are the season averages for fruit, water, and air temperatures at various points in the packingline (Tables 4 and 5). Some packers do not wax Golden Delicious, some wax all their fruit, and still others wax on demand.

Table 4. Average temperatures of fruit, water, and air in packinglines with heated air dryers.

Location 1990
Avg./High*
1991
Avg./High
1992
Avg./High
Fruit before dumping 41/52 43/65 39/58
Dump tank water 58/92 63/101 59/103
Fruit before waxing 52/70 53/77 46/61
Dryer air 120/160 108/175 115/160
Fruit at tray filler 55/73 57/79 52/66

Rise
15/36 13/34 13/30
* Avg. is average value of all packinghouses sampled.
  High is the largest value encountered


Table 5. Average temperatures of fruit, water, and air in packinglines without heated air dryers.

Location 1990
Avg./High*
1991
Avg./High
1992
Avg./High
Fruit before dumping 40/45 44/69 40/59
Dump tank water 63/105 65/104 61/106
Fruit before waxing 48/57 52/68 46/61
Fruit at tray filler 50/75 53/69 48/61

Rise
10/37 9/24 8/25
* Avg. is average value of all packinghouses sampled.
  High is the largest value encountered

Goldens that pass through a heated dryer are boxed at a higher temperature than those from lines without heated dryers (50° vs 54°F, respectively). This difference is less than one might think; however, both types of lines use warm water in the dump tank.

The temperature of the fruit at time of packing is well above optimum. Since the refrigeration system of a truck is unable to remove any heat above that of respiration, it is unlikely that apples will be cooled in transit. The simplest method of reducing fruit temperatures would be to lower the temperature of the water in the dump tank. However, dump tank water temperatures are raised to heat the skin of the fruit so that better cleaning can result. An improved shine comes from having both warmer and cleaner fruit. The industry should find a method of obtaining a good shine without raising the fruit temperature.

An alternative strategy might be to improve the cooling of boxed fruit through improved box design which would include vent spaces and allow for forced air cooling.

A project was undertaken, similar to that described in the section on Red Delicious, to obtain information on what might happen to fruit quality if apples were shipped without being cooled after packing. Ten lots of fruit were employed from the 1990-1993 crops. Nine of the ten had been stored in CA.


Firmness of Golden Delicious Held at Elevated Temperatures

By combining the data from all 10 Golden Delicious lots it is possible to predict the performance of untested lots (Table 6).

Table 6. Firmness loss in Golden Delicious from date of sampling to examination date.

Holding temp. (ºF) Days at temperature
7 14 21 28
Firmness loss (lbf)
32 -0.5 -1.2 -0.4 -1.0
40 0.0 -0.7 -0.9 -1.3
50 -0.6 -1.1 -1.5 -1.9
60 -0.8 -1.5 -1.7 -2.7
70 -0.8 -1.7 -1.9 -2.3

Using the information on this table, the minimum loss in firmness at 21 days or longer would occur in fruit held at 32°F. However, the differences in firmness as a result of temperature are most clearly illustrated when the fruit is ripened for 7 days at 70°F after being stored at the various temperatures (Figure 6). This treatment reflects the shelf life of the fruit. It becomes quite clear that fruit held above 40°F for even 7 days deteriorate rapidly.

It stands to reason that the loss in firmness by different lots of fruit would not be the same and firmness loss in different years might also be at different rates. Figure 7 illustrates the range in losses by the 10 lots of fruit from the three harvests at one temperature (50°F). It can be seen from this graph that some lots will lose a great deal of firmness while others retain firmness for a long period. Unfortunately, we cannot predict the behavior of any individual lot.


Summary

Golden Delicious quality differs from year to year. Although many in the industry think that Washington packers have fine-tuned postharvest practices so Goldens are not a problem, much work remains to be done. Firmness losses of 1 lb. or more reduce the already marginal firmness of fruit coming out of regular storage. Goldens should be stored in CA even for a short time. Other researchers have shown that rapid oxygen reduction is more effective than slow atmosphere establishment.

Temperatures should be reduced on apples prior to shipment. Forced air cooling will require new box venting to be most effective. Other apple growing districts use boxes with more vents and forced air cooling very effectively.

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(2):12-18
August 1994

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