Washington Tree Fruit Research Commission

Research Reports

Ensuring the edible quality of Washington-grown apples (2004)

FINAL PROJECT REPORT
WTFRC Project #PH-01-127
YEAR 0/0
Organization Project #13C-4164-2272
Title:Ensuring the edible quality of Washington-grown apples
PI:Eugene Kupferman
Organization:WSU Tree Fruit Research and Extension Center 1100 N. Western Avenue; Wenatchee, WA 98801; 509-663-8181 ext. 239; kupfer@wsu.edu
 PDF version of report

Co-PIs

Roger Harker, HortResearch, New Zealand

Elizabeth Mitcham, University of California, Davis

Chris Watkins, Cornell University

Nate Reed, Pennsylvania State University

Sylvia Blankenship, North Carolina State University

Randy Beaudry, Michigan State University

James Rushing, Clemson University

Collaborators

35 packinghouses in Washington State
Norm Carpenter, Jim Dougherty, Sharon Godfrey—Washington Apple Commission
Kroger Foods, Standard Fruit, Minyard Food Stores, and Brookshire in Dallas, Texas

Objectives

The objectives of this study were as follows:
1.   Summarize the worldwide information on sensory attributes, consumer attitudes and behavior that influence their choice of apples (Harker).

2.   Determine the edible quality characteristics of Washington-grown apples at time of packing, the change in quality in commercial wholesale shipments, and the final quality at retail (Kupferman). This was done through the following three studies:

a)      Washington apple quality surveys—Determined apple quality at packing in multiple packinghouses throughout the packing season for the 2000 and 2001 crops, with special emphasis on varieties new to Washington.

b)      Shipping studies—Shipped commercially packed apples of known quality to wholesale markets in Atlanta, Georgia, (2001) and Dallas, Texas, (2002) to characterize the change in quality as the result of transport and wholesale market practices.

c)      National apple retail quality survey—Employed the services of seven postharvest tree fruit scientists located in different regions of the U.S. to sample apples from retail stores to gauge their quality in retail markets.

Methodology and results

I.    Information on consumers and apples

Dr. Harker’s summary of consumer reactions to apple quality is outlined below. This information was obtained by reviewing the world’s scientific literature, Washington Apple Commission information and other commercial and scientific sources.
·         Consumers’ decisions to purchase apples are based on their beliefs, attitudes and perceptions of apples, as well as their preferences for eating quality.
·         The extent that American consumers continue to have a preference for Washington apples is critical to the survival of the Washington apple industry. Economic studies have shown that an increase in consumer preference will result in an even greater increase in the quantity of apples demanded and the industry recognizes this, responding through its expenditure on promotion and advertising of apples.
·         Bananas, apples and oranges remain as the favorite fruits of Americans by percentages of 19%, 18% and 17%, respectively.
·         Flavor and taste remain the top reason that U.S. consumers like apples (64%).
·         The literature estimates that between 13 and 55% of U.S. consumers make their choice of apples primarily based on quality, while between 9 and 29% make their choice based on price.
·         Other positive advantages that apples provide consumers include the fact that apples are healthful, refreshing and convenient (no mess) snacks. Consumers think that apples have the disadvantage of not being seen as filling (satiety), not easily shared between people and not considered a treat.
·         Health is a principal factor that influences consumers’ choice of apples, although consumers see taste and texture as the key that unlocks the door to health benefits associated with apple consumption.
·         Within the U.S., consumer choice of preferred cultivar is as much based on familiarity with the apple as it is with ethnic and/or regional differences in taste sensitivity/preference.
·         Consumer expectations of eating quality are likely to increase as a result of increased competition in the market from imported apples and new apple cultivars.
·         According to an Australian study, after a bad eating experience consumers change cultivar (58%), purchase fewer apples (31%), switch to other types of apple (24%) or stop buying for a while (17%).
·         Eating quality of apples can be defined by texture, taste, and flavor; and each of these sensory attributes can be predicted with varying accuracy using instrumental measurements.
·         U.S. consumers universally agree that a mealy or mushy apple is bad, and there is international consensus that instrumental firmness measurements can be used to predict consumer preferences for texture. From the literature information, the minimum firmness should be 13 lb. At this firmness consumers will not reject apples but may not express a positive liking of the apples.
·         Consumers dislike immature, unripe and starchy apples that often come onto the market from harvest of immature fruit. The minimum Starch Pattern Index should be 4 on a scale of 0 to 6, where 6 represents no starch staining. At this level, 90% of consumers find the apple acceptable.
·         Consumer preferences for sweetness are not easily predicted using soluble solids content (SSC) of apple, but SSC is a convenient way to ensure that apples are not harvested until they are fully mature. Minimum SSC should be at least 12%.
·         Titratable acidity is an important predictor of consumer perceptions of sweet and sour taste, but there are insufficient data to recommend values that can be used in quality standards (the values will need to be specific to individual cultivars).
·        The use of instrumental measurements to set quality thresholds can be problematic since lines of apple that are marginally above a threshold (e.g., firmness) will be judged on other sensory attributes (e.g., taste and flavor). For example, consumers are prepared to accept softer apples if they have high taste and flavor or apples with poorer taste and flavor if they have good texture.

Published work and grower presentations from this project include the following:
1.   Harker, F. Roger. 2001. Ensuring the edible quality of Washington-grown apples. Part I – consumer research. HortResearch Report, June 2001, 44 pages.
2.   Harker, Roger. 2001. Consumer response to apples (Part I): price and demand. Good Fruit Grower.
3.   Harker, Roger. 2001. Consumer response to apples (Part II): eating quality. Good Fruit Grower.
4.   Tree Fruit Postharvest Conference presentations in 2000 and 2001.

 

II.  Quality characteristics of Washington-grown apples

 

a.   Washington apple quality surveys
To investigate apple quality characteristics and the variability of fruit packed by 35 packinghouses in Washington State, samples were taken between December 2000 and August 2001.

 

The survey included an estimation of apple edible quality (firmness, soluble solids and acidity) and fruit temperature at time of packing of nine varieties. The second year of the survey included a significant amount of fruit of the newer varieties (Braeburn, Pink Lady, Cameo and Jonagold). Firmness evaluations were performed using traditional destructive technology (penetrometer) as well as nondestructive acoustical firmness.
·         The quality of apples packed between January and the end of the packing season from the 2001 crop was superior to the quality from the 2000 crop in most attributes. The largest difference in fruit quality between the two years was in Fuji and the least was in Gala.
·         Fruit quality varied to different degrees over time dependent upon variety. With most varieties, apples early in the packing season were firm, high in acidity and low in soluble solids. These factors changed slowly as fruit was packed out of regular storage. In December, fruit firmness and acidity increased as CA rooms were opened, and over time both quality parameters declined.
·         Results from the survey of the 2001 crop showed that acidity levels and firmness changed a great deal during the season while soluble solids levels changed the least. Acidity declined the most in Granny Smith, Pink Lady and Fuji as compared to other varieties. Low acidity levels and poor sugar/acid ratios result in bland flavor. This was typical of Red Delicious and Fuji at the end of the season.
·         Red Delicious: Results from the survey of the 2000 crop showed that 12% of Red Delicious apples were below 12 lbf in firmness. In the 2001 crop, 6% of apples were below 12 lbf. The quality of Red Delicious apples varied greatly among packinghouses.
·         Golden Delicious: Results from regular storage 2001 crop showed that firmness declined dramatically during the packing season. Fruit from CA storage had higher firmness than apples from regular storage. CA-stored Golden Delicious apples were variable in firmness all season.
·         Braeburn, Golden Delicious and Jonagold apples showed the greatest degree of variability (had the widest range) in apple firmness.
·         During the packing season the firmness of Braeburn and Cameo apples declined more than other varieties. Gala apples held firmness throughout the packing season. Golden Delicious apples lost firmness more dramatically following regular storage than those out of CA. Firmness of Red Delicious was not related to packing date, with both firm and soft apples encountered year around.
·         As a result of information gathered in this survey the following suggestions are made. To provide higher and more consistent quality, the industry should shorten the length of time it takes to obtain CA certification from 60 days to 45 days for both Red Delicious and Golden Delicious or raise grade standards for both firmness and soluble solids to provide a more acceptable eating experience to consumers and reduce the variability in apple to apple quality.
·         In 2000 and 2001 internal apple temperature at time of packing ranged from 34ºF to 84ºF. External temperature ranged from 44ºF to 87ºF. The upper temperatures indicate that the emphasis on appearance of waxed apples continues to force the temperatures up, which accelerates the senescence of apples.

 

Every one of the thousands of apples collected in this project this year was subjected to both destructive and nondestructive testing of firmness. The destructive instrument is an improved penetrometer called a Fruit Texture Analyzer (FTA) and reads in lbf. The nondestructive analyzer is the Acoustical Firmness Sensor (AFS) and reads in FI units. The units were compared using all the apples and, although significant (P=<0.0001), the correlation between the two was weak (r = 0.5434; r2=0.2953).

In summary, this study offers the following insights:
·         Red Delicious and Golden Delicious apples are highly variable and therefore provide inconsistent eating experiences while Gala apples have been of consistent quality all season.

·         Golden Delicious apple firmness declines rapidly during the regular storage season. Shortening the interval in CA storage from 60 to 45 days would help reduce this problem. However, firmness out of CA remains highly variable.

·         Red Delicious apple firmness was highly variable at each sampling date with a significant proportion below minimum standards. This variety would also benefit from a shorter CA treatment and higher firmness standards.
·         Gala apples have been of consistent firmness, soluble solids and acidity throughout the marketing season.
·         Apples packed later in the season have lower firmness and acidity levels than those packed earlier. Soluble solids are dependent on lot-to-lot variability rather than packing date.
·         Temperature management continues to be a challenge since fruit is heated on the packingline to temperatures that accelerate softening.

 

Published work and grower presentations from this project include the following:
1.   Three progress reports were sent to each participating packinghouse and WTFRC, one for the 2000 crop, an interim report at the end of the regular storage packing season for the 2001 crop, and a final report for the 2001 crop.
2.   The full report is available on-line at www.postharvest.tfrec.wsu.edu.
3.   Tree Fruit Postharvest Conference presentations in 2000 and 2001, WSHA annual meeting in 2001 and posters.
4.   Good Fruit Grower article.
b.   Shipping studies
Two shipping studies were conducted to determine the change in edible fruit quality from time of packing to arrival at wholesale distribution centers and on to retail stores. These trials were conducted in May 2001 with shipments to Atlanta, Georgia, and in May 2002 with shipments to Dallas, Texas. The study was done in cooperation with the Washington Apple Commission and various apple wholesaler buyers.

 

Significant findings

·         Firmness was the edible quality variable most affected by transit and wholesale practices. Fruit soluble solid and acidity levels were not affected. Fruit weight loss was affected by mildly warm fruit temperatures but was not appreciable.
·         Firmness loss was most severe on fruit that was not sufficiently cooled prior to shipment. Firmness loss was not significant on high quality fruit that was cold when packed and held in a reliable cold chain.
·         Firmness loss was highest in Gala apples (1 lbf in 7 days) when compared to Red Delicious or Golden Delicious.
·         Temperature management varied greatly between the shipping systems, both within the truck and at the distribution centers.
·         Bruising was greater in fruit that was unloaded by hand rather than using forklifts upon arrival at distribution centers.
·         Loose apples on retail shelves averaged 60ºF and ranged from 51 to 73ºF. Visual and edible quality varied greatly at retail.

 

Published work and grower presentations from this project include a Good Fruit Grower article.

 

c.   The national apple retail quality survey

A study was initiated in the second year of this project to determine the variability of fruit quality in retail stores around the country by enlisting the assistance of scientists in several states. Participating scientists were Elizabeth Mitcham, University of California, Davis; Chris Watkins, Cornell University; Nate Reed, Pennsylvania State University; Sylvia Blankenship, North Carolina State University; Randy Beaudry, Michigan State University; and James Rushing, Clemson University. Kupferman sampled fruit in markets in Yakima and Wenatchee as well.

 

In 2001, five varieties of Washington apples were sampled three times by scientists in seven states. In the first year Washington-grown Red Delicious, Golden Delicious, Fuji, Braeburn and Gala were sampled when available from loose fruit displays (10 apples per variety per store). Fruit temperature, display type (refrigerated or not), bruising, appearance, and price were noted.

 

In 2002, scientists in the same states evaluated up to seven varieties (when available) four times. All evaluations were done at the same time throughout the country. As this report is written in May 2003, there is one additional sampling period remaining.

 

 

 

Variety
Year
Firmness
(lbf)
Soluble
solids (%)
Acidity
(%)
Price
($ / lb)
Braeburn 
2001
14.6 b
13.0
0.439 b
1.26 b
2002
15.9 a
13.0
0.503 a
1.37 a

 

Fuji 
2001
14.6 b
14.3
0.247 b
1.23 b
2002
15.0 a
14.5
0.303 a
1.32 a

 

Gala 
2001
13.6 b
13.4
0.308 b
1.27 b
2002
15.2 a
13.4
0.342 a
1.42 a

 

Golden
Delicious
2001
12.9 a
13.2
0.360
1.20
2002
12.2 b
13.2
0.370
1.23

 

Red
Delicious
2001
12.5
13.5
0.219
1.13
2002
12.4
13.3
0.228
1.15

 

Pink Lady
2002
17.2
14.4
0.612
1.63

 

Granny Smith
2002
16.3
12.9
0.610
1.28

 


 

 

Variety
Table type
Firmness
(lbf)
Soluble solids (%)
Acidity
(%)
Price
($ / lb)
Temperature
(ºF)
Braeburn
Refrigerated
15.5 b
12.9
0.484
1.32
52.6 b
Unrefrigerated
16.2 a
13.2
0.523
1.34
63.8 a

 

Fuji
Refrigerated
15.0
14.4
0.273 b
1.36 a
52.6 b
Unrefrigerated
15.4
14.4
0.327 a
1.25 b
62.4 a

 

Gala
Refrigerated
14.4
13.5
0.335
1.39 a
53.6 b
Unrefrigerated
14.2
13.2
0.323
1.32 b
62.9 a

 

Golden
Delicious
Refrigerated
12.5 a
13.3
0.360
1.27 a
54.0 b
Unrefrigerated
12.2 b
13.3
0.366
1.19 b
63.3 a

 

Red
Delicious
Refrigerated
12.6 b
13.4
0.228
1.17 a
53.8 b
Unrefrigerated
12.9 a
13.7
0.223
1.08 b
63.6 a

 


 

Variety
Season
Firmness
(lbf)
Soluble solids
(%)
Acidity
(%)
Price
($ / lb)
 Braeburn
fall
18.0 a
12.9
0.614 a
1.36 b
winter
15.5 b
13.1
0.510 b
1.30 b
spring
14.9 b
13.0
0.431 bc
1.33 b
summer
14.2 c
13.3
0.421 c
1.54 a

 

 Fuji 
fall
16.8 a
14.5
0.390 a
1.41 a
winter
14.9 b
14.2
0.309 b
1.22 c
spring
14.6 c
14.6
0.236 c
1.34 b
summer
14.1 d
14.0
0.193 d
1.38 bc
 
 Gala 
fall
14.4 a
13.5
0.362 a
1.39
winter
14.4 a
13.4
0.330 ab
1.37
spring
14.4 a
13.4
0.319 b
1.35
summer
13.1 b
12.9
0.264 c
1.38

 

 Golden Delicious
fall
11.4 c
13.6
0.401 a
1.28 ab
winter
12.4 b
13.4
0.384 a
1.16 c
spring
12.7 a
13.2
0.345 b
1.26 b
summer
12.7 a
13.1
0.324 b
1.30 a

 

 Red
Delicious 
fall
13.5 a
13.2 b
0.256 a
1.11 b
winter
12.0 d
13.4 b
0.230 b
1.11 b
spring
13.0 b
13.4 b
0.216 bc
1.17 a
summer
12.7 c
14.0 a
0.209 c
1.16 a

 

Published work and grower presentations from this project will include Good Fruit Grower articles when the project is completed.

 

Overall conclusions

·         Consumers evaluate apples by first considering appearance and then firmness. If firmness is acceptable they consider sweetness and then acidity. Firmness appears to be the single most important variable in edible quality. Whether acceptable firmness levels are the same for all varieties is as yet unknown.
·         Apple quality is influenced by many factors including genetics, growing conditions and harvest maturity. It is also influenced by storage and packing procedures, as well as shipping conditions. Apples must be cold prior to shipment or they will lose firmness in transit. Soluble solids do not appear to be influenced by postharvest procedures.
·         Apple quality and appearance are maintained through most standard commercial practices prior to retail. Trucking and warehousing temperature management in the commercial companies with which we worked were sufficient to maintain quality of firm apples that had been cooled prior to shipment. Apples loaded without having been cooled lost firmness despite having been in a refrigerated truck with cold apples.
·         When viewed across various regions of the U.S., the retail handling experience is suboptimal, leaving apples stressed through poor temperature management and inferior handling practices. Adverse temperatures and bruised fruit are typical in retail environments. In other studies (for the Washington Apple Commission) we have shown that quality can remain high even in ambient, nonrefrigerated environments if fruit arrives firm and is sold quickly. Apples of marginal quality must be held cold and sold rapidly.
·         Our other studies now underway using sensory analysis to understand how consumers evaluate apple edible quality should help Washington producers know what to aim for as they try to fill the market demand for high quality apples.

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