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THE EFFECT OF RIPENING ON THE RESPONSE OF
McINTOSH APPLES TO PRESTORAGE TREATMENT
WITH HIGH 002 AND OTHER MODIFIED ATMOSPHERES

Thesis for the Degree of M. S.
MICHIGAN STATE UNIVERSITY
SUSAN ELIZABETH TAYLOR

1977

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ABSTRACT

THE EFFECT OF RIPENING ON THE RESPONSE OF
MCINTOSH APPLES TO PRESTORAGE TREATMENT WITH

HIGH CO2 AND OTHER MODIFIED ATMOSPHERES

BY

Susan Elizabeth Taylor

McIntosh fruit harvested from four different Michigan orchards
were pretreated prior to storage. Pretreatments consisted of five dif—
ferent time-temperature sequences plus a control treatment (continuous
storage in air at 0°C) in a randomized block design. Atmospheres used

during two weeks of pretreatment were: (a) 12% CO and 3% 02 (high

2

C02), (b) 0% CO and 3% 02 (controlled atmosphere or CA), and (c) air

2
at 90 mm Hg (low pressure storage or LPS). Temperature was constant at

0°C. Time-temperature sequences prior to storage in one of the above
atmospheres were: (a) no delay treatment; (b) O0 for 1 week; (c) 00
for 2 weeks; (d) 200 for 1 week; (e) 200 for 1 week, then 00C for 1
week. Fruit were held in air in each case. After termination of pre—
treatments, fruit were returned to air at 0°C for the balance of a four
to five week period, then held in CA (0% CO2
additional 22 weeks prior to evaluation of fruit quality. The only

and 3% 02) at 2.20C for an

treatment which proved beneficial in comparison with the control was

high CO applied immediately after harvest. Fruit were firmer and

2

scald was reduced. None of the treatments caused injury to the fruit

or affected titratable acidity.

THE EFFECT OF RIPENING ON THE RESPONSE OF
McINTOSH APPLES TO PRESTORAGE TREATMENT WITH

HIGH CO2 AND OTHER MODIFIED ATMOSPHERES

By

Susan Elizabeth Taylor

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE

Department of Horticulture

1977

TABLE OF CONTENTS

Page

INTRODUCTION...0000.0..0......00.0.0.0..0...000..0000.0000000.0. 1
LITERATURE REVIEW0000000000..0..0.000....0........00.0....00000. 2

High Levels of CO ........................................ 2

Controlled AtmospHere..................................... 3

Low Pressure Storage (Subatmospheric or Hypobaric
Storage)............................................... 4

MATHIM’Sm“THODS.0000.00.00.000000000000.0.000000000000.000 5
RESULTS....0..0.000000.0.....0000...0000..0.0000......0000000000 14

Fruit Maturity at Harvest................................. l4
Prestorage Ripening....................................... 14
Endogenous C H ........................................ l4
Respiration............................................ 19
Fruit Softening........................................ 19
Storage and Shelf Life.................................... 28
Firmness............................................... 28
Titratable Acidity..................................... 34
CO Injury............................................. 34
Storage Scald.......................................... 34
Other Injuries......................................... 34

DISCUSSIONooooooooooooooooooooooooooooooooocoo-0000.00.00.oooooo 41
Maturity at Harvest................ ........ ............... 41
POSt'treatment EffeCtSoo000000000000oooooooooooooooooooooo 41
Pre-CA Storageooooooocoo-0000.00.00.00... ooooo 000000000000 42
Post-CA Storageoo......................................... 45

CONCLUSIONS0000000.00.0... ....... 0.00.0...000 ....... 0.0.0.000... 48

LITERATURE CITED..00000000000.000.000.000..0000000000000....0000 49

ii

LIST OF TABLES

TABLE

1.

10.

ll.

Pretreatments applied to McIntosh apples prior to CA storage
at 00C for 22 week80000000000.000.000...00.000.00.00000000.0

Mean flesh firmness and internal ethylene for 20 McIntosh
apple fruits within six hours following harvest.............

Mean internal ethylene (ppm) for 10 McIntosh apple fruits
immediately following prestorage treatment..................

Mean internal ethylene (ppm) for 10 McIntosh apple fruits
upon transfer to CA storage on October 16, 1975.............

Effect of orchard and prestorage delay on mean internal
ethylene (ppm) for 10 McIntosh apple fruits after prestorage
treatment with high CO2 when transferred to CA storage on
October 16, 1975............................................

Effect of treatments on mean flesh firmness (kg) for 20
McIntosh apple fruits immediately following prestorage

treatment0000000000000000000000.000.000.00.000.00.000.00...0

Mean flesh firmness (kg) for 20 McIntosh apple fruits upon
transfer to CA storage on October 16, 1975..................

Effect of orchard source on mean flesh firmness (kg) for 20
McIntosh apple fruits after prestorage treatment with high

002 when transferred to CA storage on October 16, 1975......
Effects of pretreatments on mean flesh firmness (kg) for 50
McIntosh apple fruits after storage in CA for five months...

Effect of source of fruit on mean flesh firmness (kg) for
20 McIntosh apple fruits stored in CA for five months
after prestorage treatment0000000000000.000000.000000000.00.

Effect of pretreatments on mean titratable acidity for 50

McIntosh apples stored in CA for five months after pre-
Storage treatment00000 000000000000000 0 0000000000 0.0.0000.0..

iii

Page

15

18

20

21

26

27

29

30

33

35

LIST OF TABLES--continued

TABLE

12.

13.

14.

Effect of pretreatment on mean percentage (If CO injury of
McIntosh apples treated with 12% 002 for two wee s and
Stored in CA for five months..0...‘0........0.000......0...

Effect of prestorage treatments on mean percentage of scald
in McIntosh apple fruit after CA storage for five months...

Effect of pretreatments on mean percentage of McIntosh

apple fruits with internal browning after CA storage for
five month8000000000000.00..00000000000...00.0.0.0...0.0...

iv

Page

36

37

38

LIST OF FIGURES

FIGURE

A schematic diagram of the chambers and equipment used for
the prestorage treatment00000.000.000.00...000.000.00.000...

Respiration rates of 'McIntosh' apples from four orchards
during the first five days after harvest....................

Respiration rates of 'McIntosh' apple fruit after applica-
tion of prestorage treatments...............................

Mean respiration rates of high COz-treated and control
'McIntosh' apple fruit at the time of transfer to CA

storage0.0000000000.0.00.00.000.00.000...00.0.0000.00.00....

The effect of high 002 applied immediately (N0 DELAY) and
after 1 week at 0°C or 20°C, on flesh firmness of 'McIntosh'
apples from harvest (HAR) through CA (IN,OUT) and during a
subsequent week at 20°C (+ l WK)............................

Types of flesh injury that developed in‘McIntosh'apple fruit
during five months of CA storage............................

Page

17

23

25

32

40

INTRODUCTION

High levels of carbon dioxide (C02) in the prestorage atmosphere
improve post-storage marketability of apple fruit. Most research,
however, has concentrated on Golden Delicious, a cultivar relatively
resistant to C02 injury; also, the effects of postharvest ripening
as a result of delaying C02 treatment and/or low temperature storage
before treatment have not been investigated extensively. The practice
might be useful with other cultivars; therefore, a study was undertaken
to examine (a) the response of 'McIntosh' apple fruit to prestorage
treatment with high CO2 and (b) the effects of delaying treatment
and/or delaying cold storage before treatment. Two other atmospheres
not normally considered as prestorage treatments, p§£_§g, were also
used to determine their possible usefulness in limiting ripening.

These were a controlled atmosphere held at 0% CO and 3% O and storage

2 2

in air at 90 mm Hg. A randomized block design was used.

LITERATURE REVIEW

Most studies of prestorage treatments of apples have focused on
chemical means of preventing disorders (23); treatments for retarding
ripening have seldom been considered. However, the effect of prestorage

atmospheres on the overall fruit ripening process is gaining interest.

High Levels of CO

 

2

The use of elevated levels of CO2 as a prestorage treatment led

to the development of CA storage. Brooks (11) reported that apples in

38 to 40% 002 for two days at either 00 or 20°C softened more slowly

than control fruit when subsequently held at 20°. He suggested that

this treatment be used for retarding softening of fruit that was to be
shipped long distances without refrigeration. Pieniazek and Christopher
(29) reported that scald development and softening were inversely propor-

tional to level and length of exposure to CO Subsequent work was

20
published by Allen and colleagues (2,3,4,5,6), but not until the early
1970's was this method examined as a practical means of retarding
softening. Couey (18), using the cv. Golden Delicious, showed that

response to CO was proportional to concentration and duration of the

2

prestorage treatment. Effective treatments improved firmness, texture,

and flavor, and increased titratable acidity. Later, Couey (16) found

that immediate treatment with 15 to 20% CO2 for 10 days at 00 reduced

softening when apples were later transferred to 170; however, titrat—
able acidity and/or soluble solids were not measurably affected. When

held in CA storage at 00 for 7 months, the quality in May of C02-treated

fruit was equivalent to that of untreated fruit examined in February.
However, delaying treatment 10 days entirely eliminated all beneficial

effects. Couey noted C0 injury at this time. Reports (7) for the

2

1974-1975 storage season in Washington State attest to the commercial

success of the high 00 treatment for 'Golden Delicious'. Kajiura (24)

2
obtained similar results with 'Jonathan' and 'Ralls' held at 4°C in a

16 to 21% C02 atmosphere. At 12% CO2 prestorage treatment of two weeks

may benefit the storage of 'Anjou' pears (Wang and Mellenthin (35)).
The initial work with'McIntosh'apple focused on the effects on shelf

life of a 10% CO2 atmosphere alone or in combination with growth regu-

lator treatment (26). Apples pretreated with 10% CO produced less

2
ethylene (C2H4), were firmer, and were higher in titratable acidity.

Bramlage1 confirmed the beneficial effect of a C02 pretreatment on

'McIntosh' flesh firmness, and suggested further areas of study for

this cultivar.

Controlled Atmosphere

The usual long-term CA period, with 5% CO and 3% 0 for example,

2 2

has not been regarded as a prestorage treatment, per s2, although much

 

1W. J. Bramlage. 1975. Re-evaluating the CO levels for CA

apple storages. Fruit Notes. 40: 6~8. (mimeo) 2

 

work has concerned its role in retarding senescence (10,19,25,27,33).
Studies of intermittent CA treatment (19), and CA followed by air
storage, show a residual effect of CA, as suggested by Smock (33).
CA treatment of cold fruit was apparently beneficial regardless of
delay;2 however, the benefits declined as the period in air was

extended.

Low Pressure Storage (Subatmospheric or
Hypobaric Storage)

No data on the effects of low pressure storage (LPS) were avail-
able until 1947 (34), yet much is now known concerning its effects on
internal C2H4 concentration and respiration, and its mode of action in
delaying the ripening process (l4,20,21,28). Although delays in apply-
ing the LPS treatment have been tested with apples,3 no one has
reported its use as a pretreatment for fruit destined for long-term

storage.

 

2P. A. Poapst and W. R. Phillips. 1960. Delayed controlled

atmosphere storage. Rept. Canad. Com. Fruit, Veg. Preserv. 3 pp.
(mimeo)

3D. H. Dewey. 1976. Apple research project: Progress report

for 1975-1976 to the Michigan Apple Committee from Michigan State
University. 4 pp. (mimeo)

MATERIALS AND METHODS

The 'McIntosh' apples used in this study were grown in four
orchards. Lots I and II were harvested from commercial orchards near
Leslie, Michigan and Laingsburg, Michigan, respectively, on September 8,
1975. Lot III was obtained from the Graham Experiment Station,

Grand Rapids, Michigan, Lot IV from a commercial orchard near Conklin,
Michigan, and both were harvested September 15, 1975. Harvest dates
were chosen according to the estimated optimum harvest dates for 1975
as predicted by Dewey and Dilley.4 The fruit of each lot was brought
on the day of harvest to the Horticulture Research Center at East
Lansing, Michigan, and then randomized, composited, and placed immedi-
ately in either refrigerated storage at 0°C, or holding rooms at 20°C.
In all instances, fruit was held at the stated temperature for 48 hours
before initiation of the prestorage treatment. All treatments are
summarized in Table l.

The three prestorage atmospheres were as follows:

1) High C02. An Australian type open—flame generator was used to
establish a controlled atmosphere at 12% C0 - 3% O in a tight, but

2 2

unsealed, CA room (3.6 m x 2.4 m x 3.6 m). The required atmosphere, as

 

4D. H. Dewey and D. R. Dilley. 1975. Apple harvest and storage

notes for 1975. Michigan State University. l.p. (mimeo)

Table l -- Pretreatments1 applied to McIntosh apples prior to CA storage
at 0°C for 22 weeks.

 

 

 

 

 

Pretreatment Week of treatment
delay 1 2 3 4 5*
Control A0 A0 A0 A0 A0
No delay CO2 C02 A0 A0 A0
CA CA A0 A0 A0
LPS LPS A0 A0 A0
0
1 week at 0 C AO C02 C02 A0 A0
A0 CA CA A0 A0
A0 LPS LPS A0
0
2 weeks at 0 C A0 A0 C02 C02 A0
A0 A0 CA CA A0
A0 A0 LPS LPS A0
0
1 week at 20 C A20 C02 CO2 A0 A0
A20 CA CA A0 A0
A20 LPS LPS A0 A0
1 week at 20°C + A A co co A
.1 week at 0°C 20 ° 0
A20 A0 CA CA A0
A20 A0 LPS LPS A0
1 o o a 0
A0 -- air at 0 C; A20 -- air at 20 C; CO2 —— 12% CO 3% 02 at 0 C;
CA -- oz coz, 3% 02 at 0°C; LPS -- air at 0°C and 90 mm Hg.

*
Used only for fruits of orchards I and II.

measured by an Orsat gas analyzer, was established within 12 hours of
closing the room. The generator was then operated at 24 hour intervals
to maintain the atmosphere. Four replicates of five bushels each from
each orchard were treated in this manner.

2) 9A, The 12% C0 - 3% 0 storage room served as the master CA

2 2
chamber for the 5% C0 - 3% 02 atmosphere established in 2-bushel

2
capacity metal tanks. The CA tanks were fitted with plexiglass covers
and sealed tightly with gas-proof tape. Four tanks were inter—connected
through polyethylene tubing. A DYNA-VAC pump drew the atmosphere from
the master CA chamber and forced it through the tanks; two sets of four
tanks were used in this manner (Figure l). A small bag of hydrated

lime was placed in each tank to prevent the CO concentration from

2
exceeding 5%, and compressed water-pump nitrogen was used to flush each

tank twice daily in an attempt to hold the 0 level at or below 3%.

2
Despite these precautions, the actual mixture, as determined by the gas

analyzer, was approximately 0% C0 - 5% 02, with considerable variabil—

2
ity occurring from tank to tank. One bushel of fruit per treatment
from each orchard was treated.

3) LPS. One bushel of fruit per treatment from each orchard was
transferred to a plastic-lined wire basket and placed inside a hypobaric
tank. The pressure was lowered with an oil-seal vacuum pump and humidi-
fied air was drawn through the tanks continuously. Pressure was reduced

to 90 mm Hg within four hours of closing the tanks. Following treat-

ment, the apples were replaced in their original containers.

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STORAGE ROOM 3
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10

Upon completion of the prestorage treatment the apples were
placed in refrigerated storage at 0°C together with the controls.
On October 16, all fruit were transferred to a small CA storage room.
An atmosphere of 5% CO2 — 3% 02 was established by operating the

Australian open-flame generator daily; excess CO2 was eliminated from
the atmosphere by use of an hydrated lime scrubber placed within the
sealed room. On October 30, compressed water-pump nitrogen, adjusted
to a flow rate of 100 cubic feet per hour, and synchronized to operate
only with the "on" cycle of the refrigeration unit, replaced the
generator in maintaining the desired atmosphere. The atmosphere was
analyzed daily, and adjustments were made as necessary to maintain

approximately 3% O and less than 5% CO . The presence of hydrated

2 2

lime within the room limited build-up of CO to 0.2%. On several

2
occasions, 02 levels rose above 5%. The temperature was held at 2.2°C;
however, the temperature adjacent to the door of the storage room was
commonly 2.5o throughout the storage period. Failure of the thermostat
on April 1, 1976, caused the temperature in the room to fall to -50 for
16 hours; upon repair, a temperature of approximately 2.20 was main—
tained throughout the room for the remainder of the experiments.

Fruit firmness, respiration rate, and internal C H content were

2 4
measured the day of harvest. Sample size for flesh firmness and 02H4
content was 20 fruit each; g3, 1000 g of fruit was used to measure
respiration rate.

Measurements were made again upon the removal from the prestorage

treatment and before holding the fruit in air at 0°C. Sample size

H‘lll‘f‘l’lll

11

remained constant for firmness, whereas 500 g of fruit was used for
respiration rate determinations and 10 fruit for internal 02H4 levels.

Another determination was made on October 16, 1975, when fruit
were transferred to CA storage. The sample size was the same as that
for the second sampling; however, respiration was not determined for
the CA or LPS-treated fruit.

On March 18, 1976, two bushels of the high CO2 treated fruit from
each delay treatment and two bushels of the control fruit from each
orchard were removed from CA storage. On March 20, all CA and LPS-
treated fruits were removed and held at 20°C for 24 hours prior to
evaluation. One bushel of fruit from each treatment was visually evalu-

ated for the presence of external CO injury, scald, and other external-

2
ly visible disorders; 50 fruit were used for flesh firmness determina—

tions, titratable acidity, and examination for internal CO injury

2
and other internally visible disorders. One bushel of fruit from each

delay treatment of the high CO and one bushel of control fruit from

2
each orchard were examined after 7 days at 20°. At this time all fruit
were examined for external disorders, and 50 fruit were used for flesh
firmness determinations and the presence of internal disorders.

On May 14, 1976, another two bushels of high 002 fruit of each
delay and orchard, and another two bushels of the control fruit per
orchard were removed from CA storage and held at 20°C for 24 hours.

All apples were evaluated for external disorders. Fruit with freezing
injury caused by the refrigeration malfunction were eliminated from

the sample for flesh firmness and internal disorders; when possible,

50 fruit per bushel were examined.

12

Fruit characteristics were assessed as follows:

1) Respiration rate. A weighed sample of the fruit was attached
to the APRIL system (22). CO2 evolution was measured every 6 hours, and
expressed as m1 COZIkg fruit/hour.

2) 9234 content. Fairly uniform fruit, free of bruises or other

damage, were chosen and their 02H4 content was determined by flame-
ionization gas chromatography (32).

3) Flesh firmness. When possible, apples 6.4 to 7.0 cm in diam-
eter were used, taking one pressure test per fruit. Readings were made
to the nearest 8 kg with an Effigi pressure tester mounted on a drill
press stand, and employing a 1.9 cm plunger.

4) Internal disorders. Apples previously used for flesh firmness
determinations were sectioned transversely into three approximately
equal-sized segments. Each section was examined for internal CO2
injury and internal browning. Data were expressed as percentage of the
fruit affected.

5) External disorders. Visual observations on the presence of
scald and CO2 injury were expressed as percentage of fruit affected.

6) Titratable acidity. Titratable acidity was measured in the
mid-section of apples used in the determination of internal disorders.
A segment was removed from each of the fifty slices using a 1.3 cm i.d.
stainless steel cork borer, immediately placed into plastic frozen food
storage bags, and frozen. After a two week period at -10°C, samples

were removed, thawed for one hour, and macerated. Five ml of extracted

juice was strained through cheesecloth and diluted with 100 ml distilled

13

water. The titratable acidity was determined by titration with 0.1 N
sodium hydroxide to pH 8.5; the end point was determined with a pH
meter. Results were expressed as g malate/lOO ml extract.

7) Analysis of data. An analysis of variance was performed on

the data, and means were separated by an L.S.D. test at the 0.05 level,

where appropriate.

RESULTS

Fruit Maturity at Harvest

The very low internal °2°4 concentration in the fruits from
orchards III and IV (Table 2), their greater firmness (Table 2) and
their lOwer respiration rate (Figure 2) indicated that they were less

mature than fruits from orchards I and II.

Prestorage Ripening

Endogenous C

 

254

°2H4 was significantly higher in fruit held at 20°C before the
prestorage treatment than in fruit treated immediately or held at 0°
for one or two weeks (Table 3). Fruit placed immediately in the high
002 or LPS atmosphere contained significantly lower C H concentrations

2 4

than did fruit held at 0° prior to treatment. Seemingly, C2H4 levels
of fruit pretreated in the modified atmospheres were affected only by
the holding temperature encountered before treatment. This could not
be verified because, inadvertently, control fruit was not sampled at
this time.

At the time of transfer to CA storage, fruit pretreated immedi-
ately had lower levels of 02H4 than control fruit, fruit held at 0°C

. . o
for one or two weeks, or fruit subjected to the 20 delay treatments

14

15

Table 2 -- Mean flesh firmness and internal ethylene for 20 McIntosh
apple fruits within six hours following harvest.

 

 

 

Harvest date Firmness C2H4

Orchard (1975) (kg) (ppm)
I September 8 6.4 48.5

11 September 8 6.3 40.8
III September 15 8.0 0.1

IV September 15 7.2 0.1

 

16

Figure 2 -- Respiration rates of 'McIntosh' apples from four
orchards during the first five days after harvest.

ml CO,/kg/I1r

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DAYS AT 20°C
Figure 2

18

Table 3 -- Mean internal ethylene (ppm) for 10 McIntosh apple fruits

immediately following prestorage treatment.

 

 

Prestorage atmosphere

 

 

Delay and temperature C02 CA LPS
No delay 20.3a* 21.4a 22.3a
1 wk at 20°C 222.9d 457.1c 533.5o
1 wk at 20°C + 1 wk at 0°C 638.7e 679.5d 604.6c
1 wk at 0°C 98.9c 123.0b 104.9b
2 wks at 0°C 77.6b 64.5a 76.3b
Mean 193.9 269.1 268.3
L.S.D. (0.05) 14.0 57.7 39.5

 

*Values followed by the same letter (a through e) are not significant

at the 5% level.

19

(Table 4). 02H4 concentrations were highest in orchard III and lowest

for orchard IV (Table 5).

Respiration

 

Neither prestorage treatment nor atmosphere greatly influenced
respiratory activity of the fruit (Figure 3). The patterns were similar
to those observed at harvest, with fruit from orchards I and II respir-
ing more rapidly than those from orchards III and IV.

On transfer to CA storage, fruit held for 0 or one week at 0°C
before modified atmosphere storage respired most rapidly, while fruit
held at 0° for two weeks had the lowest respiration. All fruit held at
20° exhibited intermediate respiratory activity at this time. However,

differences were not significant (Figure 4).

Fruit Softening

Firmness following prestorage was significantly less in fruit held
at 20°C (Table 6). There were no significant differences between other
"delay" treatments. Differences due to prestorage atmospheres were non-
significant at this time. Firmness values were inversely related to
C2H4 concentration (Table 2).

Firmness on transfer to CA storage was least for fruit held for
one week at 20°C, regardless of subsequent treatment (Table 7). Other
treatments had negligible effects in comparison with immediate treat—
ment. The high CO2 or LPS atmosphere when applied immediately was more

effective in retarding softening than was the pretreatment with the CA

atmosphere. Firmness values for individual orchards exhibited the same

20

Table 4 -- Mean internal ethylene (ppm) for 10 McIntosh apple fruits
upon transfer to CA storage on October 16, 1975.

 

 

 

 

Prestorage delay and PrestoraggLatmosphere
temperature CO2 CA LPS
Control (no treatment) 318.8b*
No delay 100.8a 128.0a 120.5a
1 wk at 20°C 374.7bc 484.2c 362.4b
1 wk at 20°C + 1 wk at 0°C 435.3c 495.5c 367.1b
1 wk at 0°C 152.7a 176.0a 124.5a
2 wks at 0°C 185.0a 198.0ab 176.2ab
Mean”r 249.7 296.3 230.1
L.S.D. (0.05) 93.4 127.9 198.8

 

TExcludes control treatment.

*
Values followed by the same letter (a through c) are not significant
at the 5% level.

21

Table 5 -- Effect of orchard and prestorage delay on mean internal
ethylene (ppm) for 10 McIntosh apple fruits after prestorage
treatment with high 002 when transferred to CA storage on

October 16, 1975.

 

 

 

 

Prestorage delay and Orchard
temperature I II III IV

Control (no treatment) 237.8 380.4 391.8 265.2
No delay 107.0 97.6 130.6 67.9
1 wk at 20°C 313.6 422.9 411.1 351.2
1 wk at 20°C + 1 wk at 0°C 268.6 421.6 559.1 492.0
1 wk at 0°C 97.7 119.5 256.5 137.2
2 wks at 0°C 137.3 141.0 266.2 195.4

Mean 193.7 263.8 335.9 251.5

 

22

Figure 3 -- Respiration rates of 'McIntosh' apple fruit after
application of prestorage treatments.

23

 

PRESTOR AGE ATMOSPHERE

._ ............. . ca
-0000...” LPS

NO DELAY

 

 

 

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........................... .u..-...--.
................... . I .....
A 1 L ‘
J 0 g .

DAY. AT 20°C

 

 

 

Figure 3

24

<0 ou mommamuu mo
Houuooo van communal

.owmuoum
mafiu ecu um uwouw manna .nmoucHoz.
ou swag «0 means cowumuaemmu cows 11 q ouowflm

25

on

ON

q unawam

1.59.103... .x.

Ow

 

INSWLVBHL

26

Table 6 -- Effect of treatments on mean flesh firmness (kg) for 20
McIntosh apple fruits immediately following prestorage
treatment.

 

 

Prestorage atmosphere

 

 

Delay and temperature CO2 CA LPS
No delay 7.0o* 6.7b 6.46
1 wk at 20°C 4.86 4.8a 4.8a
1 wk at 20°C + 1 wk at 0°C 4.3a 4.5a 4.2a
1 wk at 0°c 6.9c 7.2b 6.9b
2 wks at 0°C , 6.9c 7.2b 6.46
Mean 6.0 6.1 5.7
L.S.D. (0.05) 0.4 0.7 1.2

 

*
Values followed by the same letter (a through c) are not significant
at the 5% level.

27

Table 7 -- Mean flesh firmness (kg) for 20 McIntosh apple fruits upon
transfer to CA storage on October 16, 1975.

 

 

 

 

 

Prestorage delay and Prestoragg atmosphere
temperature CO2 CA LPS
Control (no treatment) 5.7b
No delay 6.6c 6.1b 6.4d
1 wk at 20°C 4.2a 4.0a 4.1a
1 wk at 20°C + 1 wk at 0°C 4.7a 4.1a 4.1a
1 wk at 0°C 6.06 5.96 6.0C
2 wks at 0°C 5.76 5.9b 5.66
Mean+ 5.3 5.2 5.2
L.S.D. (0.05) 0.5 0.5 0.4
I

Excludes control treatment.

*
Values followed by the same letter (a through d) are not significantly
different at the 5% level.

28

trends as for harvest samples (Table 8). However, pressure loss was

not associated with initial maturity (see Tables 2 and 8).

Storage and Shelf Life

Firmness

Overall softening was reduced only by immediate treatment of the
fruit with high 002 (Table 9). The rate of softening during the CA
storage period was similar for control fruit and for the fruit treated
with 002 immediately or after a one week delay at 0°C; that for fruit
held one week at 20°C was slow, but only because much firmness had been
lost before storage. Following storage, the softening rates at room
temperature were similar for all treatments (Figure 5).

Fruit treated immediately with LPS initially showed a pattern of

pressure loss similar to fruit immediately treated with C0 however,

2;
final firmness was not affected (Table 9). The CA prestorage treatment
was also ineffective in retarding softening (Table 9); the total pres-
sure loss was similar to that of the control fruit throughout the
treatment and the storage period. A comparison of the orchard effects
after storage (Table 10) with those before storage (Table 2) show that
the firmest fruit initially (orchards III and IV) was still the firmest
after storage, yet consistently showed the most softening during the
course of the experiment. The parallel values of control 22: no delay
fruit for all orchards indicate that response to CO2 was not affected

by fruit maturity. This was not the case for fruits pretreated in the

CA or LPS atmospheres.

 

fl‘llfll‘l'l’lillllll‘l

 

29

Table 8 -- Effect of orchard source on mean flesh firmness (kg) for 20
McIntosh apple fruits after prestorage treatment with high

CO when transferred to CA storage on October 16, 1975.

2

 

 

 

 

Prestorage delay and Orchard
temperature I II III IV

Control (no treatment) 4.5 5.3 6.5 6.4
No delay 5.2 6.3 7.3 7.5
1 wk at 20°C 3.1 3.5 5.0 5.3
1 wk at 20°C + 1 wk at 0°C 3.2 3.4 5.2 5.0
1 wk at 0°C 4.4 5.4 6.8 7.3
2 wks at 0°C 4.2 5.1 6.7 6.7

Mean 4.1 4.5 6.3 6.4

 

30

Table 9 —— Effects of pretreatments on mean flesh firmness (kg) for 50
McIntosh apple fruits after storage in CA for five months.

 

 

Prestorage atmosphere

 

 

Prestorage delay and C02 CA LPS C02 0
temperature (after 1 day at 20 C) (after 7 days at 20 C)
Control (no treatment) 4.1a* 3.7
No delay 4.6b 4.1 4.4 4.1
1 wk at 20°C 4.0a 4.1 4.4 4.1
1 wk at 20°c+l wk at 0°C 4.0a 3.8 4.2 3.6
1 wk at 0°C 4.2a 4.1 4.6 3.7
2 wks at 0°C 4.3ab 4.0 4.1 3.8
Mean 4.2 4.0 4.3 3.9
L.S.D. (0.05) 0.4 N.S N.S. N.S.

 

1LExcludes control treatment.

*
Values followed by the same letter (a through b) are not significantly

different at the 5% level.

31

Figure 5 -- The effect of high 00% applied immediately (NO DELAY)
and after 1 week at 0 C or 20°C, on flesh firmness of
'McIntosh' apples from harvest (HAR) through CA (IN,
OUT) and during a subsequent week at 20°C (+ l WK).

FIRMNESS (kg)

32

 

 

NO DELAY

1 WK, 20°C 1 "“7 0°C

 

 

 

HAR IN OUT +1 WK

Figure 5

lArl‘l‘lIIIltII

 

 

33

 

 

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34

None of the treatments significantly affected firmness after one
week at 20°C following removal from storage, although the ”no delay" 002

fruits were somewhat firmer (Table 9; Figure 5).

Titratable Acidipy

 

No differences in titratable acidity were observed upon removal
of the fruit from storage or after holding for one week at 20°C

(Table 11).

£92 Injury
Fruit held in 12% CO2 exhibited slight amounts of internal and/or
external CO2 injury upon removal from CA storage (Table 12), but dif-

ferences between treatments were non-significant. Injury was less
evident after 7 days at 20°C than after one day, but the differences

were not significant.

 

StorageiScald
Fruit held at 0°C before treatment developed less scald than fruit

held at 20° (Table 13). High CO reduced scald in fruits held in air

2
in 0°, with the effect declining as treatment was delayed; however,
differences were not significant. This trend was no longer evident in

fruit held for 7 days at 20°. Similar trends were evident for CA

and LPS-treated.

Other Injuries
After five months of CA storage there were no differences in the
occurrence of internal browning either on removal or after 7 days at

20°C (Table 14). The types of injury are illustrated in Figure 6.

35

Table 11 —- Effect of pretreatments on mean titratable acidity for 50
McIntosh apples stored-in CA for five months after pre-

storage treatment.

 

 

Prestorage atmosphere

 

 

Prestorage delay and 002 CA LPS 0
temperature (g malate/lOO ml extract after 1 day at 20 C)

Control (no treatment) 0.32

No delay 0.40 0.28 0.45

1 wk at 20°C 0.37 0.24 0.37

1 wk at 20°C + 1 wk at 0% 0.29 0.34 0.30

1 wk at 0°C 0.11 0.79 0.22

2 wks at 0°C -— 0.42 0.19
Mean 0.29 0.41 0.31

L.S.D. (0.05) N.S. N.S N.S.

 

.1.

Excludes control treatment.

36

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37

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38

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39

Figure 6 -- Types of flesh injury that developed in McIntosh
apple fruit during five months of CA storage.
The apple in the upper right corner is free of
injury.

4O

 

Figure 6

DISCUSSION

Maturipy at Harvest

The data for firmness, 02H4 content, and respiration rate at har-
vest (Table 2 and Figure 2) were viewed as predictive of the responses
of the fruit 11) the various prestorage treatments (2,25,29,31).

As expected, the riper fruit from orchards I and II, with physiological-
ly active levels of endogenous °2°4 (12) did not respond as positively
to treatment as did fruit from orchards III and IV, which had low levels
of °2°4 (13,23,26). 02H4 initiates cell wall changes associated with
softening (23), in addition to other ripening processes (1,13). The
inverse relationship between flesh firmness and endogenous C H level

2 4
supports these findings.

Post—treatment Effects

Fruit of all treatments had physiologically active levels of
endogenous °2°4 following treatment (Table 3). The higher levels of
02H4 in fruit held at 20°C gs, 0° was expected because of the effect of
temperature on rate of 02H4 synthesis (1). Immediate treatment with

002, CA, or LPS reduced the endogenous level of 02H4 either because

of inadequate time for the autocatalysis of C before treatment (1)

2H4

or actual inhibition of °2H4 synthesis (12,14,15,25). CA interferes

41

42

with °2°4 synthesis primarily by reducing ambient 0 levels, as O is

2 2

necessary for 02H4 production (1,13,14). However, reduction of the 02
level alone was not sufficient to elicit a significant difference between

any of the 0° delay treatments and the no delay treatment. High CO may

2
have directly interfered with °2°4 production (1,15,25,26). LPS would
reduce °2°4 production by reducing 02 levels, and limiting autocatalysis
(l4,20,21). Failure to analyze the fruit at this time prevented evalu-
ation of the effectiveness of the no delay treatments. However, immedi-
ate application of the CA atmosphere appeared to be inferior to the
"double-action" of the CO2 and LPS treatments, especially when compared
to their respective no delay treatment. This may have been due to the
lack of any CO2 in the CA atmosphere. In view of the differences in
endogenous 02H4, it was expected that the fruit from different treatments
would have dissimilar respiratory patterns (9), yet no apparent differ-
ences due to atmosphere or delay treatments were noted (Figure 3). No
explanation can be offered for this discrepancy. The inverse relation-
ship of flesh firmness to °2H4 concentration at this time (Tables 6 and

3, respectively) provides further evidence that ripening was retarded.

Similar trends were present at the time of harvest (Table 2).

Pre-CA Storage

Endogenous 02H4 levels determined immediately after prestorage
treatment (Table 3) paralleled those measured on transfer to CA storage
(Table 4). In most cases, the latter were higher. Autocatalysis of

°2°4 during the pre-CA storage holding period probably caused the higher

43

levels. The lowered concentrations in fruits held at 20°C may have
resulted from senescence of these apples. Studies of climacteric-type
fruit (13,23) have shown that the 02H4 concentration preceding the
respiratory climacteric remains at a higher level for a short time, and
then drops to the preclimacteric level again.

Holding fruits at 20°C before high CO treatment reduced respira—

2
tion rate prior to transfer to CA storage (Figure 5). This is attributed
to the advanced aging of these fruits and the utilization of respiratory
substrates at the higher temperature (23,27). Holding fruits at 0° for
two weeks markedly depressed respiration, probably as a result of the

"carry-over" effect of the high CO treatment (3,36). The similar

2
respiration rates for control fruit, no delay fruit, and fruit held at
0° for one week indicate that there was no carry—over effect of the
treatments. This was due, perhaps, to the longer holding period for
these fruit before being tested for respiratory activity. However, such
a carry-over effect should have been evidenced in these when they were
tested immediately after treatment (Figure 3).

Flesh firmness values prior to the CA transfer (Table 7) paral-
leled those at termination of the prestorage treatment (Table 6), and
showed that the delay in treatment increased softening. Softening due
to holding the fruit at the higher temperature (23) was also apparent

at this time. This was most evident for the high CO treatment; the no

2

delay fruit was firmer than all other fruit, treated or control. Since

endogenous 02H4 levels in the COz-treated fruit were roughly equivalent

to those in the other no delay prestorage atmospheres, and all treatments

44

retarded °2°4 synthesis (Table 3), retardation of softening was probably
affected by factors other than the level of C2H4 present (30). Perhaps
the high levels of CO2 counteracted the softening effect of 02H4 only at

low 02H4 levels. This is suggested by the classic model of Burg and

Burg (12), although work by Mayak and Dilley (28) indicates that the

levels of C2H4 encountered at the time were above those which could be

effectively counteracted by CO . Beyer also states that slight in-

2

creases in levels of °2H4 are sufficient to negate any CO

yet Burg and Burg (15) suggested that a response to CO

2 effect (8),

2 is indicative

of the participation of °2°4 in a physiological process. Since response

to no delay CO .zs, control treatment was not affected by orchard (Table

2
8), 02H4 concentration at the time of treatment appeared to have little
influence on the COz-elicited response.

The softening which had occurred before treatment in fruit of
orchards I and II might be expected to reduce the effect of treatment,
yet Couey and Olsen (17) reported that apples initially the softest

showed the greatest reSponse to CO in terms of firmness retention;

2
additionally, Looney (26) found that CO2 treatment dramatically sup-
pressed the rate of softening in ripening fruits, as well as delaying
the onset of softening in preclimacteric fruits. The lack of a control
treatment for the 20° delays prevented verification of these findings;
a greater loss of firmness by a more appropriate control than the 20°
delay fruit would have supported the results of Couey and Olsen and of
Looney. Fruit held at 0° prior to CO treatment did not differ from

2

fruit held continuously in air at 0°; this corresponds to Looney‘s

45

report that McIntosh apples conditioned at 0°C before CO treatment lose

2
the capacity to respond to elevated levels of CO2 (26).

Post-CA Storage

The slopes of the lines in Figure 5 suggest that flesh softening
during the CA storage period was similar in all treatments except for
the 20°C delay. A difference in firmness was noted within the first
four weeks and its magnitude did not change. However, the prestorage
treatment did not influence fruit softening during the storage period,
pggnsg. This supports the statement of Looney, that softening is rela-
tively constant in storage (26). Also, fruit which was most firm at
harvest (Table 2) softened most during the CA period (Table 8). These
facts, together with data obtained by Blanpied and Dewey (10), show
that fruit will lose a certain amount of firmness over time regardless

of prior treatment. To account for the fact that the CO2 effect did

not end after treatment, Looney (26) suggested that fruit softening

required the continued presence of C If this is true, a high

2H4.
level. of CO2 in the CA atmosphere may competitively inhibit

°2H4 activity. The prestorage CO treatment, on the other hand, pre-

2

vented the build-up of excessive levels of C and thereby delayed the

2H4
onset of softening, as suggested by Couey and Olsen (17). The LPS

atmosphere also retarded softening up to the point of transfer to CA

storage, but could not have competitively inhibited C2H4—induced

46

softening up to that point. Although previous research (7,11,18,31)S

showed that the retarding effect of CO on softening carried over into

2
shelf—life as well as into CA storage, this was not observed in this
experiment. Lack of effect on titratable acidity was not unexpected.
Earlier studies (7,16,17,18,31) indicated variable effects, especially
when high levels of CO2 were used as the prestorage treatment. Looney
(26) indicates that acid catabolism is constant in storage, and there-
fore higher values at harvest are advantageous. Since acids were not
measured at harvest, it is not known whether this might be applicable
in this instance. However, Looney (26) also suggests that rapid acid
catabolism is initially dependent on levels of °2°4 above the threshold
for autocatalysis, but not upon its continual presence. Therefore, the
high levels of C2H4 at the beginning of CA storage in fruit of all
treatments may have triggered catabolism and have resulted in similar
amounts of titratable acid at the end of CA storage.

While evidence exists linking CO2 injury to maturity and location

6,7,8

in storage (l6,l7,3l,35), no differences were significant in this

experiment.

 

5M. Meheriuk, S. W. Porritt and P. D. Lidster. 1976. The effect
of carbon dioxide on controlled atmosphere storage behaviour of McIntosh
apples. Agric. Canad. Res. Stat., Summerland, B. C. Contrib. no. 439.
(Manuscript submitted to Amer. Soc. Hort. Sci. for publication.)

6W. J. Bramlage. 1975. Re—evaluating the CO
storage. Fruit Notes 40: 6-8. (mimeo)

7Ibid. 1976. NE—27 report. Univ. Mass. 2 pp. (mimeo)

8
G. D. Blanpied and F. W. Liu. 1976. NE—27 report. Cornell

University. 15 pp. (mimeo)

2 levels for CA apple

 

47

Although CO2 injury was slight, there is the danger of greater
injury that might not be offset by the gain in firmness, as suggested
previously.9 Neither CA nor LPS was effective in preventing scald
development. Perhaps ventilation at the 90 mm Hg LPS was inadequate to
remove the volatiles thought to cause scald development (23). Immediate
treatment with 002 reduced scald development markedly, while delays at
20°C increased its incidence and severity. This agrees with earlier
findings for the effects of CO2 treatment (29) and high temperature
delays (23) on scald incidence. Other injuries to the flesh of the
fruit, although prevalent, could not be associated with any treatment;

however, Blanpied and Liu10 found that high CO —treated fruit had

 

2
significantly more breakdown than controls.
9M. Meheriuk, S. W. Porritt and P. D. Lidster, 2p, cit.
10

G. D. Blanpied and F. W. Liu, pp, cit.

CONCLUSIONS

A high level of CO2 applied to 'McIntosh' apple fruit at the
beginning of the storage period was effective in retarding softening
and reducing the incidence of scald development when administered
immediately after harvest. Treatment delays of one or two weeks reduced

or negated the effectiveness of the 00 treatment. Although CO2 injury

2
and other flesh injury was not related to prestorage treatment in this
study, the potential for CO2 injury indicates that further research is
needed before a prestorage treatment is recommended for McIntosh. The

CA and LPS prestorage treatments as employed in this study were not

beneficial in prolonging the storage life of McIntosh apples.

48

LITERATURE CITED

1)

2)

3)

4)

5)

6)

7)

8)

9)

10)

ll)

12)

LITERATURE CITED

Abeles, F. B. 1973. Ethylene in Plant Biology. Academic Press.
New York. 302 pp.

Allen, F. W. 1940a. Carbon dioxide investigations: Influence of
carbon dioxide atmospheres upon cherries, plums, peaches and

peers under simulated transit conditions. Proc. Amer. Soc.

. 1940b. Influence of carbon dioxide in lengthening the

life of Bartlett pears. Proc. Amer. Soc. Hort. Sci. 37: 473-478.

. 1942. Carbon dioxide storage for Yellow Newtown apples.

and L. R. McKinnon. 1934. Storage of Yellow Newtown
apples in chambers supplied with artificial atmospheres.
Proc. Amer. Soc. Hort. Sci. 32: 146-152.

and R. M. Smock. 1938. Carbon dioxide storage of apples,
pears, plums and peaches. Proc. Amer. Soc. Hort. Sci. 35: 193-
199 0
Bartram, D. 1976. Golden Delicious apples respond to CO2 treatment.
Proc. Ann. Meeting Wash. St. Hort. Assoc. 71: 88-89.
Beyer, E., Jr. 1976. About our cover: Ethylene antidote.
HortScience. 11: 174.

Biale, J. 1960. Temperature effects on respiration rates of
climacteric type fruit. Encycl. Plant Physiol. 12: 536.

Blanpied, G. D. and D. H. Dewey. 1960. Quality and condition
changes of McIntosh apples stored in controlled atmospheres.
Quart. Bull. Mich. Agric. Exper. Stat. 42: 771-779.

Brooks, C. 1940. Effect of carbon dioxide treatment upon the rate
of ripening in apples. Proc. Amer. Soc. Hort. Sci. 37: 463-466.

Burg, S. P. and E. A. Burg. 1962. Role of ethylene in fruit ripen-
ing. Plant Physiol. 37: 179-189.

49

50

13) Burg, S. P. and E. A. Burg. 1966a. Ethylene action and the ripen-
ing of fruits. Science 148: 1190-1196.

14) . 1966b. Fruit storage at subatmospheric pressures.
Science 153: 314-315.

15) . 1967. Molecular requirements for the biological activity
of ethylene. Plant Physiol. 42: 149-152.

16) Couey, H. M. 1976. One year of commercial experience with carbon
dioxide treatment of Golden Delicious. Proc. Ann. Meeting Wash.
St. Hort. Assoc. 71: 86-87.

17) and K. L. Olsen. 1976. Storage response of 'Golden
Delicious' apples after high-carbon dioxide treatment. J. Amer.
Soc. Hort. Sci. 100: 148-150.

18) Couey, M. 1974. The commercial use of a prestorage carbon dioxide
treatment to retain firmness and quality in 'Golden Delicious'.
Proc. Ann. Meeting Wash. St. Hort. Assoc. 70: 81-84.

19) Dalrymple, D. G. 1967. The development of controlled atmosphere
storage of fruit. [Publ.] Div. Mktg. Utiliz. Sci. U. 8. Dept.
Agric. 56 pp.

20) Dilley, D.RJ 1972.Hypobaric storage--a new concept for preservation
of perishables. 102nd Ann. Rep. Mich. St. Hort. Soc. 82-89.

21) and W. J. Carpenter. 1975. Principles and applications
of hypobaric storage of cut flowers. Acta Hort. 41: 249-263.

22) , D. H. Dewey, and R. R. Dedolph. 1969. Automated system
for determining respiratory gas exchange of plant materials.
J. Amer. Soc. Hort. Sci. 94: 138-141.

23) Fidler, J. C. 25.21,, editors. 1973. Biology of apple and pear
storage: Research review no. 3 of the Commonwealth Bureau of
Horticulture and Plantation Crops. Commonwealth Agricultural
Bureaux. Farnham Royal, England. 235 pp.

24) Kajiura, I. 1974. The effects of gas concentration on fruits. IX.
The effect of different C02 and 0 levels on Jonathan and Ralls
apples in controlled atmosphere 5 orage. J. Jap. Soc. Hort. Sci.
43: 97-106. (Abstract)

25) Knee, M. 1973. Effects of controlled atmosphere storage on
respiratory metabolism of apple fruit tissue. J. Sci. Fd. Agric.
24: 1289-1298.

51

26) Looney, N. E. 1975. Control of ripening in 'McIntosh' apples. II.
Effect of growth regulators and CO on fruit ripening, storage
behaviour, and shelf life. J. Amer. Soc. Hort. Sci. 100: 332—
336.

27) Lutz, J. M. and R. E. Hardenburg. 1968. The commercial storage of
fruits, vegetables, and florist and nursery stocks. U. S. Dept.
Agric., Agric. Hndbk. no. 66.

28) Mayak, S. and D. R. Dilley. 1976. Effect of sucrose on response of
cut carnation to kinetin, ethylene, and abscisic acid. J. Amer.
Soc. Hort. Sci. 101: 583-585.

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