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APPLE PROPERTIES RELATED TO PACKAGING

BY

Thomas J. Kusza

A DISSERTATION

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

DOCTOR OF PHILOSOPHY

Department of Agricultural Engineering

1979

ABSTRACT

APPLE PROPERTIES RELATED TO PACKAGING

BY

Thomas J. Kusza

The effects of controlled atmosphere (CA) storage
on the mechanical prOperties of Red Delicious, Red Delicious
Promaline (spayed at blossom with promaline) and Ruby applies
were studied. Compression tests on apples taken from four
CA rooms Opened at intervals over a 5% month period showed
decreases in the modulus of elasticity of 0.60, 1.02 and
1.14 MPa for Red Delicious, Red Delicious Promaline and
Ruby varieties, respectively. Apples kept at room temper-
ature, (23°C), for seven days after removal from CA storage
had additional decreases of 0.49, 0.45 and 0.71 MPa for Red
Delicious, Red Delicious Promaline and Ruby respectively
when compared to apples two days out of storage.

Strain values decreased over the total storage time
0.017, 0.025 and 0.021 for the Red Delicious, Red Delicious
Promaline and Ruby varieties. Seven days of conditioning
produced increased strain values when compared to two days
of conditioning in 75 percent of the cases for all three

varieties.

Thomas J. Kusza

A damage boundary curve for pairs of apples was
developed in the laboratory using a shock machine. Level of
fruit bruising and percentage of change in grade were used
as damage criteria. A change in velocity of 1.68 m/sec or
equivalent free-fall drOp height of 0.145 m produced a grade
change from extra fancy to fancy in 10 percent of the
apples with a corresponding critical acceleration level of
15 gs.

Package cushioning could be selected to provide
isolation from critical impact forces. The damage boundary
indicates that not more than 15 gs can be transmitted to
the apple in order to maintain a 90 percent grade level of

extra fancy.

Approved:
Maj rof sor

haw

DepartmEnt Chairman

To Jo, Matt and Rachel

ii

ACKNOLWEDGMENTS

The author sincerely appreciates the guidance and
close cooPeration of his major professor, Dr. Larry J.
Segerlind, whose unending patience made this degree a
reality.

The author would also like to thank Dr. W. Bickert,
Dr. H. E. Lockhart and Dr. C. J. Mackson for their time and

counseling.

iii

LIST OF TABLES

Chapter

fibbub
01wa

TABLE OF CONTENTS

LIST OF FIGURES. . . . . . . . . . . .

INTRODUCTION . . . . . . . . . .
REVIEW OF LITERATURE. . . . . . . .

CONTROLLED ATMOSPHERE STORAGE AND ITS EFFECTS
ON MECHANICAL PROPERTIES. . . . . .

Experimental Procedure. .

Experimental Determination of Mechani

PrOperties . . . . . . . .
Discussion of CA Storag Effects on
Modulus Values. . . . . . .

3.3.1 Two Days Out of Storage '.
3.3.2 Seven Days Out of Storage.

Discussion of CA Storage Effects on
Strain Values . . . . . . .

3.4.1 Two Days Out of Storage .
3.4.2 Seven Days Out of Storage.

3.5 Comments . . . . . . . . .

DETERMINATION OF APPLE SUSCEPTIBILITY TO
BRUISING O O O O O O O O C O O

Damage Boundary Theory. . . . .
Objective . . . . . . . . .
Experimental Procedure. . . . .
Discussion of Apple Bruising Levels
Conclusions . . . . . . . .

iv

Page
vi

vii

12
14
18
21

21
24

27

29

31
4O
40
44
49

Chapter Page

5. PACKAGE DESIGN FOR MINIMIZING APPLE BRUISING . 53
5.1 Package Forms . . . . . . . . . 54

5.2 Package Design Criteria. . . . . . 55

6. SUMMARY . . . . . . . . . . . . . 61

7. CONCLUSIONS . . . . . . . . . . . . 63

8. RECOMMENDATIONS FOR FURTHER STUDY. . . . . 6S
BIBLIOGRAPHY . . . . . . . . . . . . . . 67
GENERAL REFERENCES . . . . . . . . . . . . 69

Table

1.

LIST OF TABLES

Page

CA Storage Room Conditions . . . . . . . 10
Coring Comparison-Perpendicular Versus Parallel

to Apple Core. . . . . . . . . . . ll
Modulus Values . . . . . . . . . . . 13
Analysis of Variance-Modulus Values-Between

Groups 0 O O O O O O O O O O O 0 14
Analysis of Variance--Modulus Values Over

Time. 0 O O O O O I O O O O O 0 1?
Strain Values . . . . . . . . . . . 22
Analysis of Variance--Strain Values-Between

Groups . . . . . . . . . . . . . 24
Analysis of Variance-~Strain Values Over

Time. 0 O O O O O O O O O O O O 25
Bruise Measurements--Change in Velocity. . . 47
Bruise Measurements--Critical Acceleration. . 48

vi

LIST OF FIGURES

Figure Page

1. Modulus values versus time (two days out of
storage) . . . . . . . . . . . . . 15

2. Distribution of modulus values (MPa) R-D (two
days out of storage) . . . . . . . . . 16

3. Modulus values versus time (seven days out of
storage) . . . . . . . . . . . . . l9

4. Distribution of modulus values (MPa) R-D
(stored for 5% months) . . . . . . . . 20

5. Strain values versus time (two days out of
storage) 0 O O O O O O O O O O O O 23

6. Strain values versus time (seven days out of
Storage) 0 o o o o o c o o o o o o 26

7. Shock pulse comparison . . . . . . . . . 32

8. Damage boundary for pulses of same peak acceler-

ation and same velocity change. . . . . . 34

9. Damage boundary . . . . . . . . . . . 35

10. Determination of critical velocity change. . . 37
11. Determination of critical acceleration level. . 39

12. Experimental half sine shock pulse . . . . . 42
13. Apple package mounted for shock testing . . . 45
14. Damage boundary--10 percent grade change . . . 50
15. Damage boundary--66 and 73 percent bruising . . 51
16. Static stress Pa . . . . . . . . . . . 57

17. Static stress KPa polyurethane ether 2 pcp,
12" drOp height. . . . . . . . . . . 59

vii

CHAPTER 1

INTRODUCTION

Apples are harvested during the Fall of every year.
After picking, the grower can either sell his crop or store
his apples and wait for market prices to rise. If he
chooses storage, the grower can use a controlled atmosphere
(CA) that will slow the apple metabolism and maintain its
quality.

Temperature, carbon dioxide and oxygen must be
metered to limit respiration in CA rooms. The objective
is to maintain apple firmness which is a property desired
by consumers. The firmness can be qualitatively defined
as the modulus of elasticity and quantitatively measured
in the laboratory. Since apples are stored in CA rooms for
extended periods, it is of importance to determine whether
the modulus values for the apples change during storage.

Along with being a desirable consumer attribute,
flesh firmness dicates a mechanical prOperty of the apple
related to bruising as reported by Schoorl and Williams
(1973). Nelson and Mohsenin (1968) and Schoorl and Holt
(1974) stated that high modulus values were a good indica-

tion of the bruise resistance of apples.

1

A study dbne by Schoorl and Holt (1974) indicated
that between 20 and 50 percent of the apples reaching the
market had some level of bruising. Since bruising is a
major problem, it would be invaluable if a grower could know
in advance the fragility or bruise resistance of a given
batch of apples leaving CA storage. The grower could then
take the appropriate action and provide additional protec-
tion to the apples.

Hammerle and Mohsenin (1966) reported that the
volume of bruise increased with an increase in drOp height.
If a critical drop height could be established, then the
performance curves for cushioning materials, developed for
the packaging industry could be applied to the selection of
a packaging materials for apples.

The body of this text is broken into three major
parts:

1. A study of the influence of CA storage on the
firmness of apple flesh.

2. To establish the critical velocity change and
acceleration levels which produce bruises in apples.

3. The relation of mechanical properties to bruise
resistance and how the damage boundary procedure
can be used to design a package to provide protec-

tion and maintain apple quality will be presented.

CHAPTER 2

REVIEW OF LITERATURE

The firmness of apple flesh is largely dependent
upon apple maturity as reported by Schoorl and Williams
(1973). The apple reaches a peak modulus value and then
looses its firmness as the metabolic process continues.

Nelson and Mohsenin (1968) did study the effect of
4.4°C for thirteen days and 32.2°C for one day on mechanical
properties. They reported that the high temperature accel-
erated the metabolic process, decreasing the modulus value
and increasing the level of bruising. Their conclusions
stated that apples with a high elastic modulus would ensure
a high resistance to bruising under dynamic loading.

No literature was found which discussed the effect
of storage time in CA rooms on mechanical properties of
apples.

The bruising of an apple begins with a softening
of the tissue resulting from the breakdown of cellwalls
and consequent loss of tugor; with this is associated the
release of polyphenols which are oxidized to melanin-like

compounds with consequent unsightly discoloration.

Assessment of bruising has commonly been by a rating system
based largely on diameter of the bruise O'Louglin (1964)
or by volume Mohsenin (1970).

Numerous techniques have been developed to produce
dynamic impacts resulting in bruising. Hammerle and
Mohsenin (1966) used a vertical drop-testing apparatus to
measure the effectiveness of cushioning materials in miti-
gating impact forces resulting in bruising. They reported
a fragility factor which is dependent upon the cushioning
materials, impacting specimen and the loading rate.

Nelson and Mohsenin (1968) used a pendulum impacting
apparatus with a steel impacting surface to study bruising
of apples stored at two different temperatures. They found
inconsistencies with previous work and hypothesized that
the time in storage affected the mechanical properties of
the apple.

Bittner et al. (1967) used the pendulum impacting
apparatus to evaluate cushioning materials and their energy
absorbing characteristics.

Hanna and Mohsenin (1972) impacted apples in a
polystyrene tray using a free-fall technique reported by
the American Society of Testing and Materials (D 775-61).

The investigations reported above all used single
apple contact and contacting surfaces that were either
steel plates or cushioning materials. Peleg (1972) reports
that nearly 80 percent of the apples packaged are put in

poly bags resulting in extensive apple to apple contact.

Hanna and Mohsenin (1972) report that apples packed in
polyethylene bags showed a 30 percent bruise level with
bruises less than 1.27 cm in diameter. This indicates that
three or four pound poly bags provide little protection.

Schoorl and Williams (1972) studied the effect of
drop height on apple bruising in trays and pattern packed
cases. They found a marked difference in package protective
ability in favor of the tray carton. They also noted that
the quantity of bruising could be greatly affected by the
equipment used for shock testing. Differences in impacting
surface along with the flatness of the drOp can change the
level of bruising.

Horsfield (1972) used a theoretical approach
developed from Hertz's contact theory to predict the level
of damage from two impacting bodies. By considering the
modulus of elasticity, surface radii, impact energy and
shear strength the level of damage could be predicted.
Unfortunately the measurement of the above quantities under
dynamic conditions, to avoid errors due to viscoelastic
properties, is very expensive and time consuming. It also
provides only for single apple impacts and not multiple
contacts that exist in case quantities.

Segerlind and Fabbro (1978) studied the failure
criteria for apple flesh. They concluded that apple flesh
fails when a normal strain rather than a maximum shear

stress exceeds a critical value. Their experiments also

discounted the possibility that apple flesh fails when a
normal stress exceeds a critical value.

MTS Systems (1971) in conjunction with Michigan
State University developed a methodology for testing the
resistance of electronic components to impacts. The pro-
cedure centered around using shock machines that eliminate
testing problems due to frictional platen drag and flatness
of drops. The procedure, called damage boundary, is re-
ported in the American Society of Testing and Materials
designation, D 3332-77.

Damage boundary testing develops drop height and
acceleration threshold levels above which damage does occur.
O'Brien (1964) defined drop height thresholds for various
types of fruit. Schoorl and Williams (1972) found that a
5.08 cm drOp height produces bruises on apples in full
cases.

Peleg (1972) evaluated two different package types
and used a 2 percent grade change from extra fancy to fancy
as defined by the United States Department of Agriculture
for his threshold. He reported a 3.81 cm drop height
threshold and a 7 g acceleration threshold for grade changes.

Kipp (1971) developed a damage boundary for Golden
Delicious apples in case quantities using a damage criteria
of slight to serious damage. A critical acceleration level

of 40 gs was reported.

CHAPTER 3

CONTROLLED ATMOSPHERE STORAGE AND ITS

EFFECTS ON MECHANICAL PROPERTIES

The mechanical prOperties of the apple dictate its
ability to survive dynamic inputs or free-fall drops. It
was reported earlier that as the modulus of elasticity (E)
decreases the subsequent susceptability to bruising in-
creases. Also, the failure strain (e), maximum deformation
prior to tissue rupture, was reported to be independent of
maturity level in the apple.

Since the maturity level of the apple has an over-
whelming effect on the bruising and subsequent quality, the
ability of CA storage to retard or stop the metabolic pro—
cess in apple flesh is of major concern. An apple with a
low modulus of elasticity will present problems in handling
to the grower, distributor and the retailer, by requiring
special precautions to minimize bruising and resulting loss
of quality.

The study of the effects of CA storage on the mech-

anical prOperties of modulus of elasticity and failure

 

strain are presented separately. Discussion of the data

follows each section.

3.1 Experimental Procedure

The apples used in this research were purchased from
Lynd's Fruit Farm in Pataskala, Ohio. The apples were
picked randomly from bins after they had been hand harvested.
The apples were put in full telesc0ping corrugated boxes for
either CA storage or transportation to the laboratory in
Dayton, Ohio for testing.

Three groups of apples, Red Delicious (R-D), Red
Delicious-Promaline (R-D-Promaline), and Ruby were studied.
R-D-Promaline were R-D apples that were sprayed at blossom
with the chemical Promaline manufactured by Abbott Labora-
tories, Chicago, Illinois. The purpose of the spray is to
alter the apples' growing characteristics and produce a
shape similar to a Washington State Fancy Red Delicious.
This would produce a better apple appearance and command a
higher price.

Fifty apples from each group were measured for length
and maximum diameter and the length diameter ratio was
calculated. The R-D-Promaline group approached 1.00 while
the R-D and Ruby groups were 0.87 and 0.84, reSpectively.
The mean ratios proved different at the a = 0.01 signifi-
cance level using a two-tailed z-test for two means. The
standard deviations for the R-D-Promaline, R-D and Ruby were

0.08, 0.05 and 0.05, respectively.

It can be concluded that the Promaline spray does
produce an elongated apple but there is much more variation
in apple size as evidenced by the standard deviations. This
variation could prove costly to the grower by yielding a
higher percentage of cider grade apples. A larger sample
size and an accompanying consumer appraisal of the new apple
should be performed.

Two boxes of each apples variety with a total of six
were placed in each of four CA rooms. Table 1 contains
room conditions and the dates of closing and opening. Tem-
perature, carbon dioxide and oxygen measurements were taken
at the door of each storage room at intervals of three to
six days by the grower.

3.2 Experimental Determination of
Mechanical PrOperties

 

Apples brought into the laboratory were conditioned
at 23°C (73°F) for either two or seven days. The 23°C tem-
perature was used because there were no cold storage faci-
lities available in the laboratory, and this was the average
temperature in the room. The longer conditioning period
was used to simulate warehousing conditions at either the
wholesaler or retailer level.

Using a round piece of brass tubing with a diameter
of 1.68 cm, samples were cut so that only apple flesh and
not core was pulled. Once removed from the apple body, the

sample was cut to a length of 1.905 cm by shearing both ends

10

Table l.--CA Storage Room Conditions.

 

 

Room Date Date Average Average Average
No. Closing Opening Temperature(C°) C02(%) 02(%)
1 10-24-78 1-22-79 3.4* 1.4 4.0
2 11-1-78 2-13-79 2.2 1.3 5.5
3 11-1-78 3-9-79 2.5 1.6 5.5
4 11-1-78 3-28-79 3.3 1.7 5.7

 

*Malfunction of the refrigeration equipment allowed
the temperature to rise to 6.7°C on occasion.
of the sample simultaneously to provide parallel planes for
loading.

The cylindrical apple sample was then placed in an
Instron Materials Tester, model 1130, using a 4.9 kN Tension/
Compression load cell. The crosshead speed was 10 cm per
minute and the chart paper speed was one meter per minute.

Due to size and shape variations of the apple, the
cylindrical cut was made either parallel or perpendicular
to the apple core. In order to be sure that there was
little or no variation in mechanical properties between
planes, two samples of fifty apples from each group were
randomly selected. Cylindrical specimens were all cut
parallel to the apple core for one sample and perpendicular
to the core for the other sample.

Average modulus of elasticity and strain failure
values for each sample were used to test the following null

hypothesis:

H : E-Perpendicular

O

H : E-Perpendicular

O

The alternative hypothesis were:

H : E-Perpendicular

O

H : E-Perpendicular

O

11

Table 2 contains the Z-test

E-Parallel

E-Parallel

E-Parallel

E-Parallel

statistics.

These values

were compared to the Z-values of 2.326 at an a = 0.01 and

only the strain failure sample for the Ruby group rejected

the null hypothesis.

Table 2.—-Coring Comparison-Perpendicular Versus Parallel

to Apple Core.

 

 

Group Z-Test Z-Value(a=0.01) Decision

Red Delicious

Strain Value 1.955 2.326 Accept

Modulus Value 1.588 2.326 Accept
Red Delicious Promaline

Strain Value 1.183 2.326 Accept

Modulus Value 1.808 2.326 Accept
Ruby

Strain Value 2.710 2.326 Reject

Modulus Value 0.246 2.326 Accept

 

12

From the statistical analysis in Table 2 it was
concluded that there was little variation in mechanical
prOperties of the apples relative to the orientation of the
specimen. Therefore, cyclindrical specimens were taken from
the apple either perpendicular or parallel to the stem-caylax
axis with little concern for biasing the results.

Modulus of elasticity values were calculated using
the slope from the initial loading to the point of primary
rupture. This represented the linear portion of the curve
and elastic range of the sample and resulted in a secant
modulus. The strain at failure was calculated using the
displacement of the primary rupture point.

3.3 Discussion of CA Storage Effects
on Modulus Values

 

 

Table 3 contains the modulus of elasticity values
for the three apple groups over the time period studied.

Schoorl and Williams (1973) reported no variety
differences in mechanical properties as they relate to
bruising. They investigated Delicious and Jonathan varieties
purchased from a commercial packing house. The study did
not mention the date when the tests were conducted, storage
conditions at the packing house nor the storage conditions
in the laboratory. These factors all contribute to the
maturity level and subsequent bruise resistance of the apple.
The sample size consisted of only two cases of each variety
and since their unit of evaluation was a full case this

provided little comparison.

13

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14

Using a one-way classification for statistical
analysis Table 4 indicates a significant difference in
modulus values at the a = 0.01 level between the groups.
The Ruby apples have modulus values 14 percent larger than

the other groups and were initially firmer.

Table 4.--Analysis of Variance-Modulus Values-Between Groups.

 

 

Source of Degrees of Sum of Mean
Variation Freedom Squares Square F
Varieties 2 10.09 5.04 36.00
Error 144 20.48 0.14

Total 146 30.57

 

3.3.1 Two Days Out of Storage

 

Figure l is a plot of the modulus values for the
apple samples two days after removal from CA storage. The
apples were held at 23°C for the two days. The modulus
value of each variety decreased relative to the October
values. Figure 2 is the distribution of modulus values for
the R-D variety. There is a decrease in the March group,
stored for 5% months, compared to the October group. Corre-
lation coefficients of -0.79, -0.93 and -0.78 were calcu-
lated for the Ruby, R-D and R-D-Promaline groups, respec-
tively. The lowest correlation of r = -0.78 indicates that
at least 61 percent of the variation in modulus of elasti-
city is explained by the time in storage. Table 5 is an

analysis of variance of the modulus values within each

Modulus Values (MPa)

15

 

 

Ruby 0
R-D O
4.00—1 R-D Promaline C]
C)
C)
C)
3.50 ..
C)
E!
3 00 —— C) C)
(D
C)
C)
2.50....
[3 0 El
2 00 "‘ D C]
1.50 ——
1.0 _
° 1 I 1 l I l 1
OCT NOV DEC JAN FEB MAR APRIL

Time (Months)

Figure l. Modulus values versus time (two days out of
storage).

Class Frequency (Percent)

 

16

 

 

OCT 24
(No Storage)
MAR 28__ _
A (5% Mo. Storage)
50—4 I
I“
' I
I I
' I
40.4 I \
’ I
’ I
’ I
I
30.—
I
’ I
’ I
I I
20-— I \
\
’ I
/ I
10-— I \
/ \
’ \
I, \\
—\l‘ (I I I I ’F I I
0-1 1.2 1.16 2.l0 2.'4 2.8 3.2 3.6 4.0 4.4 4.
Figure 2. Distribution of modulus values (MPa) R-D (two

days out of storage).

8

17

Table 5.--Analysis of Variance--Modulus Values Over Time.

 

 

 

 

Degrees of Sum of Mean
Source of Variation Freedom Squares Square F
Groups
Red Delicious 4 14.90 3.72 23.25
Red Delicious Promaline 4 57.44 14.36 102.57
Ruby 4 56.14 14.04 117.00
9.2.225.
Red Delicious 243 37.74 0.16
Red Delicious Promaline 245 33.90 0.14
Ruby 243 28.92 0.12
1211.
Red Delicious 247 52.64
Red Delicious Promaline 249 91.34
Ruby 247 83.06

 

18

group. The data show that there is significant differences
at the a = 0.01 level between apples stored in CA rooms.

Modulus values of apples tested in October versus
those tested at the end of March, showed significant de-
creases with time. Eighteen, 30 and 29 percent decrease in
modulus of elasticity values were recorded for R-D, R-D-
Promaline and Ruby apples, respectively over the 5% month
period.

The Promaline spray decreased the average modulus
of elasticity 0.52 MPa when compared to R-D without the
spray. It appears that R-D apple sprayed with Promaline
should not be stored since their firmness decreases signi-
ficantly with time. This actually defeats the purpose of
the Promaline to provide an improved apple in appearance
to be sold later in the year. The appearance of the R-D—
Promaline was more cylindrical with straight sides as opposed
to a traditional R-D. Also, the variation in size was much
greater with a large number being less than 5.0 cm in dia-

meter.

3.3.2 Seven Days Out of Storage

 

Figure 3 is a plot of modulus values for apples held
for seven days at 23°C after removal from storage. There
is an additional decrease in the modulus values when com-
pared with the modulus values for apples out of storage for
two days, as illustrated by Figure 4. The correlation
coefficients of -0.88, -0.76 and —0.01 were calculated for

the Ruby, R-D, and R-D-Promaline groups, respectively.

Modulus Values (MPa)

 

19

 

Ruby v
4.00— R'” O
R-D-Promaline Cl
C)
v
3.00-
V v
C)
v
C)
2.50-—
C]
2.00- Cl
C]
1.50..
1.00-
o l I l l l ML 1
OCT NOV DEC JAN FEB R APRIL
Time (Months)
Figure 3. Modulus values versus time (seven days out of

storage.)

Class Frequency (Percent)

50..

40-—

30""I

20'-

10-

 

Figure

‘\
°"‘“I I!) I I I Iz‘I
3.6 4.

4.

20

Seven days
out of storage .1

Two days
I out of storage

I\
I\
I\
I

l\

/ \

 

1.2 1.6 2.0 2.4 2.8 3.2 0

Distribution of modulus values (MPa) R-D
(stored for 58 months).

4.

I

4

21

When comparing paired two and seven day values from the
same storage room there are decreases ranging from 0.18 to
1.25 MPa with an average decrease of 0.55 MPa. This demon-
strates the importance of keeping apples at low temperatures
in order to maintain apple firmness and consumer appeal.
Comparing R-D versus R-D-Promaline, there is an
average decrease of 0.45 MPa between groups from the same
CA room. Again, the modulus of elasticity appears to be
adversely affected by the promaline spray which reduces
flesh firmness and subsequent consumer satisfaction.

3.4 Discussion of CA Storage Effects
on Strain Values

 

Table 6 contains the failure strain values for the
three groups over the time period tested. Using a one-way
classification for statistical analysis the strain values
between groups proved to be significantly different at the

a = 0.01 level as indicated in Table 7.

3.4.1 Two Days Out of Storage

Figure 5 is a plot of strain values for the three
groups of apples over the time interval studied. All three
groups show a decrease in the strain needed to rupture the
flesh when stored over a 5% month period. Correlation
coefficients of -0.97, -0.81 and -0.93 were calculated for
the Ruby, R-D and R-D-Promaline groups, respectively. The
lowest correlation coefficient of r = -0.81 indicates that
at least 66 percent of the variation in strain values can

be attributed to storage time.

22

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Strain

 

23

 

Ruby C]
__ R-D A
'130 R-D-Promaline C)
C)
U
D
.120.—
r‘ b
.110"
D D
CI
A
.100-- b
A
O O
.090-—
C) {D
.OBO-H
. 070 ‘4
0 1 I F I I I
OCT NOV DEC JAN FEB MAR APRIL

Time (Months)

Figure 5. Strain values versus time (two days out of

storage).

24

Table 7.--Ana1ysis of Variance--Strain Values-Between Groups.

 

 

Source of Degrees of Sum of Mean
Variation Freedom Squares Square F
Varieties 2 0.0036 0.0018 6.00
Error 144 0.0487 0.0003

Total 146 0.0523

 

Table 8 is an analysis of variance of strain values

within each group. The null hypothesis

is rejected at the o = 0.01 significance level.

Comparison of initial strain readings in October
with those at the end of March, indicate the failure strain
decreases 0.017, 0.025 and 0.021 for R-D, R-D-Promaline and
Ruby groups, respectively.

The R-D-Promaline apples were 0.011 units of strain
below R-D apples from the same CA room. This indicates less

force is required to produce rupture of apple tissue.

3.4.2 Seven Days Out of Storage

Figure 6 is a plot of strain values for apples con-
ditioned at 23°C for seven days after removal from storage.
The strain values decrease with time but do appear to level
off. Correlation coefficients of -0.31, -0.47 and -0.81
were calculated for the R-D, Ruby and R-D-Promaline groups,

respectively.

25

Table 8.--Analysis of Variance--Strain Values Over Time.

 

 

 

 

Source of Degrees of Sum of Mean
Variation Freedom Squares Square F
Groups
Red Delicious 4 0.0206 0.0052 26.00
Red Delicious Promaline 4 0.0212 0.0053 53.00
Ruby 4 0.0181 0.0045 22.50
Error
Red Delicious 243 0.0605 0.0002
Red Delicious Promaline 245 0.0304 0.0001
Ruby 243 0.0418 0.0002
Total
Red Delicious 247 0.0811
Red Delicious Promaline 249 0.0516
.Ruby 247 0.0599

 

Strain

.130 _.
.120 _.
.110 _.
.100 .3
.090 _.

.080 -u

r
OCT

Figure 6.

.070

 

26

Ruby 0
R-D EJ

R-D-Promaline v

I I I I I I
NOV DEC JAN FEB MAR APRIL

Time (Months)

Strain values versus time (seven days out of
storage).

27

Comparing paired values of two and seven day con-
ditioned apples from identical rooms, 75 percent of the

seven day values were larger.

3.5 Comments

Controlled atmosphere storage does slow the metabolic
process in apples but it does not stop it. The apple firm-
ness, related to modulus of elasticity, declines while the
apples are in storage and at an accelerated rate when exposed
to ambient conditions.

It appears that the grower must be careful to match
apple quality (firmness) with price. The CA storage pro-
cess is designed to delay the release of apples to the
market until prices rise, but if consumer dissatisfaction
occurs the procedure collapses.

The strain values do show a decrease but not markedly.
The total decrease is small and there is an increase in the
seven day values relative to the two day values. This could
be explained by the corresponding water potential of each
of the groups. Murase (1979) reported that the water poten-
tial level for tomato epidermis alters the critical strain
value for failure of vegetative tissue. This relationship
may hold true for apple tissue.

The decrease in modulus of elasticity and subsequent
increase in bruise potential, should specify the level of
packaging used to ship from the grower to the market.

Judicious selection of packaging materials can negate the

28

weakening of the apple flesh and provide a greater assurance

of high quality fruit arriving at the store shelf.

CHAPTER 4

DETERMINATION OF APPLE SUSCEPTIBILITY

TO BRUISING

Apples are often mechanically harvested by tree
trunk shaking equipment. Separated from their tree limbs,
the apples free-fall into a catching frame, which collects
the apples and loads them into large bins.

The harvesting procedure often produces impacting
of apples into tree limbs causing flesh rupture and subse-
quent bruising. Although the problem has been studied, no
feasible solutions have been developed. One factor minimi-
zing the problem is the apple level of maturity and conse-
quent firmness. During this stage of the processing cycle
the apple is at a maximum resistance to bruising due to its
high modulus of elasticity value. But what about subsequent
impacts encountered during shipping and the magnitude of
bruising? Chapter 3 showed that CA storage can slow the
reduction in modulus values, but it will not st0p it.

This dissertation supports previous work indicating
that as the apple maturity increases the mechanical strength

decreases. But, the question is still to determine the

29

30

magnitude of bruising associated with environmental hazards.
If the severity of the hazard is of insufficient magnitude
to produce bruising, then the apple will survive distribu-
tion with no increase in bruise level.

All distribution networks require the transfer of
goods from one point to another. Even the grower's own high-
way stand requires transfers from the packing house to the
roadside facility.

This movement and subsequent transfer between acti-
vity centers brings about the greatest probability for
incurring an impact. The physical handling of cased apples,
by either pallet load or individual units, can produce a
free-fall onto a variety of surfaces. The surfaces range
from black-top and concrete to wooden floors.

The free-fall height is dictated by the method of
handling and the transfer location. Forty pound boxes of
apples can be manually loaded or unloaded onto pallets or
directly onto trucks. Ostrem (1979) reports that a 2.7 kN
box has only a 10 percent chance of seeing a drOp over 51 cm
but, it does have a 50 percent chance of seeing a drOp in
the range from zero to 25 cm. The number of drops an indi-
vidual case experiences is controlled by the complexity of
the distribution network and the consequent transfer Oper-
ations.

Since a grower has little control over his product
once it leaves his facility, how can protection be provided

to keep bruising to a minimum? It was reported earlier that

31

the magnitude of bruising was dependent upon the impacting
surface and impact drop height, yet the grower cannot change
a concrete loading dock, nor can he supervise a commercial
carrier in the handling of his merchandise.

These two problems of control have been addressed by
the packaging industry, whereby the packing material is used
to provide protection from the distribution hazards. Imple-
mentation of packaging procedures requires the defining of
the products fragility which is the subject of the next

section.

4.1 Damage Boundary Theory

 

Consider the process of a case of apples free-falling
onto a rigid surface. Kipp (1972) reports that the abrupt
deceleration of the outer package at the termination of a
drop is communicated to the product inside. The nearly
instantaneous velocity change which takes place at the outer
surface of the package upon striking the surface is accom-
panied by local accelerations of many thousands of gs.

Packing or cushioning material is used to minimize
the shock effects by spreading the pulse over a longer
time and decreasing its magnitude. Figure 7 shows qualita-
tively what happens. The outer package experiences high
acceleration over a short time span. The internal packaging
Spreads the outer package pulse over a longer time and
decreases the magnitude of the pulse. The shaded areas are

effectively the same. The unshaded area represents the

Acceleration

 

32

Outer Package

 

Packaged Item

/

 

Figure 7.

Time

Shock pulse comparison.

.33

rebound off the cushioning material. The total area under
the Packaged Item curve produces the damaging effects.

Product sensitivity to shock is dependent upon three
parameters: shock pulse shape, maximum acceleration and
shock pulse velocity change. Since the designer has no con-
trol over the shape of the input shock pulse a "worse case"
situation provides a conservative approach to the problem.
Newton (1968) reports that the trapezoidal pulse encompasses
other expected shapes completely. Figure 8 graphically
illustrates that the trapezoidal pulse produces more damaging
effects than either the terminal peak sawtooth or half sine
pulse with the same peak acceleration and velocity change.

With wave shape accounted for by testing methodology,
the velocity change and maximum acceleration are incorporated
into a damage boundary curve defining a product fragility or
susceptibility to damage. The level of damage or damage
criteria represents the acceptable quality expected for the
apples. Bruise diameter or percentage of bruised apples
per case may be defined and then will remain constant
throughout the testing procedures. This will eliminate the
variable of evaluation from the testing sequence.

Figure 9 is a typical damage boundary curve. The
curve is defined by first experimentally determining the
critical velocity change and a corresponding point of damage.
The velocity change is calculated by integrating the area
under the shock pulse curve similar to those in Figure 7.

This value (AV) can be substituted into equation 1 to

34

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I,
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I \\\ \I\’\I~VA I \\
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Figure 9. Damage boundary.

36

calculate the critical drOp height (hf). The 9 represents

AV = I/Zghf (1)

a constant of acceleration of gravity 9.8 m/sz.

The only variable of equation 1 is the free-fall
drop height. Therefore, varying the change in velocity is
accomplished by drOpping the product from higher or lower
heights usually starting with a low velocity change. If the
product integrity is not affected, the velocity change is
increased in increments until the damage criteria is ex—
ceeded. Figure 10 graphically illustrates the procedure.
The corresponding change in velocity, or critical drOp
height, now defines the abscissa of the damage boundary.
Drop height values greater than or equal to the critical
drOp height will produce damage, while corre5ponding values
less than the critical threshold do not produce the failure
criteria.

It should be noted that the damage boundary only
considers the effects of single drops. Multiple drops of
less than critical levels may cumulatively produce fatigue
or even damage. This point will be discussed later.

The hf can be compared to environmental data as to
whether or not a hazard of this magnitude exists in the
field. If a drOp height of this severity will not be en-
countered, then no further testing need be done.

If values of hf or larger exist, then the critical

acceleration level must be determined. The critical

37

8 4
.H K
4.)

(U

LI

.3

0

fl

 

 

 

Time

Figure 10. Determination of critical velocity change.

38

acceleration is expressed in constant units of acceleration
of gravity (9.8 m/secz). A fragility of 20 gs means that
an acceleration of 20 times that of gravity is required to
produce damage.

Evaluation of the critical acceleration is accom-
plished by first selecting a change in velocity, which is
equal to the design drOp height, or the expected free-fall
height present in the environment.

With the drop height determined, the impacting sur-
face is set to induce an acceleration level below the anti-
cipated failure value. If no information is available, then
a minimum acceleration level is used.

The product is drOpped onto the impacting surface
and then inspected relative to the damage criteria. If no
damage occurs, the impacting surface is successively changed
to produce a larger acceleration level. This process is
repeated until damage occurs. Figure 11 graphically illus-
trates the procedure. Since dr0p height is held constant,
the curve areas are identical and only the shape changes.
The damage producing acceleration level becomes the ordinate
of the damage boundary curve.

Referring to Figure 9, the two lines can be connected
and their point of intersection is usually rounded. If the
connecting point is of concern, it can be calculated using
a format cited by Newton (1968).

The shaded area in Figure 9 represents damage pro-

ducing values. Theoretically the area in Figure 9 from the

39

II”
IIMJ
I \\ \\

Time

Acceleration

 

 

Figure 11. Determination of critical acceleration
level.

40

y-axis to the damage boundary indicates that as long as the
critical velocity change is not exceeded, the product can
experience an infinite acceleration level without failure.
The product is said to act as its own isolator.

Once the critical velocity change is exceeded by
environmental hazards, a cushioning material must be employed
to account for the difference in the environmental stress,
and product's ability to withstand abuse. The packing
material must keep the acceleration levels transmitted to

the product between the x-axis and the damage boundary.

4.2 Objective

 

IPrevious work has been centered in establishing
bruise levels and corresponding damage boundaries for full
case quantities of apples. Little attention has been paid
to the apple's mechanical strength or the modulus of elasti-
city. Also, full case quantities allow low replication and
make bruise analysis difficult.

The following procedure is designed to yield a
damage boundary for a single apple impacted onto another
apple. This will simulate in-case conditions and simplify

the analysis by concentrating on a single point of contact.

4.3 Experimental Procedure
A Lansmont model 65 shock machine was used to deter-
mine apple damage boundaries. The machine carriage produces
vertical impacts which are essentially flat. The perfectly

flat drops are a worst case situation, since all forces are

41

concentrated in the vertical direction. A nitrogen braking
system arrests the carriage during rebound to provide only
one drOp. The carriage surface is of sufficient strength
and rigidity to remain flat and horizontal under test
stresses and is guided in free-fall to prevent rotation or
translation in other directions.

An Endevco Model 2272 piezoelectric accelerometer
was securely fastened to the shock machine carriage to sense
the impacting acceleration. The accelerometer had a charge
sensitivity of 2.93 pc/g and a transverse sensitivity of
0.7 percent maximum. The output of the accelerometer was
fed into an Endevco Model 2718A signal conditioner. The
full-scale g output was set for 500 gs per five volts. The
internal low frequency and high frequency cut-off filters
were set at 0.3 and 3300 Hz, respectively.

The output of the signal conditioner was input to
a Tektronix Model T912 storage oscilloscope. The scope was
wired to an external trigger to allow capture of the tran-
sient shock pulse for analysis. A Polaroid camera Model
CSA was used to record the shock pulses. The maximum accel-
eration and velocity change are calculated from a photo-
graph of the shock pulse.

Figure 12 is a sample shock pulse. The time base
was set at 0.5 msec per division and the vertical scale at
50 gs per division. The change in velocity is determined

by integrating the area under the curve. The area of each

42

 

 

 

Figure 12. Experimental half sine shock pulse.

43

square centimeter is calculated by substituting the scope

settings into equation 2. Using the scope
(gs/div.)(sec./div.)(9.8m./sec.2) = AV (2)

values, the area of each square is 0.245 m/sec. The total
area under the curve is 12.4 division. Multiplying number
of division by area per division yields a total velocity
change of 3.04 m/sec. By subtituting 3.04 m/sec into
equation 1, the equivalent drOp height of 0.47 m is calcu-
lated.

The maximum acceleration level is read directly off
the shock pulse. The total number of vertical divisions
between the baseline and the shock pulse peak are multiplied
by the vertical scale sensitivity. Figure 12 has a vertical
displacement of 4.2 division multipled by 50 gs/division
yields a maximum of 225 gs.

Most apple damage results from apple to apple con-
tact, i.e., poly bags. To simulate these conditions, two
apples were bound together and the bruising between the
apple surfaces was investigated. Shrink wrap, 100 gauge
polyvinyl chloride, was used to overwrap the apples and
maintain the contact area with no slippage or multiple
impacting conditions. The 100 gauge pvc did not compress
the apples causing initial failure. The apples were wrapped
using a Weldotron L-Bar sealer and then placed stem down on
a flat surface. Heat was applied using a hand shrink gun,

drawing the plastic film. By keeping the apples on a flat

44

surface during shrinking, a uniform orientation was main-
tained for testing. The plastic shrink wrap energy did not
pre-load or compress the apples.

Figure 13 shows the apple pack mounted on the shock
machine awaiting test. The orientation of the pack provides
all acceleration forces to be vectorially concentrated in
the vertical plane. This provides the most severe situation
which can be encountered. The apples were pressed onto a
metal spike to provide a consistent orientation. The apples
were not restrained on the table because the size variation
between apples made fixturing difficult. Also, restraining
required the pre-loading of specimens providing initial
compression and thus different results. Rebounding apples
were caught to prevent additional impacts.

Single packs of apples were tested with the procedure
and equipment previously discussed in this section. The
change in velocity and acceleration levels were controlled
to pre—determined magnitudes. After mounting, the packages
were impacted once, removed from the table and stored for
24 hours. Bruise diameter measurements were then made using
a steel template with holes of 0.635, 0.952 and 1.270 cm in

diameter.

4.4 Discussion of Apple Bruising Levels

 

Red Delicious apples used in the bruise assessment
had been CA stored 129 days, processed, packaged and cold-

stored for six days at l.7°C.

45

 

Figure 13. Apple package mounted for shock testing.

46

Fifty of these apples were tested using the pro-
cedure outlined in Chapter 3. They had an average modulus
of elasticity of E = 2.89 MPa with a standard deviation of
0.43 MPa. The average rupture strain was 5 = 0.101 with a
standard deviation of 0.0128.

Table 9 contains the bruise assessments for the
three free-fall drOp heights investigated. Forty apples or
twenty shrink packages were dropped distances of at 0.145,
0.31 and 0.47 m. The bruise diameters were measured and
placed in four groups. The percentage of bruises and a
cumulative distribution were calculated for each height.

Increasing the velocity change or equivalent free-
fall drOp height produces bruises of larger diameter in each
case. By increasing the drOp height from 0.145 to 0.47 m
the percentage of apples with bruises greater than 1.270 cm
increased from 10 to 65 percent, respectively. The low drop
height of 0.145 m had its greatest percentage of fruit,
47.5, in the smallest bruise category. Bruising was not
always the same between both apples. One apple might be
bruise free while the other apple might have a bruise greater
than 1.270 cm. This phenomena occurred on either top or
bottom apple with no regularity.

Table 10 contains bruise levels of apples drOpped
from the same equivalent free-fall height of 0.69 m, but
subjected to different acceleration levels. Acceleration
levels of 15, 30 and 60 gs were investigated. By increasing

the acceleration level from 15 to 6095 the percentage of

 

47

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49

apples with bruises greater than 1.270 cm increased from

10 to 45 percent, respectively. The low acceleration level
of 15 g had its greatest percentage of apples, 75, in the
smallest bruise category.

The data in Tables 9 and 10 permit a damage boundary
to be drawn for a specified damage criteria. Figure 14
uses a damage criteria of 10 percent grade change from extra
fancy to fancy as defined by the U.S.D.A. This means that
an environmental hazard exceeding the critical velocity
change of 1.68 m/sec and having a maximum acceleration equal
to or greater than the critical acceleration level of 15 gs
will produce damage. Ten out of every one hundred apples
will have bruise diameters in excess of the U.S.D.A. criteria
of 1.270 cm.

Figure 15 is another damage boundary with the cri-
teria of bruises with diameters greater than 0.635 cm. Two
percentage curves are drawn to illustrate that as the
critical velocity change and critical acceleration level

are increased the number of bruises will also increase.

4.5 Conclusions

 

Larger changes in velocity and acceleration will
produce subsequent larger bruise diameters in each set.

The damage boundary concept can be used to predict
the effects of environmental hazards of shock on the quality
of apples. Grade changes, levels, and magnitudes of bruising

can be anticipated.

50

120 -—

\
110 -
100 -
90'7 DAMAGE
80 _j AREA
70... \
60 -: I
50 _.
40 -5
30 -

20 .4 ;::\\\

10 -1

Acceleration (9)

 

 

 

I I I I I I I I I l
0 0.50 1.00 1.50 2.00 2.50 3.00 3.5 4.00 4.5 5.00

Change in Velocity

Figure 14. Damage boundary--10 percent grade change.

120d

110-

100-

90-I

80-

g)

(

60-

50.

Acceleration

40‘

30‘

20-

10-

51

[223% Bruising

66%I&——-'
Bruising

 

 

7 , \\\\
///A

 

 

O

 

I 1 I I I I I i I I

I) 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00

Figure 15.

Change in Velocity (m/sec.)

Damage boundary--66 and 73 percent bruising.

52

Using the damage criteria of a 10 percent grade
change, the critical velocity change and the critical accel-
eration level will be 1.68 m/sec and 15 gs, respectively.

As the apple maturity increases it will become more
susceptible to bruising and damage boundary will shift

towards the origin, yielding a larger damage area.

CHAPTER 5

PACKAGE DESIGN FOR MINIMIZING APPLE BRUISING

The design Of a package begins with the defining Of
the objectives or goals Of the user. The functions Of the
package must then be Optimized to provide a feasible package
form.

For the grower, a number of criteria must be met by
the package. First, the protection afforded the apples is
Of paramount importance. If the number Of bruises exceed
consumer acceptance levels, then sales will accordingly
reflect dissatisfaction. Second, the package materials and
construction must be economically consistent with the price
the consumer is willing to pay for the product. Often the
apples and package are separated before the consumer views
the product and the buyer does not appreciate the additional
expenditure and its associated value. It is not uncommon
for the package to product cost ratio to exceed three to
one for some consumer items. Third, the packing Operations
must be considered to minimize labor and capital investment
while maximizing output. Many growers have small production

Operations limiting their capabilities. Fourth, the package

53

54

should be convenient for the consumer to handle. Fifth, the
package should not present any problems Of disposal for
either the retailer or the consumer.

The description Of package functions could be con-
tinued to include areas Of distribution, processing, motiva-
tional concerns, etc. The list will be dependent on the
marketing strategy which includes pricing, retailing outlets,

advertising, etc., or in other words--the Objectives.

5.1 Package Forms

Apple packages can be divided into primary and
secondary groups. The primary grouping provides the con-
tainment and is best exemplified by the polyethelene bag.
This category also includes inserts or spacers, and pads.
Secondary packaging starts with the corrugated box used tO
assort the primary packs into economic units Of order. This
continues with a pallet used to stock upwards Of forty boxes
into a unit load for shipping.

The minimum level Of primary packaging is the poly-
ethelene bag. Its function is solely containment Of a
specified quantity Of apples. It promotes efficient handling
by consumer and retailer and it forms the basic unit Of
purchase. It is inexpensive, but it provides no protection
for the apples.

Peleg (1972) reported on a shrink wrap Of four
apples into stick pack. This package results in a tight

unit minimizing the movement Of the apples in the secondary

55

box and subsequent contacting and resultant bruising. Peleg
did find that the critical velocity change increased in
stick pack over the polyethylene bags from 3.1 tO 3.5 m/sec.
The equivalent free-fall drop height using equation 1 are
0.5 and 0.6 m., respectively.

Premium apples are packaged in molded pulp trays
providing individual cells for complete isolation from other
apples. These trays can be displayed with apples at the
retailer level. This package reduces the bruise level, but
it is very labor intensive resulting in high packaging and
subsequent apple costs.

Hanna and MOhnsenin (1972) tested a polystrene
package providing complete encapsulation for six apples.
This pack is very expensive for both materials and labor,
but it provided damage protection from a free-fall drOp
height Of 0.9 m.

Somewhere in between the polyethylene bag and the
polystyrene package is the Optimum design. The rationale
for choosing between alternative packages is the Optimiza-
tion Of cost and protection afforded the apple, giving the

consumer maximum utility for his dollar.

5.3 Package Design Criteria
Economic considerations are important criteria in
choosing the final package design. But, as long as all Of
the factors contributing cost such as materials, labor,

transportation and overhead are included, the decision is

56

fairly straight forward. Comparison with the retail price
for apples will dictate the expenditure for packaging.

Designing a package for protection has been a com-
plex decision because Of product fragilities and the vast
number Of packing materials and subsequent configurations
to choose from. Hammerle (1966) investigated a fragility
factor, which he defined as the product weight times the
constant acceleration Of gravity, for four different materials.
By drOpping apples from increasing heights and measuring
damage he was able to show that the cushioning materials
began to isolate damaging forces as the heights were in—
creased. Unfortunately, the data does not provide design
criteria for quantity Of cushioning material used nor dO
they take into account product variation due tO maturity.
Also, the data only considers apple damage and they are use-
ful for only single apple configurations.

Chapter 4 described the damage boundary theory and
concluded that if a critical change in velocity and subse-
quent free-fall drOp height were exceeded in the environ-
ment, then protective packaging is required. The level Of
protection is defined by the critical acceleration level
for the product. The packaging material must isolate the
g forces that exceed the critical threshold or the apples
will exhibit the damage criteria.

Packaging materials with cushioning prOperties are
quantified by performance curves. Figure 16 is a sample

curve. The curve shows the peak acceleration that will be

57

Peak Acceleration 9

 

 

Static Stress Pa

Figure 16. Static Stress Pa.

58

transmitted for different values Of static-stress. The
static—stress is the mass Of the packaged item divided by
the cushion area. The curve is not confined to any specific
product or damage criteria but rather can be used for an
infinite number Of situations.

The designer compares the critical acceleration
level Of the product to the materials ability to isolate
acceleration forces. The curve in Figure 16 is the threshold.
Acceleration levels and corresponding static-stress values
above the curve will be isolated from the packaged product.
Values below the curve will be communicated to the item.

Military Handbook 304 (1972) contains curves for
twenty different materials. Many Of these materials are
able to provide the same level Of protection thus allowing
the choice Of material to be made on cost, supply, etc.
Figure 17 is a static-stress curve for polyurethane ether
developed for a free-fall height of 18 inches. Refering to
the critical acceleration data in Chapter 4, either the 15
or 30 9 levels can be located on the curve with protection
provided by either the 4, 5 or 6 inch thickness. The static-
stress working range is between 0.69 and 1.4 kPa. Using a
box Of apples Of 177.9 N (40 pounds) and the working static
stress range, a simple algebraic manipulation gives a
cushioning range Of 0.13 tO 0.26 m2. As long as we use this
amount Of material spread over the load area we will isolate
every thing above 15 or 30 gs and transmit only the 15 or

30 9 level depending which one we selected.

59

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60

With the material selected, it can then be included
in the package as an insert, pad or a number Of different
configurations. Once assembled, the final package should

be tested, so that the design criteria was not exceeded.

CHAPTER 6

SUMMARY

The mechanical properties Of three groups of apples
Ruby, R-D and R-D-Promaline were investigated along with
the effects Of CA storage on these values.

The modulus Of elasticity decreased 0.60, 1.02 and
1.14 MPa for R-D, R-D-Promaline and Ruby varieties when
stored over 5% months.

Comparing the modulus values Of apples that were
exposed tO ambient (23°C) conditions for seven days as
Opposed tO two days, the values decreased on the average
0.49, 0.45 and 0.71 MPa Of the R-D, R-D-Promaline and Ruby
varieties, respectively.

The modulus values for the R-D-Promaline versus the
R-D variety were down on the average 0.52 MPa for apples
two days out Of storage and 0.48 MPa for apples seven days
out Of storage.

Failure strains decreased 0.017, 0.025 and 0.021 for
R-D, R-D-Promaline and Ruby varieties over a 5% month CA

storage period. Comparing failure strain values Of apples

61

62

two days versus seven days out Of storage, showed an increase
in 75 percent Of the seven day values over all three groups.
Using a damage criteria Of a 10 percent grade change
from extra fancy tO fancy a damage boundary was experi-
mentally determined. The critical velocity change Of 1.68
m/sec yielded an equivalent free-fall drop height of 0.145 m.
The critical acceleration level for the same damage boundary

was 15 gs.

CHAPTER 7

CONCLUSIONS

Apples placed in controlled atmosphere storage

for extended periods tend tO decrease in firmness.
Quantitatively this can be defined as a reduction
in the modulus Of elasticity.

The effect Of controlled atmosphere storage on
failure strain levels is small. They do decrease,
but not dramatically.

Promaline spray used on Red Delicious apples tO
alter growth characteristics appears to signifi-
cantly reduce the modulus Of elasticity when the
apples are stored in controlled atmosphere rooms.
Apples stored in controlled atmosphere rooms and
then conditioned for seven days at ambient condi-
tions, exhibit reductions in modulus Of elasticity
value when compared to the value two days after
removal from storage.

Apples are bruised significantly when drOpped from
equivalent free-fall heights that exist in normal

handling procedures.

63

64

Damage boundary procedures can be used to define
critical change in velocity and critical acceleration
levels which produce bruising in Red Delicious
apples.

Protective packaging for apples can be designed
using performance curves defining the properties

Of cushioning materials.

The packaging requirements for apples shipped prior
to CA storage are markedly different from those
apples stored for extended periods. Stored apples
require additional packaging to compensate for their
increased sensitivity to bruising.

As the storage time increases the bruise resistance
decreases causing the damage boundary tO shift

towards the origin and increasing the damage re-

sulting area.

CHAPTER 8

RECOMMENDATIONS FOR FURTHER STUDY

The modulus Of elasticity values conclusively de-
creased over time indicating a loss of flesh firmness.
Corresponding strain values were erratic and did not conform
to a set pattern. Possibly a sample Of fifty apples is tOO
small to provide a smoothing effect. A sample size Of 250
apples may show a pattern Of little or no change in strain
failures over storage time.

The determination Of apple damage boundary is a
difficult process. Due to the variation in apple mechanical
prOperty, a much larger sample than twenty pairs Of apples
should be tested. This could provide some insight as to the
actual distribution within each group. Due to the complexity
Of shock-testing equipment and its limited availability, a
more universal method of evaluating apple bruise resistance
is needed.

Future investigations should center around damage
boundary testing Of apple groups with varying modulus Of

elasticity values. Once this relationship is defined, the

65

66

percentage Of bruising can be predicted by the quantitative
description Of the apple flesh firmness or modulus Of
elasticity.

Experimental calculation Of modulus values can be
done with a compression tester. This analysis will give
rapid feedback to the grower as tO the level Of protective
packaging needed to insure product quality.

Bruising Of apples is not only due to impact forces,
but also other environmental hazards such as over-the-road
vibration and compression. These hazards in combination
contribute to the failure Of packaging and subsequent apple
bruising.

Goff (1974) investigated the effects Of a sequence
Of tests modeled after the distribution environment on a
group of packages. The packages were inspected at various
points to measure the contribution Of each hazard to damage
with a final evaluation used to evaluate the total survival
rate. ASTM D-10 Committee on Packaging has developed a
series Of sequences modeling the distribution environment.
The apple testing should include an evaluation using a
sequence including shock, vibration and compression which
models a typical grower's situation. This type Of test will
tie all types of package characteristics to provide protec-

tion into a successful and cost effective design.

BIBLIOGRAPHY

Bittner, D.
1967

Goff, J. W.
1974

Hanna, M. A.
1972

BIBLIOGRAPHY

R., H. B. Manbeck, and N. N. Mohsenin

A method Of evaluating cushioning materials
used in mechanical harvesting and handling Of
fruits and vegetables. ASAE paper 66-634,
St. Joseph, Michigan.

U.S. Department Of Commerce, project NO. 4-35711.
Michigan State University, East Lansing, Michigan,
Project NO. 3108.

and N. N. Mohsenin
Pack handling Of apples. J. Agric. Engng.
Research (1972), 17, 154-167.

Horsfield, B. C., R. B. Fridley, and L. L. Claypool

1972

Kipp, W. I.
1971

Kipp: W. I.
1972

Murase, H.,
1979

Application of theory Of elasticity to the
design Of fruit harvesting and handling equip-
ment for minimum bruising. Transactions Of
the ASAE, 15(4):746-750.

Feasibility study shock and vibration testing
Of agricultural products. Lansmont Corporation,
Montorey, California, Report 22.

Product fragility assessment. Lansmont Corpora-
tion, Monterey, California.

G. E. Merva, and L. J. Segerlind
Failure mode Of vegetative tissue. ASAE paper
79-3064, St. Joseph, Michigan.

Nelson, C. W. and N. N. Mohsenin

1968

Maximum allowable static and dynamic loads and
effect Of temperature for mechanical injury in
apples. J. Agric. Engng. Research (1968),
13(4), 305-317.

67

'68

Newton, R. E.
1968 Fragility assessment theory and test procedure.
Prepared for Monterey Research Laboratory, Inc.

O'Brien, M.
1964 Fruit handling and it's associated damage.
ASAE paper 64-001, St. Joseph, Michigan.

Ostrem, F. E.
1979 An assessment of the common carrier shipping
environment. Forest Products Laboratory,
Madison, Wisconsin, Technical Report FPL 22.

Peleg, K.
1972 Development Of an improved retail package for
Michigan apples. Michigan State University
Project MICL03069.

Schoorl, D. and W. T. Williams
1972 Prediction Of drOp-testing performance of apple
packs. Queensland Journal Of Agricultural and
Animal Science, 29(1):187-197.

Schoorl, D. and W. T. Williams
1973 Robustness Of a model predicting drop-testing
performance Of fruit packs. Queensland Journal
Of Agricultural and Animal Sciences, 30(3):
247-253.

Schoorl, D. and J. E. Holt,
1974 Bruising and acceleration measurements in apple
packs. Queensland Journal Of Agricultural and
Animal Science, 31(1):83-92.

Segerlind, L. J. and I. D. Fabbro
1978 A failure criterion for apple flesh. ASAE
paper 78-3556, St. Joseph, Michigan.

GENERAL REFERENCES

Brown, G. K. and L. J. Segerling
1975 The location probabilities Of surface injuries
for some mechanically harvested apples.
Transactions Of the ASAE, 18(1):57-59.

Foley, J. T.
1972 Transporation shock and vibration description
for package designers. Sandia Laboratories
Report SC-M-72 0076, July.

Friedman, W. F. and J. J. Kipness
1977 Distribution packaging. Robert E. Krieger
Publishing Company, Huntington, New York.

Griffen, R. C. and S. Sacharow _
1972 Principles Of package develOpment. The AVI
Publishing Company, Inc., Westport, Connecticut.

Guins, S. G.
1975 Notes on package design. Okemos, Michigan.

Hammerle, J. R. and N. N. Mohsenin
1966 Some dynamic aspects Of fruit impacting hard
and soft materials. ASAE paper 65-320, St.
Joseph, Michigan.

Harris, C. M. and C. E. Crede
1976 Shock and vibration handbook. McGraw Hill.

Heldman, D. R., D. E. Marshall, L. R. Borton, and L. J.
Segerlind
1976 Influence Of handling on picking cucumber
quality. Transactions Of the ASAE, 19(6):
1194-1196, 1200.

Kindinger, P. E. and D. L. Good

1976 The apple marketing game. American Fruit Grower,
96(6):24-25.

69

70

1945 Dynamics of package cushioning. Bell Systems,
Journal, Volume 24, October.

Mustin, G. S.

1968 Theory and practice Of cushion design. Shock
and Vibration Information Center, Washington,
D.C., May.

O'Brien, M., L. L. Claypool, and S. J. Leonard
1963 Courses Of fruit bruising on transport trucks.
Hilgardia, 35(6), i 113-124.

O'Brien, M.
1964 Bin handling systems for fruits and vegetables.
Transactions Of the ASAE, 45(3), 136-137.

O'Brien, M., J. P. Gentry, and R. C. Gibson
1964 Vibrating characteristics Of fruits as related
to in-transit injury. Transaction Of the ASAE,
paper 64-309.

O'Brien, M., W. B. Goddard, and S. Gyasi
1971 Tomato damage during harvesting and handling.
ASAE, paper 71-138. ~

Peleg, K.

1978 The K. P. produce packing system. ASAE, paper
78-6538.

Stern, R. K.
1974 Military standardization handbook package
cushioning design. Department Of Defense,
Washington, D.C., MIL-HDBK 304A.

Tennes, B. R., J. J. Segerlind, and C. Burton
1974 How handling and storage affect processing yield
Of mechanically damaged apples. Transaction Of
the ASAE, 17(1), i 49-51.

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