NEWHALL AND KESTERSON:
The extent of this reduction in decay ranged
from about 30 per cent for samples packed
without fungicides or precooling to about 50
per cent for the oranges packed after "Dowicooling." The relation between decay and
number of holes was not linear. The magnitude
of the beneficial effects from added ventilation
gradually decreased. Very little gain was real
ized by going from 72 to 100 holes per bag.
Since bag strength decreases as the number of
holes increases it appears that the present legal
minimum of 72 holes per bag (4) represents
a good compromise between adequate venti
lation and bag strength.
Due to the precooling and fungicide treat
ment the decay of "Dowicooled" samples was
less than that of those packed warm without
fungicides. Ventilation had more effect in re
ducing the decay of these precooled oranges
than for the warm packed fruit.
Peel injury was very low for all samples in
these experiments.
D-LIMONENE
239
Summary
1. Decay of Hamlin and Pineapple oranges
packed in polyethylene bags in cartons decreased
as the number of holes per bag increased.
2. The reduction in decay amounted to
about 30 per cent for oranges packed without
precooling or fungicides and 50 per cent for
"Dowicooled" fruit.
3.
The legal minimum of 72 holes per bag
appears
to
be
a
good
compromise
between
adequate ventilation and bag strength.
4. Precooling with a fungicide treatment re
sulted in lower decay for the "Dowicooled"
samples than for those packed without fungi
cides or precooling.
,
„
l.Gnerson,
W.,
LITERATURE
1957.
CITED
Preliminary studies on
cooling
70° 264 272n9eS Pn°r f° packlng' Proc' Fla> State Hort- Soc-
nA T
packaging
—
r.,and F- W. Hayward, 1960. Precooling.
and fungicides
as
factors
affecting
appearance
and keeping quality of oranges in simulated transit experi
ments. Proc. Amer. Soc. Hort. Sci. 76: 229-39
\a/ • . ]<aufman/ J-' 5- E. Hardenburg and J. M. Lutz, 1956.
Weight losses and decay of Florida and California oranges
JLsr^K^rtoittlene consumer bags-ProcI960.
Commlssion
'
FACTORS AFFECTING THE AUTOXIDATION OF
D-LIMONENE DURING STORAGE
William F. Newhall and James W. Kesterson
Florida Citrus Experiment Station
Lake Alfred
The oxidative deterioration of limonene
during storage has been a substantial problem
to many citrus processors in Florida. The
oxidized product is usually unsaleable and it is
often not economical to repurify the material.
The development of undesirable flavors in some
processed citrus products, as well as the deteri
oration of essential oils of citrus, is undoubtedly
related to limonene autoxidation.
Ogston and Moore (3) reported that a sam
ple of Italian lemon oil showed no material
change in quality after ten years storage in a
full, sealed container. Konnerth (2) showed
that lemon and orange oils kept well when
stored in bottles under an atmosphere of
nitrogen. In 1932, Poore (4) published data
showing the effect of temperature, water, air
and light on the quality of limonene from
Florida Agricultural Experiment Station Journal Series No.
California lemon oil. At the end of 20 months,
the limonene was unaffected in the presence
of water if air was excluded. Marked changes
occurred in the presence of dry air and the
greatest deterioration appeared when both
water and air were present. All sealed samples
remained unchanged.
The purpose of this investigation was to de
termine the effect of other factors such as
metals, reducing agents and antioxidants on the
autoxidation rate of d-limonene in storage.
Experimental Procedure
,
Two separate series of storage experiments of
one-year duration were performed concurrently.
The first was a laboratory experiment in which
single-distilled
bottles under
The other was
test in which
stored in full
samples were stored in glass
24 different storage conditions.
a commercial warehouse storage
double-distilled limonene was
(55 gal.) drums with different
amounts of a chemical antioxidant added. These
two experiments will be discussed separately.
Both grades of d-limonene used for these two
tests were furnished by the Kuder Citrus Feed
Company of Lake Alfred, Florida.
FLORIDA STATE HORTICULTURAL SOCIETY, 1%1
240
Storage in Bottles.-Sea.led, full samples (60
ml.) and half-full (30 ml.) samples, kept open
to the air by grooved corks, were prepared to
show the effect of air on each storage condition
studied. Two-ounce clear glass bottles were used
as containers. All samples were prepared in
triplicate, so that destructive sampling was
possible at the time of analysis. They were
stored at room temperature in the dark with un
treated checks.
In the first three treatments, sufficient iron
powder, granular aluminum (8-20 mesh) and
powdered zinc, respectively, were added to just
cover the bottoms of the sample bottles. It was
felt that the fine state of division of these metals
would accelerate any surface effect they might
have if used in the fabrication of storage tanks.
The next two samples compared wet (5 ml.
of water added) with dry storage (anhydrous
sodium sulfate added).
Analyses for refractive index, optical rotation,
peroxide value and acid number were run ini
tially and at three-month intervals to determine
whether or not quality changes occurred during
storage.
Drums once opened for analysis were
discarded.
The Food and Drug Administration permits
100 p.p.m. of antioxidant as the upper limit
for use in foods. The food grade of butylated
hydroxytoluene (Ionol) used in this study was
furnished by the Shell Chemical Corporation,
a Division of the Shell Oil Company.
Experimental Results and Discussion
The changes in refractive index, optical ro
tation, peroxide value and acid number which
occurred in the bottled, single-distilled limonene
samples during storage will be presented and
discussed separately.
Table 1
The sixth treatment
was storage over a reducing agent, sodium
bisulfite,
while
the
seventh
was
storage
Change in Refracti\re Index (20°)
- 1.4721*
in
6 memths
Void
contact with Dowex 1 resin, which is effective
in the removal of peroxides. Aluminum oxide
was used in the following treatment because of
its ability to absorb oxygenated compounds.
Two sealed, half-full (30 ml.) samples were
stored over powdered iron under atmospheres
of carbon dioxide and nitrogen, respectively.
The latter treatments were the only ones for
which samples continuously open to the air
were not included.
The last two treatments
comprised limonene samples to which 50 p.p.m.
of the antioxidants butylated hydroxyamsole
and butylated hydroxytoluene were added, re
spectively. /
Analyses of the untreated check and all treat
ments for refractive index (20° C.), optical ro
tation (20° C.), peroxide value (1 minute) (5)
and acid number (1) were made after storage
periods of six and twelve months.
Storage in 55-Gal. Drums.-Butylated hydrox
ytoluene was tested to determine its effective
ness in the control of d-limonene deterioration.
Sixteen (55 gal.) drums completely filled were
divided into four groups of four drums each.
The first group contained no antioxidant and
served as a control. The remaining three groups
of drums contained 25, 50, and 100 p.p.m. of
added butylated hydroxytoluene, respectively.
The drums were filled hot and sealed so that
they would be free from air. They were then
stored in the warehouse of Kuder Citrus Feed
Company under normal commercial conditions.
12 months
Full
Full
Void
+0.011
+0.007
None
+0.011
+0.009
None
+0.017
+0.013
+0.013
None
+0.010
Check
None
+ Iron
+ Aluminum
None
None
+ Zinc
None
+ Water
None
None
None
+0.012
+0.001
+ Na2SO4 (Anhyd.)
None
+ Na2S2O5
+ Dowex 1
None
+0.005
+0.010
+0.006
None
+0.006
+0.001
+0.014
+0.013
+0.006
+ A12O3
+ Iron under CO2
None
+0.010
None
+0.012
None
...
None
+ Iron under N2
None
...
None
B.H.A.* (50 p.p.m.)
B.H.T.** (50 p.p.m.)
None
None
+0.011
+0.011
None
None
None
...
...
+0.015
+0.011
•Butylated Hydroxyariisole
••Butylated Hydroxytoluene
The changes in refractive index determined
for the various treatments described previously
are summarized in Table 1. The term "void"
is used to denote the half-full samples open to
the air. The results for the half-full samples
stored with iron under carbon dioxide or nitro
gen are included in the "Full" column because
these samples were sealed.
The data presented in Table 1 show that
there was no change in refractive index for any
of the full, sealed limonene samples except those
stored over sodium sulfate and Dowex 1 after
a period of one year. In general the samples
exposed to air showed a gradual increase in re
fractive index with storage time. Iron and zinc
metal had a slight tendency to retard this in
crease. The dry (+Na2SO4) sample of limo
nene exposed to air showed a greater increase
in refractive index and hence more deteriora
tion than the sample stored over water. The
NEWHALL AND KESTERSON:
open samples stored over Dowex 1 resin showed
the smallest increase in refractive index after
12 months. The two antioxidants were unable
to suppress the increase in refractive index
under these storage conditions.
Tabli 2
D-LIMONENE
Change in Peroxide Value
(Initial value ° 2.3^
Treatment
Full
Check
+13.6
- 1.9
- 2.1
- 1.0
+24.6
+ 2.2
+ Iron
+ Aluminum
+ Zinc
Change in Optical Rotation (20s)
(Initial value ° 4-98.70)
6 months
Full
Void
Treatment
-JLLJ
Check
+ Iron
+0.1
•26.3
+0.3
+ Aluminum
+1.1
+0.9
-14.4
-27.5
+0.3
-0.5
-22.1
-13.6
-0.1
+0.2
-25.2
•44.6
-14.8
-0.5
-0.4
-1.0
+0.3
-0.1
-I- Zinc
+ Water
(Anhyd.)
225
+ Dowex 1
+ A12O3
+ Iron under CO2
+ Iron under N2
B.H.A. (50 p.p.m.)
B.H.T. (50 p.p.m.)
+0.2
+0.1
+0.9
+0.1
+0.9
+2.4
+1.5
+1.3
+0.9
+0.9
-26.0
-30.3
-28.5
ntha
+0.1
-0.4
+0.2
-42.3
-18.1
-32.7
-24.3
-34.0
-37.3
*
-17.8
-26.7
...
...
-36.2
-28.8
*Thls sample was too dark colored to check its rotation.
In Table 2 the changes in optical rotation
of the various treatments are compared with
those of the untreated check.
The results in Table 2 show that although
there were slight fluctuations in the optical ro
tation values for the full samples, there was
almost no evidence of deterioration. All of the
samples exposed to air, however, showed a
marked decrease in optical rotation as the
period of storage increased. Of the metals, iron,
in particular, retarded the decrease in rotation
as compared with the untreated check. This
may be due to the reducing action of the iron.
It should be emphasized, however, that these
results may be misleading because the open
samples with iron were very dark colored un
like most of the other open treatments. The
dried (-|-Na2SO4) limonene sample showed
more rapid deterioration than the sample stored
over water. The open sodium bisulfite samples
were also very dark colored, like the open iron
samples, and showed accelerated deterioration.
Dowex 1 resin retarded rotation decrease where
as aluminum oxide produced a marked increase
in rotation after six months in a full container
but had little effect in the open samples. The
two antioxidants (B.H.A. and B.H.T.) showed
+ Water
+ Na2SO4 (Anhyd.)
+ Na2S2O5
-2.3
+256
+400
- 0.3
+470
B.H.T. (50 p.p.m.)
- 2.0
- 2.2
+13.2
- 0.3
+454
+438
-2.1
-1.9
-2.3
-1.9
+5.9
-2.2
-1.2
-1.9
-2.3
-2.0
-1.8
-1.9
+377
+158
+280
+284
+199
+357
0.3
+142
+30,7
+313
+322
In Table 3 the changes in the peroxide values
(1 min.) for the various treatments and the un
treated check are summarized.
The results in Table 3 show that in the
sealed check sample there was a marked in*
crease in peroxides after six months followed
by a decrease to no peroxides after 12 months
storage. This same behavior was shown by
the full sample stored over water and the full
sample containing butylated hydroxyanisole.
The reducing action (ability to suppress per
oxide formation) of iron and zinc metal was
apparent in both the full and void samples.
Iron appeared to be the most effective in this
respect. Aluminum only reduced peroxides in
the full sample stored for six months. Sodium
bisulfite was the most effective reducing agent
of all treatments. As would be expected, per
oxide build-up in the samples open to air was
quite large. In many cases, however, like the un
treated check, the total peroxides decreased as
the storage period was extended. Most of the
full samples showed a decrease in peroxides
after both six and twelve months storage. Water
in the sealed sample caused increased amounts
of peroxides compared to the sealed, dried
(-|-Na2SO4) sample after six months storage.
Table 4
Treatment
Check
+ Iron
+ Aluminum
+ Zinc
samples.
dling or shipping d-limonene.
+250
+ 85.5
+257
+356
+ A12O3
+ Iron under CO2
+ Iron under N2
B.H.A. (50 p.p.m.)
+ Na2S2O5
+ Dowex 1
that would normally be encountered in han
12 months
Full
Void
0.3
+179
little effect on rotation decrease in the open
Of course these were rigorous condi
- 1.6
Void
- 1.5
+ Dowex 1
+ Water
tions and represent abuse far beyond anything
241
+ Ma2SO4 (Anhyd.)
+ AI2O3
+ Iron
+ Iron
B.H.A.
B.H.T.
under CO2
under N2
(50 p.p.m.)
(50 p.p.m.)
Change in Acid Number
(Initial value » 0.25)
6 months
12 months
Full
Void
Full
Void
+0.18
+0.03
+0.01
-0.10
+0.18
+0.18
-0.03
-0.05
-0.05
+0.18
-0.03
+0.18
+0.18
+5.7
+0.01
-0.01
+0.01
-0.16
+ 9.4
+ 6.4
+10.0
+ 2.4
+13.8
+ 9.1
+18.4
+ 2.7
+ 9.8
+2.9
+6.0
+1.7
+3.4
+5.4
+6.3
+2.1
+4.3
+0.13
-0.07
+0.01
-0.16
-0.08
+0.13
-0.01
+5.9
+5.6
-0.17
+0.01
...
+11.4
+ 4.9
FLORIDA STATE HORTICULTURAL SOCIETY, 1961
242
After six months in a sealed container, buty-
lated hydroxytoluene appeared to be more ef
fective in reducing peroxides than butylated
hydroxyanisole. In fact the latter showed no
peroxide reduction compared to the check.
The changes in acid number for the check
and all treatments are summarized in Table 4.
The results presented in Table 4 show that
like the peroxide value, the acid number of
the sealed check sample increased slightly after
six months and then decreased after twelve
months storage. All of the open samples
showed a marked increase in acid content. Iron
and zinc tended to decrease the acid numbers.
The very marked decrease in the open samples
containing zinc was due to the actual separation
of the zinc salt of an unknown acid. Colorless
crystals (prisms) of this salt formed on the sides
of the open bottles but not in the sealed sam
ples. Therefore this zinc acid salt must have
been formed by an oxidative process. There
was little difference between the wet and dried
samples of limonene. The samples stored over
iron with an atmosphere of carbon dioxide
showed higher acid numbers than the com
parable samples stored under nitrogen. This
may have occurred since carbon dioxide, as an
acid anhydride, can combine with moisture to
give carbonic acid. This would result in higher
acid numbers and could catalyze racemization.
Butylated hydroxytoluene showed greater sup
pression of acid formation than butylated
hydroxyanisole in the open samples stored
for one year.
Changes In the Optical Rotation of d-Llnonene Stored
in Full Drums with B.H.T.*
Change in Optical Rotation
3 months
Check
B.H.T. 25 p .p.m.
B.H.T. 50 p .p.m.
B.H.T.
100
p.p.m.
-0.58
-0.38
-0.08
+0.62
6 months
-0.58
-0.58
-0.18
+0.02
9 months
12 months
-0.70
-1.01
-0.50
-0.61
-0.08
-0.08
-0.21
-0.01
♦Butylated. Hydroxytoluene
Table 5 summarizes the changes in optical ro
tation which occurred in the sealed iron drums
of d-limonene, containing various added
amounts of butylated hydroxytoluene antioxidant, during storage in a commercial warehouse
for one year. There was no change in the
initial refractive index (1.4721) of the untreat
ed control or the samples containing 25, 50, and
100 p.p.m. of butylated hydroxytoluene. The
peroxide value of the initial samples (3.8) de
creased slightly during storage but all samples
had the same final value (2.1) after 12 months
storage. Also, the acid number, which was ini
tially 0.13, only increased slightly and all sam
ples had a value of 0.20 after one year. These
constants indicate that almost no autoxidation
has occurred in any of the samples. Hence only
the results showing the changes in optical ro
tation are included in Table 5.
The results presented in Table 5 show that
butylated hydroxytoluene prevented the normal
decrease in optical rotation with increasing stor
age time shown by the untreated check. Tjiis
beneficial effect was directly proportional to the
concentration of antioxidant and the sample
containing 100 p.p.m. showed no appreciable
change in rotation after 12 months storage. In
fact this same sample showed a definite increase
in optical rotation after three months. A similar
increase in rotation was observed after six
months storage in bottles for samples containing
either butylated hydroxyanisole or butylated
hydroxytoluene at 50 p.p.m. (Table 2)
Summary and Conclusion
The effect of various added materials on the
storage stability of d-limonene at room tempera
ture in the dark has been discussed. As found
by other investigators (4, 2, 3), there was almost
no change in the physical properties of most
of the samples stored in the absence of air.
Those
continually
exposed
to
air,
however,
showed a gradual increase in refractive in
dex, peroxide value and acid number as well
as a marked decrease in optical rotation. In
the absence of air, metals, particularly iron,
showed a reducing action evident from low
peroxide values and high optical rotations.
Reducing agents such as sodium bisulfite and
Dowex 1 resin were not suitable because of their
effect on the odor and flavor of the samples.
Storage for 12 months under an inert gas such
as nitrogen or in full containers with added
butylated hydroxytoluene
(50-100 p.p.m.)
was
found to preserve the original quality of the
limonene.
The peroxide values of the full untreated
controls and many of the treatments not ex
posed to air increased to a maximum after six
months storage and then decreased to almost
zero at the 12-month examination. For this
reason,
the authors do
not feel
that a per
oxide value gives a true picture of the quality
VINES AND OBERBACHER: CARBON DIOXIDE
243
of d-limonene. The optical rotation is still
the most sensitive and diagnostic test for purity.
sure valves and any suitable gas source, a con
It is recommended that for storage in drums
(55 gal.), the drums should be filled com
pletely, preferably with hot limonene, and 50100 p.p.m. of butylated hydroxytoluene added.
This amounts to 9-18 grams of B.H.T. per
400-pound drum. The cost of this treatment
is 2.2-4.4 cents per drum (.005 to .01c/lb.). Iron
tank. This system would allow for expansion
and contraction due to temperature changes
as well as for periodic additions and withdrawals
or structural steel is recommended for tank con
struction. Air should be scrupulously excluded
by purging with nitrogen (preferred) or car
bon dioxide gas. By the use of automatic pres
stant pressure should
be
maintained on
the
of limonene.
LITERATURE
CITED
1. Guenther, E. The Essential Oils 1: 263-265.
2. Konnerth, R. A. 1926. How varied Conditions Affect
Some Essential Oils. Amer. Perfumer and Essential Oil Rev.
3. Ogston, G. H., and Moore. 1923. Alteration of Lemon
Oil on Keeping. Perfumery and Essential Oil Rec. 14: 7.
4. Poore, H. D. 1932. Analyses and Compositions of Cali
fornia Lemon and Orange Oils. United States Department of
Agriculture, Technical Bulletin No. 241.
5. Snell F. D. and Biffen, F. M. 1944. Commercial Meth
ods of Analysis, First Edition, p. 354.
CHANGES IN CARBON DIOXIDE CONCENTRATIONS WITHIN FRUIT
AND CONTAINERS DURING STORAGE
H. M. Vines and M. F. Oberbacher
Florida Citrus Commission *
Lake Alfred
Citrus and many other fresh fruits and vege
tables are marketed in film bags (polyethylene,
cellophane, pliofilm). These bags are relatively
impermeable to carbon dioxide, oxygen and
water and water vapor, and under some condi
tions these physical characteristics can be used to
advantage. Under other conditions the use of
film bags for temporary storage may have a
disastrous effect on fruit respiration and hence
upon fruit storage life.
This is a report on the change in carbon di
oxide concentrations within film bags and in
side fruit during and after various storage con
ditions and packinghouse practices.
Literature Review
The values of modified atmosphere have been
recognized since 1920 when Kidd and West (5)
began their extensive studies on "gas storage"
of apples. As a result of early works, the storage
of fruits in other than normal concentrations
of gases has become as common a practice as has
reduced temperature storage. Both tend to slow
down metabolic changes of fruit by either a
build-up of an end metabolic product or by
slowing enzymatic changes as a result of suboptimal temperature.
Florida Agricultural Experiment Stations Journal Series No.
1 In cooperation with the Florida Citrus Experiment Station.
Lake Alfred, Florida.
Biale (1) reported optimum gas concentra
tions for lemon storage to be 10 per cent oxygen
and 5 per cent carbon dioxide.
Hopkins and Loucks (3) reported 54 per cent
stem-end rot of oranges stored three weeks in
sealed containers compared to 10 per cent in
open
containers;
however,
no data was pre
sented on carbon dioxide and oxygen levels.
Decay of Oranges stored in ventilated film
bags was reduced as the number of \-inch.
holes was increased from 8 to 64 (4). Hayward
et al. (2) also reported a decrease in decay
of oranges stored in film bags containing up
to 100 holes. There were indications that
more ventilation would further reduce decay;
however, the bursting strength of the film was
sharply weakened at the upper limit. No in
ternal gas analysis was included in either of
the above reports.
Materials and Methods
A Fisher Clinical Gas Partitioner, a gas chromatography apparatus with a recorder of 1 mv
for full scale deflection, was used for quantita
tive gas analysis.
Two sets of columns were compared. The
first set was made of silica gel and Molecular
Sieve 13X. The second set contained 30 per
cent hexamethylphosphoramide (HMPA) on
60-80 mesh Columnpak and a Molecular Sieve
5A. Figure 1 shows the recorded distribution
of gas peaks as they are. detected (A. Silica GelMolecular Sieve 13X and B. HMPA-Molecular
Sieve 5A). Gas samples were taken with a hypo
dermic needle and syringe, and injected into the