Horticulture Series No. 55-2
UNITED STATES DEPARTMENT OF AGRICULTURE
AGRICULTURAL MARKETING SERVICE
BIOLOGICAL SCIENCE BRANCH
UNIVERSITY OF FLORIDA
FLORIDA AGRICULTURAL EXPERIMENT STATION
PREPACKAGING CELERY AT PRODUCTION
AREA IN FLORIDA
Prepackaged celery in cellophane bags (left) and stretch-wrapped Pliofilm
H. A. Schomer, R. K. Showalter, R. E. Hardenburg
and B. D. Thompson
The study was carried out under the provisions of the Research and Marketing Act
of 1946 and was undertaken cooperatively by:
Florida Vegetable Prepackaging Council
Paul B. Dickman, President
LaMonte Graw, Secretary
United States Department of Agriculture
Agricultural Marketing Service
Biological Science Branch
H. A. Schomer, Senior Physiologist
R. E. Hardenburg, Horticulturist
Florida Agricultural Experiment Station
R. K. Showalter, Associate Horticulturist
B. D. Thompson, Assistant Horticulturist
Introduction ......................................... 5
Discoloration of Celery Butts ................... ................ 5
Effect of Temperature ................................. 6
Effects of Chemical Treatments ............................. 6
Effect of Length of Stem ................................ 6
Types of Film and Ventilation ............................... 8
Hydrocooling ........................................ 13
Shipping Tests ................... ..................... 18
Railway Car ...................................... 18
Refrigerated Truck ................... .............. .. 20
Summary and Conclusions .................................. ..... 22
INVESTIGATIONS )F REPACKAGING (ELERY 3N ?LORIDA
AND SHIPPING 'O NORTHERN MARKETS
In Florida during the spring of 1950 a number of problems in prepackaging celery
were studied at production areas. Celery is generally harvested and hauled to packing
houses where it is graded, trimmed, washed, packed into wirebound crates, and hydro-
cooledpreparatoryto shipping. After arrival at the terminal market, much of it is un-
packed and prepared for retail stores by washing again, retrimming and wrapping in
parchment. Recently a considerable quantity at the terminal markets has been wrapped
in transparent film or placed in bags of similar material.
If packaging could be performed in the packing houses at production areas, multiple
handling operations would be eliminated. Numerous problems, however, confront the
packer when he undertakes such a program. For example, the discolored butt end of
the stalk is usually removed by trimming just before the stalk is placed in retail
channels. This cannot be done, however, if the celery has been packaged at the pro-
duction area. Other problems needing study relate to the proper films for prepackaging
celery and the need for perforation, the comparative effectiveness of hydrocooling
before and after the celery has been prepackaged and the temperatures encountered in
shipping tests from production area to market.
These are amongthe problems that received attention during March and April of the
celery shipping season in Florida. The work was performed cooperatively by the Agri-
cultural Marketing Service of the U. S. Department of Agriculture and the Horticulture
Department of the Florida Agricultural Experiment Station. Full cooperation was also
extended by a number of commercial companies who furnished aid, materials, and
DISCOLORATION OF CELERY BUTTS
In the customary retail marketing the stem at the base of the stalk is freshly trim-
med before celery is displayed for sale. If trimming is not done daily, the cut surface
becomes dark and unattractive. Such darkening may reduce sales if the consumer con-
siders it a sign of aging or otherwise undesirable. Consequently, methods of prevent-
ing darkening are highly desirable, especially for prepackaged celery.
Atlantic Commission Company, Sanford, Florida and New York, N. Y.; Chase and Company, Sanford, Florida;
Hosack Engineering and Development Organization, Sanford, Florida; American Machinery Corp., Orlando,
Effect of Temperature
Ordinarily it would be expected that holding celery at a cold temperature would pre-
vent or at least retard darkening. Such, however, was not the case. At 350 F.,
darkening of butts usually became very intense. After 2 days, the vascular ring was
often black but the pith area remained light and usually turned light brown a few days
later. Discoloration, particularly of the vascular ring, was usually slightly more pro-
nounced in the packaged than in the non-packaged celery.
At 500F, the type of discoloration of both the packaged and the non-packaged
celerywas similar to that of non-packaged celery at 350, but the discoloration was less
At 700F., the vascular ring of the cut ends of the stalks turned brown while the
pith took on a lighter rusty brown color. The discoloration was considerably less in-
tense than at 350F.
Effects Of Chemical Treatments
Four compounds, each with anti-oxidant properties, were used in varying con-
centrations on the freshly cut butts to determine whether they would prevent darkening.
Ten stalks of Pascal celery, grown on sandy soil near Sanford, were used for each
treatment. The stalks, 4 dozen per crate size, were selected from the packing belt
after they had been graded, trimmed and washed. All the butts were cut off flat at the
base of the outer leaf petioles to provide smooth, uniform surfaces. The stalks were
then stood for 30 seconds in various chemical dips, after which half of each lot were
packaged in Pliofilm bags. The rest of the stalks were held as non-packaged controls.
All the lots were then packed in wirebound celery crates with parchment liners and
stored at 500F. for subsequent examinations after 2, 4, and 6 days.
The results of the inspection on the 6th day are summarized in Table 1. The
chemical dips caused similar injury on the packaged and the non-packaged celery.
Whendifferences did occur, they were due to chemical injury which appeared as water-
soaked spots or areas on the packaged celery, and as sunken, browned, dehydrated
areas on the non-packaged celery. The killed tissue of the latter had become dehydr-
ated when exposed to the atmosphere, while little or no drying occurred within the pack-
age. Consequently, in Table 1 nodistinction is made between the packaged and the non-
Three percent sodium bisulfite (NaHSO3) was the only treatment which controlled
discoloration of the cut surface, but it produced severe injury on the part of the stalk
immersed in the solution. When 3 percent sodium bisulfite was applied to the cut sur-
face with a cotton pad some injury developed near the base of the stalk.
Effect Of Length Of Stem
A test was made to determine whether less discoloration occurred on butts of
celery when the stems were trimmed much shorter than usual. Twenty stalks of Pascal
TABLE 1 Effect of Chemical Treatments in Preventing Butt Discoloration
of Pascal Celery During Storage at 500F. for 6 days.
1% Sodium Bisulfite
3% Sodium Bisulfite
1% Sodium Bisfulite
adjusted to pH 2.4
1% Tenox II 1/
0.1% Tenox H 1/
0.1% NDGA 2/
1% Gum Guiac
0.1% Gum Guiac
Brown to black vascular ring and darkened pith area.
Injury to submerged portion of stalk consisting of water-
soaked spots (packaged) or depressed brown spots (bulk).
Slightly less discoloration of butt than in check.
Severe stalk injury. Light brown vascular ring, pith white,
dried. Satisfactory control of butt discoloration, but in-
jury to stalk must be prevented.
Only slight reduction of discoloration
Severe injury to stalk. No control of butt discoloration.
Slight injury to stalk. Only slight reduction of discoloration.
Slight injury. Only slight reduction of discoloration.
Negligible reduction of discoloration.
Blue discoloration of vascular ring and pith.
Only slight reduction of discoloration over check.
1/ 20 parts of butylated hydroxyanisole, 6 parts of propyl gallate, and 4 parts of citric acid plus 70 parts of
celery were chosen for uniformity and half of them were trimmed flat across the stem,
as is commonly done, whereas the stems of the other ten were trimmed so short that
several of the outer leaf petioles were cut free of the stem. All were then packaged in
cellophane bags, half of each lot were sealed and the rest were perforated with four
1/4 inchholes to allow exchange of air. The packages were then placed in 500 storage
and examined after 2 and 4 days.
Some discoloration occurred in all lots. There was less darkening of the cut sur-
face in the sealed than in the ventilated packages, but celery will not remain edible after
long enclosure in tightly sealed packages. In the short-trimmed lots, considerable
darkening of the cut ends of the vascular bundles of the stems and petioles occurred and
the stalks did not appear as attractive as the regularly trimmed ones.
TYPES OF FILM AND VENTILATION
Some fresh vegetables and fruits are injured by storage in sealed packages. A
rapidly respiringproduct soon uses up all the available oxygen and then must derive its
energy from anaerobic respiration, or fermentation. This is also commonly referred
to as sub-oxidation. During normal respiration carbon dioxide is liberated and ac-
cumulates in the sealed package. Various other products are also liberated during
metabolism, and they too accumulate in the package. High concentrations of carbon
dioxide and of the various other volatile products of normal and anaerobic respiration
may cause development of undesirable odors and flavors in the packaged fruit or vege-
Although celery was found to be more tolerant to carbon dioxide than many other
vegetables, when held at room temperature it did not withstand long enclosure in a
package made of relatively impermeable film sealed air-tight. Packaging machines
seldom seal packages tightly, but if a few are tightly sealed, and the product develops
objectionable qualities, their distribution may do considerable harm to the industry.
Precautions should be taken to insure ventilation of each package.
In three tests unwrapped celery and celery packaged in perforated and sealed
packages were compared. In tests 1 and 2, Pascal celery grown on sandy soil in the
Sanford area was used. For the first test nine crates of celery, packed 4 dozen stalks
per crate, were takenfromthepacking line after the celery had been trimmed, washed,
andpacked. Three of the crates received no further treatment and were held as checks.
The celery in three other crates was prepackaged in 450 MSAT-86 cellophane bags and
closed by heat sealing. The celery in the last three crates was prepackaged in open-
top bags of the same type which had four 1/4-inch vents in the bottoms.
All the test crates were then sent through a commercial hydrocooler for precool-
ing. The resultant average temperatures were as follows: check (unwrapped) 45;
open-top bags 440 and sealed bags 53. One crate from each treatment was stored at
35, one at 500 and one at 700 for later examinations. The results are summarized
in Table 2. After 4 days, the lots stored at 700 had approached or reached the end of
their salable period (shelf-life). The salability of the check and of the open-bag lots
was still fair, while the sealed packages were considered unsalable, largely because
of undesirable odors in the bags. On the seventh day, all the 70 lots were unsalable.
The leaves were yellow and the stalks had yellowed considerably. Injured or bruised
areas on the stalks had darkened and numerous patches of soft rot occurred on the
stalk, especially on the leaf blades. In many of the sealed lots stalks were often badly
decayed and had a fermented and putrid odor, while soft rot had completely converted
others to a soft, watery mass of broken-down tissue.
TABLE 2. Comparison of Pascal Celery Non-packaged and in Open-Top and Sealed MSAT
Cellophane Bags after Storage at 350, 500, and 700F.
Storage Temperature Relative Humidity
Time in 350 85% 50o 80% 700 36%
Storage Measure of Quality Open-Top Sealed Open-Top Sealed Open-Top Sealed
Check Bag Bag Check Bag Bag Check Bag Bag
4 Days Greenness of leaves Excellent Excellent Excellent Good Excellent Good Fair Fair Fair to good
Greenness of stalk Excellent Excellent Excellent Excellent Excellent Excellent Fair Fair Fair to good
Freedom from stalk Excellent Excellent Excellent Excellent Excellent Excellent Excellent Excellent Excellent
Freedom from decay Excellent Excellent Excellent Excellent Excellent Excellent Fair to good Fair Fair
Odor Excellent Excellent Excellent Excellent Excellent Excellent Good Good Very poor
Salability Excellent Excellent Excellent Good Good Excellent Fair Fair Poor
7 Days Greenness of leaves Excellent Excellent Excellent Good Fair to Fair to Poor Poor Poor
Greenness of stalk Excellent Excellent Excellent Good Good Good Fair to good Fair Fair
Freedom from stalk
Freedom from decay Excellent Excellent Excellent Fair Fair Fair Poor Poor to very Very poor
Odor Excellent Excellent Excellent Excellent Excellent Excellent Fair Poor Very poor 1/
Salability Excellent Excellent Excellent Good Good Good Poor Poor to very Very poor
10 Days Greenness of leaves Good Good Good Fair Poor Poor 2/ 2/ 2/ 2/
Greenness of stalk Excellent Good Good Good Good Good
Freedom from stalk Good Good Good Fair Good Good
Freedom from decay Good Good Good Fair Poor to fair Poor to fair
Odor Good Good Good Good Poor Poor
Salability Good Good Good Fair Poor to fair Poor
12 Days Greenness of leaves Good Good Good
Greenness of stalk Good Good Good
Freedom from stalk Fair Fair Fair
Freedom from decay Good Good Good
Odor Good Fair Fair
Salability Good Good Good
1/ Severe soft rot and putrid odor, fermented.
2/ All 70o lots discarded because of severe decay and black-heart.
Celery in the three lots held at 500 was still in fair to good condition on the seventh
day, although the leaves of the packaged lots had yellowed considerably more than those
of the non-packaged lots. On the tenth day the unwrapped check celery was the best of
the three lots and it was scored as fair in salability. The leaves of the packaged celery
were yellow and contained areas of soft rot and objectionable. odors were present in the
sealedpackages. The celery stored at 350 was still in good condition at the 12-day in-
spection, and there was little difference in the three lots.
It should be pointed out that decay generally appears to be more objectionable on
packaged celery than on non-packaged celery. Even small decayed areas of the leaves
become very conspicuous and objectionable in the package because of the wetness of
these areas, especially when they are in contact with the film. Similar decaying areas
may be as numerous in the unpackaged celery, but they usually dry and shrivel in the
air and are less conspicuous than in a moist package.
The butts of the celery stalks discolored severely in the check and open-bag lots,
but discoloration was slight on the stalks in sealed packages. However, the bags used
were colored red on the closed ends, and discoloration did not show until the stalks were
removed from the bags. At the last examination the cellophane had become limp and
did not appear fresh and crisp, and several of the bags were torn.
Test 2 was also made on Pascal celeryfrom Sanford, Florida, as in Test 1. Celery
was stored in cellophane bags at 50 for 4 days and then at 700 for 3 additional days
before examination. Whenthe bags were opened, the celery in sealed bags had an off-
odor, and its flavor was insipid and slightly off. In the perforated bags the celery had
a normal to slightly stale odor and the flavor was normal.
In Test 3 five crates of Golden celery from Zellwood, Florida, 4 dozen stalks per
crate, were selected from the regular commercial pack. The stalks were trimmed
and cutto 15-inch length and the celery was then divided into 7 lots of 30 stalks each for
separate treatment. One lot was held as the unwrapped check while the other six were
wrapped with three different films, both sealed and perforated (two 1/4-inch holes per
package). The films used were 300 MSAT-86 cellophane, 80 FM-1 Pliofilm (rubber
hydrochloride) and P912-88 Lumarith (cellulose acetate). Each stalk of celery was
placed on a sulfite paperboard slab (14 x 3 1/2 inches), overwrapped with the film,
sealed, and then the package was weighed.
Each of the 7 lots was divided equally into 3 groups for storage at 350, 500 and
room temperature. The groups for 350 and 50 storage were packed in crates lined
with parchment and stored. The third group was spread out as a display on tables in
the laboratory. During the holding period, the laboratory temperature ranged from
600 to 800 and averaged about 74. The relative humidities of the 350, 500 and 740
rooms were 85, 80 and 36 percent respectively.
Results of the test are summarized in Table 3. On the fourth day, the non-wrapp-
ed and Lumarith-wrapped lots held at room temperature had lost 11.9 and 7.6 percent
TABLE 3. Losses in Weight of Golden Celery, Non-packaged and Packaged in Lumarith, Pliofilm
and Cellophane. 1/
4DaysTotalStorage 2/ 7 Days Total Storage 2/ 9 Days Total Storage 2/
4 Days 500 4 Days 350 4 Days 500 4 Days 350
Type of Room 500 350 Room 3 Days 3 Days Room /5 Days /5 Days
Package Temp. Temp. at at Temp. at at
Room Temp. Room Temp. Room Temp. Room. Temp.
% % %% % % % % %
Non-packaged check 11.9 2.8 2.2 19.9 11.3 11.6 29.3 19.3 19.4
Lumarith P 912-88 7.6 1.6 1.1 14.7 7.3 6.7 26.3 12.8 11.8
Pliofilm FM-1 1.8 0.7 0.4 3.7 1.8 1.6 7.2 3.3 3.4
Cellophane 1.0 0.3 0.1 1.4 0.8 0.7 5.2 2.0 1.8
L. S. D. 5% 1.0 0.4 1.2 1.8 0.9 1.0 5.5 1.6 1.6
L. S. D. 1% 1.3 0.5 1.5 2.5 1.2 1.4 7.5 2.1 2.2
I/ Values are averages of 10 replicate stalks for each treatment.
2/ The relative humidity was 36 percent in room temperature storage (Average 740F.), 80 percent in 500
storage and 85 percent in 350 storage.
weight respectively and were considered too wilted to be salable. Losses from Pliofilm
and cellophane packages were 1. 8 and 1. 0 percent respectively; the difference between
these two moistureproof films was not statistically significant at the 5 percent level.
The 350 and 500 lots were in very good condition. In the packages examined, there were
no off-odors or off-flavors in any of the lots, nor were there noticeable differences in
After a 4-day storage, the two lots from 35 and 50 degrees were spread out on
laboratory tables where the average temperature was 740 F, and were examined after
an additional 3 and 5 days. At these examinations, the main difference between lots was
the wilting of the non-wrapped and Lumarith-wrapped stalks in contrast to those wrapp-
ed in Pliofilm and moistureproof cellophane. Since this was Golden celery, little or no
chlorophyll was present and therefore yellowing was not as objectionable as it was in
Pascal celery. Bruises on the stalk appeared more objectionable in the wrapped than
in the non-wrapped lots because those in the packages were wet and decay appeared to
be more active.
At the final examination after 4 days in cold storage and 5 days at room temper-
ature, some of the cellophane packages were still attractive, but the lot as a whole was
considered unsalable. The difference in weight loss in the cellophane and Pliofilm pack-
ages was not statistically significant. This lot of Golden celery stood up very well under
the conditions of the test and did not show the extent of deterioration found in lots of
In a subsequent test, commercial crates of non-packaged and stretch-wrapped
Pascal celery were placed in rooms at 35, 50, and 70 degrees and 85, 80, and 68 per-
cent relative humidity respectively. The celery was not spread out as a display, but
was held in parchment-lined crates while in storage. The celery was examined at
intervals up to 12 days and was weighed at each examination. The losses in weight
are summarized in Table 4. The values represent losses which might be expected from
holding celery at these storage temperatures. The greater loss of moisture from the
non-packaged celery were evidenced by limpness of the stalks as they were handled.
From these film tests it was concluded that the principal effect of the film pack-
age on celery quality was retardation of moisture loss. This varied among films ac-
cordingto their permeability to moisture vapor. Lumarith, which is very permeable,
only slightly retarded loss of weight due to evaporation. Consequently, condensation
rarelyformed within this package and therefore this film generally appeared dry, crisp,
and attractive. Little protection from wilting was given the produce. Stretch-wrapped
FM-1 Pliofilm and MSAT cellophane were highly resistant to the passage of moisture
vapor, there was little weight loss from the packages, and the enclosed produce re-
tained its turgidity. The high humidity of the moistureproof package encouraged decay
development unless temperatures in the package were low enough to inhibit growth of
Celery should not be sealed in air-tight packages, or off-flavors and odors will
develop. Small perforations were adequate for desired air passage through the films,
and they did not cause a significant moisture loss.
TABLE 4. Losses in Weight of Prepackaged (Stretch-wrapped in Pliofilm) and Non-
packaged Celery Held in Crates at 350, 500 and 70oF. for 2 to 12 Days.
Prepackaged (stretch-wrapped) Non-Packaged
in Storage Temperature Percent Relative Humidity
350 85% 500 -80% 700 -68% 350 -85% 500 -80% 700 68%
% % % % % %
2 Days 0.1 0.2 0.4 2.7 2.9 3.1
4 Days 0.1 0.3 0.6 4.0 4.5 5.2
6 Days 0.2 0.3 0.5 1/ 4.2 5.3 6.92/
9 Days 0.7 0.9 6.6 8.6
12 Days 0.5 1.3 9.0 12.4
1/ Considered unsalable due to yellowing and sliminess of leaves.
2/ Considered salable at markdown. Leaves yellowed as with packaged celery, but decayed areas dry and
not as objectionable as in packages.
After celery is packed in crates, it is generally precooled by passing it through a
hydrocooler in which refrigerated water showers down over the tops of the crates as
theypass through the cooler tank on a moving belt. The crates are about 2/3 immersed
in cold water of the hydrocooler tanks during the cooling period. Tests were made to
determine whether celery stalks prepackaged in cellophane bags and stretch-wrapped
in Pliofilm could be passed through the hydrocooler without damaging the packages or
making them unattractive and also to find the effect of the package on the rate of cool-
Temperatures were taken at the start of hydrocooling and 30 minutes later as the
crates emerged from the cooler. Insertion thermometers always placed in the stem
or butt of the celery stalk were used. Crates packed with 4 dozen stalks were used in
all the temperature studies. For the non-packaged celery, crates lined with parch-
ment on top, bottom and ends and for the prepackaged stalks, liners were also placed
around the sides. Averages of the temperatures obtained are summarized in Table 5.
These data show that the sealed or stretch-wrapped films reduced the average
amount of cooling of the celery 70 to 110 F. If the film bags were left open at the top,
however, cooling was as efficient as in the regular pack.
TABLE 5. The Influence of Prepackaging on Hydrocooling Celery in 330F. Water. 1/
1/ All celery placed in wirebound crates before cooling.
2/ 450 MSAT-86 cellophane open-topped bags with four 1/4-inch perforations in the bottoms. Packed in
crates with perforated end down in hydrocooler.
3/ 450 MSAT-86 cellophane bags, sealed, non-perforated.
None of the packages of stretch-wrapped celery examined in these tests was found
tobewater tight, and hydrocooler water entered the package while it was being cooled.
However, it generally drained satisfactorily, and the packages did not have an objection-
able amount of water in them the day following hydrocooling.
When celerywas packed in crates the stalks of each layer were oriented in the same
direction so that all the tops pointed to one side of the crate and all the butts to the other.
Alternate layers were oriented in opposite directions. When the crates were placed on
the moving belt of the hydrocooler, they were laid on one side so that the stalks were
standing vertically. Consequently, half of the tops pointed downward and were sub-
merged while the other half pointed upward and were above the level of the hydrocooler
water, the butt end being submerged.
While the temperatures were being taken, it was observed that submerged stalks
cooled more than those which were subjected to the shower only. The wooden slats of
the uppermost side of the crate obviously interfered with the free flow of water through
the stalks and reduced the efficiency of cooling.
It was also found that the absence of crate liners allowed 1 to 3 degrees more cool-
ing in the non-packaged and prepackaged crates except for the portions of the prepack-
aged stalks that were not submerged in the cooling water but were cooled by shower
only (Table 6). These unsubmerged portions of stretch-wrapped stalks in crates with-
out liners cooled 14 degrees as compared with only 7 in the crates with liners. A
crate laid on its bottom instead of on one side, floated, and cooled less satisfactorily
than crates cooled by the regular method (Test 5, Table 6).
During the 30 minutes in the hydrocooling tunnel, the non-packaged celery in the
regular commercial pack was cooled 24 to 26 degrees. The submerged portion of the
celery cooled two degrees more than the non-submerged portion. The submerged
portion of the stretch-wrapped celery cooled 240 and the non-submerged portion cooled
A better procedure for cooling prepackaged celery was to precool the bulk celery
and then send it directly through the packaging line. This was further demonstrated by
a test in which rates of cooling of 5 crates of celery, each treated differently, were
compared. One crate was prepackaged after hydrocooling, a second crate was pre-
packaged before hydrocooling and a third was prepackaged and not hydrocooled. In
addition, twonon-prepackaged crates were included, one was hydrocooled and the other
was not hydrocooled.
All of the crates of celery were placed in a 370F. storage room. Each crate was
buffered on all sides by celery of treatments corresponding to those of the test crates.
Air was circulated by fans, with the movement in the region of the test package being
about 170 feet per minute.
Two thermocouples were placed in each test crate, one in a celery stalk near the
TABLE 6. Temperatures of Submerged and Unsubmerged Portions of Celery Stalks
after Hydrocooling in Crates in 330 F Water.
Position Temperature Temperature
No. Type of Package in before after Degr
Hydrocooler Hydrocooling Hydrocooling Cooled
F F OF
1 Non-packaged with crate liners Submerged 71 45 26
Above water 71 47 24
Stretch-wrapped, Pliofilm with crate Submerged 71 47 24
liners Above water 71 64 7
2 Non-packaged, no crate liners Submerged 71 42 29
Above water 71 48 23
3 Stretch-wrapped, Pliofilm Submerged 71 46 25
no crate liners Above water 71 57 14
4 Stretch-wrapped, Pliofilm top and Submerged 71 47 24
bottom liners, no side liners Above water 71 55 16
5 Stretch-wrapped, Pliofilm crate bottom Submerged 71 51 20
down, with crate liners Above water 71 63 8
middle of the crate and the other one in the more exposed top layer. Records were
taken at regular intervals during the next 30 hours. The results are summarized
graphically in Figure 2. Points on the graph represent averages of the temperature
in the two positions in each crate. Both non-precooled lots had an initial temperature
of 700F. when placed in storage. After 30 hours the prepackaged celery had cooled to
45.8 and the bulk crate had cooled to 43. 2. The lot that was precooled after it was
prepackaged was placed in storage at a temperature of 65. 4 and it had cooled to 46 .50
in 10 hours and to 39.10 in 30 hours. The more rapid cooling of this lot was undoubtedly
partlydue to temperature equalization within the stalks. Both thermocouples had been
placed inadvertently in stem ends of stalks which were not submerged in the cooling
water duringhydrocooling. Judgingby results of the other precooling tests the temper-
ature of the submerged portions of the stalks was approximately 480 in which case the
average tem erature of the celery when placed in storage was actually about 520 in-
stead of 65.4 The celery that was hydrocooled and then prepackaged had a temper-
ature of 45. 50 after packaging. It was placed in cold storage when it reached 40.20
after 10 hours and gradually cooled to 38. 2 during the 30 hours it was stored. The
hydrocooled non-packaged crate reached the storage room at 51.60 which was relative-
ly high largely because of the 59.5 degree temperature of one of the sample stalks.
However, after 10 hours the average temperature had dropped below 400 and after 30
hours it was 36. 80, the lowest of all the test crates.
That hydrocooling before prepackaging was much more effective than hydrocooling
after prepacking was demonstrated by these tests. The lot precooled after stretch-
wrapping required 12 hours of cold storage at 370 to reach the same temperature as
that whichprevailed immediately after stretch-wrapping the lot precooled before it was
12 16 20
Figure 2. Rates of cooling of celery in cold storage after the following packinghouse treatments:
Prepackaged after hydrocooling
Prepackaged before hydrocooling
Prepackaged, no hydrocooling
Non-prepackaged, no hydrocooling
In order to follow prepackaged celery through regular distribution channels test
crates were placed in a railway car load and a trailer truck load and examined period-
ically after they reached terminal markets.
Seventy-five crates of prepackaged Pascal celery were included in a load of 352
crates shipped from Sanford, Florida to New York, N. Y. Fifty of the prepackaged
crates contained stalks stretch-wrapped with Pliofilm and 25 crates were filled with
celery sealed in perforated cellophane bags. The packaging was done with commerical
A circular saw (Figure 3) was used to trim the stalks to a required length before
they were stretch-wrapped with 80 FF Pliofilm at a speed of 4 dozen stalks or one
crate per minute (Figure 4). At this speed the capacity of the machine was about one
carload per day.
The bagging machine (Figure 5) was not equipped with feeding line or heat sealing
device. Its capacity was about 16 to 18 bags per minute, which was too slow for large
scale operation, but it appeared to be adapted to retail store or small chain store pre-
The rail car used was equipped with fans beneath the floor racks. All the crates
had been hydrocooled after they were packaged and the temperatures averaged 490F.
for the prepackaged and 410 for the non-packaged celery. Four recording thermo-
meters were placed in test crates after they were hydrocooled: one in the center of
each of 2 crates containing stretch-wrapped celery and one in each of 2 crates of non-
packaged celery (regular pack). Allthe testpackages were loaded at the quarter-length
position in the car. Those with the recording thermometers were placed in middle
rows, with one of the prepackaged and one regular pack in the top layer and one of each
in the bottom layer. Since the carload was to stand on the siding overnight, the fans
were run with portable motors for the 18 hours that the car was stationary. During
that time, 2700 lbs. of ice was used, as determined by the amount required to fill the
bunkers after the fans were stopped.
Temperatures taken with insertion thermometers after this additional precooling
in the car showed that the commercial non-packaged celery was 36 F while the pre-
packaged celerywas 39 to40. The thermograph records for the test crates from time
of loading or unloading are given in Figure 6. The car was unloaded in New York on
the 6th day after loading and the celery was examined. Two non-packaged and 2 pre-
packaged crates were taken to a laboratory where one crate of each kind was held at
68o to 700 for 7 days and another at 41Pto 420 for 14 days. The remainder of the pre-
packaged lots were marketed without difficulty through regular retail outlets.
The condition of all lots of celery was very good at time of unloading the car.
* The authors gratefully acknowledge the assistance of B. A. Friedman, J. Kaufman, H. Hruschka and W. A.
Radspinner, Quality Maintenance and Improvement Section, Agricultural Marketing Service, U. S. Department
of Agriculture, New York City for conducting the holding tests in the terminal market.
Figure 3. -
Trimming Celery Stalks to re-
quired Length with a Circular
Saw Prior to Stretch-Wrapping
Figure 4. -
Stretch-Wrapping Machine which
Sealed Entire Stalk in Pliofilm.
- Machine for Packaging Celery in
TOP LA Y ER
4 -, ,- - -
,, -, -, -,. .
---- r -. .---
".-= -/- - "- __
N 0 N-
Temperatures of the crates of
celery in the top layer averaged
420F, while they averaged 37.50
in the bottom layer. Celery in all
lots was fresh, green and crisp,
and no visible decay was found in
any of the crates examined. The
butts of all the stalks were in-
tensely darkened. This discolor-
ation was concealed by the colored
portion of the cellophane bags,
but was apparent through the Plio-
film stretch-wrap. Approximate-
ly one-fourth of the Pliofilm
stretch-wraps had partially open
seams (23 out of 96). The cello-
phane bags formed a much looser
wrap, but visibility through the
filmwas good because of the high
transparency of the cellophane.
I 2 3 4 5 6 7
TIME (DAYS) The results of subsequent
examinations are summarized in
Figure 6. Temperature Records of Prepackaged and Non- shel-life f all lots
Table 7. The shelf-life of all lots
packaged Crates of Celery in the Quarter- held at 68to 70F after the ship-
length Position in a Refrigerator Car from San- held at 68 to 70F after the
ford, Florida to New York, N. Y. pingperiodwas about days, after
which deterioration was rapid. The celery held at 41to 420 was still salable after 14
days. At this time, celery in the packaged lots appeared greener, fresher, and more
attractive than that in the non-packaged ones.
About the same results were obtained in the trailer truck shipping test in which 16
fiberboard cartons of prepackaged celery from Sarasota, Florida were included in a
load of prepackaged sweet corn. Half of the celery was hydrocooled from 740 to 440
before it was packaged. After being hydrocooled it was placed in 14-inch long non-
waxed cardboard trays overwrapped by hand with 300 MSAT-86 cellophane. The other
half of the celery was prepackaged in the same way, but was not hydrocooled. Twelve
packages were packed into each of the 16 fiberboard shipping cartons which had num-
erous holes for ventilation. They were then loaded into a trailer with prepackaged
sweet corn. The trailer was equipped with a mechanical refrigeration unit and tem-
peratures of 350 to 400 were maintained during the 32-hour transit period to Washing-
ton, D. C.
Condition of the celery was very good upon arrival. Eight cartons stored at 700
Table 7. Condition of Prepackaged and Non-packaged Celery Stored at Two Temperatures after
a 5-Day Shipping Period from Sanford, Florida to New York, N. Y.
Storage 3-Day Storage Period 5-Day Storage Period
and Type of Decay 1/ Decay I/
Package Leaf Color (soft rot) Salability / Leaf Color ot) Salability 1/
Temperature 6870F., Relative Humidity 86-90 Percent 2/
Non-packaged in crates Light green and 2 slight 46 salable Mostly yellow 7 slight 28 salable
turning yellow 2 borderline 13 moderate 7 borderline
Stretch-wrapped Light green 4 slight 41 salable Mostly yellow 6 slight 24 salable
Pliofilm in crates 3 moderate 4 borderline 15 moderate 6 borderline
3 unsalable 15 unsalable
Cellophane bagged in Light green 2 slight 46 salable Mostly turning 6 slight 34 salable
crates 2 border- 88 moderate 6 borderline
line 8 unsalable
7-Day Storage Period 14-Day Storage Period
Temperature 412420F., Relative Humidity 86-90 Percent
Non-packaged in crates Green None All salable Light green and None All salable
Stretch-wrapped Pliofilm Green None 47 salable Green to yellow 1 moderate 47 salable
in crates 1 borderline Mostly light green 1 unsalable
Cellophane bagged in Green None All salable Green to light 1 slight 47 salable
crates green 1 borderline
1/ Numbers indicate stalks in a 4-dozen-stalk crate.
2/ After 7 days' storage at 68-70o all packages were unsalable because of yellowed tops and excess decay.
and eight at 350 were examined at intervals. After 5 days at 700, the celery had about
reached the end of its shelf-life. That held at 350 was still in good condition after 14
days, after which it was placed at 700 to determine the length of time it could be held
satisfactorily. It too reached the end of its shelf-life after 5 days at 700.
At no time was it possible to distinguish between the non-precooled and the hydro-
cooled lots in this truck shipping test. However, cooling of the eight cartons of celery
which had not been hydrocooled was undoubtedly rapid after they were placed in the re-
frigerated trailer with the precooled sweet corn. Consequently, the test celery would
notbe comparable with that in an entire load of non-precooled celery, which would un-
doubtedly cool very slowly and would probably be inferior in quality at destination to a
load which had been precooled before shipment.
SUMMARY AND CONCLUSIONS
Celery that was prepackaged in Florida and shipped to northern markets by rail
and truck arrived there in good condition. Celery butts are usually trimmed just prior
to retail display in order to eliminate the dark discolored surface, but trimming is im-
possible if the celery is prepackaged at production area. No entirely satisfactory
chemical treatment was found for preventing discoloration. When 3 percent sodium bi-
sulfite was used butt darkening was not objectionable, but it caused injury to other
portions of stalk where contacted. More intense darkening of cut surfaces, especially
of the vascular ring, occurred at 350F. than at 500 or 700.
Moistureproof films of cellophane (MSAT-86) and Pliofilm (Stretch-wrapped FM-1)
greatly reduced moisture loss from celery. Ventilation of packages was found to be
necessary. Highhumidityin the packages encourages development of decay and makes
damaged or diseased areas appear more objectionable because of the wet surfaces which
are often in contact with the package film. Similar area on unwrapped stalks become
dried and shriveled and appear to be more superficial. Thus, only good quality celery
free from bruises and diseases should be selected for prepackaging at areas distant
frommarket. Lumarith P-912 allowedthe celeryto lose moisture at a rapid rate inter-
mediate between the loss of unwrapped celery and that wrapped in moistureproof films.
Therefore, itis less desirable as a wrapping material for celery which will have a long
Refrigeration is important for prepackaged celery because spoilage will occur rap-
idly at warm temperatures and the high relative humidities in moistureproof films.
Shelf-life of packaged or non-packaged celery of different varieties and from different
areas varies considerably, but it is approximately 2 to 5 days at 800, 4 to 8 days at
700, 7 to 10 days at 500. 9 to 14 days at 400 and 14 to 30 days at 320. Hydrocooling
celery before it is packaged is more efficient than hydrocooling after packaging, but
the latter method may be used without damaging the package and may be more practic-
able because of packing house arrangement.
The principal effect of prepackaging in films was reduction of moisture loss and
wilting. Prepackaging did not retard discoloration of bruised or cut areas, reduce
development of decay, or maintain the green color of Pascal celery longer than that
of non-packaged celery. A number of economic factors need to be studied before final
recommendations canbe made on production area prepackaging of celery. Research on
other phases not included in this study have shown numerous advantages in handling and
marketing prepackaged vegetables. On this basis it can be assumed that waste and
breakage of stalks in the stores due to handling by customers would be greatly reduced
and the sanitary aspect of sealed packages appeals to a great many customers. Re-
tailers who package celery before displaying it for sale could reduce the labor and ex-
pense of multiple handling operations by obtaining celery prepackaged at the production