Group Title: Circular Florida Cooperative Extension Service
Title: Precooling strawberries
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Title: Precooling strawberries
Series Title: Circular Florida Cooperative Extension Service
Physical Description: 8 p. : ill. ; 28 cm.
Language: English
Creator: Talbot, Michael T ( Michael Thomas ), 1948-
Chau, Khe V
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1991
Subject: Strawberries -- Precooling   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Includes bibliographical references.
Statement of Responsibility: Michael T. Talbot and Khe V. Chau.
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Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA6935
ltuf - AHR4416
oclc - 24153203
alephbibnum - 001639392
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Circular 942

Precooling strawberries

Michael T. Talbot and Khe V. Chau

Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida
John T. Woeste, dean

V' ij~i~

Michael T. Talbot and Khe V. Chau are assistant professor and professor, respectively, Department of Agricultural Engineering,
IFAS, University of Florida, Gainesville, FL 32611

Strawberries are one of the most delicate and
highly perishable fruits. Their nonclimacteric
physiological characteristics dictate that they must
be harvested in an essentially ripe condition. The
quality of fresh strawberries depends on their
maturity and appearance (red color intensity and
distribution, fruit size and shape, freedom from
defects and decay), firmness, and flavor (deter-
mined by amounts of sugars, organic acids, pheno-
lics, and characteristic aroma volatiles). The
principal decays likely to affect strawberries are
gray-mold and Rhizopus rots. Even a small
amount of infestation can quickly spread through-
out an entire package.
The most important factors in attaining and
maintaining good quality are harvesting at the
fully-ripe stage, avoiding physical injuries during
all handling steps, enforcing strict quality control
procedures, prompt precooling, and providing
proper temperature and relative humidity during
transport and handling at destination.
Loss of strawberry quality is not acceptable to
consumers. The parameters which largely deter-
mine quality cause the quality to decrease rapidly
at ambient temperatures; therefore, proper tem-
perature management is important. Proper tem-
perature management of strawberries begins with
precooling (rapid removal of field heat) from field
temperatures which can be as high as 30C (86F).
Rapid removal of field heat is critical to retard
deterioration of strawberries. The recommendation
for maximum quality retention of strawberries is
precooling to near 0C (320F) within 1 hour of
harvest and maintaining at 0C (320F) throughout
the marketing channels [3]1. For commercial
strawberry operations in Florida, cooling to this
ideal criterion is approached (in practice straw-
berries are cooled and shipped at 20 to 5C (350 to
41F)) but depends on various factors, including
volume of strawberries handled, cooling and
handling equipment availability and capability,
economics, energy, and market conditions.
Strawberries are an important crop in the
United States. Nationally, Florida follows Califor-
nia in fresh strawberry production with an average
annual value of $68.4 million for the last 5 years
[2]. Fresh strawberry yields in Florida averaged
1,867 flats per acre with 9.5 million flats packed off
5.1 thousand acres, with a season average f.o.b. of

'Numbers in brackets refer to cited references.

$7.20 per flat over the last 5 years, with record
crops the last two years.
Strawberry growers and packers in Florida are
aware of the value of their crop and of the quality
demands of consumers. They are using good
temperature management but are interested in
additional improvements. Most strawberries in
Florida are forced-air cooled in fiberboard flats
stacked on pallets. Room cooling of strawberries is
not an acceptable precooling method nor is reliance
on refrigerated trucks during transit.
This publication presents quality parameters,
cooling requirements, cooling methods, and man-
agement guidelines for maintaining the quality of
Florida strawberries. Studies conducted to estab-
lish the relationship between cooling rate and air
flow rate and the effects of new vent hole designs
on cooling rates of strawberries are discussed.
Management guidelines or recommendations to the
packinghouse operators concerning possible system
performance improvements are presented, such as
increasing resident time within the forced-air
precooler to achieve better cooling or lowering the
cold room temperature to prevent warming of
precooled strawberries.

Quality parameters
United States grade standards for strawberries
allow for three grades: U.S. 1, Combination, and
U.S. 2. The principal grade is U.S. 1. Although
Florida shippers may not use U.S. grades for
shipping, these, or similar grades, are used for
inspection purposes at destination. Therefore, all
growers should be aware of the grade specifica-
tions. If the strawberries do not meet the grade
standards when they are picked, then it is simply
impossible for them to make grade at destination.
Strawberries of one variety or with similar
varietal characteristics with the cap (calyx) at-
tached, which are firm, not overripe or undevel-
oped, and which are free from mold or decay and
free from damage caused by dirt, moisture, foreign
matter, disease, insects, mechanical or other means
are U.S. 1. Each strawberry must have at least 3/4
of its surface showing a pink or red color and the
minimum diameter of each strawberry must not be
less than 3/4 inch.

Cooling requirements
Understanding of the cooling requirements of
horticultural commodities requires an adequate
knowledge of their biological responses. Fresh

horticultural crops are living organisms, carrying
on many biological processes essential to the
maintenance of life. They must remain alive and
healthy until processed or consumed. Energy that
is needed for these life processes comes from the
food reserves that accumulated while the commodi-
ties were still attached to the plant [4].
Respiration is the process by which the food
reserves are converted to energy. Through a
complex sequence of steps, stored food reserves
(sugars and starches) are converted to organic acids
and subsequently to simple carbon compounds.
Oxygen from the surrounding air is used in the
process while carbon dioxide is released. Some of
the energy is used to maintain the life processes
while excess energy is released in the form of heat,
called "vital heat." This heat must be considered in
the temperature management program.
The respiration rate varies with commodity, in
addition to variety, maturity or stage of ripeness,
injuries, temperature, and other stress related
factors. Strawberries have a high respiration rate,
12 to 18 mg CO/kg-h (2,700 to 3,900 Btu per ton
per day) at 0C (32F) [3]. The major determinate of
respiration activity is the product temperature.
Since the final result of respiration activity is
product deterioration and senescence, achieving as
low a respiration rate as possible is desirable. For
each 10C (180F) temperature increase, respiration
activity increases by a factor 2 to 4 [3]. For ex-
ample, the respiration of strawberries at 10C
(50F) is 49 to 95 mg CO/kg-h (10,800 to 20,900
Btu per ton per day), four to five times greater than
at 0C (320F). Therefore, strawberries must be
rapidly precooled to slow their metabolism (physi-
ological deterioration) in order to provide maximum
quality and storage life for shipping and handling
Strawberries are not a chilling-sensitive crop
(crops which must be stored at temperatures
generally above 10C (50F) to prevent physiological
damage). Therefore, they can be safely cooled to a
temperature of C (320F). The recommendation
listed in the introduction indicated the requirement
of precooling to near 0C (32F) within 1 hour of
harvest and maintaining at 0C (32F) throughout
the marketing channels. The required rate of
cooling during precooling can be expressed in terms
of the half-cooling time or the 7/8-cooling time.
These values remain constant for the particular set
of precooling conditions from which they are
determined. The half-cooling time is the time
required to remove one half of the temperature
difference between the initial pulp temperature and

the cooling medium temperature. For commercial
precooling, it is recommended [6] that 7/8 of the
difference between the pulp temperature and the
cooling medium temperature be removed prior to
storage and transport. Under ideal circumstances
the 7/8 cooling time is equal to about three times
the amount of the half-cooling time.
For example, if strawberries are harvested at
30C (860F) and cooled in a forced-air cooler with ar
air temperature of 1. 1C (340F) the half-cooling tim
would be the time required to remove 14.5C (26F)
or for the strawberries to cool to 15.50C (600F)3. Foi
the same situation, the 7/8-cooling time would be
the time required to remove 25.30C (45.5F)4 or for
the strawberries to cool to 4.7C (40.50F). By
developing a precooling schedule [6] the 7/8-cooling
time could be established. Therefore after precool-
ing for a time period equal to the 7/8-cooling time o
by determining the pulp temperature was 4.7C
(40.5"F)5, the strawberries would be removed from
the precooler and moved to cold storage for addi-
tional cooling to 0C (320F).
Cooling schedules should be utilized to maximiz(
efficiency. Use of a schedule allows cooling times t(
be adjusted based on the initial temperature of the
berries. Strawberries coming from the field at
18.3C (650F) do not need to be cooled for as long as
fruits arriving at 32.2C (900F). Leaving strawber-
ries in the forced-air cooler longer than necessary
can lead to undesirable water loss because of rapid
air movement. On the other hand, inadequate
cooling can lead to rapid deterioration due to high

Cooling methods
The selection of a particular precooling method i1
determined by several factors, including: the rate o:
cooling required, compatibility of the method with
the commodities to be cooled, subsequent storage
and shipping conditions, and equipment and
operating costs.
During precooling, the sensible heat (or field
heat) from the product is transferred to the ambi-
ent cooling medium. The rate of heat transfer, or
cooling rate, is critical for the efficient removal of
field heat and is dependent upon three factors:
time, temperature, and contact. In order to achieve
maximum cooling, the product must remain in the
precooler for sufficient time to remove the heat

2 [30 1.1] 1/2 = 14.5
3 [30 14.5] = 15.5
4 [30 1.1] 7/8 = 25.3
' [30 25.3] = 4.7

([86 34] 1/2 = 26)
([86 26] = 60)
([86 34] 7/8 = 45.5)
([86- 45.5] = 40.5)

(7/8-cooling time). This is particularly important
during busy periods when it may be tempting to
"push" product through the precooler. A correctly-
sized precooler should have sufficient capacity so as
to provide adequate resident time for precooling,
while at the same time not slowing subsequent
packing and/or handling operations. The cooling
medium (air) must be maintained at a constant
temperature throughout the cooling period. If the
refrigeration system is undersized for the capacity
of product requiring precooling, the temperature of
the medium will increase over time. The cooling
medium must also have intimate contact with the
surfaces of the strawberry. Inappropriately-
designed containers can markedly reduce flow of
the cooling medium.
The cooling rate is not only dependent upon
time, temperature, and contact with the commod-
ity; it is also dependent on the cooling method
employed. As noted above, most strawberries in
Florida are forced-air cooled. Hydrocooling (show-
ering or immersion in chilled water) is not recom-
mended because wet berries are much more suscep-
tible to decay. Cooling with crushed or slush ice is
even worse because the berries are likely to sustain
physical damage. Vacuum-cooling would produce
critical moisture loss and procedures using water
spray could not be used. Again, room-cooling of
strawberries is not an acceptable precooling method
nor is reliance on refrigerated trucks during

Forced-air cooling (pressure cooling)
Forced-air cooling, which has been described in
detail in various publications, can solve many
difficult cooling problems because it provides for
cold air movement through, rather than around,
containers. The system, which creates a slight
pressure gradient to cause air to flow through
container vents, achieves rapid cooling as a result
of the direct contact between cold air and warm
product. With proper design, fast, uniform cooling
can be achieved through unitized pallet loads of
containers. Various cooler designs can be used,
depending on specific needs. Converting existing
cooling facilities to forced-air cooling is often simple
and inexpensive, provided sufficient refrigeration
capacity and cooling surfaces (evaporator coils) are
available. Some variations in forced-air cooler
design are described here.

Forced-air tunnel
This is the more traditional forced-air cooling
system. Essentially, two rows of palletized contain-

ers or bins are placed on either side of an exhaust
fan, leaving an aisle between rows. The aisle and
the open end are then covered to create an air
plenum tunnel (Figure 1). With the exhaust fan
operating, a slight negative air pressure is created
within the plenum tunnel. Cold air from the room
then moves through any openings in or between
containers toward the low-pressure zone, cooling
the product as it moves. The exhaust fan can be a
portable unit that is placed to direct the warm
exhaust air toward the air return of the cold room,
or it can be a permanent unit which also circulates
the air over the cooling surface and returns it to the
cold room (Figure 2).

Figure 1. Forced-air tunnel with portable exhaust fan.

Figure 2. Forced-air cooler with permanent constructed air

Cold wall

This is a permanently constructed air plenum
equipped with an exhaust fan. It is often located at
one end or side of a cold room, with the exhaust fan
designed to move air over the cooling surface.
Openings are located along the room side of the
plenum against which stacks on pallet loads of
containers can be placed. Various damper designs
have been developed so that air flow is blocked
except when a pallet is in place. Each pallet will
start cooling as soon as it is in place; thus, there is
no need to await deliveries to complete a tunnel.
Shelves are often built so that multilayers of pallets
can be cooled with this system. Different packages,
and even partial pallets, can be accommodated by
proper design of the damper system. This is a
benefit in some operations where a range of com-
modities or varieties is handled. Each pallet must
be promptly moved from the cooler as soon as it is
cooled in order to avoid unnecessary desiccation
from continued rapid air flow over the product.
The usual design air-flow rate for strawberry
cooling is 2.1x10 m3/s per kg (2 ft3/min per Ib) of
fruit with the air temperature at 1.70C (35"F) [5].
The cooling time varies from 1.5 to 2.5 hours
depending on initial temperature of the fruit. In
practice, air-flow rate generally varies from
1.0x103 to 4.2x10-3 m3/s per kg (1 to 4 ft3/min per Ib)
of fruit.
Strawberries are usually precooled at the pack-
inghouse in pallets consisted of 96 open-top fiber-
board, single-layer tray cartons (Figure 3) contain-
ing eight 1-quart or 12 1-pint containers (Figure 4),
weighing approximately 454 kg (1,000 pounds).
The pallet is usually three cartons deep, two
cartons wide, and 16 high. Most boxes are con-
structed in such a manner that tray cartons are
connected together with wires and each carton is
connected to the carton below with tabs protruding
up into the carton above for load stability (Figure
5). The cartons have enough open area to allow for
passage of cooling air (Figure 6). Cold air is forced
through the pallet and recycled through a refrigera-
tion unit.

Container venting
Effective container venting is essential for
forced-air cooling to work efficiently. Cold air must
be able to pass through all parts of a container. For
this to happen, container vents must remain open
after stacking. Thus, venting patterns are impor-
tant. Too little venting will restrict air flow; too
much venting will weaken the container.

The standard strawberry carton has a vent hole
that looks like a channel with sloping sides cut in
the upper fourth of two opposite sides of the carton

Figure 3. Forced-air cooling pallet loaded with tray cartons of

Figure 4. Pint container in tray carton.

Figure 5. Wire tabs for connecting tray cartons.

Figure 6. Vent opening In standard catrton.

(Figure 6). The opening represents 14% of the side
of carton. Cooling experiment research [1] with
other designs, shown in Figure 7 (half-cartons were
used instead of full cartons because of the symme-
try of the carton design), was conducted to find the
effect of different vent hole configurations. Table 1
shows the vent hole sizes and percent openings for
each design. The three new vent hole designs were
tested against the standard container. All new
vent hole designs were found to improve cooling
time. There was no significant difference among
the new designs. Table 2 summarizes the effects of
the new vent hole designs on the cooling time for
the last basket (three cartons with three pint
baskets per carton) downstream and also for the
average of all fruit. The results of the statistical
analysis indicated that the three-hole and four-hole
designs are significantly better in cooling the
strawberries than the standard crate. The increase
in cooling efficiency of the new design is more
pronounced at the lower air flow rates.
The reason for more efficient cooling with the
new designs is probably due to better air flow
patterns inside the carton. With the standard
carton, the vent hole is cut at the very top edge of
the carton. When the air is forced through the vent
hole, it tends to continue through the gap between
the top of the baskets and the bottom of the carton
immediately above, thus by-passing most of the
fruit. With the new designs, the vent holes are
more uniformly distributed, forcing more air to flow
through the fruit. Before the new designs are
adopted, however, tests must be conducted to
ensure the strength of the new containers.
The cooling research [1] also established the
relationship between cooling rate and air flow rate.
Table 2 indicates a large increase in cooling rate

Standard Carton

4-Hole Design


3-Hole Design

7-Hole Design

** *

Figure 7. Standard and experimental strawberry carton vent-
hole configurations (half-cartons were used Instead of full
cartons because of the symmetry of the carton design).

Table 1. Vent-hole sizes and percent opening for different
Configuration Diameter, m (inch) % Opening
Standard 14.0
3-hole 38.1x10- (1.5) 13.5
4-hole 38.1x10- (1.5) 18.0
7-hole 25.4x10- (1.0) 14.0

Table 2. Seven-eighths cooling time (minutes) as function of
vent hole designs (basket number 9, and average of
all fruit).
Vent hole configuration
Air flow rate std. hole 3 holes 4 hols holes
last avg. last avg. last avg. last avg.
m3/s kg basket all basket all basket all basket all
(ftP/b min) fruit fruit fruit fruit
1.04x10'(1.0) 160 122 132 98 136 100 136 100
2.08x10-3(2.0) 82 64 76 52 72 50 82 62
4.16x10 (4.0) 74 52 70 50 68 46 68 48
6.24x10 (6.0) 52 34 50 34 46 32 46 32

when the air flow rate was increased from 1.0x103
to 2.1x10-3 m3/(kg s) (1.0 to 2.0 ft3/min Ib) and a
relatively small increase at higher flow rates.
Cooling time was shown to also be a function of
location of the fruit in the carton with respect to the
entering air. The more downstream the location,
the longer the cooling time. Table 3 shows the
effect of fruit location on cooling time at various air
flow rates.
For all air flow rates tested, it took approxi-
mately twice as long for the last basket to reach 7/8
cooling as it did for the first basket. Table 4 pre-
sents this bed effect in terms of the temperature
gradient along the flow path at the time the first
pint achieved 7/8 cooling. A temperature gradient
of5 to 60C (9 to 10.80F) exists between the first

(coldest) pint and the last (hottest) pint. This
shows that care must be taken when choosing a
fruit to measure the temperature to determine
when cooling is completed. In some packinghouses,
the operators use the fruit on top of the first basket
to gage the degree of cooling because it is the most
readily accessible fruit. Table 5 shows the tem-
perature gradient in the strawberries when the top
fruit of the first basket has reached 7/8 cooling. A
temperature difference of 4C (7.2F) exists between
the top fruit and the average temperature of basket
1, and 11C (19.80F) exists between the top fruit
and the average temperature of basket 9.

Room cooling, storage, and shipping
The simplest and slowest cooling method is room
cooling, in which the bulk or containerized com-
modity is placed in a refrigerated room for several
hours or days. Air is circulated by the existing fans
from the evaporator coil in the room. Vented
containers and proper stacking are critical to
minimize obstructions to air flow and ensure
optimal heat removal. Room cooling alone is
satisfactory only for commodities with a low respi-
ration rate, such as mature potatoes and onions.
For strawberries it should be used only after
precooling for 7/8-cooling time, during short-period
storage prior to shipment. Refrigerated trucks
should be precooled prior to loading the precooled
strawberries. After precooling, top icing of straw-
berries is not desirable during holding or transport.

Modified atmosphere
Refrigeration is sometimes supplemented with
modified atmosphere during transit or storage.
With solid loads, the modified atmosphere may be
established for the entire transport vehicle. Plastic
shrouds are, more commonly, placed over indi-
vidual pallets equipped with a base that can be
sealed. Pallet bags are installed after cooling,
usually just before loading for transport. Carbon
dioxide (CO2) is then injected into the package to
establish the desired atmosphere. Elevated levels
of carbon dioxide (10 to 30%) slow the respiration
rate of the fruit and reduce the activity of decay
causing organisms, thus extending storage and
market life. Carbon dioxide atmospheres of 30% or
greater can cause off-flavor. Recent studies [4]
indicated that carbon dioxide treatment was of
little benefit when storage temperatures were
maintained below 5C (410F). Therefore, if transit
and storage temperatures are maintained below
about 2.2C (36F) there is little need for the carbon
dioxide treatment. Practically speaking, consider-

able evidence indicates that strawberries are often
exposed to temperatures above 4.40C (40F) during
transport and in these cases the carbon dioxide
treatments may be beneficial.

Management guidelines
The following management guidelines or recom-
mendations summarize the important post-harvesi
information discussed above.
Strawberries should be handled gently at all
times to maintain quality since they are so easily
bruised. Bruised berries are very susceptible to
decay. Anytime a fruit is bruised, the bruised areas
will discolor. In addition, bruising increases water
loss. Only sound fruit should be shipped, because
decay fungi can easily spread throughout each
shipping container. Berries without stem caps are
particularly perishable. Strict grading should
eliminate out-of-grade berries. It important to
acknowledge that while proper post-harvest cooling
and handling techniques can help maintain produce
quality, the quality packed can never be improved.
Flats should not be overfilled because stacking
will cause crushing. After packing, strawberries
should be kept in the shade and transported to the
cooler as soon as possible. The temperature of
harvested strawberries in the field can get up to
300C (86oF), and higher when exposed to sun; and
when fruits are allowed to remain at this tempera-
ture for 4 hours, marketability drops by at least
40%. Again, very careful handling of the packed
strawberries is essential to maintaining quality.
A well-designed forced-air cooler should be
maintained at a constant temperature near 0C
(320F). As noted above, the air flow rate has a
definite effect on the cooling rate of strawberries in
cartons and new vent hole designs can improve
cooling efficiency. A cooling schedule should be
developed for the forced-air cooler to maximize
efficiency. Use of a schedule allows cooling times t
be adjusted based on the initial temperature of the
berries and prevents inadequate or excessive
precooling resident time.
Temperatures should be measured with a
reliable electronic thermometer. Fruit pulp tem-
peratures should be taken prior to precooling and
during precooling. Fruit temperatures should be
measured on the warm side of the cooler (inside of
stack in systems that draw air through the berries;
outside of stack in system which blow air through
the berries). Care should be taken in sampling the
strawberry temperatures to determine when


cooling is completed. There is a large difference in
the temperature between the fruit near the air inlet
and the fruit in the last basket downstream.
Precooler personnel should be trained to use proper
strawberry temperature measurement techniques.
Leaving strawberries in the forced-air cooler longer
than necessary can lead to undesirable water loss
because of rapid air movement. On the other hand,
inadequate cooling can lead to rapid deterioration
due to high temperatures.
Following cooling, strawberries should be stored
in a cold room maintained at 0-1.1 C (32-34oF) for
the shortest time possible. The cold room tempera-
ture should be colder than the temperature of the
berries leaving the precooler. In addition to ineffi-
cient use of refrigeration, berries that have been
cooled and then allowed to rewarm (causing mois-
ture to condense on them) are extremely suscep-
tible to decay. Humidity as well as temperature
must be controlled in storage facilities. If the air
inside the storage room is too dry, water will
evaporate from the strawberries and they will
become soft and shriveled. At a storage room
temperature of OoC (320F), the relative humidity
should be from 90 to 95 percent. Much of the water
that evaporates from the fruit condenses on the
inside surfaces of the room or is absorbed into
packing materials. Under certain atmospheric
conditions, it may be necessary to add moisture
with a humidification system.
Trailers that are to carry strawberries should be
precooled to 1.1C (34F) prior to loading. Also,
extreme care must be exercised in loading
palletized units to prevent shifting during transit
by using strapping and corner boards. Proper
bracing is a must for palletized strawberry ship-
ments. The pallet units should be loaded away
from the walls to prevent outside heat from trans-
ferring directly into the berries.

This publication presents cooling requirements,
cooling methods, quality parameters, and manage-
ment guidelines for maintaining the quality of
Florida strawberries. Studies conducted to estab-
lish the relationship between cooling rate and air
flow rate and the effects of new vent hole designs
on cooling rates of strawberries are discussed.
Management guidelines or recommendations to the
packinghouse operators concerning possible system
performance improvements are presented, such as
increasing resident time within the forced-air
precooler to achieve better cooling or lowering the

Table 3. Cooling time as function of fruit location. There were
nine baskets along the flow path.
Air flow rates 7/8-Cooling time (minutes)
m3/kg s (ftt/min Ib) Basket 1 Basket 3 Basket 6 Basket 9
1.04x10" (1.0) 84 102 134 160
2.08x10- (2.0) 48 56 72 82
4.16x103 (4.0) 38 46 58 74

6.24x103 (6.0) 28 28 34 52

Table 4. Temperature distribution at the time basket 1 reaches
7/8-cooling time for standard cartons.
Air flow rates Temperature, C (OF)
m3/kg s (ft/Ib min)
Basket 1 Basket 5 Basket 9 Mass Avg.
(3 cartons)

1.04x10 (1.0) 4.7 (40.5) 5.6 (42.1) 10.6 (51.1)


2.08x10-3 (2.0) 4.7 (40.5) 6.5 (43.7) 10.2 (50.4) 6.7 (44.1)
4.16x10- (4.0) 4.7(40.5) 6.7(44.1) 11.1 (52.0) 7.1 (44.8)
6.24x103 (6.0) 4.4 (40.5) 5.0 (41.0) 10.7 (51.3) 5.9 (42.6)

Table 5. Temperature of top fruit in the first basket compared
to the average temperature of the last basket at
7/8-cooling time of top fruit.
Air flow rates Temperature, OC (OF)
m3/kg s (ft/lb min)
Top Fruit Basket 1 Basket 9
1.04x103 (1.0) 4.6(40.3) 9.8(49.6) 16.3(61.3)
2.08x10- (2.0) 4.6 (40.3) 8.8(47.8) 15.1 (59.2)
4.16x103 (4.0) 4.7(40.5) 9.2(48.6) 16.2(61.2)
6.24x103 (6.0) 4.2 (40.5) 7.9(46.2) 15.1 (59.2)

cold room temperature to prevent warming of
precooled strawberries. To continue delivery of a
high-quality product, growers need to grow and
harvest high-quality strawberries, and after-
harvest product quality must be maintained with
the right precooling, handling, and storage

1. Arifin, B.B. and K.V. Chau. 1988. Cooling of
strawberries in cartons with new vent hole
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