Note: Descriptions are shown in the official language in which they were submitted.
1~0386~
In U. S. Patent ~o. 3,333,967 a method is dis-
closed for preserving mature but less than fully ripe
fruits, especially tropical varieties, under hypobaric
conditions of about 100 to 400 millimeters of mercury
(mm Hg) absolute pressure, at the relatively warm storage
temperature of about 15 C in nearly water saturated, flowing
air. This method gave useful results on a laboratory scale,
and under favorable conditions on a larger scale, with non-
ripe, tropical fruits such as avocados, tomatoes, limes,
10. and especially bananas. However, upon later study and
research I discovered that hypobaric storage is applicable
to a wide variety of non-mineral produce and matter in
addition to mature but less than fully ripe tropical fruit.
~ discovered that various novel forces, factors and combina-
tions thereof, and related conditions which affect and/or
coact with each other advantageously, may, or should, be
employed to achieve desired, optimum storage and preserva-
tion of such produce and matter at different, principally
20. lower, temperatures and/or pressures. Especially, upon
enlarging the scale of the hypobaric system, including the
size of the hypobaric storage chamber, to commercial
size I learned that the said method and means disclosed in
U. S. Patent No. 3,333,967 under various unfavorable con-
ditions failed to accomplish their intended purpose, and/or
failed to provide or maintain the operating conditions
that are important for successful large scale commercial
operations. For example, my said method, when used on a
large commercial scale, without help from much reduced
30. air through-flow tended not to provide or maintain relative
humidity at a high enough value to prevent desiccation of
the stored commodity.
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On the other hand, my experimental work with
large commercial size units (such as semi-trailers ~or
highway transport or large Sea-gOing shipping containers,
for maritime transport), posed novel and practical prob-
lems, the solutions of which required me to make radical
and significant improvements upon my prior patented inven-
tion. These improvements comprise the subject matter dis-
closed and claimed in this application as will be revealed
in the following pages hereof. For example, I discovered
10. how to use and profit by, and avoid deleterious consequen-
ces of, the refrigeration effect incident to free air
expansion and water evaporation when air is bubbled through
a body of humidifying water which is relatively smaller
in relation to the whole storage space than was the body
of water in relation to the size of a conventional laboratory
vacuum vessel. Similarly, the greater volume of air moved
to and from a large storage space and passed through the
relatively smaller body of water, tended to cool, and/or
even freeze, the water and impair or prevent the attainment
20. of necessary and desirable relative humidity in the storage
space.
I have now discovered that a relatively broad
spectrum of correlated hypobaric pressures and low tempera-
tures at high relative humidity is operational in preserv-
ing non-mineral matter, different classes of which vary
markedly in their required or permissible storage conditions
for best results. In general, cold storage temperatures
have had known limits sufficiently low to preserve non-
mineral matter against spoilage and yet not so low as to
30. freeze or impart chilling damage or contribute to any other
ill effect. Similarly, subatmospheric storage pressures
can be so low as to reach an "inversion point" below which
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insufficient oxygen is available to sustain aerobic res-
piration by living matter. When this happens the material
may shift to a fermentative type of respiration which
yields waste products causing spoilage rather than preserva-
tion of the non-mineral matter. I find that pressure and
temperature often interact in such a way that each factor
influences the lowest and/or highest permissible value
of the other, which is needed to create the most beneficial
storage condition. It presently appears that the best com-
10. bination of these and other factors can be determined onlyby carefully controlled tests. Highly humid air is impor-
tant for stored products to avoid desiccation and hypobaric
pressures tend to be detrimental in this respect because
they facilitate the rate of diffusion of water vapor from
the tissues of the non-mineral matter. When air expands
and then passes through humidifying water under hypobaric
conditions, there is a refrigerating effect, as mentioned
above. While this cooling often or sometimes is desirable
to lessen the work of, or eliminate other ways and means
20. of cooling the chamber, refrigerating by evaporation of
water runs counter to the objective here of creating and
maintaining high humidity. As the water cools, its vapor
pressure is lowered and it tends to add progressively less
water vapor to the incoming air so that the relative humid-
ity in the chamber is reduced. In extreme cases, such as
storage conditions near 0 C, the water of the humidifier
can even freeze because of evaporative cooling. Freezing
can be avoided or delayed by adding known non-volatile
anti-freeze agents to the water, such as brine or ethylene
30. glycol, but this has the adverse effect of lowering the
vapor pressure of the water in proportion to the freezing
point depression. This further reduces the degree of
10386B!7
water saturation of the passing air to an even more un-
acceptable level, causing still greater desiccation of
the product. Under such conditions, the matter being
stored can be spoiled rather than preserved.
Summary of the Invention
A primary object of the invention is to provide
optimal, correlated conditions of temperature, pressure,
humidity and air flow for storing different categories,
respectively of non-mineral matter. In the present method,
a preferred correlation is established and continuously
10. maintained between ranges of temperature, air flo~, hypobaric
pressure and humidity for the storage of particular items
and/or categories of non-mineral matter. ~his is accomplished
by simple, reliable means which consume or employ essen-
tially only air,water, and a modest amount of energy.
In one form of my invention, the non-mineral
matter is placed within a treating chamber, and a non-
deleterious gas such as air, is humidified by contact-
ing the gas with heated water and then passing the humi-
dified gas into the chamber into contact with such matter.
20. My references herein to air and humidi~ied air will compre-
hend equivalent non-deleterious gases and humidified gases
unless otherwise noted. Concurrently a hypobaric pressure,
and a temperature correlated with the pressure, are main-
tained within the chamber, the hypobaric pressure and
correlated temperature being dependent upon the nature of
the matter to be stored, and providing pressure-temperature-
humidity-air flow conditions effective to preserve the
matter for a prolonged period of time as compared with
exposure to atmospheric conditions and with my prior patent.
An object of my invention is to improve upon my
prior patent, and extend the field of usefulness and the
benefits and advantages of subatmospheric storage, and
10386~7
subatmospheric cold storage, to the preservation of non-mineral
or metabolically active matter, produce and commodities beyond
the contemplation and f acility of the teaching of that patent.
The temperature of the water supply in my improved method
and means is so raised or maintained relative to the temperature
within the chamber, and the contact time of the gas with the
water is so prolonged or repeated, that a relative humidity in
the gas is assured preferably at or near 100~, and not sub-
stantially less than 80%.
~0 Briefly speaking, the present invention provides a method
of preserving non-mineral matter in cool, humid air in an en-
clDsed space comprising taking air from and adding air to the
~pace, maintaining the air pressure in the space substantially
between 4 mm Hg. absolute and 200 mm Hg. absolute, maintaining
the air temperature in said space substantially between minus
2 C and plus 15 C., maintaining the relative humidity in the
space substantially between 80% and 100%, the temperature of
water employed to maintain the humidity being maintained suf-
ficiently higher than the temperature within the space to pro-
vide a relative humidity in the air of between 80% and 100%,
and selecting correlated pressures, temperatures and humidity
with respect to the nature of the particular matter to be
preserved.
The above method can be embodied in hypobaric storage
apparatus providing an enclosed space adapted to receive meta-
bolically active matter to be stored and preserved, charact-
erized by means for maintaining a hypobaric pressure in the
space, means for maintaining a desired temperature within the
space, means for evacuating air from the space and passing
fresh air into the space at a controlled rate, means for humi-
difying the air in the space, and means for selecting cor-
related pressure, temperature, air movement and relative
humidity with respect to the na~ure of the matter to be preserved.
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Other objects, improvements and advantages will appear
herein, reference being made to il7ustrative examples in the
following pages, and to the attached drawings.
Brief De_cription of the Drawings
In the accompanying drawing:
Figure 1 is in part a schematic flow diagram and in
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p~rt a diagrammatic representatior of one form of chamber or
container and apparatus embodying and/or for practicing my
invention: and
Figure 2 is a flow diagram and representation like
Figure 1 of another form of chamber or container, and apparatus.
Description of the Preferred Embodiments
In general, there are at least five factors or
conditions mutually influencing the storage of non-mineral matter
in my hypobaric system, namely:
1. The kind or category of the stored,
non-mineral matter.
2. Air pressure in the storage chamber.
3. A~r temperature in the storage chamber.
4. Humidity of air in the storage chamber.
. Rate of air flow into and out of the
storage chamber, and circulation of
air therein.
There is relatively broad operational range of
cool-to-cold temperatures, hypobaric pressures, high humidity
and air flow rates in which most non-mineral matter can be stored
ad~antageously as compared with atmospheric conditions and those
described in my prior patent. Within these basic ranges, the
nature of the commodity constituting the non-mineral matter
determines optimum temperature-pressure-air flow conditions which
can differ widely for different kinds of commodities. However,
in all cases it presently appears that a desired high humidity
level should be maintained to protect the commodity, regardless
of other conditions. Although this humidity level preferably
should be close to 100%, in cases such as storing limes, for
example, a slightly lower humidity is preferred to discourage
the growth of molds. Reference is made to the co-pending
Canadian application of Ellen A. M. Burg and me, Serial No.
166,018 filed March 13, 1973 for an alternative way of
1~' .
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di scouraging the growth of molds. Gross air movement to and
from the storage chamber removes deleterious gases which tend
to ~e given off by and from the stored matter or produce, but
increasing the rate of through-flow of air tends to bear ad-
versely on the maintenance of desirably high humidity because
of the aforementioned evaporative cooling effect. Internal
recirculation of air within the chamber facilitates rehumidifi-
cation if the air is recycled through the humidification
means, and insures that all the stored contents of the
cham~er are bathed in about the same atmosphere and hence
kept at a uniform temperature. On the other hand, increasing
the rate of recirculation of air within the chamber tends to
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103~68~7
dry the non-mineral matter, as described below, so that
optimal storage usually is realized only at a specific
range of air flow.
More particularly, my present improvement is
applicable to a wide range of commodities including, in
different classes or categories, not only mature but less
than fully ripe fruit, but also ripe fruit, vegetables, cut
flowers, potted plants, meat products, especially fowl
such as chickens, dried (non-living) materials such as
alfalfa pellets, vegetables and vegetative matter such as
rooted and non-rooted cuttings, and still other respiring
plant materials such as bulbs, corms, seeds, nuts, tubers
and the like. Such non-mineral matter of different kinds
and classes respectively may, as I have presently learned,
be stored with advantage at pressures between about 4
mm H~ and 100 mm Hg and at temperatures between about
minus 2 C to about plus 15C with exceptions for particular
kinds of matter and circumstances wherein the said upper
limits of one or the other, temperature or pressure, may
be exceeded advantageously; all taken with my preferred
conditions of humidity and air movement. The minimum storage
pressure, unless it is determined by oxygen availability,
can be almost as low as the vapor pressure of water at
the temperature of storage. If the storage pressure were
to reach the vapor pressure of water at the storage temper-
ature, the water in the product and humidifier would boil
and my method, as presently understood, would be impaired,
if not rendered inoperable. Optimal correlated ranges of
temperature, pressure, humidity and air flow within the
herein stated ranges for specific commodities and/or classes
of commodities are not readily predictable without careful
experiment and research, preferably on both laboratory and
commercial scales.
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103~6~7
It is presently believed to be desirable to store
commodities at the lowest temperature which does not cause
chilling damage. Pressure may also play a role with respect
to operable temperature because, at least in some cases,
cold damage seems to be caused by accumulation of volatile
metabolic products such as farnescence or acetaldehyde.
Since hypobaric pressures tend to remove these products,
they sometimes alleviate, delay or reduce the symptoms of
cold damage and permit storage at temperatures which other-
10. wise might impart cold damage. In other cases, ~ecause theoxygen partial pressure is reduced under hypobaric condi-
tions, there is an increase of adverse cold temperature
reactions such as peel pitting, and browning in certain
fruits if the storage pressure is too low, whereas at high
pressures the chilling effect still may be alleviated with
the same commodity. For example, unwaxed Tahiti Persian
limes keep their green color best if they are stored at
80 mm Hg pressure and 9C, but they experience chilling
damage at that pressure and a temperature of 7C. At 7 C
20. they are best stored at 150 mm Hg, in which case they ~eep
their green color without rind breakdown for many months.
However, at that pressure they develop rind breakdown if the
temperature is lowered to 5C. In order to prevent rind
breakdown at 5C, the pressure must be elevated to 250
to 300 mm Hg, in which case the treated fruits experience
less cold damage than fruits stored at atmospheric pressure
and the same temperature. Similar results have been ob-
tained with Marsh and Ruby red grapefruit. For these
reasons it has not been possible for me to predict or
30. extrapolate from studies of cold tolerance of various
commodities under atmospheric conditions all the aspects
~03.868 7
of behavior that many non-mineral commodities will exhibit
under hypobaric conditions.
Similarly, I have found it difficult, if not
impossible, to predict or extrapolate directly from the few
available studies of the chilling effect on chilling damage
at reduced partial pressures of oxygen at standard con-
ditions, what the effect, or corresponding effect, will be
on storage at subatmospheric pressures. In part the lack
of agreement between studies at atmospheric and subatmos-
lO. pheric pressure is due to the fact that under hypobaricconditions external oxygen enters the tissue of a commodity
by diffusion more readily than under atmospheric conditions,
and in addition the rate of oxygen consumption appears to
be different under the two conditions even though the oxygen
partial pressure is the same. In both cases respiration
and heat evolution are greatly reduced when the oxygen avail-
ability is restricted, but progressively the tissues stored
under hypobaric conditions continue to decrease in respira-
tion rate, ultimately reaching far lower values than com-
20. parable samples kept at the same oxygen partial pressureat atmospheric pressure.
For example, as presently understood, at a rela-
tive humidity of about, and above, 80 percent and at given
storage temperatures as shown in examples below, the storage
of cut flowers is improved by pressures at and above 100 mm
Hg, but markedly so at 40 to 70 mm Hg. A pressure of 40
mm Hg or less is preferred for roses. While apples and
pears may be stored in a pressure range of about 100 to
150 mm Hg, markedly improved results are obtained at
30. pressures in the range of about 40 to 80 mm Hg. Vegetative
materials such as cuttings, rooted cuttings, and potted
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103B6~7
plants which have been examined store best with respect to
pressure within the 60 to 80 mm Hg range. Most vegetables
except lettuce store best at a range within 50 to 80 mm
Hg. Avocadoes are best stored at a pressure of about 40
to 80 mm Hg. Produce, I have noticed to be best stored
in the 100 to 400 mm Hg range, tends to be mature but less
than fully ripe bananas and limes as specified in my prior U.S.
patent. Departing from that patent I have now learned
that fully ripe fruit, such as strawberries, cherries,
10. grapefruits, tomatoes and blueberries, are also well stored
in the 80-400 mm Hg range but at much lower temperatures
mentioned in Examples 18, 19, 20, 23 and 24 below.
Classification of the various and numerous kinds
and varieties of non-mineral matter in respect to the bene-
ficience of their response to my presently preferred con-
ditions of and for storage and preservation thereof within
my improved method and means, will suggest itself from the
preceding pages and the following numbered "Examples" and
lettered "Tables". In these examples and tables, it is to
20. be assumed that (1) the relative humidity was created and
maintained above 8~/~ and as high as practicable and de-
sirable for the preservation and storage of the particular
matter or produce as variously taught herein, (2) through-
put of air in terms of volumes of the storage chamber per
hour did not fall below an efficient and desirable minimum
according to the precepts hereof, and (3) the rate of in-
ternal circulation of the humid atmosphere of the storage
chamber sufficed to bathe all the stored contents of the
c hamber adequately and also to humidify or rehumidify said
30. atmosphere to create and/or maintain the desired and most
appropriate relative humidity in said chamber in view of the
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103~6B7
kind of matter of produce being preserved under the accom-
panying conditions of temperature and subatmospheric pres-
sure which are specified in the several Examples and Tables.
The comparison in days of Storage Life between prior art
cold storage at atmospheric pressure and as a result of
my employment of my improved method, measure the compara-
tive advantage of the latter. In the examples, the distinc-
tions from, and aavantages over my prior patent, appear at
least in part in terms of improved results gained through
10. the lower temperatures and/or pressures employed in my new
and improved methods.
The following examples are intended to illustrate
my invention and are not intended to limit or impair the
scope of the claims. Where reference is made below to
"cold storage" as such, it is meant that such storage is
old and conventional at atmospheric pressure, not LPS
storage according to my present improvement.
Example 1
McIntosh, Red delicious, Golden delicious and
20. Jonathan apples were stored at 60 mm Hg and at 150 mm Hg,
each batch at 0 to 1C. Under normal cold storage conditions
at these temperatures the different varieties may be kept
for 2 to 4 months, except that in the case of McIntosh
apples, chilling damage would be expected. After 6 months
storage at 60 mm Hg, all varieties still retained their
initial firmness, color, flavor and shelf-life, whereas
at 150 mm Hg they had developed considerable aroma and
were approaching full ripeness. After 8 months, fruits
stored at 60 mm Hg still retained at-harvest appearance, and
30. had acquired a shelf-life after removal from storage which
was considerably longer than that at harvest. Fruits stored
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110386B7
at 150 mm Hg were completely ripe at this time and their
shelf-life foreshortened.
Example 2
In a companion experiment to that of Example 1,
performed at 6C, similar results were obtained for the
apples except that the storage life at each pressure con-
dition was vastly reduced compared to that at 0 to 1C.
All fruits used in ~xamples 1 and 2 were harvested in an
optimal condition for storage; that is, before ripening had
10. begun, but after the fruit had fully matured. Surprisingly,
when fruits were harvested for storage after they had begun
to ripen, under hypobaric conditions at 0 to 1C they were
preserved nearly as well as those picked at an earlier stage
of development. This performance was unexpected because
such fruit cannot be preserved in a controlled atmosphere
depleted of oxygen and augmented with carbon dioxide at
atmospheric pressure. The enhanced shelf-life of apples
stored for 6 to 8 months at 60 mm Hg is commercially de-
sirable, and in addition allows the fruit to be shipped to
20. market at a lower cost without refrigeration, or to be
transferred to cold storage before subsequent marketing.
Example 3
Bartlett, Clapp and Commice pears were stored at
60 mm Hg and also at 150 mm Hg and at mi~us 1C to plus
1 C. Under normal cold storage at these temperatures
the pears may be preserved for one and a half to three months.
At 150 mm Hg the storage was improved, but at 60 mm Hg the
pears kept for 4 to 6 months in satisfactory condition.
upon subsequent removal from storage, the pears ripened
30. properly with no internal browning and had a normal shelf-
life.
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Exam~le 4
In a companion experiment to that of Example 3
using Clapp pears, a pressure of40mm Hg proved to be superior
to 60 mm Hg in prolonging storage life. In another like
experiment, Bartlett pears were stored at 6C and separately
at 40 mm Hg and at 60 mm Hg. Under these conditions they
responaed to hypobaric storage as before but at each pres-
sure their storage life was shorter than at minus 1C to
plufi 1C.
10. ExamPle 5
Cut roses, carnations, chrysanthemum ana aster
blossoms were stored at pressures ranging from 50 to 150
mm Hg and at 0 to 3C. Under normal cold storage condi-
tions in the dry state, the flowers faded within 1 to 2
weeks even when wrapped with perforated polyethylene film.
Under hypobaric conditions, relatively small but signifi-
cant benefit was realized at pressures of 100 to ~50 mm
Hg, but at 40 to 80 mm Hg even without plastic wrap, the
flowers were preserved in excellent condition for 4 to 6
20. weeks and still retained nearly their initial shelf-life.
The blooms respond to commercial flower preservatives.
Storage life of flowers under hypobaric conditions is
further improved by using thin, perforated plastic wraps.
ExamPle 6
Potted Chrysanthemum plants, vars. ~eptune,
Golden Anne, Delaware and Bright Golden Anne, were stored
at pressures ranging from 40 to 150 mm Hg and at 0 to 4C.
The plants were selected to have flower buds at various
stages of opening. Under normal cold storage conditions, the
30. shelf-life of the blooms after the plants are removed from
storage, begins to decline if the plants have been stored
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103~6~7
for more than one week. Under hypobaric conditions relative-
ly small but significant benefit was realized at pressures
ranging from 100 to 150 mm Hg, but at 40 to 80 mm Hg the
plants were kept for 4 weeks without any diminution in the
subsequent shelf-life of the blooms. Even tightly closed
flower buds subsequently opened, whereas they aborted on
plants removed from normal cold storage after about one
week.
ExamPle 7
10. ~on-rooted cuttings of Chrysanthemum, vars.
~eptune, Golden Anne, Delaware and Bright Golden Anne,
were stored at 60 to 150 mm Hg and at 0 to 4 C. Under
normal cold storage conditions such cuttings lose their
viability within 3 to 6 weeks even when they are wrapped
in perforated plastic sheets. ~nder hypobaric conditions,
storagè was improved at 100 to 150 mm Hg, but at 60 to
80 mm Hg, the cuttings remained viable for more than 12
weeks without plastic wrap. Similar results were obtained
with rooted cuttings, except that under normal cold storage
20. conditions, they develop apical and leaf yellowing within
about one week, whereas this does not occur for about 12
weeks at 60 mm Hg. Storage of the rooted cuttings is an
example of the application of the method to "potted"
cold-tolerant plants.
Example 8
Fresh green onions are difficult to store using
only standard refrigeration. At 0 to 3C they remain in
a saleable condition for only 2 to 3 days. Under hypobaric
conditions small but significant advantage is gained at
30. pressures ranging from 100 to 150 mm Hg at 0 C to 3C, but
at 60 to 80 mm Hg the scallions remain in a saleable state
for more than 3 weeks.
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ExamPle 9
Fryer chickens, under normal cold storage con-
ditions at 0 to 3 C with no external wrap developed an
unpleasant odor, experienced extensive shrinkage, and
became covered with plaques of Pseudomonas bacteria within
3 to 7 days. Chickens stored at 100 to 150 mm Hg benefited
from the treatment, but at 60 to 80 mm Hg during a two week
period, odor, shrinkage and Pseudomonas development were
almost completely prevented.
10. EXAMPLE 10
At 11C under normal cold storage conditions,
cut floral spikes of Wax Ginger wrapped in perforated plastic,
become unsaleable within 5 to 7 days mainly because of de-
terioration of the leaves. Soon thereafter the flower also
browns and desiccates. Under hypobaric conditions, a sig-
nificant benefit is obtained at a pressure higher than 100
mm Hg at similar temperature even without plastic wrap.
However, at 50 to 60 mm Hg both the leaves and bloom are
preserved for 4 to 5 weeks. Subsequently, upon removal
20. from storage, the floral spikes displayed a nearly normal
shelf-life.
ExamPle 11
The cut bloom of Heliconia latispathea developed
necrotic spots and faded within about 1~ days when stored
at 10C under normal cold storage conditions. Hypobaric
storage in the pressure range between 100 and 150 mm Hg pro-
longs storage life at this temperature, but at lower pres-
sures, such as 60 mm Hg, the bloom is preserved for as
long as 40 days.
30. Example 12
Vanda joacquim blooms stored at 10C under normal cold
storage conditions faded and dehisced in about 2 weeks.
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Under hypobaric conditions in the pressure range between
100 and 150 mm Hg, and at the same temperature, the orchid
blossoms had enhanced storage life. However, the effect
was not nearly as marked as that at lower pressures, such
as 40 mm Hg at the same temperature. Under these condi-
tions, the blooms were preserved for more than 40 days
and subsequently displayed nearly normal shelf-life.
ExamPle 13
Choquette avocados ripen in 8 to 9 days when
10. stored under normal cold storage conditions at 12C.
Hypobaric pressures ranging from 100 to 150 mm Hg at 12C
significantly extend storage life, but lower pressures in
the range between 40 and 100 mm Hg are even more efficacious,
allowing the fruit to be stored for about 25 to 26 days.
Similar results were obtained at 15C except all fruit
ripened more rapidly than at 12C. At 10C chilling
damage soon became apparent, but those fruits under hy-
pobaric conditions were the last to develop this disorder.
Example 14
20. At 10C under normal cold storage conditions
Waldin avocados ripened in 12 to 16 days. Hypobaric pres-
sures ranging from 100 to 150 mm Hg at 10C extended the
storage life significantly but were not nearly as effica-
cious as pressures ranging from 60 to 80 mm Hg at the same
temperature, which allowed the fruit to be stored for about
30 days. At 12 C all fruits ripened more rapidly than at
10C but those under hypobaric conditions were still
preserved for the longest time. At 8C the avocados ex-
perienced chilling damage, albeit those under hypobaric
30. conditions ~ere the last to develop the disorder.
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ExamPle 15
At 8C under normal cold storage conditions,
Lula avocados ripened in 23 to 30 days, whereas under hypo-
baric conditions in the pressure range between 40 and 80
mm Hg and at the same temperature, they were preserved for
75 to 100 days. Higher pressures, in the range between
100 and 150 mm Hg at 8C are effective but not as much so
in preventing ripening. At 10 to 15C the fruits ripened
progressively more rapidly, but those under hypobaric con-
10. ditions still were preserved for longer periods of timethan those at atmospheric pressure. Chilling damage oc-
curred when the temperature was lowered to 6C, but fruits
kept under hypobaric conditions were the last to develop
this disorder.
ExamPle 16
Booth 8 avocados stored at 8C under normal cold
storage conditions ripened in about 8 to 12 days, whereas
hypobaric pressures in the range between 40 and 80 mm Hg
at the same temperature preserved them for about 45 days.
20. Higher pressures, in the range from 100 to 150 mm Hg at the
same temperature were efficacious also but not as much as
at the lower pressures. Between 10 and 15 C ripening
occurred progressively more rapidly, but fruits stored
under hypobaric conditions were still preserved for a
much longer time than those kept under atmospheric con-
dition. Chilling damage developed at 6C, but only very
slowly in fruits stored at a low pressure. In general
the storage of avocados is further improved and desicca-
tion prevented if the fruits are kept in plastic bags
30. with small perforations.
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Example 17
The storage of green peppers, cucumbers, pole-
beans and snap-beans was better at 8 to 10C under hypo-
baric conditions in the pressure range between 100 and
150 mm Hg than it was under normal cold storage at those
temperatures. However, at pressures ranging from 60 to
80 mm Hg and at the same temperatures, better results were
obtained. For example, at 8 to 10C under cold storage,
green peppers were preserved for 16 to 18 days, whereas
10. at 80 mm Hg and 8 to 10C, they remained fresh for 46
days. At 5 to 8C snap-beans spoil in 7 to 10 days using
conventional cold storage, but are preserved for about 26
days at 60 mm Hg at the same temperatures. In cold storage
at 8C, cucumbers can be kept for 10 to 14 days, whereas
at 80 mm Hg and 8C they are preserved for 41 days. Pole-
beans can be preserved for 10 to 13 days at 8C in cold
storage, but remain in good condition for 30 days at 60
mm Hg and 8C.
Example 18
20. Ripe strawberries, vars. Tioga and Florida 90,
normally spoil within 5 to 7 days if stored at 0 to 2 C
by conventional cold storage means, whereas they are pre-
served for about 4 weeks at 0 to 2 C at pressures ranging
from 80 to 200 mm Hg.
ExamPle 19
Vine-ripe tomatoes spoiled in about 8 to 10
days at 0 to 2C in cold storage, but were preserved for
more than one month at 100 mm Hg and 0 to 2C.
Example 20
30. Blueberries were kept up to 4 weeks in a saleable
condition under normal cold storage at 0 to 1C, but remained
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in good condition for at least 6 weeks at that temperature
and pressures ranging from 80 to 200 mm Hg.
Example 21
Iceburg lettuce remains saleable for about 2
weeks, if it is stored under cold storage conditions at 0
to 4C, but remained fresh for about 4 weeks at those tem-
peratures in the pressure range between 80 to 200 mm Hg.
~ot only did the leaves stay crisper under hypobaric con-
ditions, but also the butts remained whiter. Pressures in
10. the range between 150 to 200 mm Hg are preferred, because
my present observation is that lower pressures can induce
a disorder known as "pink-rib" which renders the appear-
ance of the lettuce less attractive.
ExamPle 22
Pineapples, in a ripe and fully colored state,
were stored for about 9 to 12 days at 12 C using standard
cold storage. Pineapples from the same lot were stored for
24 to 30 days at 5C but at pressures in the range between
60 and 120 mm Hg.
20. ExamPle 23
Valencia oranges were stored for 72 days at 5C
by means of cold storage, but for 157 days at the same tem-
perature and at pressures ranging from 70 to 110 mm Hg.
ExamPle 24
Ruby red grapefruit developed peel pitting and
lost its flavor within 4-6 weeks when stored at 6C by
means of cold storage. Flavor was retained but the peel
still pitted during 90 days storage at the same tempera-
ture, using hypobaric pressures in the range between
30. 80-150 mm Hg. However at 250-400 mm Hg peel pitting was
prevented and flavor retention improved during 90 days storage.
--19--
103~
Some of the foregoing data as well as additional
storage data are presented by the following Tables A
through E to illustrate the marked superiority in preserving
non-mineral matter by my present invention as compared with
my prior patent and with storage under conventional cold
storage conditions at substantially atmospheric pressur~.
~n the tables, data obtained by my present improved method
is represented as "LPS", that is, low pressure system.
TABLE A
10. NON-RIPE FULLY MATURE FRUIT
Temp. Storage Life - Days ~PS Pressure
Variety (C) cold Storage LPS Storage mm. Hq.
Banana, Valery 13 10-14 90-150*' 40-200
Tomato (breaker) I5 10-12 28-42*80-100
Avocado,Choquette 13 8-9 25-2640-100
Avocado, Waldin 10 12-16 22-30 60-80
Avocado, Lula 7 23-30 75-100J 40-60
Avocado, Booth 8 7 8-12 45-60 40-80
Lime, Tahiti 7-10 14-35 60-9080-150
20. Pineapple 7-10 10-14 28-30*80-150
Apple,Mclntosh 0-0.6 60-120240-270 60
Apple, Red
Delicious 0-0.6 60-120 240-27060
Apple, Golden
Delicious 0-0.6 90-120 240-27060
~pple,Jonathan 0-0.6 60-90240-270 60
Pear,Bartlett 0-0.6 75-90 150-18050
Pear, Clapp 0-0.6 45-60 120-15050
Peach, Cardinal 0-1 14-2128-35 80
30. ~ectarine 0-1 11-20 28-3580-120
*Storage life is limited in these instances by mold develop-
ment at the indicated times.
-20-
1~3868~7
Table ~
RIPE, FU~LY MATURE FRUI~S
Temp. Storage Life - Days LPS Pressure
Variety (C) Cold Storage LPS Storaqe mm-.Hg.
Pineapple 14 9-12 24-30* 70-120
Orange, Valencia 4 72 157 70-110
Grapefruit,
Ruby Red 5-6 30-40 90-120 250-400
Strawberry,Fla.
10.90 and Tioga 0-2 5-7 21-28* 80-200
Cherry, sweet 0-2 14 28 80-200
Tomato (vine-
ripe) 0-2 8-10 30-45 100
Blueberry 0.5 28 42* 80-200
*Storage life is limited in these instances by mold
development at the indicated times.
Table C
VEGETABLES.
Temp. Storage Life-Days LPS Pressure
20. varietY (C) cold Storaqe LPS Storaqe mm. Hq.
Green pepper7-10 16-18 46* 80
Cucumber 7 10-14 41* 80
Bean, pole 7 10-13 30* 60
Bean, snap 4-7 7-10 26* 60
Onion, green0-2 2-3 15 50
Lettuce,iceberg 0-2 14 28 80-200
*Storage life is limited in these instances by mold
development at the indicated times.
103B6~7
Table D
FLOWERS - CUT
Temp. Storage Life - Days LPS Pressure,
Variety (C) Cold Storaqe LPS Storage mm. H~.
Wax ginger 11 5-7 28-35 50
Heliconia latis-
pathea 12 10 41* 60
Vanda ~oacquim 12 16 41 40
Carnation 0-2 10 26-33 40-60
10. Rose~ sweetheart 0 7-14 26-33 40
Chrysanthemum0-2 6-8 21-28 70
*Storage life is limited in these instances by
mold development at the indicated times.
Table E
VEGETATIVE MATERIALS: Chrysanthemums; potted
plants and cuttings (vars. ~eptune, Golden
Anne, Delaware and Briqht Golden Anne
Temp. Storage Life - DaysLPS Pressure
VarietY ~C) Cold Storaqe LPS Storaqemm.Hg.
20. Potted plants 0-2 7 28 60-80
~on-rooted
cuttings 0-2 14-42 84 60
Rooted cuttings 0-2 7 84 60
While 100 percent relative humidity in the air
that is caused to flow about the non-mineral matter usually
is best, at least in theory, it has been determined that
relative humidities as low as about 80 percent are per-
missible. Preferably, the humidity should be higher than
about 90 percent. Even relative humidities of about 80
30. percent are often difficult to maintain continuously and
uniformly under hypobaric conditions in a large, commercial
size chamber. When the incoming air is cold it picks up
-22-
103~
relatively less water vapor in passing through a humidifierhaving a set water temperature, whereas when the incoming
air is warm it picks up more water vapor and may even drop
condensate water on the floor of the vacuum chamber upon
cooling to the temperature of the chamber. Therfore some
means of stabilizing the temperature of the incoming air
is highly desirable in order to avoid humidity fluctua-
tions within the storage cham~er. A problem also arises
in connection with the fact that not all of the incoming
10. air necessarily enters through the humidifier. In some
instances, as when incoming air is used to drive pneumatic-
ally actuated equipment in the chamber, it may initially
and intentionally bypass the humidifier. In other instances,
for example in a large commercial structure such as a con-
crete warehouse, a certain amount of in-leakage of air
through the surfaces and seams is unavoidable, and this
air upon expanding within the structure will have a low
content of water vapor. For these reasons it is highly
desirable to provide means for recirculating air
20. within the vacuum chamber, so that all or some part of
the air repeatedly passes through the humidifier and
therefore, regardless of its route of entry into the chamber,
it will become saturated, or sufficiently saturated, with
water vapor at the temperature within the chamber. Recir-
culating the air through the humidifier has the additional
advantage that it tends to compensate for inefficiency in
the humidification system. Generally I have found that even
when wicks, atomizers or other devices are used to increase
the efficiency of the humidification process, it is diffi-
30. cult, if not impracticable, to saturate the incoming airin a single pass through a humidifier of economically modest
~03~6a~7
capacity without increasing the water temperature to a high
value. A further factor influencing the attainment of a
constant, high relative humidity in a vacuum storage chamber
is the aforementioned evaporative refrigeration effect. In
a relatively small apparatus the high surface to volume
ratio of the water bath favors sufficient heat exchange be-
tween the water and surrounding atmosphere to cause the
water temperature to approach that within the storage
chamber in which the water bath is situated. ~ormally, not
lO. less than about l/4 chamber volumes of rarified air should
be passed through the hypobaric chamber each hour to flush
away undesirable vapors and gases, such as ethylene and
carbon dioxide, produced by the stored non-mineral matter.
Such a rate of through-flow of air will, normally, also
supply sufficient oxygen to replace that consumed by respira-
tion. This through-flow or through-put of air does not sub-
stantially lower the water temperature if the chamber volume
to water volume is small, for example from about 20:1 to
about 200:1, because of the low rate of cooling and rapid
20. heat exchange between the water vessel and surrounding
atmosphere. However, in a large apparatus where the ratio
of the chamber volume to water volume may be in the order
of lO00 or more to 1, the cooling effect is relatively much
greater and the heat exchange between the water reservoir
and surrounding atmosphere less rapid because of an unfavor-
able surface to volume ratio in the larger water reservoir.
Under these and other adverse conditions, evaporative cool-
ing tends to reduce the water temperature so that a humidity
of even 80 percent cannot be sustained in the vacuum storage
30. chamber without doing more than merely passing the input air
through a body of water once.
-24-
10;~368~7
The present invention continually attains a de-
sired relative humidity preferably by preconditioning the
incoming air to have a temperature close to that in the
storage chamber and maintaining the temperature of the water
in the humidifier at least equal to or higher than that of
the air in the storage chamber. It is also preferable to
prolong or multiply the contact time between the circulat-
ing air and the water, for example by recirculating the air
through the humidifier, if that be necessary, or by utiliz-
10. ing spray atomizers, percolating devices, or wicks. Iprefer that heat be supplied to the water to maintain its
temperature at or above that of the temperature in the
storage chamber, for example, from about 2C to about 20C
higher. The heat energy may be obtained from different
sources or a combination of sources. For example, heat may
be garnered from the interior of the chamber by various
means such as circulating heat exchange fluid in tubes
which are in intimate contact with an internal surface,
preferably metal, of the chamber and/or recirculating
20. the gas within the chamber to contact it with a heat ex-
change su~face which transfers the heat to the water in the
humidifier. While this method of heating the water is
useful and serves the dual function of keeping the chamber
cool, by itself it never quite raises the temperature of
the water to closer than a few degrees lower than that of
the chamber air. Moreover, when the ambient environment
is colder than the desired chamber temperature so that
heating rather than cooling is needed to maintain the
chamber at the desired temperature condition, it is not
possible to garner any heat from the chamber walls or
interior to keep the water warm. Under these conditions,
-25-
~03B6~7
supplementary heat must be added. This can be done in asecond stage of humidification by subsequently contact-
ing the air with a second water source maintained 2 to 20C
hotter than the chamber air temperature. The air preferably
passes through the second humidification stage without
experiencing a pressure drop; otherwise a back pressure is
created in the first stage humidifier and its efficacy
is greatly diminished. A convenient solution to this
problem is to spray humidify with warm water in the second
10. stage. Alternatively, as indicated in the accompanying
drawing, the additional heat may be supplied all in a single
stage by spray humidifying and heating the water in the con-
duit leading from the water reservoir to the spray nozzle.
When use is not made of the refrigeration effect and/or
when heat rather than refrigeration is required to maintain
the desired chamber temperature, heat may be added directly
to the water in the reservoir. This can be accomplished by
warming heat exchange fluid passing in conduits through
the reservoir, by heating the gas contacted with the water,
20. directly heating the water with an electric immersion heater
or some other means, or some combination of these effects.
Preferably, the application of heat, from whatever source,
is controlled and regulated to maintain the temperature
of the water within a desired range.
Loss of water from the stored non-mineral matter
tends to occur, especially during a prolonged storage
period, even when the relative humidity of the gas in the
chamber is at or close to 100 percent, since the stored
commodity because of its respiration is slightly warmer than
30. the atmosphere in the vacuum storage chamber and therefore
the vapor pressure of water within the commodity is greater
-26-
1036 6~7
than that in the said atmosphere. Thus water vapor tendsto escape into the hypobaric air. The rate of escape of
water is roughly proportional to the rate of movement of
air over the commodity, and therefore under these conditions
I prefer that air circulation or recirculation be kept at
or near the minimum required to maintain temperature and
humidity uniformity in the storage chamber. Water loss of
this nature can be slowed or prevented by wrapping the stored,
non-mineral matter in water-retention means such as in sheets
10. of synthetic, resinous plastic or a perforated bag of the
same material. Synthetic, resinous plastics which can be
used include polyethylene, polypropylene, polyvinyl chloride,
polyvinyl butyral, polymethacrylate esters, and the like,
although polyethylene is preferred because it tends to
restrict the movement of water while allowing the passage
of gases such as oxygen ethylene and carbon dioxide. Such
plastics not only are impermeable to water, or nearly so,
but in addition they shield the surface of the stored com-
modity from air movement. They do not interfere with the
20. operation of the hypobaric process but to the contrary
tend to prolong storage life of certain commodities. With
avocados and bananas, ripening is actually slowed by
plastic wraps when the commodity is placed in a vacuum
chamber maintained in accordance with the present invention.
The accompanying Figure 1 illustrates what to me
is a presently preferred apparatus for carrying out my
hypobaric storage methods and improvements. Referring to
the drawing, an insulated vacuum chamber 10 is capable of
withstanding inward forces of at least 15 pounds per square
30. inch. A humidifier tank 11 containing water 12 is situated
within vacuum chamber 10. Air is continuously evacuated
-27
103868 7
from the chamber by a conventional vacuum pump P at a
rate influenced in part, if desired, by the degree of clo-
sure of valve 14 in line 15. The rate of flow of air through
the chamber and the pressure in the chamber may be adjusted
primarily by valves 14 and 30 and regulator 32 to provide
between about 0.25 to 10 changes of chamber air per hour.
That is to say, the through-flow or through-put of air at
chamber pressure is preferably from about 1/4 to 10 times
the volume of the storage space per hour. Atmospheric air
10. enters the system through conduit 16, on the right as viewed,
passing through an air filter 17 where deleterious particu-
late matter is removed. The filter may contain charcoal,
inert pellets coated with permanganate salt (marketed
under the trademark "Purafil"), molecular sieves or other
purifying agents alone or in combination to remove atmos-
pheric contaminants such as carbon mo~oxide and ethylene.
These gases and ~arious other unsaturated atmos-
pheric contaminants influence biological processes in such
a way that they cause fruit ripening, scald, senescence,
20. aging, abscission or twisting of leaves, stems and floral
parts, fading of flowers, chlorosis of leaves, and certain
physiological disorders such as sepal wilt in orchids,
"sleep" of carnations, and browning of lettuce. Fortu-
nately, when atmospheric air enters the vacuum chamber it
expands so that the partial pressure of any contaminant
is reduced proportionately. under hypobaric conditions,
if the pressure in the vacuum chamber is sufficiently low,
the concentrations of contaminants tend to be reduced to
values lower than those needed to influence biological
30. processes adversely except under conditions of severe
atmospheric pollution. In that event, filter 17 will be
-28-
~03~68~7
called upon to remove the undesirable vapors. The rate offlow of incoming air at atmospheric pressure is pre~erably
indicated by a rotameter 18 or other flow meter. The num-
ber of chamber volumes of subatmospheric air moved per hour
may be calculated from the chamber volume and rate of flow
of atmospheric air entering the chamber.
Preferably the incoming air is preconditioned to
or toward the temperature within the vacuum chamber 10,
for example, by passing it through a heat exchanger 20
10. where it exchanges heat with the rarified air leaving the
vacuum chamber. Preconditioning in heat exchanger 20 makes
use of the cold air leaving the vacuum chamber and therefore
lowers the temperature of the incoming air if it be warmer,
without increasing the overall refrigeration requirement
for the chamber. Then preferably the input air is passed
through sec~ion 21 of conduit 16 which may be longer than,
or comprise a plurality of, the single length as shown,
and has intimate contact with the inner wall of the vacuum
chamber 10. Air in section 21 of conduit 16 exchanges heat
20. with the wall and with the rarified air within the chamber
and thus the temperature of the incoming air approaches
more closely that of the air within the chamber than would
be the case if only heat exchanger 20 were used. The method
of preconditioning works in the same way when the ambient
temperature is lower than the desired storage temperature
in the vacuum chamber, in which case the incoming air will
be heated instead of cooled.
The input air flows through parts 22, 23, 38,
and 39 of conduit 16 to enter the vacuum chamber 10. All
30. parts of the conduit 16 downstream of heat exchanger 20
-29-
~03E~6~7
which lie outside of the chamber should be insulated as
suggested at 19. Branch conduit 22 leads to the side
inlet of the annular high pressure injector iet of a
conventional venturi-type air-mover 24. A relatively
small volume of air at atmospheric pressure flows through
branch part 22 and through the injector of the air-mover
at high velocity because it drops in pressure from atmos-
pheric to the low pressure obtaining within the vacuum
chamber and within humidifier 11. This induces a large
10. flow of air through the low pressure body of the air-
mover 24. Air is thus drawn into inlet elbow 28 from the
chamber 10 and into humidifier 11 above the water level
of reservoir 12 whence it flows upwardly through water
spray from nozzle 35 and out from the humidifier at outlet
25. The humid air is recirculated in this way throughout
the chamber 10 as indicated by arrows 27. A fraction of
the moving air is withdrawn from the chamber 10 by vacuum
pump P through conduit 15, and the remainder is preferably
drawn to the air-mover via elbow 28 for continued recircu-
20. lation. The recirculating air preferably passes over orthrough a heat exchange coil C of a conventional refriger-
ation and heating system not shown, which provides heating
and cooling, as need be, responsible to a conventional
temperature sensing device, not shown, located within
chamber 10.
Air can also be moved by conventional fans or
~lowers disposed in the chamber, but this usually requires
electric motors and is more costly to operate and maintain
than a pneumatic air-mover. Moreover, electric motors are
30. exothermic and increase the refrigeration needed to main-
tain low temperatures in the chamber.
-30-
- 10386B7
The rate of recirculation of chamber atmosphere
is controlled by valve 30 in branch conduit 22, and be
judged from reading vacuum gauge 31. The amount in pounds,
of air exhausted from the vacuum chamber needs to be greater
than the amount entering through conduit 22 to the air-
mover 24 and to or through any and all other pneumatically
actuated devices such, for example, as spray nozzle 35.
Incidentally, valve 57 is always closed except when chamber
pressure is to be raised to atmospheric as described below.
lO. The direction of air movement need not be the
same as that shown in the diagram wherein air is expelled
over the top of the load L. See Figure 2. As shown in
Fig. l, air is directed over the heat exchange coil C to
the fa~ side of the vacuum chamber whence it returns to
elbow 28 by passing horizontally through all the load,
assuming that the load is stacked and arranged to favor
horizontal air movement. Alternatively, as shown in Fig. 2
and more fully described below, the direction of air flow
may be altered by locating the air-mover 24 up at 25 to
20. direct recirculated air into the top of the humidifier so
that air leaving the humidifier may be directed under the
floor or a false floor, of the vacuum chamber to force
air below the load and then vertically upwardly through
the load, assuming it has been stacked and arranged to favor
vertical flow.
Referring back to Fig. 1, incoming air also may
be directed to pass through branch conduit 23 to and
through a vacuum regulator 32, and thence preferably
through check valve 26, to humidifier ll, bubbling through
30. the water reservoir 12, if desired, before comingling
with the recirculating air in the upper part of the
103868 7
humidifier. To avoid excessive frothing and foaming of wat-
e-r 12 when air bubbles through it, a non-volatile antifoam
agent such as a silicone compound can be added to the
water. Regulator 32, which may be conventional diaphragm
type, continuously senses the pressure within the vacuum
chamber through a line 29 and compares this to atmospheric
reference pressure, allowing just enough air as shown by
flowmeter 42 to enter humidifier ll to maintain a set dif-
ference between the chamber and atmosphere. To maintain
10. pressure within the vacuum chamber at an absolute rather
than relative value, it is necessary to establish an ab-
solute reference pressure in the regulator. This can be
accomplished by having a sealed, absolute vacuum in a vessel,
not shown, as the reference pressure, or by using such an
absolute pressure regulator, not shown, to establish an
absolute pressure in the reference side of regulator 32
which is lower than any anticipated atmospheric pressure
but higher than the desired pressure intended to be main-
tained in chamber lO as indicated by absolute pressure
20. gauge 33.
Absolute pressure regulation is not highly essen-
tial in stationary facilities, but is recommended in trans-
portable containers which are likely to encounter severe
fluctuations in atmospheric pressure according to change
in altitude on land and hurricanes at sea.
Air entering humidifier 11 through conduit 23
is humidified as it bubbles through the water 12 and/or
is exposed to water spray from conventional siphon-fed
pneumatic spray atmoziation nozzle 35. The nozzle is
30. actuated by the pneumatic force and motion of atmospheric
air as it expands, flows and decreases in pressure to lift
-32-
~03~6~
water to the nozzle in conduit 36 and eject the water into
the air and water vapor space 13 of the humidifier above
the water 12. In-line water filter 37 prevents clogging
of the nozzle. Air is supplied to the nozzle through parts
38 and 39 of conduit 16. The rate of air and water utiliza-
tion by the nozzle depends upon the pneumatic force applied,
which can be adjusted by valve 40 to a desired pressure,
as read on a vacuum gauge 41. Relatively small amounts of
air are consumed in a spray nozzle so numerous nozzles can
10. be used if required. It is advantageous, and with some
nozzles 35, necessary, to shield the outlet of the nozzle
from the turbulence caused by circulating air, which other-
wise may disturb the venturi effect within the nozzle,
impairing its operation. Alternatively, hydraulic atomiz-
ing nozzles may be used, in which case, a water pump would
be required to circulate water to the nozzles from the
reservoir 12 in the humidifier 11.
As discussed above, evaporative cooling causes
the water temperature to tend to be lower than the air
20. temperature in the chamber. When the water temperature
in humidifier 11 is l~wer than the air temperature within
the chamber 10, the humidity in the chamber falls below
100 percent and then there is a tendency for stored com-
modities generally indicated at 4~, to desiccate. My
preferred solution to this problem is to heat the water.
In the preferred embodiment shown in the drawing, the
water 12 is heated by an electric immersion heater 47
responsive to a thermostat 48 and water temperature sensing
element 49, so that the water temperature can be held at
30. any desired value. Although an electric immersion heater
is shown, any appropriate, controlled method of heating
-33-
~03B~
the water suffices. To attain desired relative humidityin the chamber 10, I prefer that the water be kept at or
about 2C to 20C warmer than the temperature of the air
in the chamber. The exact temperature for optimum humidity
depends to considerable extent upon the amount of air re-
circulation and rehumidification through the humidifier,
and the efficiency of the humidification process.
When valve 30 is closed so that no air recircula-
tion occurs, all air enters the chamber through conduits
10. 23, 38 and 39. If valve 40 is also closed, so that the
spray nozzle 35 cannot function, the efficiency of the humi-
dification process will be reduced to the single pass of
air bubbling through the water 12. Consequently the tem-
perature of water 12 will have to be raised relatively
high above chamber air temperature to provide saturated
or satisfactory humidity in the chamber. If the spray
nozzle 35 is also operated by opening valve 40, the water
temperature can be adjusted to a lower value, and if the air-
mover 24 is also operated by opening valve 30, a still lower
20. water temperature will suffice to achieve saturated or
satisfactory humidity in the chamber.
An additional heater 61 located in conduit 36
is made responsive to temperature sensing element 62 by
thermoregulator 63. This heater serves to warm the water
entering the spray nozzle 35 to a desired temperature.
When evaporative cooling is sought or employed to cool, or
help cool, the vacuum chamber 10, the water temperature
in reservoir 11 should be lower than the air temperature
in the chamber. Then to maintain desirable relative
30. humidity the water ejected from the spray nozzle is
heated to a higher temperature than the air in the chamber.
-34-
10386~7
In this manner evaporative cooling is used to advantageand the relative humidity is raised by warming the water to
be sprayed.
Similarly relative humidity can be controlled and
held at values lower than 100 percent, by setting the water
temperature to the relatively cool value required to main-
tain the desired lower humidity. Control of the humidity
at a value slightly lower than 100 percent has the advan-
tage with some commodities that it decreases mold develop-
10. ment without causing an unacceptable amount of desiccation.
It is possible to operate the apparatus at airtemperatures even lower than minus 2C without danger of
freezing the water if the water temperature is raised more
than 2C by adding heat. A non-volatile antifreeze com-
pound can be mixed with the water to prevent freezing
during periods of inoperation, and a desired humidity
still can be attained in spite of the additional lowering
of the vapor pressure of the water in the humidifier caused
by the dissolved solute. This is accomplished by raising
20. the water temperature to a higher value than otherwise
would be necessary in the absence of the antifreeze compound.
Humidification is improved by continuously re-
circulating at least part of the air in chamber 10 through
the humidifier. This humidifies dry air that may have
entered by inleakage through the walls or seams of the
vacuum chamber and/or through the pneumatically operated
devices mentioned above. water evaporated from the humidi-
fier is replaced from an external source through conduit
52 as required. In a preferred method of water replenish-
30. ment, the entry of water through an inlet conduit 52 ismade responsive to a standard float leveling device 53 which
-35-
~03~68~7
senses or equals the water level in humidifier ll. Airpressure equalizing bypass line 54 connects water level
device 53 with chamber lO. To avoid accumulation of salt,
scale and other impurities in the water 12 of the humidi-
fier due to continued water evaporation, water entering at
52 should be purified, for example by passage through a
reverse osmosis membrane and/or deionizing resins of
the mixed bed type, and impure water should be removed
as may be necessary from time to time, or continuously by
lO. a positive displacement pump 65 via conduit 66, for example.
The humidifier need not be located within the
vacuum chamber so long as its operation and results as
herein described are preserved. If it is located exter-
nally to the vacuum chamber and appropriately connected
therewith, it and all associated parts and connections
should be insulated and constructed to withstand atmos-
pheric pressure. Placing the humidifier outside the vacuum
chamber is convenient for the operation of a fixed ware-
house facility in that this permits easy access at atmos-
20. pheric pressure to the humidifying and air-moving equipment
while the warehouse is evacuated down to small absolute
pressures taught to be used herein. The arrangement in
the drawing is particular~y suited to self contained trans-
portable containers and other equipment which requires com-
pact utilization of space.
~ o raise the pressure in chamber lO to atmos-
pheric and to open the chamber ~or access, valve 14 in line
15 and valve 56 in line 16 are shut, vacuum pump P is stopped,
and valve 57 in bypass line 58 and valve 59 in conduit
30. 60 are opened. Valve 59 admits atmospheric air and
pressure to the chamber lO. Valve 57 admits air at chamber
-36-
1031~6~7
pressure to the line between check valve 26 and regula-
tor 32.
Figure 2 illustrates another preferred apparatus
for carrying out my hypobaric storage methods and improve-
ments in which there are differences with respect to the
apparatus of Figure 1 that will presently appear. For
example, air is circulated in different directions within
chamber 10 and in the humiaifier 70. Provision is also
made to humidify all or only part of the recirculated air
10. as well as to remove excess and entrained water from air
leaving the humidifier. Like parts in Figures 1 and 2
are designated by the same reference characters.
More particularly, air-mover 71 corresponding
to air-mover 24 is operated by incoming air in line 22
as in Figure 1. However, air-mover 71 discharges into an
upper portion of the humidifier 70 and induces air from
the upper levels of chamber 10 to or toward the humidifier
and at or across an adjustable damper or baffle 72 which is
disposed to admit all or part of the air emitted by air-
20. mover 71 to the upper space 13 of the humidifier 70 ordivert all or part of such air downwardly into the pipe 73
to the lower part of the chamber 10 beneath the load L of
stored material 45 therein. Air leaves ~he humidifier 70
through a side port 74 into a conventional filter-mist
eliminator 75 which conventionally spins out entrained water
droplets. The water collects at the bottom of the eliminator
75 and drains by gravity back to the water supply 12 through
conduit 76. Air leaves the filter-mist eliminator 75
through conduit 77, rejoining in conduit 73 the air, if
30. any, which bypassed the humidifier. All the recirculated
air is expelled beneath the stacks of boxes 45 of load L,
-37-
10386~7
to recirculate vertically upwardly throughout the cham~er 10as suggested by arrows 78. A fraction of the moving air is
withdrawn from the chamber 10 by ~acuum pump P through
outlet conduit 15, and the remainder is drawn to the air-
mover 71 via inlet 79 to continue recirculation. In this
example, the recirculating air is given no alternative but
to pass upwardly through the load L and moves either to
air-mover inlet 79 or outlet 15. ~nder normal steady opera-
tion as much air will enter the chamber 10 as will be sucked
10. out of it. If all of the recirculating air emitted by
air-mover 71 were directed through humidifier 70 and should
the air-mover and humidifier be of sufficient capacity,
the air could cause an undesirable carry-over of entrapped
water droplets from the humidifier. To control this,
baffle 72 is provided to divert part of the recirculating
air around the humidifier. In this way a high velocity
of air movement can be sustained to favor, for ~xample,
rapid cool-down of a newly stored commodity and subse-
quent maintenance of a constant temperature in the vacuum
20. chamber. Simultaneously, a sufficient portion of the air,
if such is required, can be continuously recycled through
the humidifier to ensure that its relative humidity is
maintained at a desired level.
In Figure 2, heat exchanger 20, line 15, and pipe
16 near the exchanger may be insulated as at 80. Instead
of providing the displacement pump 65 and conduit 66 of
Figure 1 to remove impure water from the humidifier 70,
I have found that it frequently suffices to drain the
reservoir during periods of inoperation when the vacuum
30, in chamber 10 has been released as by draining line 51
through conduit 81 and valve 82. In the form of my
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~03~6~7
apparatus in Figure 2, I prefer not to use the check valve26 in line 23 as shown in Figure 1, but instead dispose the
regulator 32 at a higher elevation than the water level
in the humidifier 70 as shown at the left of Figure 2.
The moisture content of the air in chamber 10
is measured by device 85, which may be any type of conven-
tional relative humidity indicator insensitive to atmos-
pheric pressure. For example, a wet and dry bulb resis-
tance or other type of thermometer, or a membrane actuated
10. hygrometer may be used. I prefer an electronic dew point
indicator having a heated, wire wound, salt coated bobbin
83 as sensor, and a thermister probe 84 to measure the air
temperature in chamber 10. The dew point probe is accurate
at a high humidity, does not become water soaked under
these conditions, and is not influenced by air pressure or
transient changes in ambient temperature. When the dew
point equals the set temperature in chamber 10 the relative
humidity is 100 percent. If desired, the moisture content
of the air in chamber 10 can be continuously controlled by
20. making heaters 61 and/or 47 responsive to moisture sensing
device 85, conveying signals from device 85 through, supple-
menting and/or superceding thermostats 63 and 48 respect-
ively, via line 86 upon closing switch 87 for that purpose.
Storage of non-mineral matter at my newly dis-
covered low absolute pressures taught herein facilitates
diffusive escape of vapors such as carbon dioxide, ethylene,
farnescene, acetaldehyde, and various metabolic waste pro-
ducts produced within plant material, as well as various
putrefying odors produced within an~mal material. carbon
30. dioxide is undesirable because it causes surface scald on
plant materials. Ethylene induces fruit ripening, flower
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10386~7
fading, leaf and flower petal abscission, loss of chloro-
phyll, aging, senescence, and physiological disorders such
as sepal wilt of orchids and "sleep`' of carnations. Farnes-
cene and acetaldehyde have been implicated in apple scald
and chilling damage, respectively. Low absolute pressure
also decreases the partial pressure of oxygen available to
support metabolic activity, and reduces a living material's
respiration rate. In the case of plant material the ability
to produce and respond to ethylene is impaired at low oxygen
10, partial pressure, The growth of aerobic bacteria and cer-
tain molds is retarded, and various undesirable animal forms,
such as insects and nematodes, which sometimes infest and
develop in stored animal and plant commodities, may be de-
stroyed both by lack of oxygen and hypobaric pressure.
Decreasing a commodity's respiration rate not
only delays the aging and spoiling processes, but also
reduces the amount of respiratory heat generated. A much
smaller volume of heat containing atmospheric air is needed
to effect an air change under hypobaric conditions than
20. under atmospheric conditions, and the present method util-
izes pneumatic force rather than heat yielding electrically
powered blowers and water pumps to cause air humidification
and circulation. For all of these reasons the total re-
frigeration capacity to sustain a living plant or animal
material at a specific temperature under hypobaric condi-
tions is usually about one-third that needed to maintain
the same temperature when the commodity is preserved at
atmospheric pressure in "cold storage".
Oxygen deprivation below the inversion point
30. should be avoided for living plant or animal matter. But
in the case of non-living plant and animal matter, oxygen
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103868 7
deprivation need not determine the lowest permissiblepressure. Instead the pressure may be lowered to a value
just slightly higher than the vapor pressure of water at
the storage temperature.
The number of chamber volumes of air passed per
hour through the storage chamber is ordinarily not critical,
provided it is sufficient to prevent accumulation of un-
desired vapors in those cases when such vapors diffuse
from the matter. Rapid recirculation of air internally
10. within the chamber even as often as 200 times per hour
keeps the temperature more uniform, especially when the
chamber is packed with small spaces between boxes of fruit,
vegetables, flowers and the like. During usual operation
through-put of air only ranges from about 1/4 to 10 chamber
volumes per hour regardless of the rate of air internal
recirculation.
While I have disclosed preferred ways of practic-
ing my improvement and preferred forms, and embodiments
thereof, other ways and forms, as well as changes and other
20. improvements therein and thereon will occur to those skilled
in the art who come to know and understand my invention,
all without departing from the essence and substance thereof.
Therefore I do not want my patent to be restricted merely
to that which is specifically disclosed herein, nor in
any manner inconsistent with the progress by which the
art has been promoted by my improvement.
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