CA1038687A

CA1038687A - Low temperature hypobaric storage of metabolically active matter

Info

Publication number: CA1038687A
Application number: CA166,019A
Authority: CA
Inventors: Stanley P. Burg
Original assignee: Grumman Allied Industries Inc
Current assignee: Grumman Allied Industries Inc
Priority date: 1972-04-20
Filing date: 1973-03-13
Publication date: 1978-09-19
Also published as: BE798546A; NL7305738A; IT980882B; NL175784B; IL42081A0; DE2319375A1; IL42081A; FR2181080A1; FR2181080B1; GB1426917A

Abstract

Abstract of Disclosure The preservation of non-mineral matter such as fruits, vegetables, meats, cut flowers, and the like is disclosed, characterized by storage at controlled and correlated conditions of hypobaric pressure, temperature, humidity and air movement Preferably, a non-deleterious gas such as air is humidified by contracting it with heated water from a supply, and then passing the humid air through, and when advisable, recirculating and/or rehumidifying the air within a storage chamber containing the non-mineral matter under conditions of hypobaric pressure and relatively low temperature. The temperature of the humidifying water is so related to the temperature of the atmosphere within the chamber as to provide, preferably, a relative humidity of or slightly less than 100%, but not substantially less than 80 percent. Storage of non-mineral matter in this manner delays or prevents spoilage resulting from such causes as aging, senescence, putrefaction, desiccation, ripening, and the like, and preserves it for a long period of time as, for example, between harvest and an advantage-ously delayed date of sale or consumption of such matter.

Description

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.

~3Y36~7 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

-2-~0386~7 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.
~ -a-db~

10386~7 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 _ 3_~
- `-db/ .~

- -- 10386~
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~' .

~, sv/

- ~.0386~7 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 -6a-sv/
A

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.

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 _g_ 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 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 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.

103~6~
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 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.

103~
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.

- 10386~7 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.

10386~7 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.

~Q38~7 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 1038~7 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.

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.

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 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.

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, ~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 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 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 ~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 ~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.

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 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 ~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 ~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.

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 ~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 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, 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 ~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 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 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.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of preserving non-mineral matter in cool, humid air in an enclosed space comprising taking air from and adding air to said space, maintaining the air pressure in said space substantially between 4 mm Hg. absolute and 200 mm Hg.
absolute, maintaining the air temperature in said space sub-stantially between minus 2° C and plus 15° C., maintaining the relative humidity in said space substantially between 80% and 100%, the temperature of water employed to maintain said humi-dity being maintained sufficiently higher than the temperature within said space to provide a relative humidity in said 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.

2. The method of claim 1 wherein the stored matter comprises vegetative materials and floral crops such as potted chrysanthemums, potted azaleas and Easter Lilies, rooted and non-rooted chrysanthemum cuttings, rooted and non-rooted car-nation and geranium cuttings, cut flower such as snapdragon, carnation, roses, chrysanthemums and gladiolus, and green onions, apples, pears, nectarines and peaches, and the air temp-erature is maintained between about minus 1° and plus 4°C.

3. The method of claim 1 wherein the stored matter com-prises mature green tomatoes, avocados, green peppers, cucum-bers, snap and pole beans, red ginger, helicania latispathea, and vanda joapquim, and the temperature is maintained above about 5°C and below about 13°C.

4. The method of claim 1 with the steps of cooling said air and recirculating cool humid air over and about said matter.

5. The method of claim 1 with the step of wrapping said matter with material tending to retain water vapor in the space between the surface of said matter and said material.

6. The method of claim 1 with the step of humidifying said air by adding water thereto at a temperature not substan-tially less than the temperature of the air in said space.

7. A method according to claim 1, comprising the step of pre-conditioning said fresh air entering said space to a temperature, pressure and humidity proximate the corresponding conditions of the air in said space.

8. A method according to claim 1 including the steps of providing a supply of water, adding water vapor to said air from said supply, and maintaining the temperature of said supplied water no cooler than the temperature of said air.

9. A method according to claim 8, wherein air is con-tinuously removed from, and fresh air is continuously supplied to, said space, and said fresh air is moved into contact with a body of the supplied water which is held at said temperature.

10. A method according to either claim 7 or 8, wherein the temperature of the supplied water is maintained substantially between 2° C. to 20° C. higher than the temperature of the air in said space.

11. The method of claim 1 in which said heated water is introduced into said air through an hydraulic water atomizer with the step of exposing the water supply to atmospheric pressure to force the water into said space.

12. The method of claim 1 with the steps of removing low pressure air from, and supplying higher pressure fresh air to said space, humidifying part of said air on its way to said space and inducing circulation of humid air within said space by the movement of another part of said air into said space through a pneumatically actuated air mover.

13. The method of claim 1 with the step of wrapping said matter in water retention means enclosing said matter and retarding water-loss therefrom and enhancing heat transfer therefrom.

14. A method according to claim 1 wherein water em-ployed to maintain said humidity contains a non-volatile dis-solved antifreeze agent and the solution is heated to a propor-tionately higher temperature correlated to the concentration of said dissolved antifreeze agent than the temperature in said space, in order to raise the vapor pressure of the solution suf-ficiently to provide a relative humidity of at least 80 percent in said space.

15. A method according to claim 1 wherein humid air is exhausted from said space and fresh air is added to said space at a rate no more than about ten times the volume of said space at the reduced pressure thereof per hour.

16. A method according to claim 1 comprising the steps of withdrawing humid rarefied air from said space, admitting atmospheric air at reduced pressure in two paths into said space, inducing input of water to said space by the inflow of air in one of said paths, and inducing air at subatmospheric pressure to move into contact with said water by the inflow of air in the other of said paths.

17. A method according to claim 1 wherein air is with-drawn from said space and air from without said space is added thereto through a siphon fed pneumatic water atomizer, and wherein the water drawn through said atomizer is heated to no less than the temperature of the air in said space.

18. A method according to claim 1 comprising the step of recirculating a portion or all of said air in said space into contact with water employed to maintain said humidity in order to maintain the relative humidity of said air in said ?pace at not less than 80 percent.

19. A method according to claim 1 in which said matter comprises cut flowers, wherein said pressure is substantially within the range of 40 mm Hg. to 80 mm Hg., and said temperature is substantially within the range of 0° C. to 12° C.

20. A method according to claim 1 in which said matter comprises peaches, tomatoes, limes and nectarines, wherein said pressure is substantially within the range of 80 mm Hg. to 150 mm Hg., and said temperature is substantially within the range of 0° C. to 15° C.

21. A method according to claim 1 in which said matter comprises cuttings, rooted cuttings, non-rooted cuttings, and potted plants, wherein said pressure is substantially within the range of 40 mm Hg. to 80 mm Hg., and said temperature is substantially within the range of 0° C. to 4° C.

22. A method according to claim 1 in which said matter comprises vegetables, wherein said pressure is substantially within the range of 50 mm Hg. to 80 mm Hg., and said temperature is substantially within the range of 0° C. to 10° C.

23. A method according to claim 1 in which said matter comprises fully ripe fruit, wherein said pressure is substan-tially within the range of 70 mm Hg. to 200 mm Hg., and said temperature is substantially within the range of 0° C. to 14°C.

24. A method according to claim 1 in which said matter comprises apples and pears, wherein said pressure is substan-tially within the range of 40 mm Hg. to 60 mm Hg., and said temperature is substantially within the range of minus 1° C. to plus 2° C.

25. A method according to claim 1 in which said matter comprises avocados, wherein said pressure is substantially within the range of 40 mm Hg. to 100 mm Hg., and said temperature is substantially within the range of 7° C. to 13° C.

26. A method according to claim 1 for storing and pre-serving non-ripe fully mature fruit of the class exemplified by Mcintosh apples, Red Delicious apples, Jonathan apples, Bartlett Commice and Clapp pears, nectarines and Cardinal peaches, wherein said temperature is between approximately minus 1° C.
and plus 2° C., and said pressure is between approximately 40 mm Hg. and 120 mm Hg.

27. A method according to claim 1 for storing and pre-serving non-ripe mature tropical fruit exemplified by tomatoes, avocados, limes and pineapple, wherein said temperature is between approximately 7° C. and 15° C., and said pressure is between approximately 40 mm Hg. and 150 mm Hg.

28. Storage apparatus comprising an enclosed space, with walls constructed to withstand the force of a vacuum and adapted to receive and preserve metabolically active matter stored therein, means for evacuating said space, refrigeration means for maintaining a selected temperature within said space, means for admitting fresh air at a restricted rate into said space when said evacuating means withdraws air therefore and maintaining a flow of air through said space, water-humidifying means for humidifying said moving air, and means for maintaining the temperature of the water for said humidifying means not detrimentally less than the temperature of air in said space and maintaining a desired relative humidity in said space.

29. Storage apparatus of claim 28 with air mover means for recirculating said air within said space.

30. The storage apparatus of claim 28 in which said humidifying means includes means for spraying water into said moving air, and means for heating the water to be sprayed.

31. The storage apparatus of claim 30 with means for diverting part of said fresh air to said spray means.

32. The storage apparatus of claim 28 in which said humidifying means includes a reservoir of water, means for passing said air into contact with said water, and means for heating said water.

33. The storage apparatus of claim 28 in which said humidifying means comprises a spray of water, and means for recirculating said air within said space and into contact with the water of said spray.

34. The storage apparatus of claim 28 in which said water-humidifying means comprises a compartment segregated from but in communication with said enclosed space, and means for diverting unevaporated water from entering said enclosed space.

35. The storage apparatus of claim 28 with means for moving humid air from said humidifying means into said enclosed space, and means for heating said water sufficiently to raise the relative humidity of said humid air to between about 80% and 100%.

36. The storage apparatus of claim 35 with means for spraying said water in the path of air moving to said space.

37. The storage apparatus of claim 35 with means responsive to the moisture content of the air in said space for controlling the temperature of said water.

38. The storage apparatus of claim 28 with means responsive to the moisture content of the air in said space for controlling the temperature of the water of said humidifying means.

39. The storage apparatus of claim 28 in which cool-ing is accomplished by tubes containing heat-transfer fluid and having intimate contact with the interior of the walls enclosing said space.

40. The storage apparatus of claim 39 in which said tubes are arranged as pairs adjacent each other, one tube of each pair carrying fluid in one direction and the other in the opposite direction.

41. Hypobaric storage apparatus comprising a sealed space for receiving metabolically active matter to be preserved, means for maintaining sub-atmospheric pressure in said space, means for maintaining an appropriate temperature in said space, means for transmitting a restricted fresh air flow into said space, means for humidifying said air and means for removing air from said space, the apparatus being characterized in that the walls defining said space are constructed to withstand a pressure in said space as low as about 4mm Hg., that said means for maintaining a sub-atmospheric pressure is adapted to maintain it between about 4mm Hg. and 200 mm Hg., that said means for maintaining the temperature is adapted to maintain a temperature between about minus 2° and plus 15°C, that said means for main-taining the humidity is adapted to maintain a relative humidity between about 80% and 100% and that the humidifying means comprises means for maintaining the temperature of water in said humidifying means within a range tending to maintain said relative humidity.

42. Storage apparatus of claim 41 with means for raising the air pressure in said space to alleviate undesirable adaptation of said matter to a prolonged low oxygen environment.

43. Storage apparatus of claim 42 with means for changing said pressure cyclically.

44. Storage apparatus of claim 41 with means for changing the relative humidity in said space comprising means for raising the temperature of water to be vaporized to raise said relative humidity and lowering the said temperature to lower the said relative humidity.

45. Storage apparatus of claim 41 wherein said humid-ifying means comprises a body of water through which air is passed and a water spray, and said means for maintaining the water temperature is adapted to maintain temperature indepen-dently in said body of water and in said water spray.

46. Storage apparatus of claim 41 wherein said humid-ifying means comprises a tank containing a body of water and a vapor space above the water, an air outlet from said vapor space leading to said sealed space, an inlet to said vapor space, and means for moving less-humid air into said vapor space and moving more-humid air from said vapor space into said sealed space.

47. Storage apparatus of claim 46 with a water spray disposed to project water particles into said less humid air opposite the air movement, and wherein said last named means moves said less humid air from said sealed space and recirculates air and vapor through said spaces.

48. Storage apparatus of claim 46 wherein fresh air is induced into said vapor space with means for lowering the temperature of the fresh air relative the temperature of humid air therein, and wherein fresh water is introduced into said humidifying device with means for raising the temperature of the water.

49. Storage apparatus of claim 41 wherein fresh air is induced into said humidifying device with means for lowering the temperature of the fresh air relative the temperature of air in said apparatus, and wherein fresh water is introduced into said humidifying device with means for raising the temperature of the water relative to the said temperature of air in said apparatus.

50. Hypobaric storage apparatus providing an enclosed spaced adapted to receive metabolically active matter to be stored and preserved, characterized by means for maintaining a hypobaric pressure in said space, means for maintaining a desired temperature within said space, means for evacuating air from said space and passing fresh air into said space at a controlled rate, means for humidifying the air in said space, and means for selecting correlated pressure, temperature, air movement and relative humidity with respect to the nature of the matter to be preserved.

51. Storage apparatus of claim 50 characterized by means for recirculating air within said space, and means for humidifying and cooling said recirculated air comprising project-ing finely divided water particles into the path of said re-circulating air.

52. The storage apparatus of claim 51 with mist eli-minator means for removing entrained water droplets from said recirculated and humidified air, and means for adding fresh air to said recirculated air with the humidification thereof.

53. The storage apparatus of claim 50 characterized in that said humidifying means includes means for heating water for humidifying said air and means for increasing the temperature of said water to increase the relative humidity of said air.

54. Storage apparatus of claim 53 with means for cooling the walls of said enclosed space.

55. Storage apparatus of claim 50 characterized by means responsive to the moisture content of the air in said space for controlling the temperature of the water for humidi-fying said air.

56. Storage apparatus of claim 50 wherein said humi-difying means comprises a body of water and a vapor making space wherein water is evaporated, an outlet from said vapor making space leading to said enclosed space, a water spray disposed to project water through said outlet into said vapor making space, an inlet to said vapor making space, and means for moving less-humid air into said vapor making space and moving more-humid air from said outlet into said enclosed space.

57. Storage apparatus of claim 56 with means for removing entrained water droplets from said more-humid air be-fore it passes into said enclosed space.

58. Storage apparatus of claim 56 wherein said last named means moves said less-humid air from said enclosed space and recirculates air and water vapor through said space.

59. Storage apparatus of claim 50 with means for maintaining a difference between the pressure in said space and ambient atmosphere.

60. Storage apparatus of claim 50 with means for maintaining absolute pressure in said space.

61. Storage apparatus of claim 50 with means for recirculating air from said enclosed space through said humi-difying means, and means for controlling the rate of recircula-ting said air.

62. Storage apparatus of claim 50 with means for heat-ing the humidifying water and increasing the relative humidity of the air in said space, and means for cooling the walls of said space comprising heat-transfer fluid in contact with the walls enclosing said space.

63. Storage apparatus of claim 62 in which said heat transfer fluid is moved in adjacent tubes arranged in pairs connected to carry said fluid in opposite direction.

64. Storage apparatus of claim 50 wherein said humid-ifying means comprises a water supply in communication with said enclosed space, means for maintaining the liquid level of said supply, fluid conducting means for bringing ambient,fresh air to said humidifying means and into contact with water of said supply to enhance the humidity of said air at the temperature and pressure of said space, means comprising a pressure regulating valve for controlling the flow of said fresh air to maintain the hypobaric pressure desired in said space, and means for preventing water from flowing from said supply into said valve when the pressure in said space is raised to ambient pressure.

65. Storage apparatus of claim 64 wherein said regulating valve is disposed at a level above the liquid level of said water supply.