Abstract:
A method for removing dissolved oxygen from a plant product such as grapes or the like and for maintaining it in a controlled atmosphere when it is placed in mechanical means for harvesting, transport and storage, said means comprising a collection tank which receives the plant product which is present in a solid and a liquid state in this tank, said removal and controlled atmosphere being provided by using an inert gas, said tank having a lower portion or first part and a second upper part or portion into which the product is introduced when being placed in the tank. Provision is made for the use of said inert gas in an initial solid state, its subsequent sublimation and the interaction of the gas in gaseous state thus produced with said product inside the tank.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a §371 of International PCT Application PCT/EP2010/052601, filed Mar. 2, 2010, which claims §119(a) foreign priority to Italian patent application MI2009A000319, filed Mar. 5, 2009. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a method for protecting harvested plant products, for example but not exclusively grapes, by removing the dissolved oxygen and maintaining the products in a controlled atmosphere having a specified composition, according to the preamble of the principal claim. The invention also relates to equipment for the application of the aforementioned method. 
     2. Related Art 
     It is known that oxygen dissolved in or in contact with plant substances, particularly liquids of plant origin, is a cause of alterations which are harmful to the preservation of the sensory qualities of the substances. These liquids are generally formed during the operations of harvesting the plant products, especially where such harvesting is carried out with mechanical means. 
     For example, but not exclusively, reference may be made to grapes, especially in cases in which they are harvested by mechanical means. When compared with conventional manual harvesting, the mechanical harvesting of grapes has considerable advantages in terms of economics and management, enabling the harvesting operations to be conducted at lower cost and in a shorter time. 
     On the other hand, the use of such a procedure is impeded by problems of degradation of the potential quality of the grapes harvested by this method, which inevitably results in the breaking of the fruits and the outflow of a product in a liquid state known as the must. Since some components of the must are oxidized by contact with the oxygen present in the air, the potential quality is decreased. 
     This is one factor which sets serious limits on mechanical harvesting methods in cases where the grapes are to be processed into high-quality wines. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to propose a method and equipment for overcoming these limitations by preventing the oxidation of the must by removing the oxygen dissolved therein and protecting both the must and the fruit in an atmosphere having a lower or zero content of oxygen. 
     A further object of the invention is to propose a method and equipment of the aforementioned type which can be applied and produced in a simple way and at low cost. 
     These and other objects, which will be evident to those skilled in the art, are achieved by a method and equipment according to the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       To facilitate the understanding of the present invention, the following drawings are attached purely by way of non-limiting examples. In these drawings, 
         FIG. 1  shows a schematic view of equipment according to the invention; 
         FIG. 2  shows a schematic view of part of the equipment of  FIG. 1 ; 
         FIGS. 3A and 3B  show schematic views of two variants of parts of the equipment of  FIG. 1 ; 
         FIG. 4  shows a schematic view of a different part of the equipment of  FIG. 1 ; 
         FIG. 5  shows a schematic view of a variant of a part of the equipment of  FIG. 1 ; and 
         FIG. 6  shows a schematic view of a simplified version of the equipment of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made to  FIGS. 1 ,  2 ,  3 ,  4 ,  5  and  6 , in which identical reference numerals correspond to identical components. 
       FIG. 1  shows the whole of the invention, composed of a first part A, comprising components indicated by ( 1 ) to ( 21 ), for producing gaseous CO 2 , and another, second part B, comprising components ( 30 ) to ( 40 ), for containing the harvested product in a deoxygenating protective atmosphere. 
       FIG. 1  shows a vessel  1  for containing CO 2  in the solid state, in powder form, referred to hereinafter as “dry ice”, or in the form of pellets or other forms with various dimensions. These solid forms, by way of non-limiting example, are all denoted by the term “solid CO 2 ” in the following text, if they are not described in further detail. 
     The vessel  1 , referred to hereinafter as a “sublimer”, is provided with a hatch  3  for filling with solid CO 2 , a pierced plate or grid  2  for supporting the solid CO 2  and allowing the passage and distribution of the gaseous CO 2  as described below, and lines for supplying and extracting a gas. 
     The gas supply line comprises a duct or pipe  4  provided with a valve member  4 A for regulating the flow in the aforesaid pipe; the gas extraction line comprises ducts or pipes  5  and  6  and a pump  10 . This pump is capable of making the mixture of gases flow between the sublimer  1  and a heat exchange member  20 , referred to below as an “exchanger”, in which the gas absorbs heat from a fluid supplied from a line  21 , becomes heated, and transfers the heat absorbed in this way to the solid CO 2  present in the sublimer  1 , as a result of which the CO 2  sublimes and enters the gaseous state. This line  21  is connected to a heat source for heating the circulating gas, as described below. 
     The CO 2  in the gaseous state produced in this way cannot be absorbed by the internal recycling circuit formed by the ducts  4 ,  5  and  6 , since this circuit has a constant volume and operates at a virtually constant pressure. Consequently the CO 2  is allowed to flow out through the pipes  7  and  9  and is directed towards the second part B of the equipment, and in particular towards a tank  30  containing the harvested product to be treated. 
     The gas can be vented into the air through a pipe  8  and its valve member  8 A if necessary. 
     Part B of the equipment comprises the tank  30  for containing the harvested product; this tank is provided with a separating element or grid  31  to separate the solid parts, namely the fruits in the case of grapes, contained in a first portion  30 B of the tank, from the product in the liquid state, which is must in the case of grapes, contained in a second portion  30 A of the tank; this part B comprises the duct or pipe  9  for receiving the CO 2  in the gaseous state, provided with a regulating valve member  9 A, a duct  33 , provided with a valve member  33 A for transferring the CO 2  in the gaseous state from the first portion or lower part  30 A to the second portion or upper part  30 B of the tank  30 , and, if necessary, comprises a hatch  32  for the introduction of the harvested product and for covering the tank, and a further duct  34  for venting the gas into the atmosphere. 
     A further duct  35  provided with a valve member  35 A can transfer the product in the liquid state from the tank portion  30 B to the portion  30 A if the separator element  31  is not a pierced grid but is simply a supporting element without communicating holes between the portions  30 A and  30 B. 
     A duct  38  with a valve member  38 A enables the product in the liquid state to be extracted from the lower or first portion  30 A of the tank. The product in the solid state can be discharged from the second portion  30 B by tipping the tank or by using extraction means such as screws or other known means which are not shown in the drawing. 
     If the extraction is carried out by tipping, or in any case if the tank  30  is movable with respect to the sublimer  1 , the duct  9  is to be made from flexible material so as to allow the tank  30  to move relative to said sublimer. 
     A measuring device  36  for measuring the composition of the atmosphere present inside the tank can be used to discover the composition of this atmosphere; two temperature gauges  39  and  40 , inserted into the first and second portions  30 A and  30 B of the tank respectively, can be used to discover the temperature of the liquid state and the solid state of the harvested product present in these portions. 
     If the tank  30  is used without the aid of part A of the equipment which produces gaseous CO 2  (components  1  to  21 ), it is possible to dispense with the supply duct or line  9  and to provide the tank with a hatch  37 , placed in part  30 A to allow a sufficient quantity of solid CO 2  to be introduced into the first portion  30 A to develop the necessary amount of the substance in the gaseous state. This development takes place following the contact, and consequent heat exchange, between the solid CO 2  and the harvested product in the liquid state, which is must in the case of grapes, which will percolate (or be transferred) from the second portion  30 B to the first portion  30 A, starting from the moment when the harvested product  30 B is introduced. 
     A brief description is provided below to illustrate the operation of the invention and the method according to the invention. 
     The generation of the gaseous CO 2 , hereinafter simply referred to as “gas”, takes place as a result of the sublimation of the solid CO 2  contained in the sublimer  1  following the contact with the recirculated mixture which is suitably heated in the exchanger  20 . In order to obtain CO 2  in the gaseous state, the method employed in the present invention uses the process of sublimation of solid CO 2  by means of an external heat source by heating the recirculating CO 2 , and, subsequently, by exchanging heat between the latter and the solid CO 2  contained in the sublimer  1 , by direct contact between the recirculating gas and the solid CO 2 . 
     The exchanger  20  transfers heat to the mixture which passes through it (this mixture initially being composed of air) through the pipe  6 , the heat being drawn from a fluid circulating in the line  21  connected to the heat source. The heat source used can be either ambient air or other sources at a higher temperature such as cooling apparatus, for example the radiator, of the engine of the means for harvesting or moving the product. 
     Ambient air can be used as a heat source because of the sublimation temperature of solid CO 2 , which, at the pressures at which the invention is applied, that is to say at an atmospheric pressure of up to 4-5 bar, is, to a degree of approximation sufficient for our purposes, within the range from −78° C. to −50° C. These temperatures are suitable for the formation of a good thermal gradient with the external air to contribute to an efficient heat exchange and enable the desired sublimation to take place. 
     As regards the constructional characteristics of the operation of the invention, namely internal recirculation in part A of the equipment  1 , using a circuit composed of the sublimer  1 , the pump  10  and the pipes  4 ,  5  and  6 , hereinafter referred to as the “sublimation circuit”, a volume of gas equal to the volume of CO 2  which is sublimed as a result of the heat exchange with the recirculating mixture flows out of the sublimer  1  through the pipes  5  and  7  and is available for delivery to the tank  30 , in which the process of removing the dissolved oxygen and forming an atmosphere composed predominantly or entirely of CO 2  takes place. 
     The CO 2  composition of the gas mixture flowing out of the pipe  7  changes to an initial transient level and then reaches high values which, for the purposes of the present invention, can be considered to be those of a pure gas. In particular, when the system is first started up, air is present in the sublimation circuit, this air being subsequently enriched with gaseous CO 2  as the operation of the system continues. 
     For guidance, and with a degree of approximation sufficient for the present purposes, the oxygen content in the mixture present in the pipe  7  can be considered to decrease at least 2.5 times on each sublimation of a quantity of CO 2  equal to the volume of the circuit; this means that, after the sublimation of a volume of CO 2  equal to four times the volume of the sublimation circuit, the oxygen content in the gas will be less than 1%, which is more than adequate for the purposes of the present invention. 
     If it is necessary to supply the tank  30  with a gas having a specified reduced oxygen content, venting to the exterior must be carried out, using the pipe  8 , until the gas reaches the required value before being supplied to the tank  30 . 
     For practical purposes, since the harvested product arriving in the tank  30  is in contact with the external air, it is not necessary to vent the mixture initially, and the mixture formed in the sublimer  1  can be supplied directly to the tank  30 , since in any case this mixture has a lower oxygen content than air. 
     As regards the constructional characteristics of the sublimer  1 , it should be noted that the grid  2  is suitable for the purpose if the solid CO 2  is in the form of pellets or blocks of various shapes and sizes, since these forms are characterized in that they allow the gas to pass with a sufficiently uniform distribution over the surfaces of the solid CO 2  to provide satisfactory heat exchange. 
     However, if the solid CO 2  is present in the form of powder, or “dry ice” as it is commonly called, the grid  2  may be inadequate because of the tendency of the dry ice to become compacted, thus forming preferential paths with decreased potential for heat exchange and consequently for the sublimation according to the invention. 
     To overcome the tendency to compaction, where dry ice is used, it is possible to make special arrangements, for example by using hooded dispensers as described more fully below and illustrated in  FIGS. 2 ,  3  and  4 . 
       FIG. 2  shows the position of a hood  50  for dispensing the gas on a base  52  placed on the bottom of the sublimer  1 . 
       FIGS. 3A and 3B  show two possible embodiments of this hood  50  which operate in an identical way, and differ only in their shapes and sizes. In the drawings, the number  51  indicates the upper part, or cupola, of the hood  50 , which is of hemispherical shape in the case of  FIG. 3A  and cubic or parallelepipedal in  FIG. 3B . Each of the hoods in the aforesaid drawings has one face  51 A which has no closing side piece. 
     The hood may be made in any of the stated shapes or in any other shape, provided that it allows the formation of a space with a height (H), as shown in  FIGS. 3A and 3B , and a perimeter equal to that of the open part of the hood (in the form of a circumference in the case of  3 A, or in the form of a base square or rectangle in the case of  3 B). The pressure of the gas acts in this space, as described more fully below, to create a force capable of breaking up any compacted areas of the solid CO 2 , thus enabling the gas to flow out and pass through the body of the dry ice to create an efficient heat exchange. 
       FIGS. 3A and 3B  show how a gas dispenser  53  is located inside the hood; the hood is supported on the base  52  by supports  54 . The arrow  55  indicates the flow of the gas out of the face  51 A of the hood, this gas being supplied to the dispenser  53  through the duct  4 . 
       FIG. 4  shows a possible location of a hood  50  with a pipe  57 , connected to the pipe  4 , for supplying it with the gas, said pipe being provided with holes for dispensing the gas  56  directly into the sublimer  1  in the proximity of its base  52 . It should be noted that it is possible to place a plurality of hoods  50  and a plurality of holes  56  in the proximity of said base, in suitable geometrical arrangements, to enable the hoods to be used to prevent the formation of any agglomerations, and to enable the holes to be used to improve the distribution of the gas in the body of the solid CO 2 . 
     In the invention as described above, the hood is used as a device for multiplying the effect of the pressure by increasing the area to which it is applied, in order to break up any compacted structures. Another arrangement which may be made to avoid the formation of compacted areas, or to break them up if compaction has occurred, is that of making the sublimer  1  vibrate by known methods, this vibration occurring naturally if the sublimer is installed on moving mechanical means such as mechanical grape harvesters. 
     Another possible arrangement for avoiding the formation of compacted areas is that of providing the sublimer  1  with mechanical agitation, not shown in the drawings, produced by known methods (using internal agitators, for example). 
     The gas produced in this way in the sublimer  1  is brought into contact with the liquid, which is must if the harvested product is grapes, contained in the lower part of the tank  30 A, by a method such as bubbling at a plurality of points, to promote the removal of the dissolved oxygen, after which the gas passes through the grid  31  and mixes with the gaseous state present in the upper part  30 B to form therein an atmosphere which has a low oxygen content or is free of oxygen. 
       FIG. 5  shows a different method for distributing the gas in the upper part  30 B of the tank  30  in a case in which the filling of the tank with its contents takes place continuously, as in a mechanical grape harvester, or on a number of separate occasions. 
     This different embodiment of the invention enables the gas to be directed from the lower part  30 A, where it arrives through the supply duct  9 , provided with a gas distributor  9 K located within the product in the liquid state, to the upper part  30 B by initially passing through the pierced grid  31  and then, when this creates excessive resistance to the passage of the gas due to the head of the harvested product present in this upper part  30 B, by flowing through the aforesaid duct  33  which is connected to ducts or pipes  48 ,  41  and  49  provided with valve members  41 A and  49 A or one-way valves  42  and  50  operating according to a predefined pressure difference between their upstream and downstream sides. 
     A duct  45  connected to the pipe  9  and provided, if necessary with a detector or pressure gauge M  44 , a valve member  45 A and a one-way valve  46  operating according to a predefined pressure difference enables the gas to be supplied to the upper part  30 B of the tank, through the ducts  48 ,  41  and  49  in the case in which the excessive presence of the product in the liquid state in  30 A impedes, or prevents, the passage of the gas through the duct  33 . 
     To enable the invention to be understood more fully, it should be noted that, since CO 2  in the gaseous state is heavier than air, it is possible to make use of this second characteristic of the CO 2  to optimize the formation of the protective atmosphere in the second tank portion  30 B in contact with the contents. This can be achieved by introducing the CO 2  as closely as possible above the surface of the contents, in order to use its density to provide a “piston effect” to displace the mixture lean in CO 2  towards the outside, thus minimising phenomena of mixing between the incoming gas and the gas already present which has a lower CO 2  content. This makes it possible to obtain a higher CO 2  content in the aforesaid part or portion  30 B for the same quantity of introduced gas, and consequently a greater reduction in the oxygen content, thus providing more effective protection. 
     The above facts are even more evident if it is considered that, when the product is loaded into said portion  30 B, this operation inevitably creates turbulence in the tank, causing greater mixing with external air in the areas closer to the filling aperture  32 . 
     In  FIG. 5 , a pipe  47  provided with a valve member  47 A can be used to vent the gas to the outside. 
     The operation of the equipment as shown in  FIG. 5  and the application of the method by means of this equipment comprise different operating procedures such as the one which uses only the valve members  45 A,  41 A and  49 A, and in this case the one-way valves  46 ,  42  and  50  are not present in the equipment. 
     These different embodiments will now be described. 
     Use of the Valve Members  45 A,  41 A and  49 A 
     If the aforesaid valve members are used, the supply of gas commences with the valves  45 A,  47 A,  41 A and  49 A closed; thus the gas enters the lower part of the tank  30 A through the duct  9  and the distributor  9 K and reaches the upper part of the tank  30 B by passing through the grid  31 . 
     When the pressure gauge  44  indicates that a specified pressure has been exceeded, making it difficult for the gas to reach the part or portion  30 B by passing through the grid  31 , the valve  41 A is opened and the gas is supplied to the part or portion  30 B through the duct  33  and the duct  41 . 
     As the part  30 B of the tank continues to be filled up to a level above the outflow of the duct  41  into the tank portion  30 B, the gas pressure required to supply the gas increases, and when it has reached a specified level the valve member  49 A is opened. Thus the gas is supplied to the part of the tank  30 B through the ducts  33  and  49 , and is no longer supplied through the duct  41 . 
     If the pressure as detected by the pressure gauge  44  does not decrease following the opening of the valve  41 A or of the valves  41 A and  49 A (indicating the presence of pressure losses in the duct  33 ), the valve member  45 A is opened and the gas is supplied to said part  30 B by using the ducts  45 ,  48 ,  41  and/or  49 , without passing through the part or portion of the tank  30 A. 
     It should be noted that, when the valve member  45 A is closed, if there is a total or partial obstruction in the distribution member or distributor  9 K, the pressure will rise in the duct  45 , and if this rise is such that the valve member  45 A has to be opened, the pressure detected by the pressure gauge  44  decreases and the gas flows through the duct  33  into the lower part  30 A of the tank, and from there into the upper part  30 B through the grid  31 . Conversely, if the aforesaid pressure decrease is not present, this means that the passage of the gas through the duct  33  is impeded by both the lower part of the tank  30 A and the head of fluid in the upper part  30 B. 
     In this case, the gas is supplied to the second part of the tank  30 B without passing through the grid  31 , but by using the ducts  48 ,  41  and/or  49 , as described above. 
     Purely by way of example, the preceding description considers the case in which there are two lines, namely  41  and  49 , for supplying gas to the second part  30 B of the tank  30 . In fact, there may be one or more than two of these lines, depending on the geometrical characteristics of the tank. 
     If there are more than two supply ducts, the gas is supplied by following preceding procedure extended to cover all the ducts which are present. 
     All the valve members which have been described, and other functional members of the equipment which may not have been described, but which are commonly used in fluid supply and distribution equipment (such as members for controlling the flow rate, pressure and temperature, as well as the composition) are advantageously operated automatically by programmable logic controllers (PLCs) or similar units capable of reading the values recorded by the aforesaid members and of acting on the valve members by suitable control operations. This unit or units are not shown in the drawings. 
     Use of One-Way Valves  42 ,  46 ,  50   
     If the aforementioned one-way valves opening according to specified pressure differences are used, the pressure differences must be established in such a way that the pressure difference for opening the one-way valve  46  is greater than the pressure difference for opening the one-way valve  50  and the latter is greater than the pressure difference for opening the one-way valve  42 . The purpose of this arrangement is to ensure that, when the valve  46  opens, the valve  42  opens next, and the valve  50  opens subsequently if the flow in the duct  41  is impeded. 
     The aforementioned pressure differences must be lower than the opening pressure of a safety valve  43  (fitted on a pipe  43 K connected to the duct  48 ) to ensure that the gas is not expelled to the outside through this safety valve  43  instead of being supplied to the parts  30 A and/or  30 B of the tank  30 . 
     If the above constraints on the opening pressures of the one-way valves are complied with, then the gas supplied to the first part  30 A of the tank through the duct  9  and the distributor  9 K initially passes through the grid  31  to reach the second part  30 B. If the grid is obstructed, or impedes the creation of a pressure drop required to allow the gas to flow which is greater than that required to make the CO 2  flow from the supply duct  41  with the one-way valve  42 , the gas passes through the ducts  33 ,  48  and  41 . 
     If resistance to the passage of the gas through the supply duct  33  is simultaneously created in the latter, for example as a result of a blockage or the complete filling of the first part  30 A of the tank  30 , and if this resistance is greater than that present in the duct  45  and the one-way valve  46 , the gas will flow through the duct  45 . 
     If the above constraints on the opening pressures of the one-way valves are complied with, then the gas supplied to the first part  30 A of the tank  30  through the duct  9  and the distributor  9 K initially passes through the grid  31  to reach the second part  30 B. If the grid is obstructed, or impedes the creation of a pressure drop required to allow the gas to flow which is greater than that required to make the CO 2  flow from the supply duct  41  with the one-way valve  42 , the gas passes through the ducts  33 ,  48  and  41 . 
     If resistance to the passage of the gas through the supply duct  33  is simultaneously created in the latter, for example as a result of a blockage or the complete filling of the first part  30 A of the tank  30 , and if this resistance is greater than that present in the duct  45  and the one-way valve  46 , the gas will flow through the duct  45 . 
     Clearly, if there is a plurality of connections for the introduction of the gas into the tank, the procedure continues with cyclic repetition of the above processes. 
     To facilitate understanding, and without in any way detracting from the general applicability of the invention, an example of the invention is described below using numerical values. 
     It will be assumed that the maximum possible pressure in the circuit is 0.3 bar (for example because the circuit is provided with a safety valve  43  which is triggered at 0.3 bar), and that the gas is to be made to pass through the grid  31  until a head of harvested product of less than 50 cm is present above the grid, this being assumed to be equivalent, by way of example and provided that the harvested product has the same density as water, to a pressure of 0.05 bar generated in the first part of the tank  30 A. If the opening pressure of the one-way valve  42  is set to 0.05 bar (and if the outflow of the duct  41  into the portion  30 B is placed at a height of more than 50 cm with respect to the grid  31 , for example at 60 cm), then when this pressure is exceeded in the first part  30 A the gas will flow into the second part  30 B through the ducts  33 ,  48  and  41 , passing through the one-way valve  42 . 
     Similarly, if the opening pressure of the one-way valve  50  is set at a higher level than that of the valve  42 , for example at 0.09 bar (in other words when the second part  30 B is filled with fluid to a level 40 cm above the outflow of the duct  41  into it), then when this value is exceeded in the ducts  48  and  49  the gas will flow to the second part of the tank  30 B through the duct  49 , assuming, obviously, that the outflow of this duct into the portion  30 B has been placed at a height of more than 40 cm above the outflow of the duct  41  into the portion  30 B. 
     Furthermore, if, by way of non-limiting example, the pressure for opening the one-way valve  46  is set at 0.1 bar, then, if the gas in the circuit formed by the duct  9  and the distributor  9 K encounters a resistance of more than 0.1 bar to its passage, it will be supplied to the first part  30 A of the tank  30  through the ducts  45  and  33 . If the duct  33  also offers excessive resistance, for example due to the resistance to the passage of the gas through the grid  31  or due to the head of fluid present in the second part of the tank  30 B, the gas will pass through the ducts  45 ,  48  and  41  or  45 ,  48  and  49 , and will thus be supplied to the part  30 B of the tank  30 . 
     The choice of the ducts through which the gas flows, namely  45 ,  48  and  41  or  45 ,  48  and  49 , will therefore depend on the minimum resistance present in  41  and  42  respectively. This choice is made automatically as a function of the choice of the pressures required for opening the one-way valves  42 ,  46  and  50 . 
       FIG. 6  shows a simplified version of the invention, in which the gas is formed from solid CO 2  by placing the latter directly in the first part or lower portion  30 A of the tank  30  before the commencement of the loading of the harvested product into the second part or upper portion  30 B of the tank. When the harvested product has been loaded in, its liquid state enters the first part of the tank  30 A by percolating through the grid  31 , or, if the grid is made with a closed base, through the duct  35  provided with a valve member  35   a.    
     On reaching the lower part  30 A, the product in the liquid state, in contact with the solid CO 2 , transfers heat to the latter which sublimes and flows into the second portion  30 B, either by passing through the pierced grid  31  or through a duct  70 , in a similar way to that described above. 
     The solid CO 2  placed in the part  30 A starts to sublime even before the product in the liquid state percolates on to it, since the solid CO 2  absorbs the heat required for its sublimation from the contact with the part  30 A itself; this fact does not invalidate the invention, since the gaseous CO 2  formed in this way contributes to the decrease of the oxygen present in the container, and therefore, when the liquid percolates into the container, the atmosphere is already suitable for its treatment. 
     However, in order to limit the sublimation in the absence of harvested product, as described above, it is possible to insulate the part  30 A thermally, which in any case will be done if it is desired to supply a quantity of solid CO 2  to the aforesaid part  30 A such that it not only deoxygenates and protects the content, but also cools the liquid component contained therein. 
     The duct  70  can be provided with a one-way valve which opens at a specified pressure. This valve is not shown in the drawings, since its operation is similar to that described above. 
     Various embodiments of the invention have been described. However, other embodiments are possible in accordance with the above description and are to be considered as falling within the scope of the following claims. 
     It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.