Abstract:
The invention relates to packaging comprising a breathable valve, intended to extend the green life of perishable products. The packaging comprises a flexible container ( 1 ) and a breathable valve assembly ( 2 ) that can be used to control the concentration of oxygen, carbon dioxide, water vapor and ethylene in the atmosphere inside the container, such as to maintain a desired value depending on the weight and the respiration rate of the product. The breathable valve assembly ( 2 ) comprises a ring ( 3 ) and a breathable lid ( 4 ) assembled in order to close the flexible container ( 1 ). The packaging is advantageous over the prior art in that it can be assembled without using any heat-sealing technique and in that it can extend the green life of perishable products, such as fruits and vegetables.

Description:
PURPOSE 
       [0001]    The present invention relates to the packaging of perishable items such as vegetables and fruits, in particular to the means for controlling gas composition in the atmosphere inside the container and facilitating manual closure, for instance, of the packing without using automatic techniques such as heat sealing. 
       DESCRIPTION OF PRIOR ART 
       [0002]    Some perishable products, such as vegetables and fruits, continue their ripening and ageing process after being harvested. During ripening and ageing, the product undergoes a respiratory process characterized by oxygen absorption and the release of carbon dioxide and ethylene. Additionally, the product transpires moisture, reducing its weight. Decreasing respiration and transpiration in the packaging is critical to extend the green life of perishable products. Another problem associated with uncontrolled respiration is reaching a high concentration of carbon dioxide in the atmosphere inside the packaging, which can affect the organoleptic properties of the perishable product. 
         [0003]    Prior art includes some alternatives for the control of respiration and transpiration in packaging perishable products. These technologies include the following: transportation in refrigerated containers; hypobaric packaging, containers with devices that remove ethylene; active packaging that traps oxygen, carbon dioxide, and ethylene; modified atmosphere packaging, coatings on cardboard; direct chemical or physical treatment on the product; and breathable packaging. Compared with breathable packaging, other technologies have some disadvantages, such as the possibility of damage due to low temperatures in refrigerated alternatives, high costs, consumer perception, and difficulties in packaging operations. 
         [0004]    Breathable packaging is one of the most commonly used packaging for perishable products due to its benefits in terms of costs. Breathable packaging technology offers various options, including: high permeability films; macro and microperforated films; permeable patches and windows; air vents and valves. 
         [0005]    Macro and micro perforated films have been disclosed in several patents (U.S. Pat. No. 5,130,152, US2005180664, DE202005011737, GB1106265, GB1134667, GB2141688, and JP6199385). This alternative has some disadvantages, such as the need to seal the mouth of the packaging, the product may block some of the perforations, and the need for additional operations in the manufacture of the film or bag. 
         [0006]    Permeable patches and windows have been disclosed in prior art (U.S. Pat. No. 4,842,875, U.S. Pat. No. 4,943,440, U.S. Pat. No. 5,045,331, GB1071586, FR2686577, and CN1036539). The main disadvantages of this technology are: the need to seal the mouth of the packaging and the need for additional operations in the manufacture of the film or bag. 
         [0007]    Air vents have been disclosed in prior art (US2004131731, US2007257040, US2008116098, WO2007008459, WO2010141467, and JP2002308293). The main disadvantages of this technology are: the need to seal the mouth of the packaging and the need for additional operations in the manufacture of the bag. 
         [0008]    Although some valves have been disclosed in prior art (U.S. Pat. No. 3,937,396, U.S. Pat. No. 5,996,800, US2003152296, WO2004108557, WO2004043191, EP0700839, JP1279073, JP11301743, and JP2006125559), all valves require sealing the bag, as well as additional operations in the manufacturing of the bag. 
         [0009]    The packaging of the present invention discloses a combination of a flexible container and a breathable valve, composed in turn by a ring and a breathable lid to extend the green life of perishable products, such as fruits and vegetables. The packaging of the present invention provides the possibility of mechanical assembly, either manually or automatically, without the need of heat-sealing technology or additional operations in the manufacture of the bags; it can also be opened and reopened in ripening chambers; it is recyclable and affordable. In addition, extending the green life of the product can increase the growth period of the fruit or vegetable in the plant. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention provides a packaging with a breathable valve to extend the green life of perishable products that undergo a respiratory process after being harvested, such as vegetables and fruits. The packaging comprises a flexible container and a valve assembly that is assembled in the mouth of the flexible package in order to create a controlled gaseous atmosphere inside the package. In turn, the valve assembly comprises a ring located outside the flexible container and a breathable lid located inside the flexible container; these two components can be mechanically assembled without the need of heat sealing technologies to close the mouth of the flexible container. The breathable lid has fastening means to attach both parts to the middle of the flexible container, which can be an interference fit and pressure fittings. The breathable lid can be a plastic cover with multiple microperforations or nanoperforations, or an annular section that allows the installation of a permeable membrane interspersed among the ring, the flexible container and the breathable lid. 
         [0011]    The permeable membrane can be a cavitated, microperforated, or nanoperforated film. The concentration of oxygen, water vapor, carbon dioxide, and ethylene is controlled by the permeation of the breathable lid, the weight and respiration rate of the packed perishable product. The permeation of the breathable lid is controlled by the number and size of micro and nanoperforations, in the case of the plastic cover and the micro and nanoperforated film; and by gas permeability, in the case of the cavitated film. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0012]      FIG. 1  illustrates a breathable valve ( 2 ) assembled and installed in the mouth of the flexible container ( 1 ). The figure also shows an interference fit as fastening means and a micro or nanoperforated plastic cover as breathable lid ( 4 ). In this particular embodiment, the breathable lid ( 4 ) has a circular cavity to allow good assembly by interference with the ring ( 3 ). 
           [0013]      FIG. 2  illustrates a breathable valve ( 2 ) assembled and installed in the mouth of the flexible container ( 1 ). The figure also shows an interference fit as fastening means and a micro or nanoperforated plastic cover as breathable lid ( 4 ). 
           [0014]      FIG. 3  illustrates a breathable valve ( 2 ) assembled, a pressure fitting ( 6 ) as fastening means and a micro or nanoperforated plastic cover as breathable lid ( 4 ). 
           [0015]      FIG. 4  illustrates a breathable valve ( 2 ) assembled, a pressure fitting ( 6 ) as fastening means and a micro or nanoperforated plastic cover as breathable lid ( 4 ). The figure also illustrates a rectangular channel ( 7 ) to facilitate release without moving parts of the pieces to be assembled by pressure ( 6 ). 
           [0016]      FIG. 5  illustrates a breathable valve ( 2 ) assembled, an interference fit ( 8 ) in the ring ( 3 ) as fastening means and a micro or nanoperforated plastic cover as breathable lid ( 4 ). 
           [0017]      FIG. 6  illustrates another embodiment of the invention using a breathable valve ( 2 ) of square shape, an interference fit as fastening means and a micro or nanoperforated plastic cover as breathable lid ( 4 ). 
           [0018]      FIG. 7  illustrates another embodiment of the invention using a breathable valve ( 2 ) of triangular shape, an interference fit as fastening means and a micro or nanoperforated plastic cover as breathable lid ( 4 ). 
           [0019]      FIG. 8  illustrates another embodiment of the invention wherein the breathable lid of the valve assembly is an annular section, allowing the installation of a permeable membrane ( 10 ) interspersed among the ring ( 3 ), the flexible container ( 1 ) and the breathable ring ( 9 ). 
           [0020]      FIG. 9  illustrates the evolution of oxygen and carbon dioxide concentration over time for two prototypes made in accordance with the present invention. It evaluates two microperforated plastic covers with 11 and 18 microperforations that range between 250 and 300 microns in diameter. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    The present invention provides a packaging fitted with a breathable valve designed to extend the green life of perishable products that undergo a respiratory process after being harvested, such as vegetables and fruits. With reference to the embodiment illustrated in  FIGS. 1 and 2 , the packaging comprises a flexible container ( 1 ) characterized by the presence of at least one mouth, and at least one valve assembly ( 2 ) consisting of two parts: a ring ( 3 ), located on the periphery and the outer surface of the flexible container&#39;s mouth ( 1 ), and a breathable lid ( 4 ), which mechanically fits to the inner part of the ring ( 3 ), such that the material of the flexible container&#39;s mouth ( 1 ) is fastened between the breathable lid ( 4 ) and the ring ( 3 ). 
         [0022]    The flexible container ( 1 ) is a flexible film, manufactured for example by casting, blowing extrusion, flat film extrusion, coextrusion, or lamination. The polymeric film is manufactured with a polymer preferably selected from the group comprising polyethylene, polypropylene, polyethylene terephthalate, polyamide, polystyrene copolymers, cellophane, polylactic acid, cellulose acetate, thermoplastic starch and its derivatives, and mixtures thereof. 
         [0023]    With reference to  FIGS. 3 and 4 , the valve assembly ( 2 ) comprises two parts: the ring ( 3 ) and the breathable lid ( 4 ), which can be mechanically fitted and do not need using heat sealing technologies to close the flexible container&#39;s mouth ( 1 ), or additional operations in the manufacture of the bag. The breathable lid ( 4 ) has fastening means to attach both parts to the flexible container ( 1 ) such that the film that forms the container&#39;s mouth is fixed between the two sides of the valve. The embodiment illustrated in  FIGS. 3 and 4  uses a pressure fitting ( 6 ).  FIGS. 3 and 4  also illustrate a rectangular channel ( 7 ) in the breathable lid ( 4 ) to facilitate release without moving parts of the pieces to be assembled by pressure ( 6 ). 
         [0024]    With reference to  FIGS. 1 ,  2  and  5 , in another embodiment of the present invention, the fastening means for attaching both parts of the valve assembly ( 2 ) to the flexible container ( 1 ) are an interference fit on the ring ( 3 ) and a breathable lid ( 4 ). In this sense, it is desirable for the breathable lid ( 4 ) to have tapered sidewalls to facilitate assembly with the ring ( 3 ). With reference to  FIG. 5 , in a particular embodiment of the present invention, the interference fit is produced between an extension ( 8 ) of the breathable lid ( 4 ) and the corresponding cavity in the ring ( 3 ). With reference to  FIGS. 5 to 7 , although the preferred embodiment is a ring ( 3 ) and a breathable plug ( 4 ) of circular shape, it is possible to use other shapes, such as triangular or polygonal. 
         [0025]    The ring ( 3 ) and breathable lid ( 4 ) of the valve assembly ( 2 ) may be manufactured by injection molding or press molding, using a polymer preferably from the group comprising thermoplastic polyurethane, vulcanized thermoplastic, thermoplastic elastomers, polyethylene, polypropylene, polyethylene terephthalate, polyamide, polystyrene copolymers, polylactic acid, cellulose acetate, thermoplastic starch and its derivatives, and mixtures thereof. In a particular embodiment of the present invention, the ring ( 3 ) and breathable lid ( 4 ) of the valve assembly ( 2 ) are made of a material whose hardness should be less than the one that produces a mark on the fruit or vegetable. For example, the hardness for bananas must be less than 80 Shore A for bananas, preferably less than 60 Shore A, in order to ensure that the bananas are not damaged or dented by the valve. The use of rounded contours is advantageous for this same reason. 
         [0026]    With reference to  FIGS. 1 to 7 , in another embodiment, the breathable lid ( 4 ) can be a plastic cover characterized by multiple micro or nanoperforations ( 5 ). 
         [0027]    With reference to  FIG. 8 , another embodiment of the present invention uses an annular section ( 9 ) that allows the installation of a permeable membrane ( 10 ) interspersed among the ring ( 3 ), the flexible container ( 1 ), and the annular section ( 9 ). The permeable membrane ( 10 ) can be a cavitated, microperforated, or nanoperforated film. The cavitation film may be manufactured using a cavitation load such as calcium carbonate. The microperforated film may be manufactured using for example mechanical, laser, or electrostatic technology. The present invention can use any type of breathable lid ( 4 ), even with the permeable membrane ( 10 ) interspersed between the ring ( 3 ) and the flexible container ( 1 ). The annular section ( 9 ) of this embodiment is mechanically fitted to the ring ( 3 ) and the flexible container&#39;s mouth ( 1 ) for tensioning the permeable membrane ( 10 ). 
         [0028]    The concentration of oxygen, water vapor, carbon dioxide, and ethylene can be controlled by the permeation of the breathable lid ( 4 ), and the weight and respiration rate of the packed perishable product. The permeation of the breathable lid ( 4 ) is controlled by the number and size of micro and nanoperforations, in the case of the plastic cover and the micro and nanoperforated film, and by gas permeability, in the case of the cavitated film. 
       EXAMPLES 
       [0029]    The following examples were obtained using a packaging prototype comprising a breathable valve for perishable products: 
       Example 1 
       [0030]    This example evaluates a packaging prototype of the present invention having the following characteristics: the flexible container is a bag made of a 30-microns thick polyethylene film with dimensions of 300 by 380 mm, a valve assemblage with an internal diameter of 32 mm with a plastic cover with 11 microperforations between 250 and 300 microns. Approximately 1.2 kg of bananas were packed and their green life at room temperature and cooled to 13° C. was evaluated. The prototype of the disclosed packaging was then compared to the following technologies available in the state of the art: a 30-microns thick microperforated bag with 50 microperforations with a diameter of 200 microns, and a 30-microns thick macroperforated bag with 12 perforations with a diameter of 12.5 mm. The packaging comprising a breathable valve increases green life, decreases weight loss, and reduces the conversion of starch in carbohydrates (measured as degrees Brix). 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                 Degrees 
                 Weight 
               
               
                   
                 Green Life 
                 Brix 
                 Loss, % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Breathable valve with 11 
                 More than 28 
                 12.0 
                 0.49 
               
               
                 microperforations between 250 
                 days 
               
               
                 and 300 micros at room 
               
               
                 temperature 
               
               
                 Breathable valve with 11 
                 More than 28 
                 6.0 
                 0.17 
               
               
                 microperforations between 250 
                 days 
               
               
                 and 300 micros at 13° C. 
               
               
                 Microperforated bag with 50 
                 28 days 
                 11.5 
                 0.15 
               
               
                 microperforations with a diameter 
               
               
                 of 200 microns at 13° C. 
               
               
                 Macroperforated bag with 12 
                 25 days 
                 14.5 
                 0.60 
               
               
                 perforations with a diameter of 
               
               
                 12.5 mm at 13° C. 
               
               
                   
               
             
          
         
       
     
       Example 2 
       [0031]    This example evaluates a packaging prototype of the present invention with the following characteristics: the flexible container is a bag made of a 30-microns thick polyethylene film with dimensions of 300 by 380 mm, a valve assemblage with an internal diameter of 32 mm with an annular section, and a mechanically microperforated film. Approximately 1.2 kg of bananas was packed and their green life cooled to 13° C. was evaluated. The prototype of the disclosed packaging was compared to the technologies available in the state of the art mentioned in Example 1. The packaging comprising a breathable valve increases green life, decreases weight loss, and reduces the conversion of starch in carbohydrates (measured as degrees Brix). 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 Degrees 
                 Weight 
               
               
                   
                 Green Life 
                 Brix 
                 Loss, % 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Breathable valve with a 
                 More than 28 
                 5.0 
                 0.06 
               
               
                 mechanical microperforated film 
                 days 
               
               
                 in the annular section at 13° C. 
               
               
                 Microperforated bag with 50 
                 28 days 
                 11.5 
                 0.15 
               
               
                 microperforations with a diameter 
               
               
                 of 200 microns at 13° C. 
               
               
                 Macroperforated bag with 12 
                 25 days 
                 14.5 
                 0.60 
               
               
                 perforations with a diameter of 
               
               
                 12.5 mm at 13° C. 
               
               
                   
               
             
          
         
       
     
       Example 3 
       [0032]    This example compares the evolution of oxygen and carbon dioxide concentration at 13° C. for two plastic covers with 11 and 18 perforations. The same flexible container was used, the same valve assembly and the same number of bananas in Example 1. With reference to  FIG. 9 , after 4 days the concentration of gases becomes regulated to a constant value that depends on the number of perforations. 
       Example 4 
       [0033]    An important characteristic of the breathable valve&#39;s materials is its hardness and contours, in that no damage is caused to the perishable product while packing. This example evaluates the effect that the hardness and contours of the material of the packaging comprising a breathable valve has on the bananas. The effect of 3.5 kg (approximately three bunches of green bananas) applied to the breathable valve and on the banana peel was evaluated. Using a Shore A hardness of less than 80 and a valve with a rounded contour is essential to prevent the banana peel from denting. 
         [0000]    
       
         
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
             
             
               
                   
                   
               
               
                   
                 Hardness 
                   
               
             
          
           
               
                 Material 
                 Shore A 
                 Shore D 
                 Surface 
                 Result 
               
               
                   
               
               
                 Polyurethane 
                 80 
                   
                 Rounded 
                 No dents 
               
               
                 Polyurethane 
                 80 
                   
                 Sharp edges 
                 Dents 
               
               
                 High density polyethylene 
                   
                 55 
                 Sharp edges 
                 Dents 
               
               
                 Polypropylene 
                   
                 78 
                 Rounded 
                 Dents 
               
               
                 Rubber 
                 62 
                   
                 Rounded 
                 No dents 
               
               
                   
               
             
          
         
       
     
         [0034]    The above methods, figures, and examples are merely illustrative of the inventive concept. Any person skilled in the art will understand that evident variations and enhancements may be made without departing from the inventive concept, which is defined only by the following claims.