Stock material or miscellaneous articles – Structurally defined web or sheet – Including aperture
Patent
1994-01-21
1997-09-30
Watkins, William
Stock material or miscellaneous articles
Structurally defined web or sheet
Including aperture
428131, 428132, 428134, 428135, 428137, 428913, 426326, 426324, 426316, 426415, 426118, 383102, 383103, B32B 324, B65D 6500
Patent
active
056724063
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a material having a passage therethrough. (The passage may be completely closable.) Such material has a wide variety of applications. For illustration, the invention will be described with reference to one such application, namely packaging of edible produce, in particular to maintain it in a preservative atmosphere, bearing in mind that the requirements can vary with temperature.
All harvested vegetables, flowers and fruits continue to respire, absorbing oxygen and emitting carbon dioxide. A number of parallel biological paths are involved leading to loss of weight (although loss of water is usually the main cause of weight loss), some heat production, loss or change of flavour, change of texture, and discoloration of outer surfaces or cut surfaces or in the body of the product. The growth and excretions of micro-organisms present at harvesting can produce other changes. Virtually all these changes are deleterious to the acceptability of the product to the consumer.
Respiration increases with increasing temperature. The main method of increasing storage life is therefore to hold the product at lowered temperatures, often a little above 0.degree. C. However some products (e.g. runner beans, cucumbers, green peppers, tomatoes, bananas) cannot be stored below 5.degree.-11.degree. C. Respiration rates show a wide range, broccoli being nearly 10.sup.2 times as fast as onions or potatoes. Values also vary with variety within a given species, cropping and harvesting methods used, year of crop and degree of ripeness.
It might be thought that the respiration rate (in particular the carbon dioxide production rate) could be sharply reduced by lowering the concentration of oxygen. However below 2-3% (depending on product) anaerobic processes begin, due to both the product and its accompanying micro-organisms. These, usually, produce rapid and unacceptable tainting of flavour. Alcohol production by yeasts often predominates while aldehydes are often the main cause of unacceptability.
If a product is wrapped in a sealed impermeable packaging system then even a modest respirer such as tomatoes soon lowers the oxygen concentration to anaerobic conditions. Ripening of tomatoes is completely inhibited and does not resume when the package is opened and many of the fruits develop rots or suffer fungal attack. (An atmosphere of 6% oxygen retards ripening, which however recommences on opening to air, with no adverse effects on eating quality.) To overcome this rot problem, it is known to pass such a sealed impermeable pack (preferably after a short period of storage and temperature reduction, to allow the oxygen concentration to drop rapidly), under an adjustable mechanical `pecking` head which punches in the necessary holes, e.g. typically three holes of0.4 mm.sup.2 per pack. Changing their diameter or number provides easy adjustment for product type, variety type, weight and expected downstream conditions before consumption etc--always provided the basic knowledge is available. However, by itself, this has been found to give inadequate variation with temperature.
An alternative approach to this problem has been to devise selectively permeable materials which can be used as panels in gas-impermeable wrapping materials for fresh fruit, vegetables or flowers. These panels can be of a microporous material having greater CO.sub.2 permeability than O.sub.2 permeability, and it has been proposed to use that area of material as will transmit oxygen at the same rate as the packaged contents will consume it. However, this presupposes a certain temperature of storage, as oxygen consumption of produce increases much more sharply with temperature than does the oxygen transmissibility of the material. At accidentally high temperatures, therefore, the oxygen within such a wrapping will be consumed much faster than it can be replenished, leading to anaerobic conditions and their drawbacks as already described.
It is known that high carbon dioxide concentrations inhibit micro-orga
REFERENCES:
patent: 3026209 (1962-03-01), Wiblack et al.
patent: 3040966 (1962-06-01), Crane
patent: 3097787 (1963-07-01), Schur
patent: 3245606 (1966-04-01), Crane
patent: 3795749 (1974-03-01), Cummin et al.
patent: 4141487 (1979-02-01), Faust et al.
patent: 4419373 (1983-12-01), Oppermann
patent: 4497431 (1985-02-01), Fay
patent: 4503561 (1985-03-01), Bruno
patent: 4530440 (1985-07-01), Leong
patent: 4541426 (1985-09-01), Webster
patent: 4740378 (1988-04-01), Jameson
patent: 4805398 (1989-02-01), Jourdain et al.
patent: 4886372 (1989-12-01), Greengrass et al.
patent: 4944187 (1990-07-01), Frick et al.
patent: 5053594 (1991-10-01), Thota et al.
patent: 5114766 (1992-05-01), Jacques
patent: 5254354 (1993-10-01), Stewart
patent: 5330811 (1994-07-01), Buchalter
Printout Abstracts "Freshhold", Ventflex, Hercules and DRG Ventflex.
Process Industry Journa Jul./Aug. 1989 p. 9 "Creating the right atmosphere".
Independent "Packing discovery prolongs shelf-like" Jun. 1989.
Bevis Michael John
Challis Anthony Arthur Leonard
British Technology Group Limited
Watkins William
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