Food or edible material: processes – compositions – and products – Packaged or wrapped product – Packaging structure cooperating with food generated gas
Reexamination Certificate
1999-08-23
2001-04-03
Brouillette, Gabrielle (Department: 1761)
Food or edible material: processes, compositions, and products
Packaged or wrapped product
Packaging structure cooperating with food generated gas
C426S107000, C426S106000, C426S415000, C426S395000, C428S913000
Reexamination Certificate
active
06210724
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to containers with temperature-sensitive properties, particularly for packaging fresh fruit and other foodstuffs.
2. Introduction to the Invention
It is well known to package objects in sealed containers. When biological materials are packaged, it is desirable that the atmosphere within the container should be correlated with the stored material and the storage temperature. For materials to be stored below room temperature, the desired atmosphere is low in oxygen, because this minimizes the production of pathogens. One technique for producing the desired modified atmosphere is to use a container having one or more atmosphere-control members (ACMs) whose permeability to gases is substantially greater than the rest of the container. An ACM can be, for example, composed of a microporous film, optionally coated with a thin layer of a polymer. Another technique is to fill the container, before it is sealed, with a desired mixture of gases. Reference may be made for example to U.S. Pat. Nos. 4,734,324 (Hill), 4,830,863 (Jones), 4,842,875 (Anderson), 4,879,078 (Antoon), 4,910,032 (Antoon), 4,923,703 (Antoon), 5,045,331 (Antoon), 5,160,768 (Antoon) and 5,254,354 (Stewart); copending, commonly assigned Application Serial No.09/121,082; International Publication Nos. WO 96/38495, and WO 99/12825; and European Patent No.676920, and European Patent Applications Nos. 0,351,115 and 351,116 (Courtaulds). The entire disclosure of each of those documents is incorporated herein by reference for all purposes.
SUMMARY OF THE INVENTION
Various problems can arise when the temperature within a sealed container becomes excessive. With biological materials, especially fruit, the low level of oxygen which is desirable at low temperatures can be dangerous at higher temperatures, because it promotes the production of pathogens. This is particularly dangerous when visual inspection does not reveal the presence of such pathogens. For example, cut melons which have been stored at room temperature in a sealed package can appear fresh even when high concentrations of pathogens are present. Another problem is that when a package of biological materials is filled with a mixture of gases at the time of packaging, in order to provide a desired atmosphere at that time, changes in the biological materials after they have been packaged can make the mixture of gases undesirable after a day or two (or more). A different problem arises when microwaves are used to cook a foodstuff in a sealed package, thus generating dangerously high temperatures and pressures within the package.
The present invention solves such problems by providing a simple and effective way of venting a sealed package when it reaches an excessive temperature and/or after a particular time. The invention can also be used to increase the rate at which gases can pass out of and into a sealed container, in response to an increase in temperature, without opening the container. The invention can also be used to provide an indication of the thermal history of a sealed package or other article.
The invention makes use of a temperature-sensitive cover unit which is secured to a wall of the container. The cover unit includes a barrier member which covers a window in the wall. Usually, the barrier member prevents all gases from passing through the window; however the invention includes the possibility that the barrier member has limited permeability to gases. The window is usually a simple aperture, but can be an atmosphere-control member. The barrier member is secured over the window by a layer of adhesive which is selected so that it loses adhesive strength when it is heated to the elevated temperature at which the container is to be vented. The cover unit also contains a base member and a force member. The base member is secured to the container. The force member, at the desired elevated temperature, changes shape and causes the barrier member to move so that at least part of the window is opened to the ambient atmosphere. Preferably, the base, barrier and force members are adjacent parts of a single component, e.g. a strip of polymeric material. However, many other possibilities exist. For example, the base, force and barrier members can be indistinguishable parts of the same member, or the force and barrier members can be indistinguishable parts of the same member.
The force member is preferably elastically deformed, in which case the container is vented when the elastic recovery forces exceed the adhesive forces. Alternatively, the force member can be stable at lower temperatures, but be heat-recoverable (i.e. tend to change shape) at an elevated temperature equal to or below the temperature at which the container is to be vented. The adhesive bond generally fails over a period of time which depends on the temperature. Thus, the bond will fail slowly, if at all, at relatively low temperatures and more rapidly as the temperature increases. This makes it possible to use the control unit to vent a package (e.g. a gas filled package) after a desired period of time at a relatively low temperature.
If it is observed that the barrier member is no longer secured over the window, this indicates that the package has passed through a time-temperature regime sufficient to cause the barrier member to be pulled away from the window, even if the temperature at the time of observation is relatively low. This makes it possible use the cover unit to indicate the thermal history of a sealed package. It is also possible to use certain cover units to provide an approximately quantitative indication of the thermal history of a sealed package. In a cover unit to be used in this way, there are two additional requirements. First, the barrier member must be secured to the base member by a layer of adhesive which has an axis of substantial length. Second, the recovery forces which are generated by the force member must tend to peel the barrier member away from the base member along a line at an angle, preferably at a right angle, to the axis. In this way, at any particular time, the length of the barrier member which has peeled away from the base member is an indication of the thermal history of the article. When the cover unit is used solely as an indicator of thermal history, as discussed above, it can be used with any article, since its value does not depend on the presence of an aperture in the package or other article.
In a first aspect, this invention provides a sealed package including a cover unit as described above. Such a package, for example, comprises
(A) a sealed container which defines an interior space, and
(B) an object within the interior space;
the sealed container comprising
(1) walls which
(a) define the interior space, and
(b) contain a window through which gases can pass into or out of the interior space; and
(2) a temperature-sensitive cover unit which comprises
(a) a base member which is secured to a wall of the container,
(b) a barrier member which is secured over the window and reduces the rate at which gases pass through the window,
(c) a layer of an adhesive which secures the barrier member over the window, and which loses adhesive strength if it is heated from the first temperature to an elevated temperature, and
(d) a force member which, when the cover unit is heated from the first temperature to the elevated temperature, changes shape and causes the barrier member to move so that it uncovers at least part of the window, thereby increasing the rate at which gases pass through the window.
It should be noted that such a package may be vented after an extended time (e.g. 12 to 72 hours) at the first temperature (i.e. without any increase in temperature), because the adhesive bond fails through creep of the adhesive securing the barrier member over the aperture.
In a second aspect, this invention provides an empty container including a cover unit as described above or a precursor for a cover unit as described above, i.e. a cover unit which can be converted into the desired cover
Clarke Raymond
James Steven
Larson Andrew W.
Brouillette Gabrielle
Landec Corporation
Madsen Robert
Sheldon & Mak
LandOfFree
Temperature-responsive containers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Temperature-responsive containers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Temperature-responsive containers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2441756