WO1996006733A1

WO1996006733A1 - A freezer storage bag

Info

Publication number: WO1996006733A1
Application number: PCT/US1995/010862
Authority: WO
Inventors: Zain E. M. Saad; Douglas P. Gundlach; Virginia D. Karul; Roger D. Vrooman; Roger V. Mcintosh; Richard Dawkins; David A. Smith; Michael A. Babinec; Linda W. Allison; Claudia J. Gerardo
Original assignee: Dowbrands Inc.
Priority date: 1994-08-26
Filing date: 1995-08-28
Publication date: 1996-03-07
Also published as: JP3621418B2; US5804265A; EP0776270A4; EP0776270A1; AU3416595A; CA2198484A1; CA2198484C; JPH10505046A

Abstract

A freezer storage bag comprising a multibag of at least two bags, the first bag being the inner most (food-contacting) bag ('linerbag') (11), the second bag ('support bag') (12) surrounding the liner (11) and being connected to the liner (11) at the liner's mouth (55), characterized in that the liner (11) is thermoplastic and has a thickness (t) of less than 2.0 mil (50 micrometers). Preferably, the liner's mouth (55) is sealed via a blanket seal to the support's throat. Preferably, the liner is embossed film. In contrast to existing freezer bags, the improved bag has a very pliable liner (11) that conforms to moist food and reduces freezer burn during storage of repackaged red meat. Various related aspects of the invention are also disclosed.

Description

A FREEZER STORAGE BAG

BACKGROUND

This invention primarily concerns the packaging of food, particularly meat but is applicable to packaging other articles or items. The invention was made during attempts to make improved "freezer bags" for repackaging and freezer storing uncooked red meat by the "consumer" in a mannerthat reduces so called "freezer burn". However, various aspects of the invention also apply to the "commercial " packaging or repackaging of food, such as by a supermarket or by butchers at a slaughterhouse. Other aspects of the invention include methods for preparing the improved freezer bags; methods for using the bags; the packages of meat; and certain types of thermoplastic film being particularly suitable for use as meat- contacting packaging material.

Reclosable Plastic Storage bags are extremely old in the art. Today, plastic bags are typically available to the public in cartons identified for specific recommended "end use" (such as Storage Bags, Heavy Duty Freezer Bags, Vegetable Bags, Trash Bags). Often the bag itself is labeled by "end use", for example, "ZIPLOC* BRAND Heavy Duty Freezer Bags".

The term "Freezer Bag" is hereby defined as a bag having significant functional utility in the storage of food in a freezer. "Freezer Bags" are typically available in the following sizes: 2 gallon (7.6 L); 1 (3.8 L) gallon; pleated 1/2 gallon (1.9 L); quart (0.9 L); and pint (0.5 L). The term "Freezer Burn" is hereby defined as the name for the dehydration that occurs when unpackaged or improperly packaged food is stored in the low humidity atmosphere of a freezer (see "Packaging Foods With Plastics", by Wilmer A. Jenkins and James P. Harrington, published in 1991 by Technomic Publishing Co., Inc., at page 305).

Freezer burn has remained a major complaint among consumers despite the commercial success of thick plastic freezer bags. In the short-term, freezer burn can be a reversible process. In the long-term, however, freezer burn causes a complex deterioration of food quality involving undesirable texture changes followed by chemical changes such as degradation of pigments and oxidative rancidity of lipids. Taste, aroma, mouth feel and color can all be ruined. Freezer burn of raw red meat is particularly critical because of its impact upon the color of the meat.

Aforementioned "Packaging Foods With Plastics" provides an excellent state of the art summary, with all the information on (commercial) "packaging fresh red meat collected in Chapter Seven". Curiously, the book does not appear to mention freezer burn, apart from defining it in the glossary. "Keeping Food Fresh" is the title of an article in "Consumer Reports", for March,

1994, at pages 143-147. The article is too recent to be available as prior art to the extent that this application designates the United States. Nevertheless its contents are of interest in showing the absence of certain types of prior art, and therefore enhancing the patentability of the present invention.

The "Consumer Reports" article attempts to answer the question as to which packaging material (plastic, aluminum, waxed paper, bags, wraps or reusable containers) do the best job of (1) keeping food fresh for "the long haul", (2) at lowest overall cost, and (3) with minimum adverse environmental impact. It "top rates" ZIPLOC* Pleated Freezer Bags (at page 145). It points out that food stored in plastic containers can suffer from freezer burn if the container contains too much air. Concerning "wraps" (plastic films and freezer papers) it advised against double wrapping because of cost and environmental reasons and "our tests showed that double wrapping doesn't afford much extra protection any way". Nowhere does the article disclose or suggest the invention described hereinafter.

The patent literature contains descriptions of various types of bags having liners or double walls including some space between the walls. Some of these patents relate to the transportation and storage of food. U.S. Patent 4,211,091 (Campbell) concerns an "Insulated Lunch Bag". U.S. Patent 4,211, 267 (Skovgaard) describes a "Carrying Bag" for "getting home with frozen food before it thaws". U.S. Patent 4,797,010 (assigned to Nabisco Brands) discloses a duplex paper bag as a "reheatable, resealable package for fried food". U.S. Patent 4,358,466 (assigned to The Dow Chemical Company) relates to an improved " Freezer To Microwave Oven Bag". The bag is formed of two wing shaped pouches on each side of an upright spout. U.S. Patent 5,005,679 (Hjelle) concerns "Tote Bags Equipped With A Cooling Chamber". All of these food bags appear to have very thick food contacting walls compared to the invention described hereinafter. None of these patents appear to focus on freezer burn.

Books on "Home Freezing" are of interest to this invention. Concerning "Wrapping Meat for the Freezer", the book "Rodale's Complete Book of Home Freezing" by Marilyn Hodges and the Rodale Test Kitchen staff (1984) suggested the inconvenient method of wrapping meat chunks in a single layer of freezer paper and "sucking out the air with a straw" (trying to avoid getting blood into ones mouth) in order to reduce the amount of dehydration in the freezer (see page 173).

There is clearly still a great need to improve existing methods of packaging fresh meat, as determined by consumer surveys, coupled with the fact that there is a 45 billion dollar retail market in the U.S. alone, consuming about 225 million dollars worth of plastic packaging materials annually. SUMMARY OF THE INVENTION

In contrast to the known prior art, it has now been surprisingly discovered that certain types of multiple walled plastic bags (defined herein as "multibags") are better than corresponding single wall freezer bags (having equal or greater weight than the multiple walled bags) for use as a functional freezer bag for preserving red meat without freezer burn. All of the independent claims hereinafter concern different but related broad aspects of the invention, and are hereby incorporated by reference. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 A is a front elevational view of a prior art reclosable thermoplastic single wall bag having a zipper.

Figure 1B is a cross-sectional view taken along reference line 1B-1B of Figure 1A.

Figure 2A is a front elevational view of a double wall bag in accordance with the present invention, (i) having a thin inner wall or liner, and (ii) having "common side seals" between the inner and outer walls and, optionally, (iii) a vent through the outer wall to connect the space between the inner and outer walls to the atmosphere outside the outer wall; and mouth seal that is optionally a blanket heat seal.

Figure 2B is a partial cross-sectional view taken along line 2B-2B of Figure 2A.

Figure 2C is a partial cross-sectional view taken along line 2C-2C of Figure 2A.

Figure 3A is a front elevational view of another double wall bag of the present invention, with "separate side seals".

Figure 3B is a partial cross-sectional view taken along line 3B-3B of Figure 3A.

Figure 3C is a cross-sectional view taken along line 3C-3C of Figure 3B.

Figure 4A is a front elevational view of a further double wall bag of the present invention, with the space between the inner and outer walls connected with the space within the inner bag.

Figure 4B is a partial cross-sectional view taken along line 4B-4B of Figure 4A.

Figure 4C is a partial cross-sectional view taken along line 4C-4C of Figure 4B.

Figure 5A is also a front elevational view of a double wall bag of the present invention, with the space between the inner and outer walls connected to the space within the inner bag.

Figure 5B is a partial cross-sectional view along line 5B-5B of Figure 5A.

Figure 5C is a partial cross-sectional view along line 5C-5C of Figure 5A.

Figure 6A s a front elevational view of a package of " meat in a closed bag" of the invention. Figure 6B is a cross-sectional view taken along reference line 6B-6B of Figure 6A.

Figure 7 is a diagrammatic flow diagram for one manual process of the present invention for making experimental freezer bags.

Figure 8 is a diagrammatic flow diagram for a process of the present invention for making freezer bags (with a common edge seal between the liner bag and support bag). Figure 9A is a front elevational view of a double wall bag in accordance with the present invention, having a liner bag prepared from textured, particularly embossed film on at least the inside surface 11S.

Figure 9B is a cross-sectional view taken along reference line 9B-9B of Figure 9A. Figure 10A is an isometric view of one process for preparing mouth seals that are extruded blanket seals. DETAILED DESCRIPTION OF THE INVENTION

According to a first aspect of the invention, there is provided a freezer bag comprising a multibag of at least two bags, the first bag being the innermost, that is, (hereinafter "liner"), the second bag (hereinafter "support") surrounding the liner, the support bag having a mouth and a throat, and the liner bag having a mouth, and a mouth-seal connecting the liner's mouth to the support's throat, characterized in that: the liner is thermoplastic and has a thickness (t) of less than 2.0 mil (50 micron). According to a second aspect, there is provided a multibag of at least two bags, the first bag being both thermoplastic and the innermost bag (hereinafter "liner") the second bag (hereinafter "support") surrounding the liner, the support bag having a mouth and a throat, and the liner bag having a mouth, and a mouth-seal connecting the liner's mouth to the support's throat characterized in that: the mouth-seal is a blanket heat seal.

In a third aspect, the present invention provides a multibag of at least two bags, the first bag being the inner most (hereafter "liner"), the second bag (hereinafter "support") surrounding the liner and, the support bag having a mouth and a throat, and the liner bag having a mouth, and a mouth-seal connecting the liner's mouth to the support's throat, characterized in that the liner is textured.

The present invention also provides thermoplastic nonhalogenated film for use as meat-contacting packaging material, characterized by the combination: (i) the film has a thickness (t) of less than 2 mil (50 μm); (ii) the film has a Transverse Direction 2 percent Secant Modulus (TDSM) of less than 40,000 psi/100 percent extension (1.86 x 10^β Pa/100 percent extension) when determined in accordance with ASTM D 882-83 (Standard Test methods for Tensile Properties of Thin Plastic Sheeting), Method A with a jaw gap of 4 inches (10 cm) for test specimens having an initial width of 1 inch (2.5 cm), except that the Initial Strain Rate is 0.25 inches per inch per minute (0.25 cm per cm per minute) with a crosshead speed of 1 inch (2.5 cm) per minute; (iϋ) the film has a calculated value, Z-value of less than 20,000 mil³ psi (2.25 mm³-kPa)/100 percent extension wherein Z-value equals (t³)x(TDSM);

(iv) at least one surface of the film has a contact angle in a range of from 65° to 75° at room temperature (20°C) relative to raw beef meat juice, as determined by Advancing Contact Angle Determination with a Contact Goniometer (A-100 Rόme-Hart); and (v) the film is an embossed film.

Further, the invention provides a process for preparing reclosable thermoplastic bags by the steps of (a) forwarding a first thermoplastic film having a thickness greater than 1 mil (25 μm) and having mateable male and female closure elements along opposed edges of the thermoplastic film; (b) folding the film and mating the male and female closure elements; (c) seal cutting to length in the machine direction to form bags, and stacking and packing the bags, characterized by the additional steps of:

(d) In parallel with step (a), forwarding a sheet of thermoplastic film having a thickness (t) of less than 2 mil (50 μm);

(e) Prior to step (b) overlaying and aligning the second thermoplastic film onto the first thermoplastic film between the male and female closure elements;

(f) Still prior to step (b), heat-sealing the second thermoplastic film to the first thermoplastic film at two locations, adjacent to and between the male and female closure elements; and,

(g) In step (c), seal cutting to form a common edge seal between the liner bag and support bag.

The invention also provides aged frozen freezer bagged beef having a frozen age of at least 6 months and having metmyoglobin (MMb) at the beef's surface; characterized in ^tha^t:

The amount of MMb at the surface of the beef is less than 60 percent of the total myoglobin content as determined by a conventional absorption spectrophotometry test. Certain terms used in this specification are hereby defined as follows: "Multiwall (noun)" is a "multiwall bag" (in accordance with Webster's "complete" dictionary at page 1486);

"Multiwall (adjective)" is "having a wall made-up of several layers" (in accordance with Websters "complete" dictionary at page 1486).

A "double bag" is two bags, one within the other, which double bag can be separated into two separate bags, which separate bags can then reform the double bag (as for bagging groceries at a supermarket).

A "duplex bag" is hereby defined as an integral bag consisting of an outer support bag and an inner liner bag, wherein the liner bag is partly (but not completely) joined to the support bag.

A "multibag" is hereby defined as an integral bag having at least an outer support bag and an inner liner bag, wherein the liner bag is partly (but not completely) joined to the support bag; and optionally additional layers between the liner bag and the support bag. The simplest form of a multibag is a duplex bag. The term "multibag" does not appear in Webster's Dictionary.

The liner bag of the freezer bag of the invention preferably has a Transverse Direction 2 percent Secant Modulus (TDSM) of less than 40,000 (preferably less than 27,000) psi/100 percent extension (1.86 x 10⁸ Pa/100 percent extension) when determined in accordance with ASTM D 882-83 (Standard Test Methods for Tensile Properties of Thin Plastic Sheeting), Method A with a jaw gap of 4 inches (10 cm) for test specimens having an initial width of 1 inch (2.5 cm), except that the Initial Strain Rate is 0.25 inches per inch per minute (0.25 cm per cm per minute) with a crosshead speed of 1 inch (2.5 cm) per minute. When TDSM has a value less than 27,000 units, such products are typically prepared by so-called well known cast-film processes. When TDSM has a value in a range of 27,000 to 40,000 units, such products

5 are typically prepared by well know blown-film proesses. Such liners suitably comprises thermoplastic film having a calculated value, Z-value, of less than 60,000 mil³ psi (6.75 mm³ kPa)/100 percent extension wherein Z-value equals (t³)x(TDSM). Preferably, the liner's Z-value is less than 20,000 mil³ psi (2.25 mm³*kPa)/100 percent extension; especially in a range from 2,000 to 10,000 mil³ psi (0.2 to 1.1 mm³-kPa); and most preferably in a range from 3,000 to

10 6,000.

Suitably the thermoplastic film comprises homopolymers and copolymers of ethylene having a specific gravity of less than 0.930 gm/cc.

In a preferred embodiment, the multibag consists of 2 bags and wherein the support has a Z-value in a range of 50,000 to 150,000 mil³ psi (5.6 to 16.9 mm³-kPa)/100 percent

15 extension.

Thickness of films (t and T) are easily determined by conventional spacing loaded thickness gauges.

Advantageously, the liner's food contactable surface has a contact angle in an amount from 65° to 75° at room temperature (20°C) relative to raw beef meat juice, as

20 determined by Advancing Contact Angle Determination with a Contact Goniometer (A-100 Rέme-Hart). The liner's food contactable surface suitably has been corona-treated. Usually, the liner's thickness (t) will be in a range of 0.3 to 1.0 mil (8 to 25 μm); preferably 0.5 to 0.7 mil (12 to 18 μm) and the support bag's thickness (T) will be in a range from 1.0 to 4.0 mi I (25 to 100 μm); preferably from 1.3 to 3.0 mil (35 to 75 μm); and more preferably from 1.5 to 2.0 mil (40 to

25 50 μm). However, other thickness can be used.

Suitably, the support bag is thermoplastic.

Usually, the freezer bag will have a liquid storage capacity in a range of 1 pint to 2 gallons. The space between the liner bag and the support bag can be vented to atmosphere outside the support; essentially unvented and containing constant mass of material; or vented

30 to the space within the liner bag. In the latter option, the seal between the support bag's throat and the liner bag's mouth suitably is discontinuous and the space between the liner and the support comprises hygroscopic material. Preferably, the hygroscopic material is selected from hydroxypropyl methylcellulose and polyvinyl alcohol. The liner bag can be connected to the support bag by common edge seals or the liner bags edge seals can be separate from the

35 support-bags's edge seals.

The support bag may comprise mateable male and female closure elements along opposed inner surfaces of the support bag. The liner bag can have a color or texture that is different from the color or texture of at least part of the support bag. It is particularly preferred that the liner bag is textured, for example, embossed. It has been found that liner film having an embossed surface has greater cling to raw red meat as determined by a static coefficient of friction test analogous to that described in ASTM D 1894-87. When the liner bag is textured the upper thickness limitation of the first embodiment is not applicable. Thicknesses of up to 3.0 mil may be used when the liner's film is embossed.

Preferably, the connection between the liner bag and the support bag is such that the liner can be stroked to conform to the external geometry of a ribeye steak placed within the liner bag.

The multibags can have more than two layers. For example, it can have three layers and in this embodiment it is preferred that the third layer is located between the liner bag and the support bag and causes the liner bag to be conformable to the outside geometry of food within the liner bag while food in the bag is being frozen. Suitably, the liner's thickness (t) is in a range from 1.0 to 2.0 mil (25 to 50 μm), and the third bag is formed of elastic fabric. It is preferred that the support bag is sealed to the liner bag by a "mouth seal " that is a "blanket heat seal," preferably an "extruded heat seal." By "extruded blanket seal", we mean a blanket seal that is extruded directly onto the overlapped liner film and support film. However, the mouth-seal can also be made by using (i) conventional hot melt adhesion between the liner and the support; or (2) conventional hot press sealing; or even some form of solvent sealing. EXAMPLES OF THE INVENTION

The experimental work that led to the aspects of the invention claimed hereinafter involved time-

-consuming hand fabrication of numerous different types of "multibag" defined above; repackaging of meat in the multibags; and evaluation of the per ormance of the multibags relative to each other and other controls being commercially available freezer bags, during and after many months of storage in a freezer.

The experimental work involved the sequential evaluation of three main types of prototype, types A, B, and C described below. TYPE-A PROTOTYPES Type-A prototypes were all three-layer multibags made essentially in accordance with Figures 5A, 5B and 5C having a support bag (12), a liner bag (11), a third layer (77), and vent holes (11c) for venting the space between the liner bag and the support bag to the space within the liner bag.

More specifically, Type-A1 multibags were fabricated as follows: a. A support bag (12) being an outer layer of polyethylene film (used for making

ZIPLOC^® storage bag 1.75 mil (45 μm); b. A liner bag (11) being an inner layer of polyethylene film 1.75 mil (45 μm) thick with 800 microholes (11c) having hole diameters of 10 μm as vent holes to permit moisture to move freely into and out of the middle layer; and c. A third layer (77) being a hygroscopic film having a thickness of 1.5 mil (38 μm) and moisture content of around 10 percent by weight (METHOCEL* cellulose ethers film made by Polymer Films, Inc.-Rockville, CT). METHOCEL* is a registered Trademark of The Dow Chemical Company. More specifically, typical properties of the film are found in the June, 1986 data sheet of Polymer Films Inc., for the product named "EM IIDO Water Soluble Film". The product was identified as having the primary constituent being Hydroxypropyl Methyl Cellulose Resin having CAS No of 009004-65-3.

Further, it will be noted from Figure 5A that the edge seals AD and BC of the support bag (12) are essentially "common" with the edge seals ad and be of the liner bag (11). TYPE-B PROTOTYPES

Type-B prototypes were all three-layer multibags essentially similar to the Type-A prototypes except that the liner bag (11) had a thickness of 1.2 mil (30 μm) (instead of 1.75 mil (45 μm)); and except the liner (11) had no microholes therein and that the space between the liner bag and the support bag was essentially completely unvented. TYPE-C PROTOTYPES

Type-C prototypes were all multibags of the duplex variety as shown in Figures 2A, 2B, 2C, 3A, 3B, 3C, 4A, 4B and 4C and having a support bag (12) having a thickness of 1.75 mil (45 μm) and a liner bag (11) having a thickness of 0.6 mil (15 μm) without any "third layer or wall" between the liner bag and the support bag. The mouth seal AB between the liner's mouth and the support's throat was a hot press seal rather than the blanket seal 55 shown in Figures 2A, 2B and 3A and 3B. The Type-C multibags were given a secondary classification (denoted by the letter

"C" or the letter "S" dependent upon whether the bags had "common edge seals" or "separate edge seals". The liner's edge seals are shown on the lines ad and be in Figures 2A, 3A and 4A. The edge seals of the support bag (12) are shown by the lines AD and BC in Figures 2A, 3A and 4A. Clearly, in Figure 2Athe edge seals are essentially "common"; whereas in Figures 3A and 4A the edge seals are "separate" .

The bags were fabricated by hand. Figure 7 is a diagrammatic flow diagram for making Type-CC multibags.

The Type-C multibags were given a tertiary classification (1 , 2, or 3) according to whether the space between the su pport bag ( 12) and the I i ner bag ( 11 ) was ( 1 ) vented to the space within the liner bag (as shown in Figure 4C); or (2) not vented (as shown in Figures 3A, 3B and 3C); or (3) vented to the surrounding atmosphere (as shown by the vent (99) in dotted line in Figures 2A and 2B). The Type-C multibags could be given a fourth clarification dependent upon whether the "mouth seal" is merely a "simple hot press sea I" (hereinafter SHPS) "not simple hot press seal" (hereinafter NSHPS).

Examples of NSHPS include both "hot melt adhesion" and "blanket heat seal " (hereinafter BHS) particularly wherein a blanket strip is extruded onto both the inner mouth of the liner and the inner throat of the support (hereinafter EBHS). One possible EBHS process is illustrated in Figure 10. EBHS permits high speed. EVALUATION PROCEDURE

All prototype multibags were essentially evaluated relative to control bags in the o following way by actually using the bags as potential freezer bags containing boneless beef steak.

1. Beef steak samples were initially weighed before packing in the bags. Each bag had one beef steak. The bags were placed in a commercial freezer with a set point of 0°F (-18°C). 5 2. The freezer was occasionally opened and closed for the purpose of observing the samples.

3. Physical observation (including bags conformation around steaks, formation of ice crystals, visible dry spots, and discoloration) were made daily during the first two weeks and then once every week for the next eight months for prototypes Type-A and Type-B. Type-C was 0 physically observed over a period of three months. Frozen beef steaks were photographed in color both inside and outside the bags, then thawed and photographed again.

4. Percent weight loss and the amount of drips were measured on the thawed steaks. Amount of drips is defined as the blood-like fluid exuding from frozen meat upon thawing. 5 5. "Unexpected effects" were noted as appropriate.

SHORT TERM RESULTS - TYPES A, B AND C

Various Type-A prototypes and Type-B prototypes were evaluated simultaneously, and sequentially in a staggered manner.

Type-A 1 described above was evaluated because the film was hygroscopic and in 0 the hope that it might help to prevent moisture escaping from the meat during storage in the freezer.

However, an unexpected result occurred almost immediately. In particular it was discovered that, with a hygroscopic film layer between the liner bag and the support bag, the hygroscopic layer and the liner bag changed shape very rapidly and "conformed " to the shape 5 of the beef steak. In other words it was highly beneficial in excluding air from the space around the beef steak.

It came as a second major surprise when the Type-B multibag also tightly conformed the liner bag around the steak as a short-term phenomenon. The apparent success of the Type-B multibag led to the design of the Type-C multibag. Two types of Type-C bags were evaluated: Type-CC2 and Type-CS2. Again a surprisingly result occurred. The Type-CC2 multibag appears to conform more easily to the shape of the beef steak at packaging and "before" the beef steak package is placed in the freezer as shown in Figure 6A. With hindsight, it is possible to make various speculations based upon the fact that the unvented bag essentially has constant mass of air between the liner bag and the support bag.

LONG-TERM RESULTS - TYPES A AND B

Beef steaks in regular freezer bags (control) developed many large ice crystals and o severe discoloration (bright red color faded into faint brown). Severe freezer burn, as evidenced by large discolored dry spots, was observed on the steak in both frozen and thawed states.

Beef steaks in the Type-A three-layer multibags (with a perforated inner layer) were in excellent condition. Formation of ice crystals was significantly reduced, the bright red 5 color was maintained and no discoloration was observed. No freezer burn on the surface of the steaks was observed.

The Type-B three-layer multibags with nonperforated film as the inner layer showed similar results to those obtained with Type-A multibags.

A key hindsight observation that may explain the significant difference in quality 0 per ormance between the control bags and the three-layer bags is that the middle and inner layers of the three-layer bags had tightly conformed around the steak which resulted in reducing air pockets and subsequent formation of ice crystals.

A comparison of weight loss and amount of drips between treatments showed that weight loss of the steaks correlated well with the amount of formation of ice crystals. Beef 5 steaks stored in regular freezer bags had a severe weight loss (up to 20.5 percent) in eight months and the amount of drips was 2.06 percent. Beef steaks stored in the three-layer bags

(with a perforated inner layer) had a significantly less weight loss (4.3 percent) than the control and the amount of drips was 1.93 percent. The least amount of weight loss (1.9 percent) and drips (0.26 percent) was measured with steaks stored in the three-layer bags (with 0 nonperforated inner layer). The difference in performance between the three-layer bags and control bags relate to the ability of the three-layer bags to conform tightly around the meat, which led to minimizing air pockets. As a result of conforming, the dehydration process, that leads to freezer burn, was reduced significantly.

It was concluded that the quality of frozen beef steaks, stored in the Type-A and 5 Type-B three-layer multibags was superior compared to regular freezer storage bags (control).

The freezer burn was minimized significantly due to the conforming of the inner and middle layers of the three-layer bags onto the beef steaks. LONG-TERM RESULTS - TYPE-C

The Type-CC2 and Type-CS2 multibags also performed significantly better than the commercially available freezer bags used as control. Their superior performance can be attributed, with the benefit of hindsight, to the tendency of the liner bag to "conform" to the food and minimize the headspace available for ice formation. It should perhaps be noted that performance advantages of these prototypes were less significant in tests with irregularly shaped food such as broccoli and chicken with bones.

Various properties of the Type-C liner bag and support bag were measured and compared with the corresponding properties of the commercially available freezer bags. For example, Relative Stiffness, as determined by the DowBrands Relative Flexural Stiffness in the

Transverse Direction of the Type-C liner was 1 to 2 orders of magnitude lower than commercially available "freezer bags" (for example, 5,300 psi cubic mils compared with 304,000 psi cubic mils) (34 kPa/mm³).

Claims

WHAT IS CLAIMED IS:

. A freezer bag comprising a multibag of at least two bags, the first bag being the innermost, that is, (hereinafter "liner"), the second bag (hereinafter "support") 5 surrounding the liner, the support bag having a mouth and a throat, and the liner bag having a mouth, and a mouth-seal connecting the liner's mouth to the support's throat, characterized in that: the liner is thermoplastic and has a thickness (t) of less than 2.0 mil (50 micron).

2. A freezer bag according to Claim 1 wherein the liner has a Transverse Direction 1 o 2 percent Secant Modulus (TDSM) of less than 40,000 psi/100 percent extension (1.86 x 10⁸

Pa/100 percent extension) when determined in accordance with ASTM D 882-83 (Standard Test Methods for Tensile Properties of Thin Plastic Sheeting), Method A with a jaw gap of 4 inches (10 cm) for test specimens having an initial width of 1 inch, (2.5 cm) except that the Initial Strain Rate is 0.25 inches per inch per minute (0.25 cm per cm per minute) with a crosshead speed of 1 15 inch (2.5 cm) per minute.

3. A freezer bag according to Claim 2 wherein the liner comprises thermoplastic film having a calculated value, "Z-value," of less than 60,000 mil³ psi (6.75 mm³ kPa)/100 percent extension wherein Z-value equals (t³)x(TDSM).

4. A freezer bag according to Claim 3 wherein the liner's Z-value is less than 20 20,000 mil³ psi (2.25 mm³-kPa)/100 percent extension (preferably in a range from 2,000 to

10,000 (mil³ psi (0.2 to 1.1 mm³-kPa); and most preferably in a range from 3,000 to 6,000 mil³ psi (0.35 to 0.7 mm³-kPa)).

5. A freezer bag according to Claim 3 or Claim 4 wherein the multibag consists of 2 bags and wherein the support has a Z-value in a range of 50,000 to 150,000 mil³ psi (5.6 to

25 16.9 mm³-kPa)/100 percent extension.

6. A freezer bag according to Claim 3 wherein the thermoplastic film comprises homopolymers and copolymers of ethylene having a specific gravity of less than 0.930 gm/cm³.

7. A freezer bag according to any one of the preceding claims wherein the liner's food contactable surface has a contact angle in a range of from 65° to 75° at room temperature

30 (20°C) relative to raw beef meat juice, as determined by Advancing Contact Angle Determination with a Contact Goniometer (A-100 Rame-Hart).

8. A freezer bag according to any one of the preceding claims wherein the liner's food contactable surface has been corona-treated.

9. A freezer bag according to Claim 1 wherein the liner's thickness (t) is in a range 35 of 0.3 to 1.0 mil (8 to 25 μm) (preferably 0.5 to 0.7 mil (12 to 18 μm)).

10. A freezer bag according to any one of the preceding claims wherein the support bag's thickness (T) is in a range from 1.0 to 4.0 mil (25 to 100 μm) (preferably from 1.3 to 3.0 mil (35 to 75 μm); and more preferably from 1.5 to 2.0 mil (40 to 50 μm)). 11. A freezer bag according to any one of the preceding cla^; s having a liquid storage capacity in a range of 1 pint to 2 gallons (0.5 to 7.6 L).

12. A freezer bag according to any one of the preceding Claims wherein the space between the liner bag and the support bag is vented to atmosphere outside the support. 13. A freezer bag according to any one of the preceding Claims wherein the space between the liner and the support is essentially unvented.

14. A freezer bag according to any one of the preceding claims wherein the space between the liner and the support is vented to the space within the liner bag.

15. A freezer bag according to Claim 14 wherein the connection between the o support bag and the I i ner bags throat is disconti nuous.

16. A freezer bag according to Claim 14 wherein the space between the liner and the support comprises hygroscopic material.

17. A freezer bag according to Claim 16 wherein the hygroscopic material is selected from hydroxypropyl methylcellulose and polyvinyl alcohol. 5 18. A freezer bag according to any one of the preceding claims wherein the support bag has edge seals in a direction transverse to the mouth seal connecting the support bag and the liner bag, and the liner bag has edge seals in a direction transverse to the mouth seal connecting the support bag and the liner bag, and wherein the liner bag is connected to the support bag by common edge seals. 0 19- A freezer bag according to any one ofthe preceding Claims 1 to 17 wherein the support bag has edge seals in a direction transverse to the mouth seal connecting the support bag and the liner bag, and the liner bag has edge seals in a direction transverse to the mouth seal connecting the support bag and the liner bag, and wherein the liner bags edge seals are separate from the support-bags's edge seals. 5 20. A freezer bag according to any one of the preceding claims wherein the support bag comprises mateable male and female closure elements along opposed inner surfaces of the support bag.

21. A freezer bag according to any one of the preceding claims wherein the liner bag has a color or texture that is different from the color or texture of at least part of the 0 support bag.

22. A freezer bag according to any one of the preceding claims wherein the connection between the liner bag and the support bag is such that the liner can be stroked to conform to the external geometry of a ribeye steak placed within the liner bag.

23. A freezer bag according to any one of Claims 1 to 4 and 6 to 22 wherein the 5 multibag is a three-layer bag, with the third layer being located between the liner bag and the support bag and causing the liner bag to be conformable to the outside geometry of food within the liner bag while food in the bag is being frozen. 24. A freezer bag according to Claim 23 wherein the liner's thickness (t) is in a range from 1.0 to 2.0 mil (25 to 50 μm), and the third bag is formed of an elastic fabric.

25. A process for preparing reclosable thermoplastic bags by the steps of (a) forwarding a first thermoplastic film having a thickness greater than 1 mil (25 μm) and having mateable male and female closure elements along opposed edges of the thermoplastic film; (b) folding the film and mating the male and female closure elements; (c) seal cutting to length in the machine direction to form bags, and stacking and packing the bags, characterized by the additional steps of:

26. A bag obtainable by the process of Claim 25.

27. A bag obtained by the process of Claim 25. 28. Use of a bag of any one of Claims 1 to 24 in packaging food.

29. A use according to Claim 28 for packaging red meat.

30. A use according to Claim 29 for repackaging red meat for cold storage.

31. A use according to Claim 28 for consumer repackaging.

32. A package of food com prising a bag of any one of Claims 1 to 24 and food within the bag.

33. A process for preparing a package of Claim 32 comprising the steps of:

(A) Placing the food to be packaged into the liner bag;

(B) Stroking the food through the bag thereby puckering the liner bag to conform to the external geometry of the food and thereby exhausting air from the liner bag; and (C) Closing the support bag while avoiding significant reentry of air.

34. A package obtainable by the process of Claim 33.

35. A package according to Claim 34 prepared by the process of Claim 33.

36. Use ofthe package of Claim 32 in preserving the food.

37. Aged frozen freezer bagged beef having a frozen age of at least 6 months and having metmyoglobin (MMb) at the beef's surface; characterized in that:

The amount of MMb at the surface of the beef is less than 60 percent of the total myoglobin content as determined by a conventional absorption spectrophotometry test. 38. Use of a bag of any one of Claims 1 to 24 for applications other than packaging food.

39. Thermoplastic nonhalogenated film for use as meat-contacting packaging material, characterized by the combination:

5 (i) the film has a thickness (t) of less than 2 mil (50 μm);

(ii) the film has a Transverse Direction 2 percent Secant Modulus (TDSM) of less than 40,000 psi/100 percent extension (1.86 x 10⁸ Pa/100 percent extension) when determined in accordance with ASTM D 882-83 (Standard Test methods for Tensile Properties of Thin Plastic Sheeting), Method A with a jaw gap of 4 inches (10 cm) for test specimens having an initial 10 width of 1 inch (2.5 cm), except that the Initial Strain Rate is 0.25 inches per inch per minute (0.25 cm per cm per minute) with a crosshead speed of 1 inch (2.5 cm) per minute;

(iii) the film has a calculated value, Z-value of less than 20,000 mil³ psi (2.25 mm³-kPa)/100 percent extension wherein Z-value equals (t³)x(TDSM);

(iv) at least one surface of the film has a contact angle in a range of from 65° to 15 75° at room temperature (20°C) relative to raw beef meat juice, as determined by Advancing Contact Angle Determination with a Contact Goniometer (A-100 Rάme-Hart); and (v) the film is an embossed film.

40. A multibag of at least two bags, the first bag being both thermoplastic and the innermost bag (hereinafter "liner) the second bag (hereinafter "support") surrounding the 0 liner, the support bag having a mouth and a throat, and the liner bag having a mouth, and a mouth-seal connecting the liner's mouth to the support's throat characterized in that: the mouth-seal is selected from a hot melt adhesion seal and a blanket heat seal.

41. The multibag of Claim 40 wherein the blanket heat-seal is an "extruded" heat seal. 5 42. The multibag of Claim 40 or Claim 41 wherein the liner bag is an embossed liner bag having a thickness in a range of from 0.5 to 3.0 mil (15 to 75 μm) as determined by a test wherein.

43. The multibag of any one of Claims 40 to 42 wherein the support is thermoplastic. 0 44. The multibag of any one of Claims 40 to 43 wherein the multibag is a freezer bag.

45. The multibag of any one of Claims 40 to 44 wherein the multibag is reclosable.

46. A multibag of at least two bags, the first bag being the inner most (hereafter 5 "liner"), the second bag (hereinafter "support") surrounding the liner and, the support bag having a mouth and a throat, and the liner bag having a mouth, and a mouth-seal connecting the liner's mouth to the support's throat, characterized in that the liner is textured. 47. A multibag of Claim 46 wherein the liner is thermoplastic and has a thickness of less than 3.0 mil (76 micron) and wherein the mouth-seal is an extruded blanket . val.

48. A multibag of Claim 46 wherein the liner's inner surface is embossed.