PACUGIMS FILMS AND iVIE:AT COLO3”

DUAXZ 0. VESTdRBZRG UNION CARBIDE: CORPORATION

The subject for this morning’s talk is listed as packaging films and meat color, I have taken the liberty to broaden the area to be discussed since it is very difficult to pick out one quality factor and relate it alone to packaging films, I would rather title the talk as packaging films and meat quality. It is true that the color of meat is a very important factor in the marketability of a meat item but probably less important than other factors which can affect the quality of a product being sold by a manufacturer to his customers. It is true that in many cases meat color can reflect how the meat product has been treated during the normal manufacturing process and in the distribution and handling of the product to the display case where it is finally sold. On the other hand, one only has to look in the meat display case of the local supermarket to see the number of sophisticated packages and packaging techniques which have been developed through the cooperation of film manufacturer, equipment manufacturer, and meat packer to protect the quality of the meat item to the consumer.

I have divided ny talk into three general areas, I plan to first discuss the requirements placed on the packaging material by the type of meat product being packaged, specifically fresh retail meat cuts, processed meats, and primal and subprimal neat cuts. Secondly, I will discuss the procedures available to film manufacturers to build in required filn properties for packaging the various types of meat. Finally, I will talk about the various films which have been developed or adapted for use in packaging meats with their attributes and shortcomings and how they were overcome to make useful packaging films.

It is important to remember that the purpose of the package used to market a product, be it meat or any other product, is to preserve the quality factors formulated into the product on manufacture until the product is delivered to the final user--the consumer. For the package to perform at the highest efficiency, some factors (table 1) have to be assumed regardless of the meat item being packaged. The meat product has to be of good quality on manufacture. If the product is a retail fresh neat cut, it should be fresh, tender, and pod tasting with low microbiological contamination. If it is a processed meat item such as weiners or bologna, it must be made from good quality meat ingredients and be processed correctly, The package can only protect the quality of product going into it, not

* Presented at the 24th Annual Reciprocal Meat Conference of the American Meat Science Association, 1971, 361 create it. Secondly, adequate storage temperature control is required throughout the whole chain of distribution of the meat product to the consumer. LOW microbiological contamination, by using acceptable sanitary conditions on manufacture and packaging, also is necessary to prevent rapid microbiological spoilage. If these factors are net, the package can help in preserving the quality of the meat product for the consumer. All packaging raterials being used have to have the approval of the Food and Drug Administration for safe contact with meat products, If the meat plant is F'ederally inspected or by some state organiaatlon, the packaging materials also require approval by the USDA or possibly state organizations. What are the main factors which we wish to protect when narketing meat for retail use (table Z)? The important quality factors of retail neat cuts as they are rarketed at the present tine are to allow for red bloom color develoaent of the meat, prevent moisture loss, and prevent handling contanination. The housewife is the individual who purchases most retail neat cuts today and sets these requirements. The color of the meat is very frportant to her since she relates meat freshness and general quality to the presence of the bright cherry red color of normal meat bloom. Secondly, moisture loss *om the package has to be prevented since dehydration reduces neat quality, and if large losses occur, can also lead to problems with governmental Inspectors. Prevention of contamination on handling is necessazy to assure product quality since the retail cut is handled frequently during normal marketing procedures.

What are the important requisites for fil. materials used to package retail meat cuts (table 3)? To allow for color developnent, the fPZI must be highly permeable to oxygen. The meat pigment, myoglobin, can react with oxygen in two manners (table 4). If high concentrations of oxygen are present, the myoglobin fonns omyoglobin, a complex with the oxygen molecule, which has the attractive, bright, cherry red color. However, if low concentrations of oxygen are present, oxidation of myoglobin is favored to forts the unattractive brown or gray color of netmyoglobin. The film must be highly permeable to oxygen so that an abundant supply of oxygen will be present at the meat surface to form the cherry red color expected by the housewife. Since the housewife believes it is necessary to see the meat product she is purchasing to satisfy her belief of quality, the packaging film must possess excellent optical properties to show the meat uut in an attractive manner. And last, but far from the least in importance, the film and package rust retain Integrity on handling because the housewife usually punches, pokes, and feels the product prior to purchasing and normally doesn't purchase the first package she exantnes. Therefore, when she returns the package to the display case it must still be an attractive package after this punching and poking so that the next housewife would be interested in purchasing it. What length of time are we talking about in display case shelf life? This can be from 1 to 2 days up to 4 or 3 days depending upon the temperature of the display case. The longer shelf lives are obtained at temperatares nearer the freezing point of meat, 27-~8~F. TABLE 1. FACTORS ASSUMED FOR PACKAGING MEAT PHODUCTS

- ~~

1, Quality product.

2. Adequate storage temperature controls.

3. low microbiological contamination.

4. Approved polymers and additives for meat contact.

TABLE 2. FACTORS AFFECTING THE QUALITY OF FRESH RETAIL MEAT CUTS

~~

1. Allow for red bloom development. 2. Prevent moisture loss.

3. Prevent handling contamination.

TABLE 3. FILM REQUIRENENTS FOR PACKAGING FRESH RhTAIL MEAT CUTS

1. Permeable to oxygen. 2. Moisture barrier.

3. Possess excellent optical properties.

4. Retain integrity on handling. 363

TABLE 4. COLORED PIGMENTS OF MEAT PRODUCTS

Myoglobin Oxymyoglobin

(bright red)

Metmyoglobln Nit Myoglobin roso- t

(brown) Oxidation (Pink 1 364 A contrast in ,packaging requirements results when one talks about packaging processed meat items such as weiners, bologna, bacon, and hams, The packaging techniques developed for processed meats require some completely different properties. There are about four main factors related to quality which we are attempting to protect when packaging processed meats (table 5). Protection of these factors results in longer useful shelf life and a better product quality guarantee during marketing. These factors are prevention of microbiological spoilage, prevention of rancidity of fat, -prevention of loss of cured meat color, and dehydration of the meat product. Microbiological contamination will occur to some extent in any manufacturing process but using good quality meat trimmings for manufacture, good processing conditions and good sanitary practices throughout the processing and packaging areas will greatly aid in controlling microbiological spoilage. Rancidity of fat can easily occur in processed meats because of the high fat level present, Again, using good quality starting materials will help to keep rancidity to a minimum during manufacture and deter loss of product quality, The attractive pink color produced during the curing process with nitrite is also a desirable factor requiring protection,

The packaging technique which has developed and grown over the past ten years or so depends on the elimination of oxygen in contact with the processed meats since most of the degradation processes mentioned require oxygen to occur, This has resulted in the development of the tremendous vacuum packaging procedure and gas flush techniques,

What are the film requirements for use in vacuum packaging (table 6)? There are about eight factors required of a film to be used in vacuum and gas flushing procedures. The major factor is the film must be an excellent barrier to oxygen so that when oxygen is removed from around the product on packaging it, cannot reenter the package to degrade product quality. The presence of oxygen accompanied by poor product temperature control contributes to the growth of microorganisms on the product surface and interior. This affects product quality and rapidly shortens useful product shelf life. Most bacteria, yeasts and molds require the presence of oxygen to multiply; therefore, removal of oxygen diminishes the rate of growth considerably. Development of rancidity in fat and degradation of cured meat color in the presence of light also occurs at a more rapid rate when high concentrations of oxygen are present: again, the rate of development and degradation can be reduced considerably by removal of oxygen from the package, The requirement of oxygen barrier level to prevent color degradation varies from one processed meat product to another, Studies at our laboratory indicated that packaging sliced items such as bologna with interior product surfaces exposed requires fibs of much lower oxygen transmission rate than products such as frankfurters. F’ilols nith oxygen transmission rates less than 1 cc/lOO in2- 24 hrs. ATM were required to package sliced bologna while transmission rates of about 2.5 cc/IOO in2. 24 hrs*ATM were required for f’rankfurters. 365 TABLE 5. FACTORS AFFECTING SHELF LIIQ QUALITY OF PROCESSED MEATS

1. Microbiological contamination.

2. Rancidity of fat,

3. Degradation of cured meat color.

4. Dehydration.

TABLE 6. F'ILM REQUIREMENTS FOR PACKAGING PROCESSED MEATS

~~ ~ __ ~~~ -~ -~ ~ ~~

1. Barrier to oxygen,

2, Barrier to moisture. 3. Form hermetic seals. 4. Tough, puncture-resistant packages. 5. Good optical propertiee. 6. Thenoformable,

7. Can be printed.

8. Can be used on packaging machines. herall oxygen concentration in the package is very important since good internal package vacuum has to be combined with low oxygen permeable films to make acceptable packages. For packaging sliced bologna internal vacuums of 29 in. of Hg were required to prevent oxidation of the cured meat pigment. Lower vacuums of 27 to 28 in. of Hg were adequate to protect frankfurter color, These different requirements nay be related to the difference in the nature of a freshly cut sausage surface as compared to skin formed during sausage manufac t we.

The film must also be a barrier to moisture so continued moisture loss does not occur from the product. I realize that vacuum packages contain free liquid but it does not escape from the package so continued dehydration does not occur, Incidentally, this free liquid affords a nice environment for bacterial growth thus increasing the importance of low microbiological contaaination on production and handling of the product during 'packaging. Gas flushing techniques solve the problem of free liquid in the package, However, it is difficult to eliminate defective packages which could lead to rapid product deterioration, Therefore, great care has to be taken when gas flushing to assure hermetically sealed packages and oxygen is flushed to safe levels. The packaging films must also form hermetic seals, Loss of vacuum through a poor or broken seal during handling and shipping nullifies the vacuum packaging advantage. Similarily, the films should be tough and puncture-proof so that vacuum is not easily lost during normal distribution channels, Good optical properties are also required to present the product in an attractive manner--clear, sparkly films are always attractive. An advantageous property and also required for use on many automatic packaging machines is the property of thermofonability into cuts to hold the product, This gives a flat surface to form hermetic seals, The film should be printable to advertise product and manufacturer names in an attractive manner and finally, the film has to perform in an efficient manner on packaging machinery.

The last meat packaging area I will discuss is the packaging of primal and subprimal cuts, The processing of beef carcasses into fabricated cuts at central locations has grown by leaps and bounds over the past few years, This procedure is being done both by meat packers and large supermarket chains. It allows for good quality control of the fabricated cuts and makes best use of labor available. What are the quality factors important with these types of meat cuts (table 7)? To assure quality product for the consumer of the meat, growth of microorganisms has to be prevented to allow for distribution times and aging of the product in the package, if desired, Secondly, the natural pigment of the meat has to be protected so that when the fabricated cut is processed into retail cuts normal bloom of pigment occurs, Excessive shrinkage of the product has to be also prevented during storqe and distribution. 367

How is this obtained? Again it has been by vacuum packaging procedures to protect the quality of the meat (table 8). First of all, the fila must be a barrier to oxygen as with processed meats, Removal of oxygen *om the environment of the product deters the growth of most bacteria, yeasts, and molds thus delaying micro- biological spoilage. Vacum paakaging also protects the myoglobin pigment in the kesh meat since oxidation cannot occur. When the vacuum package is opened and cut into retail cuts, normal bloom of the myoglobin to oxymyoglobin results for retail marketing. Again, the fila should be a barrier to moisture loss and finally, the package must retail integrity during normal handling and shipping channels since vacuum loss would negate vacuum packaging. Microbiological growth and discoloration of the fabricated cut surfaces result in excessive trlmming required for a marketable product. This triamlng results in loss of msrketable meat and high processing costs.

The film manufacturer has a variety of procedures available to him to build in the desired properties for packaging meat products (table 9). The general teahniques available to him are polymer chemical oomposition, use of additives, production techniques, and laaination or coextrusion of fibs. By selection of the polymer building blocks, the monomers Bed, general characteristics can be bullt into the polymer. The use of monomers composed of carbon and hydrogen such as ethylene produce polymers which are generally moisture barriers but relatively high in gas permeability. Inclusion of halogens like chlorine or flourlne create excellent barrier properties in the polymer but results In polymers which are inherently brittle. Addition of small quantities of other monomers to make "copolymers" such as acrylates and acetates tend to build in softness since the polymer structure is disrupted.

The addition of additives to a polymer can make a polymer into a commercially feasible film. Additives vary in their use *OB materials which can be added to externally soften a polymer called plasticimrs, materials which make the polymer thermally stable so it can be processed into a film, and to materials which prevent surfaces of the film fkom sticking to one another--anti-blocking additives. The production technique is also a means to vary fila properties. Most of the plastics used today to make fibs are thermoplastic and the general production technique ia to extrude the polymer into a film in the molten state, The stretching techniques used to make the flla initially or post stretching techniques at aontrolled temperatures can result in filas of quite different mechanical properties,

And finally, if all the desired properties cannot he built into a sin& flh, variom compositions can be made lamination of two or more fibs together into a ccmposite flk or by aoextmsion to build in desired properties. Thin has been a very important procedure for film to be mod for vmum packaging of processed meats. :6d

TABLE 7. FACTORS AFFECTING THE QUALITY OF PRIMAL FRESH MEAT CUTS

1. Prevent microbiological spoilage.

2. Prevent the degradation of meat pigment myoglobin.

3. Prevent moisture loss,

TABLE 8. FILF! REQUIREMENTS FOR PRESERVING THE QUALITY OF PRIMAL PEAT CUTS

-~ ~ ~ ~- ~~ -

1. Barrier to oxygen.

2. Barrier to moisture, 3. Retain package integrity in normal handling and shipment channels.

TABLE 9. METHODS AVAILABLE TO OBTAIN DESIRED PLASTIC FILM PROPERTIES

1. Polymer chemical composition. 2. Use of additives.

3, Production technique,

4. hination or coextrusion. 369 The types of film which are presently being used in the meat industry can be classified as six general types. They are those based on cellophane, polyethylene and related copolymers, polyvinyl- chloride copolymer films based on vinyl chloride as the main constituent, polyvinylidene chloride copolymers based on vinylidene chloride as the main constituent, polyesters made from diacids and dialcahol monomers and nylons containfng the amide type of linkage. Cellophane (table 10) is one of the oldest plastics used in fila form and has been used extensively in meat packaging for many years. Two types are used which are either lacquer coated or polymer coated depending on usage. Corrercial products are produced by DuPont, Avisco, and Olin Hatheson. Lacquer coated films are used to package fresh meat which one would not expect because of the usual listed permeability properties of cellophane, men cellophane is wetted out the permeability of oxJrgen and moisture increase tremendously from the 1 to 5 cc mi1/100 ln2- 24 hrsmATM level of the dq state and 0.5 to 1 gm mil/ 100 in2* 24 hrs*ATM moisture permeability level to the point where the film transmits moisture as though the film were not there and oxygen transmission levels high enough to allow good formation of oxymyoglobin on the meat surface. Since moisture is lost rapidly from the wetted film the surface is coated with a lacquer such as nitrocellulose to prevent excessive moisture loss. The lacquer coated side anst not be in contact with the neat surface as this would prevent moisture absorption by the cellophane. The physical properties of cellophane are not extremely high and tensile strength, tear strength, and impact strength are decreased on absorption of water, Polymer coated films are used for vacuum packaging in pouch fom by protecting the cellophane *om absorbing moisture. Having the necessary oxygen barrier properties in the dry state, makes it useful to package many processed meat items. Heat seals of the tack type can be made with the lacquer coated film to hold the packsge together! good heat seals can be made with polymer coated film.

Another classification of polymers which are used extensively for packaging meats are the polyethylenes and related palymers (table 11). Tuo general types of polyethylene are available which are made by different production techniques-regular blown film and oriented film made by selectively stretching film at elevated temperatures after a preliainary film has been formed. Commercial maes you may be faailiar with are PERFLEX of UCC, VisQueen of Ethyl Corporation and Polifllm of DOW for bloun fihs while Cryovac L is used by W. R. Grace and Co. , Clysar by DuPont and PERFLEX S by Union Carbide for oriented films . The production techniques of these fibs are a good illustration to what extent physical properties can be changed. The tensile strength and elongation of blown polyethylene fib normally are of the order of 1200 to 3000 psi and with relatively high elongations up to TOO percent. Oriented films,on the other hand, have tensile TABLE 10. PROPERTIES OF CELLOPHANE FILMS

Lacquer coated Polymer coated Conumerclal names film flh DuPont DuPont Avisco Avisco Olln Olin

Yield (sq ln/lb/0.001 in. thickness ) 19,500 19,500 Tensile strength (lb/ln2) 7,000-16,000 7,000-16,000

Elongation at break (%) 15-25 25-50 Tear strength (gm/O.OOl In. thickness ) 2-10 7-1 5 Impact strength (kg-cn) 8-1 5 5-1 5

Haze (9) 2-5 2-5 Gloss ($) 75 75 Oxygen transmission rate (cc-mil/IoO in2-24 ~S-ATM) 1-5 1-2 Moisture vapor transmission rate (gm-mil/IOO id-24 hrs-ATM) 0.5-1 0.5-1 General Tack Heat Seals Heat Sealable nOiStW8 Sm6itiVe Eblly Printed Easily Printed TABLE 11 . PROPEATIES OF POLYETHYLENE FILMS

Blown flh Oriented film Commercial napes PERF'LEX--Union Carbide Cryovar, L--W. R. Crace VisQueen--Ethyl Corp. ClySar--DuPent PQlifi h--Dou PER-X S-lhrion Carbide

Yield (sq in/lb/0.001 in. thickness) 30,000 30,000 Tensile strength (1b/in2) 1,200-3,000 7,000-1 1,000 Elongation (a) 200-700 100-250

Tear strength (gm/O. 001 in. thickness ) 100400 20-25

Impact strength (kg-cm) 7-8 25-30 Hate (SI 2-5 2-6 ClOSS ($) 80-90 70-90 Oxygen trsnsnission rate (cc-mil/IOO in2-24 hra-ATM) 250-700 250-500

Xoisturo vapor transmission rate (gm-mil/lOO in2-24 hrs-ATW) 1.o-1.5 1.o-1.5

Comments Ehsily sealed. Heat 608lable. Helps stabilize Shrinkable. thexuofonlng of R0qt1ir.8 treatment of laBinate film. for printing. Requires treatment for printlag. strengths of 2 to 10 times higher than blown films and lowering of elongation characteristics, Orientation also lowers the tear strength and increases the impact strength of the polyethylene film because of the orientation of the polper molecules on stretching under controlled temperature conditions. This also builds in the advantageous property of shrinkability which makes the film useful in packaging techniques where the fila can be shrunk over a product. Polyethylene films have been used in two general meat packaging areas. Polyethylene and related copolymers have been used for pac-ing fresh meat to a limited extent because of desirable oxygen permeability and low moisture transmission rate, It does not have very low haze levels one would desire for a very attractive retail package; some package attractiveness is lost on handling because of poor elastic properties. Polyethylene has been used extensively in the pckaging of processed meats in laminated films where it serves as the sealant layer since it foms excellent hermetic seals, The film also contributes some stability to the laminate film on themo- forming. A copolymer film related to polyethylene which is now being widely used for the sealant layer is Iolon manufactured by DuPont. This polymer is an iomomer material, made from ethylene and meth- acrylic acid crosslinked between the acid groups with bases. Iolon not only retains the sealing properties of polyethylene but adds much additional stability to laminate film when thenaofonned.

Polyvinyl chloride copolymer films (table l;?) are an interesting type of fib because the addition of additives to the resin formulation greatly alters the properties of the film. This makes vinyl films useful for packaging both fresh retail meat cuts and vacuum packaging of processed meats. The vinyl films are usually referred to as soft vinyl film and semi-rigid vinyl fila or sheeting, Common commercial naaes a.re Resinite of Bordon Chemical Co. and Prime Wrap of Goodyear for soft films and Reynolon of Reynolds for semi- rigid sheeting and sheeting sold by Standard Packaging Co. and Tenneco. The major difference in these two types of film is the level of softener or plasticizer added to the polymer formulation, At high plasticizer levels soft films are obtained which can be either elastic or shrinkable depending upon production technique while low levels of plasticizer results in stiffer fihs which again can be made shrinkable if desired. This difference in plasticizer level reflects in higher tensile strengths of the low plasticized material, lower elongation, similar tear and impact strengths. But the one property which is greatly different is the oxygen permeability such that soft vinyl film is used to packaging fresh retail meat cuts while the semi-rigid or thick sheeting has been used for packaging processed meat items because of the relatively low levels of oxygen transmission in 10 to 20 mil sheets. Addition of other barrier materials in thin coatings can lower the permeability further. For f’resh retail packages the film has good sparkle, very clear and is relatively elastic so that finger marks and punches will mostly disappear and give good package appearance even after excessive handling. This, of course, is desirable for retail packages, The TABLs 12. PROPERTIES OF POLYVINYL CHLORIDE FILMS - - - - __ - - Soft plastlcieed Semi-rigid vinyl film vinyl ilk Couercial mea Resinite--Bordon Cherioal Reynolon--Reynolds Prime Yrap--Cood$oar standard mekaging eo. PVC-1 o--Avi8CO Tenn8co

Yield (6q in/lb/0.001 in. thickness) 22,000 22,000 Tensile strength (1b/in2) 3,000=4,000 6,000-1 2,000

Elongation ($) 275-350 75-125 Tear strength (ep/O.OOl in. thiokneas) 15-20 10-15 15-20 10-1 5 1-2 1-2 86-90 80-90

10-100

22-27 3-1 5 Comments Heat sealable. Tharmoformable. Elrstla or shrinkable Heat sealable. forms aan be printed. Can be printed.

w w 3 74 soft vinyl is heat sealable to form relatively strong packages. This film has taken over the retail packaging market from cellophane during the last 5 years and is the most widely used material today at the retail level. The semi-rigid material, because of its strength and additional advantage of being easily thennoformed at elevated temperatures, has been used to fom deep cups to hold product and thermofonned backiqqs of packages. Because of this material, the growth of the rigid or semi-rigid packages for bologna, luncheon meats has been possible. To assure sufficient oxygen tarrier properties and to assure hermetic seals the vinyl sheeting has been coated with thin layers of barrier material and polyethylene or one of its copolymers to make excellent laminate film.

The polyvinylidene chloride copolymers (table I3) containing vinylidene chloride as the major constituent are usually referred to generically as Sarans or PW. Commercial names are Cryovac S of W 9, Grace, ’*an ‘kap of DObl and PERFLEX 55, 66 of UCC . PVDC is a widely used polymer in both bag and in thin coatings on other barrier films because of its excellent barrier properties to both oxygen and moisture, PVDC is a material which is relatively brittle and is usually plasticized to various levels to make it a useful, flexible material in bag form. The film is quite strong and is made shrinkable by preferential extrusion stretching techniques, Optical properties of usmade from this material have relatively good clarity and %loss but not to the levels of other polymers such as polyethylene or the vinyls, One disadvantage of the PVDC type materials is that it requires special sealing techniques, RF sealing, to form hermetic seals. “hen used in bag form the packages are sealed using a metallic clip to give final closure to the package. Because of the barrier properties of PVDC, bags are used to vacuum package processed meats and in the vacuum packwing of primal and subprimal meat cuts. The packa.ge can be shrunk in hot water to form an attractive tight pouch on the meat item. The other major use of PVK is as a thin coating on other barrier films to insure sufficient barrier properties for packaging various processed meat items.

?olyester films (table 14) are also used extensively for packaging meats, mainly of the processed types. Common commercial names for polyesters are Mylar of 3uPont and ScotchPak of 3M. The polyesters have extremely high mechanical strength with films having tensile strengths up to 3O,OOO psi, high tear strengths and excellent Impact strengths. In fact, it is difficult to punch a hole in Mylar film unless you have sharp finger nails. Mylar comes in heat shrinkable types and some which can be thermofomed to a limited extent of about 3/4 inch, It is a very good barrier to oxygen as well as to moisture. Again, Mylar is used in both pouch form of unsupported film but probably more extensively as the barrier layer of a laminate film. Kylar is difficult to seal so that wide solvent seals are used on bigs used to vacuum pckage chunked items. Since it is difficult to seal, pouches are closed like PVDC bags using a metallic clip and heat shrinking the pouch on the product after evacuation. Mylar film 375 TABLE 13. PROP~IESOF POLYVINYLIDENE CHLORIDE COPOLYMEXt FILMS

Cryovaa S--U. R. Grace Saran Urap-DOU Goluercisl names PERFLEX 55, 66-Union Carbide

Yield (sq in/lb/0.001 in. thickness) 16,000 Tensile strength (1b/in2) 10,000-14,000 Elongation (a) 80-120

Tear strength (gm/O .001 In. thickness ) 10-20 Impact strength (kg-um) 10-12

~aee(g) 10-25

Gloss (%) 50-60

Oxygen transmission rate (cc-mi1/100 in2-24 hrs-ATM) 1-1 5

Moisture vapor transmission rate (g.-mil/lOO 1112-24hrs-ATM) 0.1-1.5 Couents Shrinkable. Used as pouches and coating in laminate films. Hie;h frequency sealing required. TABLE 14. PROPERTIES OF POLYESTER FILMS

Couuuercial names Mylar--DuPont Scotchpak--3M __ -~

Yield (sq in/lb/O, 001 in, thickness ) 20,000

Tensile strength (Ib/in2) 17,000 and greater Elangat ion (%) 70-130

Tear strength (gm/O.OOl in. thickness) 13-80 Impact strength (kg-cn) 25-30

Haze (%) 2-7

Gloss (&) 70-90 Oxygen transmission rate (cc-mil/l 00 in2-24 hrs-ATM) 1-3 Moisture vapor transmission rate (gm-mi1/100 id-24 hrs-ATM) 1

Comment s Shrinkable types available. Themofomable. Difficult to seal, 377 is used more extensively as a laahate fib, with or without a coating of PVDC to Improve barrier properties, and uith a Iqer of polyethylene or modifled polyethylene as the sealant layer, It is used most extensively as the non-draun layer of these packages since it has only llmited drawing capabilities-as mentioned previously of about 3/4 inch since many pouch failtlres occur on deeper drauing.

In eonjunction with Mylar, many vacuum packages used the last type of film to be discussed (table 15). This barrier film is nylon and I will refer to it as Nylon 6 since this is the nylon most widely used in meat packaging. The majority of film is manufactured by Allied Chemical Co. and sold with the trade nark of Capran C. It has good mechanical properties of tensile strength, and tear strength but with relatively low impact strength. Barrier properties are adequate and in most applications Hylon is coated with a thin layer of PMC , The major attribute of Nylon 6 is the ease with uhich it can be thermofonsd with very few pouch failures. Since heat seals are not the best with Nylon 6, a polyethylene layer or modified polyethylene is laminated to the coated fila to be compatible with the larlnated mylar film uhiah is usually wed for the non-dmwn portion of the package, Coating of the nylon also prevents moisture from reaching the film from the product. Bcvrier properties would decrease since nylon is moisture sensitive. In conclusion, I hope I have been able to summarize briefly for you this morning the state of the art of plastic film med presently for packaging various types of meat. One can ask how meat packaging will change in the future. I feel one of the major changes in meat packaging will be in the area of retail meat cuts. With the increased cost for labor, cost of store space, shortage of labor, interest in more efficient operations, and closer quality control, centralized prodaction of retail meat cuts appears very attractive. The packaging, I feel, will be done in some caae8 neat paakers and others by supermarket ohains. One prwedare which may be introduced at this step is the retailing of frozen meats which I feel still depends on a very strong marketing and educational prograa. This procedurs i$ the next logical step following centralieed breaking of ca,rcasses into prlnal and subprimal meat cuts. If the past ten years can be wed aa 8 guide, I am sure paokaging raterial suppliers working in cooperation with meat packers and supermarket chain8 will develop the technology required for major paukaging changes, 372 TABLE 15. PROPERTIES OF NYLON 6 FIIMS

Commercial names Capran 77C--Allied Chemical

Yield (sq in/lb/0.001 In. thickness) 24,500

Tensile strength (1b/in2) 10,000-15,000

Elongation (%) 250-500

Tear strength (gm/O. 001 in, thickness ) 50-90

Impact strength (kg-cm) 2-3 Haze (%) 2-0

Gloss (46) 70-90

Oxygen txansmission rate (ccai1/100 id-24 hrs-ATM) 3 -7 Moisture vapor transmission rate (gm-mil/lOO in2-24 hrs-ATH) 9 Comments Thermoformable. Moisture sensitive.