Meat wrapping requires non-toxic and lightweight plastic materials capable of protecting the product from rough handling and harmful micro-organisms.
The factors coming into play when selecting suitable packaging materials include the all-important cold chain, which take into account the time frame of meat distribution and shelf-life, food manufacturer/ distributor prerequisites such as brand labeling, and package type, size and cost, and market issues such as pricing.
As meat spoilage can largely be attributed to packaging techniques in addition to meat product type, it is important to understand what causes meat discolouration and how to prevent it from happening.
All fresh meat, fresh meat products, and processed meats are subject to spoilage. This happens when bacteria draw their food from their environment and return their waste products to that same environment, with the waste products over time resulting in meat losing its aesthetic appeal.
Oxymyglobin, the predominant pigment in fresh meat giving it its bright red colour, is responsible for the customer’s perception of “freshness” and “quality”. Under conditions of limited oxygen availability metmyoglobin – the brown pigment – forms. Meat packaged in a suitable moisture barrier packaging film will not lose surface moisture and consequently will not dry out and darken.
When supply of oxygen to the meat is interrupted, the predominant pigment becomes the purple-coloured myoglobin – the colour of aged, vacuum-packed meat.
MAP systems with high oxygen and carbon dioxide (CO2) concentrations improve colour and shelf-life over that of permeable overwrapped packages. (Oxygen contributes to colour and carbon dioxide establishes shelf-life.)
The use of CO2 in a MAP system slows growth of spoilage and pathogenic bacteria to aid shelf-life extension. However, if a high proportion of CO2 gas is used in MAP, the gas may be absorbed to the point where the package collapses. If a large amount of gas is absorbed by the product, it may also lead to physical disruption during cooking because of expansion from regeneration of the gas.
Because of the need to limit gas absorption and avoid discoloration of fresh meat, CO2 typically has been combined with nitrogen (N2) or oxygen and limited to about 30% of the blend for MAP.
A more advanced method of MAP is normally done with a gas mixture of 0.4% carbon monoxide (CO), 30% CO2 and 69.6% nitrogen (N2). This mixture offers the advantage of a stable fresh meat colour for at least 28 days for ground beef and at least 35 days for steaks and roasts with no oxidation-induced alterations.
Because the permeability of packing films increases with temperature, temperature abuse of vacuum-packed meat may lead to colour deterioration in the same way as packing in film with too high a permeability.
The shelf-life of vacuum-packaged fresh meat with a good barrier material is generally reported as approximately 21 days. From an optimal quality point of view, vacuum-packaged frozen, whole-muscle beef has a recommended shelf-life of 12 months.
All types of meat packaging are designed with the purpose of hygienically storing products while optimising shelf-life, and all have their advantages and disadvantages. The choice of type of packaging depends for the most part on the food processor’s product turnaround time.
It is also important to bear in mind that automated systems are preferable, as they involve minimal meat handling.
The four types of packaging commonly used are overwrapping or stretch wrapping, flow wrapping or HFFS (including masterbag), thermoforming/vacuum packaging (including skin packaging) and tray sealing.
The most common form of fresh meat packaging in the retail marketplace is air-permeable overwrap, which typically consists of a foam tray and absorbent pad resting under the cut of meat covered with clear film which is permeable to moisture and oxygen.
While this package type is the most economical, and if automated delivers a constantly consistent packaged product, it also yields the shortest shelf-life due to continued exposure to oxygen.
The expected shelf-life of air-permeable overwrap packages is three to seven days depending on whether the meat product is ground or whole muscle. Ground beef will have a shorter expected shelf-life than whole-muscle beef.
Flow wrapping (HFFS), one of the most flexible packaging concepts, can use a variety of different types of film – from non-barrier BOPP (Biaxially Oriented Polypropylene) film to laminated, high-barrier shrinkable film with MAP. This type of packaging is a horizontal-motion, automated process in which product of any shape, typically packed in a tray, is wrapped in clear or printed film. The end result is a trayed-product encased with the chosen film and a three-sided seal.
There are new trends developing in the European markets to flow wrap meat products without a tray, with aim of cost savings and reducing packaging weight and waste disposal.
The flow wrapping process, with the correct barrier film and MAP, provides meat products with good shelf-life (seven to ten days). Its advantages include the flexibility to operate at high speeds with different size and shaped products.
A masterbag with
high barrier film is typically used to encase several individual pre-packed units. The masterbag concept is an extension of the flow wrapping process. Three to four individual overwrapped meat packs are flow wrapped together in a MAP masterbag.
The idea is to extend the shelf-life of the grouped products until the masterbag is opened at the retail store. The overwrapped products are then displayed as normal with the standard overwrapped product shelf-life.
Vacuum packaging is typically accomplished through the use of a bag or pouch with very low moisture and oxygen transmission rates. The air is removed from the package via a vacuum chamber and the package is heat sealed
There are two types of machines: vacuum chamber machines, where the whole bag and contents fit inside the machine, and external bag machines, where only the end of the bag fits into the machine and the rest of the bag and the contents remain outside of the machine.
All external bag machines work by clamping the open end of the vacuum bag (sometimes called a vacuum pouch) whilst the air is being removed. Because the end of the bag is clamped shut, this type of machine needs to use a special type of bag with a finely ribbed or textured back surface so that the air can be removed easily.
More expensive vacuum chamber machines resemble a stainless steel box into which the vacuum pouch and contents are placed and the lid closed over them. The entire chamber is then vacuumed and the pouch is heat sealed. This type of machine does not need ribbed bags and as a result the vacuum pouches are cheaper than those which work best in the external bag machine.
Vacuum chamber machines are ideal where large volumes of similar sized items are being vacuum packed and are widely used by in the food packaging industry.
Thermoforming is theoretically an automated process of the vacuum bag system. The thermoformed material can be flexible or of a rigid construction.
In this process the pouch, bag or tray is moulded by the machine. Plastic film is preheated to a pliable forming temperature, formed to a specific shape in a mold. Product is then placed in the preformed packs at the loading area of the machine. The product laden packs are vacuumed or gas flushed in the sealing station. The sealed packs are trimmed to the required individual pack shape and size.
The key advantages of thermoforming are the reduction of packaging cost, automation, higher production capacities and improved vacuum and sealing results.
A family of the thermoforming process is skin packaging, which is attractive with high consumer appeal, pilfer resistant, fixes the product position and enhances product shape. The packaging offers good shelf-life similar to a vacuum pack, but is expensive.
The products are placed in the packaging machine, usually on a rigid film which serves as the bottom layer of the final package. Another flexible film – the top layer, which is heated for increased flexibility – drapes itself from above around the product, resembling a tight “skin” on the product surface.
The skin-like coverage of the product takes place in a sealing station in the packaging machine, where the top and bottom films are sealed around the edges. Individual packages are separated by cutting around the bottom seal perimeter.
Tray sealing machines are used to “lid” a preformed tray. The tray sealing machine can be manual, semi-automatic or fully-automatic.
Product is placed in a preformed tray and sealed in a sealing station. Higher-end tray sealers offer hermetic sealing with the option of MAP for shelf-life extension and colour enhancement. With the correct barrier tray and anti-fog lid material, an up-market, tamperproof package can be created.
In addition to selecting packaging types and machines, there is a more pressing matter concerning meat processors right now: amended and/or supplementary labels on their packaged food in accordance to the new regulations of labelling and advertising of foodstuffs under the Foodstuffs, Cosmetics and Disinfectants Act of 1972, which will come into effect on 1 March 2011.
Under the new regulations, provisions have to be made on-pack for the new and comprehensive details required regarding information such as allergens, use of product, storage of product, and list of ingredients.
In the meat industry the regulations apply to refrigerated and frozen unprocessed meat, processed meat, raw-processed meat and ready-to-eat food items and encompass ingredients such as brine, additives, preservatives, natural or artificial sweeteners, salt and omega 3 fatty acids.
In keeping with the new regulations, known as R146, the definition of the word “name” means a word or words giving a true description of the nature of a food product and being sufficiently accurate to avoid misleading or confusing the consumer as to the true nature, physical condition, type of packing medium, style condition and type of treatment it has undergone.
Many food labels make ambitious and often false promises, but that will soon change. Some terminology that operators in the meat industry have to watch out for is:
• “all natural”: This implies meat that is
minimally processed with no artificial or
• “country of origin”: It states where livestock
was raised, slaughtered and processed. If
processes were undertaken in multiple
countries, as in the case of some ground
meat, they should all
• “grass fed”: Simply put, it means that
animals eat grass. However, “grass-fed” animals can also be fed
grain, and can be
raised on grass in confinement, as long as
they have access to (even small) pasture.
• “free range”: Strictly speaking, this means
that the animal has some outdoor access.
• “organic”: This term indicates that livestock
wasn’t treated with hormones or antibiotics
and was fed a
• “humanely raised”; “certified humane”:
This addresses the treatment of living
animals. Producers and
retailers may also
make claims about how the animal is handled
between slaughter and purchase.
Where is all this information supposed to go? One solution is provided by Pyrotec PackMedia, who has not only attained proficiency on the full scope of the new legislation, but has also designed various on-pack devices which can be tailored to get around the space concern.
Pyrotec Packmedia’s Fix-A-Form label™ is an affordable solution and consists of printed leaflets similar to a booklet with self-adhesive labels. The label provides ample space to accommodate additional information without affecting the legibility of the copy or visual appeal of the product.