Packing of meat and meat products
GOSPODARKA MIĘSNA 07/2005
Hanna Gajewska Szczerba
The concept of packaging should be understood as industrial products intended for containing goods during production and trade. When talking about packaging, one should not ignore their functional, promotional and advertising values as well as ecological functions. The classically understood function of individual immediate packaging is that it exists to protect the product.
However, it should satisfy all the people through whose hands it will pass.
The selection of the appropriate packaging material and form for a specific food product depends on many factors. The most important among them are factors directly related to the physicochemical properties of the packaged product. These include, for example, the chemical composition, the physical state of the product, its texture, porosity, as well as the storage time and conditions in which it will remain until consumed by the consumer.
It is very important to know the processes (mechanisms) and factors stimulating the physical, chemical, biochemical and biological changes occurring in the product during storage, which limit its shelf life.
The packaging must also take into account the method and conditions in which the product will be transported to recipients. In this case, it is primarily about anticipating potential mechanical exposures affecting the packaging and the product contained in it.
Functions of individual direct packaging in meat processing
It should be noted that these are single-use packaging and after fulfilling their technological functions, they are thrown away, which creates an additional problem of disposal.
The packaging, on the one hand, serves as a barrier protecting against the harmful effects of external factors and, on the other hand, influences the creation of the cryptoclimate in which the product is located, should prevent mechanical deformations of the packaged product.
This is inextricably linked to the biophysicochemical characteristics and rheological properties of the food product, such as meat and meat products.
Raw or cured meat and meat products, with or without bones, in one piece or minced, are packed. Many criteria are taken into account when selecting packaging materials, such as water vapor permeability, gas permeability, mechanical strength, weldability, transparency and cost.
Packaging films, characterized by various barrier properties in relation to gases and water vapor, are used for packaging meat and meat products using a vacuum and in a modified atmosphere (MAP (Modłfied Atmosphere Packaging) and controlled CAP (Controlled Atmosphere Packaging).
The packaging material must constitute a barrier both to moisture (it should retain it inside the packaging) and to oxygen.
The search for packaging materials with optimal properties has led to the fact that today almost exclusively combined, multi-layer materials are used.
Combined foils use, among others: the following materials and their derivatives:
• polyethylene (PE),
• polyester (polyethylene terephthalate - PET),
• polyamide (PA, especially polyamide PA 6),
• polypropylene (PP),
• polystyrene (PS),
• polyvinyl chloride (PVC),
• polyvinylidene chloride (vinylidene dichloride - PVDC),
• ethylene vinyl alcohol (ethylene vinyl alcohol copolymer - EVOH) i
• acrylonitrile copolymers.
Among many packaging materials, the cheapest is polyethylene (PE) foil, but meat packed in it, e.g. deboned beef, loses the desired red color within 1-2 days due to the fact that PE foil is permeable to oxygen, which oxidizes the red meat dye. – myoglobin, transforming it into brown metmyoglobin.
Similarly, PVC (polyvinyl chloride) foil can be used to temporarily protect food against environmental conditions.
The meat industry uses flexible, semi-rigid and rigid packaging materials (foils) as well as foil laminates with various technical parameters, such as thickness and resistance to mechanical damage, permeability to gases, water vapor and ultraviolet (UV) radiation, weldability, thermoformability. and heat shrinkage or resistance to low and high temperatures.
Multi-layer foils are more often used than single- or double-layer ones. Many multi-layer materials are used to pack meat and meat products, including: PA/PE, OPA/PE, PET/PE, PETmet/PE, PET/PYDC/PE and other foils.
The outer layer of the multi-layer foil packaging mainly takes care of mechanical stability, the middle layer acts as an oxygen barrier, while the inner coating ensures tearing and puncture resistance of the seal and the packaging.
Special weldable layers guarantee welding safety. For example, new generation shrink bags can consist of six layers of different polymer films. One of them may be, for example, low-density polyethylene (PE-LD), which is characterized by very good weldability.
The development of trade and the distribution network requires increasingly longer shelf life of processed meat products, which usually means the use of packaging materials with increasing barrier properties, i.e. lower oxygen permeability. However, under the influence of increased humidity, the barrier properties of some barrier polymers, e.g. EVOH and PA 6, may decrease.
The barrier layer of the laminate must be protected against water absorption by using protective layers or by modification, e.g. with amorphous polyamide.
Transparent foils and bags coated with silicon oxides (SiOx) constitute a very good barrier to gases, water vapor and aromatic substances. They are used for packaging products, as well as their pasteurization and sterilization. They do not have the "retort shock" effect, i.e. they do not reduce their barrier properties during thermal treatments.
In practice, multilayer films containing an oxygen absorber based on an inorganic compound that reacts with oxygen irreversibly can also be used. It does not come into direct contact with the product and cannot migrate to it. This extends the shelf life of a product sensitive to oxygen, e.g. meat or sliced cold cuts.
Foils with a layer protecting the product against UV radiation are also used. This barrier is independent of other properties of the foil. During storage, it does not lose its functional properties and does not transfer to the packaged product. Thanks to this, such films do not raise any objections from the point of view of food law. They are used for packaging cooked hams, as well as raw sausages and smoked meats.
The use of a protective layer in packaging against UV radiation and oxygen absorption makes it possible to exceed the previously achieved limits of product durability. Unlike aluminum foils, they are susceptible to deep embossing, permanently bind oxygen in the packaging, and ensure good product visibility.
Ready-made trays for packaging in the MAP or CAP system are popular packaging.
They are made of popular polymers such as polypropylene, polyethylene or polystyrene. Polypropylene (PP) trays can be rigid, thin-walled or made of foamed plastic (EPP), with or without an EVOH gas barrier. They are colorful, light, durable and aesthetic.
Packaged products can be pasteurized and sterilized and heated in microwave ovens.
Expanded polystyrene is used to produce gas-impermeable multi-layer trays, hermetically closed with a barrier multi-layer polyethylene foil.
The bottom part of the packaging has a layer that absorbs juice leaking from the meat during storage. This is a special solution because additional, special moisture absorbers are most often used - inserts made of absorbent cellulose.
Packing in a vacuum environment
Vacuum packaging involves evacuating air from the package, which is then tightly closed, usually by heat sealing. Removing most of the air from the package can be thought of as modifying the atmosphere around the packaged product.
It is believed that vacuum packaging allows the product to maintain better quality during its natural shelf life rather than being a way to extend this period. This is due to the inability to completely remove oxygen from the packaging, even when using a deep vacuum, and the impact of other factors causing product spoilage, including: development of anaerobic microorganisms.
Vacuum packaging protects the product, maintains its quantity and quality, and above all, durability. In particular, it prevents:
• drying and thus changing the color of the outer surface of the product,
• oxidation of the surface layers of meat and meat products.
• development of microorganisms,
• loss and mixing of aromas
• during storage,
• weight loss,
• sublimation upon freezing.
Important applications of vacuum packaging include packing large pieces of deboned beef into PA/PE laminate bags.
The meat must be characterized by low microbiological contamination, which should include, among others: be a consequence of maintaining high hygiene of animal slaughter and carcass cutting and maintaining the cold chain, i.e. a maximum temperature of 8 +-10°C during cutting and O ~ 2°C (maximum 4°C) during packaging.
If such conditions are maintained, 10 kg portions of meat can be stored at 0°C for up to two months. In this case, vacuum packaging significantly delays the ripening of the meat and protects against weight loss.
The packaging of meat elements should protect them against unfavorable factors, and above all: mechanical damage, dust, touching, microorganisms, loss or absorption of water, the influence of light, loss of aroma.
The shelf life of vacuum-packed meat, the microbiological condition of which was appropriate before packaging and the storage temperature correct, is usually nine weeks, and deterioration after this time occurs due to souring.
The main benefits of the vacuum packaging method: early separation of consumption meat from processing meat, reducing the need for cooling space, extending the storage period, reducing weight loss, the ability to meet consumer requirements and provide better information by placing prints on the packaging.
In practice, various forms and shapes of vacuum packaging are used, e.g. sealed bags, heat-shrinkable packaging (foils).
The vacuum used during packaging should be at least 95%, but ideally it should range from 98 to 99%.
When using sealed vacuum bags, so-called corners are often formed. dead spaces where meat juice can accumulate. This phenomenon is of particular importance for the aesthetics and microbiological durability of packaged meat.
Of this, among others: Therefore, the size of the bag should be selected appropriately. Excessive juice leakage can be eliminated by using absorbent cellulose inserts, on which microorganisms multiply intensively. This phenomenon can be prevented by using shrink bags.
Under the influence of an appropriate, precisely defined temperature, they adapt their shape to the packed meat, leaving no empty spaces.
An additional secondary welding operation can also be used, which is the cheapest solution.
It involves subjecting the finished packaging to a very short thermal exposure, the time of which is less than one second, while the temperature used does not reach 100°C. As a result, the empty, flat parts of the vacuum packaging will bond together, reducing the space for possible leaks.
In packaging formed on roll machines, these spaces can be eliminated by sticking the free surfaces of the packaging together. Vacuum packaging can also be used for meat with bones, e.g. pork loin, bacon, shank or pork ribs. Meat with a pH value in the range of 5.7 to 5.9 should be packaged no later than 48 hours after the animal is slaughtered.
The best results are achieved by packing in shrink bags.
Air is removed from packages containing portions of meat and then they are shrunk for several seconds in hot water at a temperature of 87 - 89°C, in a stream of steam or in hot air. As a result, the product is tightly wrapped in foil, which prevents the leakage of meat juice by up to 20% compared to other packaging systems.
However, vacuum packaging poses many sensory and hygienic problems. After prolonged storage of meat packed with this system, a "vacuum packaging odor" occurs in the packaging caused by the activity of microorganisms. Moreover, prolonged storage in a vacuum causes excessive, undesirable tenderness of the meat and changes in its color (formation of metmyoglobin) caused by the presence of oxygen in the packaging.
The oxidized form of myoglobin is most intensively produced at an oxygen content of 5 - 10%. Table 1 shows the relationship between the oxygen permeability of packaging foils and the permissible storage time of beef at a temperature of + 0°C.
In practice, vacuum packaging of several kilogram blocks of pasteurized ham is also used to prevent the jelly from leaking out, which prevents both loss of its weight and loss of palatability.
Important applications of this type of packaging also include the packaging of sliced meats, in particular ham, bacon and bacon.
Vacuum packaging of fragile products that are susceptible to
