Ultimate guide to MAP modified atmosphere packaging

Development history of modified atmosphere packaging

The first commercial application of MAP modified atmosphere packaging was for CAS of fruits and vegetables. In the early 1930s, fresh carcasses were exported from New Zealand and Australia under the CAS. The initial development mainly involved the storage and transportation of bulk food. In the 1930s, studies on the effect of gas on extending the shelf life of food were carried out on fresh meat. Killefer (1930) reported that when meat is stored in a 100% CO2 atmosphere, the shelf life of frozen pork and lamb doubles. The first published research on poultry products was carried out in the 1930s; fresh poultry is stored in a 100% carbon dioxide atmosphere, which significantly extends the shelf life.

The shelf life of the chicken portion was reported that as the CO2 concentration in the storage environment rises to 25% CO2, the impact on shelf life becomes greater.

MAP modified atmosphere packaging of fresh meat for retailing market was introduced in the early 1970s. Meat processing and packaging in Europe developed in the 1980s, mainly producing MAP meat in consumer packaging for distribution at the point of sale. In recent years, in the ever-changing retail environment, the supply of packaged foods including meat has increased significantly. , Poultry, fish, bacon, bread, cake, potato chips, cheese, and lettuce. The retail sales of MAP packaging products in the UK increased from approximately 2 billion packages in the mid-1990s to 2.8 billion packages in 1998. Meat products accounted for 29% and 15% of MAP’s total food retail sales respectively (Anon, 1999).

Gases used in Modified atmosphere packaging

The three main gases used in MAP modified atmosphere packaging are O2, CO2, and N2. The choice of gas depends entirely on the food to be packaged. These gases are used alone or in combination and are usually used to balance the safety shelf life and the best sensory properties. Rare or inert gases (such as argon) are used commercially in products such as coffee and snacks, but there is limited literature on their uses and benefits. Experimental uses of carbon monoxide (CO) and sulfur dioxide (SO2) have also been reported.

Carbon dioxide

Carbon dioxide (CO2) is a colorless gas with a slightly pungent odor at very high concentrations. It will suffocate when exposed to moisture and is slightly corrosive. CO2 is easily soluble in water (1.57 g/kg at 100 kPa, 20°C) to form carbonic acid (H2CO3), which increases the acidity of the solution and lowers the pH value. This gas is also soluble in lipids and other organic compounds. The solubility of CO2 increases with decreasing temperature. For this reason, the antibacterial activity of CO2 is significantly higher at temperatures below 10°C than at 15°C or higher. This has important implications for the food MAP discussed later. Due to the reduced air space, the high solubility of CO2 will cause the packaging to deteriorate. In some MAP applications, compressed packaging is preferred, such as cheese in retail packaging.

Oxygen

Oxygen (O2) is a highly reactive, odorless, and colorless gas that promotes combustion. Its solubility in water is very low (0.040 g/kg at 100 kPa, 20 °C). Oxygen can cause many types of food spoilage reactions, including fat. Oxidation, blackening reaction, and pigment oxidation. The most common perishable bacteria and fungi require oxygen to grow. In order to extend the shelf life of food, the atmosphere of the package must therefore contain low concentrations of residual O2. Foods with low O2 concentrations can cause quality and safety issues (such as poor discoloration of red meat pigments, aging of fruits and vegetables, and growth of food-borne bacteria), which should be considered when selecting gaseous formulations for prepackaged foods.

Nitrogen

Nitrogen (N2) is a relatively inert gas, odorless, tasteless or colorless, has a lower density than air, is non-flammable, and has low solubility in water (0.018 g kg-1 to 100 kPa, 20°C) and other food ingredients Nitrogen does not support the growth of aerobic microorganisms, so it inhibits the growth of aerobic spoilage, but cannot prevent the growth of anaerobic bacteria. The N2 in the gas mixture compensates for the decrease in volume caused by the dissolution of CO2.

Carbon monoxide

Carbon monoxide (CO) is a colorless, odorless, and odorless gas that is highly reactive and flammable. Its water solubility is poor, but it is relatively soluble in some organic solvents. The CO was investigated and approved in the meat MAP. Used to prevent browning of packaged lettuce in the United States. Commercial use is restricted due to its toxicity and the formation of potentially explosive mixtures with air.

Noble gases

Noble gases are a class of non-reactive elements, including helium (He), argon (Ar), xenon (Xe) and neon (Ne). These gases are now used in many foods, such as potato snacks. Although it is scientifically difficult to understand how the use of inert gases provides savings over N2, they are still in use, indicating that there may be benefits that have not yet been announced. For you to use.

The influence of gases on the activity of bacteria, yeasts, and molds

Food may contain many kinds of microorganisms, including bacteria and their spores, yeasts, molds, protozoa, and viruses. Although packaging experts are most concerned about preventing the growth of bacteria, yeasts, and molds in food, it should be noted that even if some pathogens do not grow in food, they will exceed the shelf life and cause food poisoning. Or consumer disease. This section discusses the main microbial groups that MAP modified atmosphere packaging can control or affect.

Effect of oxygen

Bacteria, yeasts, and molds have different respiratory and metabolic requirements and can be grouped according to their oxygen requirements.

Aerobes: They require O2 to grow and include the ubiquitous Pseudomonas gram-negative spoilage bacteria. This group also includes some pathogenic bacteria, such as Vibrio parahaemolyticus. Note that some other Vibrio species are classified as facultative aerobes.

Microaerophiles: They grow at low O2 concentrations. Therefore, the hypoxic environment is selective for some major pathogens (such as Campylobacter jejuni and Listeria monocytogenes). Certain microaerobic bacteria, such as Lactobacillus. Even under conditions of low oxygen levels, higher CO2 levels may be required to achieve optimal growth.

Facultative anaerobes: They usually grow best under O2, but they can grow without it. These include several important genera of the Enterobacteriaceae, including pathogens such as Escherichia coli, Salmonella and Shigella, Staphylococcus aureus, Listeria monocytogenes, Brucella, Vibrio, enzymatic Yeast. And some Bacillus species. Aeromonas hydrophila is an emerging pathogen, especially related to fish and fish products. Many strains are psychrophilic, and some can grow at a temperature of 3 to 5°C.

Anaerobes: They are inhibited or eliminated by the presence of O2, for example by the pathogenic bacterium Clostridium botulinum. Removal of oxygen, such as in vacuum packaging, limits the growth of aerobic spoilage and pathogenic bacteria, thereby extending the shelf life. The above are other microorganisms that can grow under these conditions, including the pathogens Escherichia coli and hydrophile.

Effect of carbon dioxide

The antibacterial properties of CO2 have long been known (Valley & Rettger, 1927). Recent studies have shown that CO2 is effective against psychrotrophic bacteria (King & Nagel, 1975) and can extend the shelf life of foods stored at low temperatures.

There are several theories about the actual mechanism behind the carbon dioxide effect. Generally speaking, CO2 will increase the lag period and generation time of microorganisms, and this effect is expected to increase at lower temperatures. Antibacterial mechanisms, including lowering CO2 pH, inhibiting succinate oxidase when CO2 concentration is higher than 10%, inhibiting certain decarboxylase and cell membrane changes (Valley & Rettger, 1927; King & Nagel, 1975; Gill & Tan, 1979; En Foss and Morin, 1981). Various researchers including Daniels and others have also studied the area. (1985). The susceptibility of some pathogenic bacteria and perishable bacteria to CO2 is shown in Table 10. As mentioned in Section 10, Gram-negative bacteria are more inhibited than Gram-positive bacteria. CO2 exposure is highly dependent on temperature. Therefore, in order to protect the health of consumers, the integrity of temperature control must be maintained throughout the supply chain. CO2 can stimulate Clostridium botulinum (Eklund, 1982).

CO2 is easily soluble in water and lipids, especially at low temperatures, so adsorption adjustment is required. In fresh meat, until the container is destroyed. The latter occurs when CO2 is the main gas and the gas is dissolved in the water and fat phases of the product. To counteract this effect, an insoluble gas such as nitrogen can be used. If CO2 is needed to control the growth of bacteria and mold, usually at least 20% is used.

Effect of nitrogen

Nitrogen is a relatively inert gas. It is used to replace the air in MAP, especially O2. By removing air and O2, the growth of aerobic decomposition organisms is inhibited or stopped. Put pressure on the packaging to avoid tearing the packaging of foods with high moisture and fat content. For example, due to the solubility of CO2 in water and fat, these products tend to absorb CO2 from the packaging environment.

Modified atmosphere packaging materials

Choosing the most suitable packaging materials is critical to maintaining food quality and safety in MAP modified atmosphere packaging. Flexible and semi-rigid plastics and plastic laminates are the most commonly used materials for MAP Foods. Plastic materials account for about one-third of all food packaging needs, and their use is expected to increase.

Relatively easy to shape, lightweight, good transparency, heat sealing and strength are some of the characteristics of plastics, making them suitable as food packaging materials. Promote the development of plastics that are more suitable for specific applications in food packaging.

However, none of the plastics has properties suitable for all food packaging applications. Plastic packaging materials can be composed of a single layer of a single plastic, but most (if not all) MAP films are multi-layer structures composed of multiple layers of different plastics. National technology or coating technology, different types of plastics can be combined to form rigid films, sheets or bags. By carefully selecting each plastic component, a material that has important packaging characteristics and best meets the requirements can be developed.

MAP’s plastic containers are most commonly used as flexible films for bags, pouches, pillows, and top straps, or as rigid and semi-rigid structures for bottom trays, plates, glasses, and cups. Commonly used flexible plastic laminates are made of polyethylene (PE), polypropylene (PP), polyamide (nylon), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyvinylidene chloride (PVdC) and ethylene vinyl alcohol (EVOH). Semi-rigid structures are usually made of PP, PET, PVC-U and expanded polystyrene.

Main plastics used in modified atmosphere packaging

The following content is a brief overview of the commonly used plastics for MAP modified atmosphere packaging applications.

1. Ethylene vinyl alcohol (EVOH): As long as it is dry, polyvinyl alcohol (PVOH) has excellent gas barrier properties. In the presence of moisture, PVOH will absorb water, causing the plastic to swell and soften. Under these conditions, the gas barrier properties of PVOH are significantly reduced. In order to provide higher polymer stability for commercial use, PVOH is copolymerized with ethylene to form EVOH. The gas barrier of EVOH in the dry state is lower than that of PVOH, but EVOH is less sensitive to moisture, so it is widely used. It is used as a gas barrier in MAP modified atmosphere packaging applications. This material has good processing properties, so it is suitable for processing into plastic films and structures. EVOH is always laminated in the form of a film, usually about 5 microns thick, sandwiched between hydrophobic polymers (such as polyethylene or polypropylene) to protect the polymer from moisture. EVOH also has high mechanical strength, high oil and organic solvent resistance, and high thermal stability.
2. Polyethylenes (PE): Polyethylene is a group of synthetic polymers with the simplest structure and the most commonly used packaging plastic material. There are several types of polyethylene, which can be classified according to their density. They are all composed of a carbon backbone with a certain degree of side chain branching, which affects low-density polyethylene (LDPE) (density 0.910-0.925 gcm-3), and is usually used in the form of film, while high-density polyethylene (HDPE) (density 0.940.) G/cm3) is often used for rigid and semi-rigid. PE is characterized by poor gas barrier, but its hydrophobicity makes it a very good water vapor barrier. Therefore, in MAP applications that require high gas barrier properties, polyethylene cannot be used alone as a packaging material. The relatively low temperature is about 100 to 120°C (depending on density and crystallinity).The less branched version, called Linear Low Density Polyethylene (LLDPE), can provide good heat sealability and is used as a lining to impart heat sealability to the bottom and top plates.
   Materials based on modified polyethylene having ionic bonds between chains are called ionomers. They have improved heat-seal properties, allowing them to seal gravy, fat and powder more effectively. The monomer also forms an effective heat seal with aluminum. Suryln is a trademark of DuPont’s ionomer materials. Ethylene-vinyl acetate copolymer, or ethylene-vinyl acetate (EVA), has better heat sealing properties than LDPE and is used as a heat seal layer in some MAP modified atmosphere packaging applications.
3. Polyamides (PA): Polyamides are a group of plastics commonly referred to as nylons, which are often used for food packaging. Nylon generally has high tensile strength, good puncture resistance and abrasion resistance, and good air tightness. The moisture in the nylon structure breaks the bonds between the chains and adversely affects its properties, including gas barrier properties. Under conditions of high relative humidity, the gas transmission rate of nylon membranes usually increases. However, commercially available nylon stockings are less affected by their relatively high strength and rigidity, so they are very suitable for use as a vacuum bag for fresh meat. The end of the hard bone can penetrate other plastic materials. In this case, nylon is usually laminated with polyethylene to provide heat sealability.
4. Polyethylene terephthalate (PET): Polyethylene terephthalate is the most commonly used polyester in food packaging. PET has a good barrier to gas and water vapor, high strength, good transparency, and high temperature resistance. Crystalline PET (CPET) has poor optical properties, but has better resistance to melting when heated to temperature. Flexible PET film is used for barrier pouches and top webs as cover material for trays. CPET is used to make double-sided bakeware, and its high temperature resistance makes it an ideal container for convection microwave cooking.
5. Polypropylene (PP): Polypropylene is a multifunctional polymer used in flexible, rigid and semi-rigid packaging structures. MAP modified atmosphere packaging applications are usually designed for rigid floor pallets. PP has good barrier properties to water vapor, but poor barrier properties to gases. The gas transmission rate PP melts at approximately 170 °C. Therefore, it can be used as a container for heating low-fat food in a microwave oven. It should not be used for microwaving fatty foods, where temperatures in excess of its melting point could be reached. Foamed PP is used to provide the structural properties in laminates for MAP thermoformed base trays, where it is combined with an EVOH barrier and a PE heat sealing layer.
6. Polystyrene (PS): Pure polystyrene is a stiff, brittle material and has limited use in MAP modified atmosphere packaging applications. Expanded PS (EPS) which is formed from low density blown particles has been used for many years as a base tray for overwrapped fresh meat, fish and poultry products. Foamed PS has recently been used as a structural layer for pre-formed MAP base tray applications. The high gas permeability of foamed PS requires the material to be laminated to a plastic such as EVOH that provides the required gas barrier properties.
7. Polyvinyl chloride (PVC): Polyvinyl chloride has a relatively low softening temperature and good processing properties and is therefore an ideal material for producing thermoformed packaging structures. Although a poor gas barrier in its plasticised form, unplasticised PVC has improved gas and water vapour barrier properties which can at best be described as moderate. Oil and grease resistance are excellent, but PVC can be softened by certain organic solvents. It is a common structural material in MAP thermoformed base trays, where it is laminated to PE to provide the required heat sealing properties.
8. Polyvinylidene chloride (PVdC): Polyvinylidene chloride (a copolymer of vinyl chloride and vinylidene chloride) possesses excellent gas, water vapour and odour barrier properties, with good resistance to oil, grease and organic solvents. Unlike EVOH, the gas barrier properties of PVdC are not significantly affected by the presence of moisture. PVdC effectively heat seals to itself and to other materials. The high temperature resistance enables uses in packs for hot filling and sterilisation processes. Homopolymers and copolymers of PVdC are some of the best commercially available barriers for food packaging applications.

Factors to consider in the selection of modified atmosphere packaging materials

Several factors must be considered when selecting package materials for MAP modified atmosphere packaging applications.

1. Food contact approval: Packaging materials in contact with food should not transfer any packaging ingredients to the food in quantities that may cause harm to consumers. In Europe, all packaging that comes into contact with food must comply with EU directives from Framework Directive 89/109/EEC and containing plastic. Directive 90/128/EEC. The supplier must demonstrate that the migration rate from plastic packaging to food is lower than the recommended value and that it is safe to use plastic packaging as expected.
2. Gas and vapor barrier properties: The packaging materials of MAP modified atmosphere packaging must have the gas and vapor barrier levels required for specific food applications, and some materials such as glass and metal (provided they have sufficient thickness and are free of porosity or other defects) are common. Barrier gas and steam, plastics have varying degrees of permeability to gas and steam. These molecules pass through the plastic packaging material through a mass transfer process called permeability. Through plastic materials without defects such as cracks and perforations” (Hernández, 1996). Essentially, gas molecules are absorbed by the plastic surface, transmitted through the material through a diffusion process, and then desorbed on the opposite surface. The driving force of gas permeation through the polymer membrane Is the gas concentration difference between each s. The concentration gradient moves the flow of permeable molecules from the high concentration side to the low concentration side. In MAP, there is a gas concentration gradient between the headspace of the package and the environment. Due to the gas in the package Ingredients, packaging materials must be gas impermeable (barrier). The transfer rate is a measure of the gas or water barrier properties of packaging materials.
   It is important that packaging technicians have detailed knowledge of the gas and vapor transmission rate of the materials used for MAP modified atmosphere packaging; this data should be given in the packaging specifications. Its performance mainly depends on the type of plastic, permeable gas, or steam and its partial pressure difference and temperature in the material. Generally speaking, it is the permeability of synthetic polymers compared with CO2, its permeability is approximately three to five times that of O2. There is no commercially available plastic that can completely block gas and vapor, so choose the material according to the product type, required durability, gas composition, and availability. And cost.
3. Optical properties: Good optical properties, such as high gloss and transparency, are essential for bag, pouch and top web materials to satisfy consumer demand for a clear view of the product. To provide attractive appearance and shelf impact, some base tray materials are available in various colours. This also enhances the visual appeal of the product against the tray and helps consumers to identify product ranges and brands on the supermarket shelf. PET, PP and EPS trays are supplied in a range of colours. PVC trays are generally used in their natural form to provide a transparent pack.
4. Antifogging properties: Condensation (fogging) of water vapour on the inner surface of food packs can occur when the temperature of the pack environment is reduced, resulting in a temperature differential between the pack contents and the packaging material.Fogging of the inner surface of lidding film is a result of light scattering by the small droplets of condensed moisture that leads to poor product visibility and an aesthetically unpleasing appearance of the pack. This can be overcome by applying antifogging agents to the plastic heat sealing layer, either as an internal additive or as an external coating. These chemicals decrease the surface energy of the packaging film which enables moisture to spread as a thin film across the under surface of the pack rather than collecting as visible droplets. Antifogging agents include fatty acid esters. Most lidding materials are available with antifog properties, and commonly treated plastics include LDPE, LLDPE, EVA and PET.
5. Mechanical properties: Resistance to tearing and puncture and good machine handling characteristics are important in optimising the packaging operation and maintaining pack integrity during forming and subsequent handling and distribution. A further important characteristic of laminates and co-extruded films and sheets is the ability of layers to bond effectively together during the packaging operation and during subsequent storage and handling. Certain organic compounds may have an adverse effect on bond strength to the extent that weakened bonds can result in layers peeling apart.
6. Heat sealing properties: Effective heat seals are essential for maintaining the desired gas composition within the pack. The ability to form effective heat seals through contamination such as meat juices, powders, fats and oils is an advantage in many applications. Heat seal quality is dependent on many factors including seal material, seal width and machine settings such as temperature, pressure and dwell time.

MAP Modified Atmosphere Packaging Machines

Modified atmosphere packaging machines types

Kangbeite Food Packaging Machinery Co., Ltd. offers 4 types of MAP modified atmosphere packaging machines.

Modified atmosphere packaging machines use pre-made trays

1. Vertical type MAP machines KBT450 series
2. Inline type MAP machines KBT1000 series
3. Ultra speed MAP machines KBT550 series

Thermoforming packaging machine for MAP, that uses 1 roll of rigid film to form the trays automatically, and another 1 roll of lidding film for tray sealing.

How to choose modified atmosphere packaging machines

Reliable modified atmosphere packaging machines are important fixed assets of any food factory. Select the right MAP machine can benefit your food business by improving production efficiency, saving material cost, preventing waste, and reduce labor cost.

Here are 5 factors to consider when purchasing modified atmosphere packaging machines:

1. Choose modified atmosphere packaging machines with proper capacities. You certainly don’t want to buy a large machine when the business scale is still small, but you certainly don’t want to waste the chance to expand your business. So observe the market and select a MAP machine that fits your current capacity, but has proper potential capacities.
2. Purchase modified atmosphere packaging machine before the production season. Most MAP machines are customized according to the customer’s package size and capacity requirement. The lead time can be from 15 working days to 50 working days. And in international business, the sea shipping will take 15-60 days. So you need to make a plan to schedule the purchase of MAP machines 2-3 months before production season. Another benefit of early purchasing is that you will have time to make modifications if anything unexpected happens.
3. Select MAP machines with high quality, minimum issues. High-quality MAP machines can improve your production efficiency, minimize time and labor cost.
4. Select the modified atmosphere packaging machine manufacturing factory that is professional. A MAP machine is well designed with many details and perfect combination of many delicate spare parts. Professional packaging machine manufacturers always have the motivation to improve the machines in core designs and details.
5. Select the modified atmosphere packaging machine manufacturing factory that has local service. Kangbeite Packaging Machinery has several local service agents in worldwide countries. If you are interested in joining us as a local service partner in your country, please contact us