MAP Tray Sealer Machines

What is Modified Atmosphere Packaging

Modified Atmosphere Packaging is a food packaging techology to extend food shelf-life, which is also known as gas filling, gas flushing, protective atmosphere packaging, or reduced oxygen packaging. The atmosphere filled in the package atmosphere has been modified in some way, usually with one or a combination of three gases: nitrogen, carbon dioxide, and oxygen, depends on the physical and chemical properties of the food.
Modified Atmosphere enables fresh and minimally processed packaged food products to maintain visual, textural and nutritional appeal so it is a highly effective method to help retailers deliver added value to their food customers.

Why use Modified Atmosphere Packaging

Because consumers love natural and fresh. Once food, including fruits, vegetables, or animal products is harvested or slaughtered, it will remain in an environment suitable for bacteria, which continue to use existing carbohydrates, proteins, fats, and nutrients to function. These continuous processes lead to degradation, including undesirable color changes, loss of flavor, and poor texture. The action of enzymes can also cause food to spoil. All these issues can be solved by the implementation of MAP modified atmosphere packaging. The benefits of MAP packaging:

MAP Modified Atmosphere Packaging Gases List and Mixture Recommendations

MAP packaging is to fill in food-grade purity gas or mixed gases to containers. The purity gases are delivered either as a liquid in stainless steel micro bulk or bulk containers or as a gas in high-pressure cylinders or gas generators.

Though one of the purposes of MAP is to extend shelf life, the selection of correct mixture of gases for MAP is not always simply choose a combination that provides the longest shelf-life. Because MAP also means fresh and natural, keeping of original flavor, color and texture. In some cases, to sacrifice some shelf-life to ensure an enhanced visual appearance of MAP packaged food products is necessary.

MAP never only means longest shelf life, NO!

Main Gases

The three main gases that are most often used in modified atmosphere packaging are O2, CO2, and N2. The choice of gas is very dependent on the food product being packed. Used solely or in combination, these gases are commonly used to balance safe shelf life extension with optimal organoleptic properties of the food. Inert gases such as argon are in commercial use for products such as coffee and snack products; however, the applications of Argon are very limited.

1. Nitrogen (N2): Nitrogen is an inert gas (un-reactive gas) with no odour, taste, or colour. Nitrogen has a lower density than air, non-flammable and has a low solubility in water (0.018 g/kg at 100 kPa, 20° C) and other food constituents. Nitrogen does not support the growth of aerobic microbes and therefore inhibits the growth aerobic spoilage but does not prevent the growth of anaerobic bacteria. The low solubility of nitrogen in foods can be used as a filler gas to prevent pack collapse by including sufficient N2 in the gas mix to balance the volume decrease due to CO2 going into solution. Pack collapse is caused by food products that contain high-moisture and fat, as these foods absorb carbon dioxide from the atmosphere. In MAP modified atmosphere packaging of dried snack products, 100% nitrogen is used to prevent oxidative rancidity.
2. Carbon dioxide (CO2): Carbon dioxide is a colourless gas with a slight pungent odour at very high concentrations. It is an asphyxiant and slightly corrosive in the presence of moisture. CO2 dissolves readily in water (1.57 g/kg @ at 100 kPa, 20° C) to produce carbonic acid (H2CO3) that increases the acidity of the solution and reduces the pH. This gas is also soluble in lipids and some other organic compounds. The solubility of CO2 increases with decreasing temperature. For this reason, the antimicrobial activity of CO2 is markedly greater at temperatures below 10° C than at 15° C or higher. This has significant implications for MAP of foods. The high solubility of CO2 can result in pack collapse due the reduction of headspace volume. In some MAP applications, pack collapse is favoured, for example in flow wrapped cheese for retail sale. Carbon dioxide inhibits the growth of most aerobic bacterias. Generally, higher level of CO2 means longer shelf-life. But many high-moisture and fat-containing foods will absorb CO2, excess levels of CO2 in Modified Atmosphere Packaging can cause package collapse, flavour tainting and drip loss. So it is important to find the balance between the desirable shelf-life and the degree to which any negative effects can be tolerated. A minimum of 20% CO2 is recommended in mixed gases to control bacteria growth.
3. Oxygen (O2): Oxygen is a colourless, odourless gas that is highly reactive and supports combustion. It has a low solubility in water (0.040 g/kg at 100 kPa, 20° C). Oxygen promotes several types of deteriorative reactions in foods including fat oxidation, browning reactions and pigment oxidation. Most of the common spoilage bacteria and fungi require oxygen for growth. Therefore, to increase shelf life of foods the MAP Modified Atmosphere Packaging should contain a low concentration of residual oxygen. It should be noted that in some foods a low concentrations of oxygen can result in quality and safety problems (for example unfavourable colour changes in red meat pigments, senescence in fruit and vegetables, growth of food poisoning bacteria) and this must be taken into account when selecting the gaseous composition for a packaged food. There are often good reasons for Oxygen to be present in Modified Atmosphere Packaging, including Maintain fresh and natural color of food products (i.e. red meat); Maintain respiration of fresh vegetables and fruits; Inhibit the growth of anaerobic organisms (some vegetables and fish).
4. Argon (Ar): Argon has the same properties as Nitrogen. It is a chemically inert, tasteless, odorless gas that is heavier than nitrogen and does not affect microorganisms to any greater degree. Argon can be used in Modified Atmosphere Packaging to replace nitrogen in most applications because it also inhibits enzymic activities, microbial growth, and degradative chemical reactions. Its solubility (twice that of nitrogen) and certain molecular characteristics give it special properties for use with vegetables. Under certain conditions, it slows down metabolic reactions and reduces respiration. Argon can certainly benefit to MAP process, but you should learn the additional cost of the gas beforehand.

Other gases

1. Carbon Monoxide (CO): Carbon monoxide is a toxic, colorless, odorless, flammable gas. It is stable at up to 400°C with respect to decomposition into carbon and oxygen. Results have shown that the use of carbon monoxide (CO) in MAP Modified Atmosphere Packaging with high levels of CO2 can increase shelf-life and retain the bright red color of meat cuts. Note that the use of CO in MAP is not allowed in Europe.
2. Ozone (O3): Ozone gas is an unstable form of oxygen that has been noted for its oxidizing and disinfecting properties and use in the preservation of food. It can only be delivered safely up to about 15% concentrations in air or oxygen, having only a half-life of 20min in clean water. One of its major benefits is that it will break down to harmless elemental oxygen. Because of its instability, it is generated onsite from clean air or oxygen close to where it is required. The application of ozone gas in MAP Modified Atmosphere Packaging is to improve both shelf-life and safety of foods. But a successful offering is limited due to ozone’s non-specific oxidizing capacity and short life. This means it is just as likely to attack the pack as the microbial contaminants, and any effect will be only for the first few minutes of the pack’s life. After this, the ozone will have reacted, leaving slightly higher oxygen content. Too much ozone can cause pack damage or discoloration and may oxidize the surface of the product causing the release of nutrients which will encourage the growth of the organisms you are trying to control.

Recommended MAP gas mixtures

It’s always a tough topic for those MAP projects starters to determine the right gas mixture for their products. The following table lists the general gas mixtures, only for your reference. Please always take tests for your MAP packaging production.

How does Modified Atmosphere Packaging work

The Modified Atmosphere Package environment is formed from finely balanced mixed normal atmospheric gases. The finely balanced MAP gas mix slows down the product aging process to reduce color loss, odor, and off-taste resulting from product deterioration, spoilage, and rancidity caused by mold and other anaerobic organisms.
A carefully controlled Modified Atmosphere Package achieves and maintains an optimal respiration rate to preserve the fresh color, taste, and nutrient content of red meat, seafood, minimally processed fruits, and vegetables, pasta, prepared foods, cheese, baked goods, cured meats, and dried foods throughout the extended shelf life.

MAP Modified Atmosphere Packaging can do the job because the filled-in gases can control the micro-organisms in the food.

There are mainly four types of bacteria, yeasts and moulds according to their different respiratory and metabolic needs and oxygen requirement for metabolic and growth processes.

1. Aerobic Microbes: Require oxygen for respiration and growth, e.g. Pseudomonas species, some Bacillus species, Acinetobacter/Moraxella species, Micrococcus species, film yeasts and moulds. Therefore some control of these organisms can be obtained by excluding oxygen from a pack.
2. Anaerobic Microbes: Do not require oxygen to grow and many are inhibited or killed by small quantities of oxygen, e.g. Clostridium species.
3. Microaerophilic Microbes: Require low levels of oxygen for optimum growth. Some also require increased levels of carbon dioxide for optimum growth, e.g. Campylobacter and Lactobacillus species.
4. Facultative Anaerobic Microbes: Can respire and grow with and without air or oxygen, e.g. Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Brochothrix species, Salmonella species, Vibrio species, fermentative yeasts and some Bacillus species.

MAP Modified Atmosphere Packaging Materials

There are several types of packaging materials for MAP Modified Atmosphere Packaging according to packaging format, including Pouch, Flow wrap (horizontal or vertical type), Pre-made tray pack, Thermoforming MAP pack.

Considerations in choosing MAP materials

Choosing MAP Modified Atmosphere Packaging materials involves multiple factors, including the products properties, packaging method, storage environment, retailing packages appearance requirements, domestic consuming processing method (ie, microwavable), etc. When choosing MAP materials, the following considerations must be taken into account:

1. Most importantly: gas transmission rates and barrier properties: The choice of MAP Modified Atmosphere Packaging materials is largely determined by their gas and water vapour transmission rates. Materials such as polyester (PET), nylon (PA), polyvinylidene chloride (PVdC) and ethylene-vinyl alcohol copolymer (EVOH) provide good gas barriers but in many cases poor water vapour barriers.
2. Water vapour and aroma barrier properties: Polythene, polypropylene and ethylene-vinyl acetate have too high gas transmission rates to maintain a chosen gas mixture or vacuum for long enough to provide an adequate shelf-life for most products. But, they are good barriers to water vapour and hence prevent products from drying out or dry products from becoming moist
3. Heat sealability: It is important that a hermetic seal is formed in order that there are no leaks and the gas mixture is maintained within the pack. Typical sealing layers are LDPE, PP, EVA, Metallocene and Surlyn (registered name with Dupont).
4. Seal strength and quality: This is affected by temperature, pressure and dwell time. So it is necessary to choose a material that performs within the parameters of the MAP machines’ sealing cycle and line speed. It is also very important that there is compatibility between the materials being sealed together to ensure the required integrity and characteristics (i.e. peelable or permanent).
5. Transparency: Anti-mist coatings applied to the top web or anti-fog masterbatch added to the material during extrusion prevent the formation of water droplets on the inside surface allowing the product to remain clearly visible. The choice of material itself can also affect the pack transparency depending on its clarity and gloss.
6. Thermoformability: Materials may be formed to produce either rigid trays for later lidding applications or semi-rigid/flexible pockets for an inline form fill and seal application

Generally speaking, materials in rigid applications possess relatively poor gas barrier properties at low thickness. The thickness, however, that is necessary to achieve acceptable pack rigidity increases the gas barrier properties to a level suitable for many applications. As the thickness of a formed tray/pocket has a direct relation to the barrier properties, it is essential to consider forming tool design, material flow characteristics and film thickness when choosing a material. Further barrier may be added to material structures, such as EVOH, to help with extending shelf life longer.

MAP films types

Typical MAP Modified Atmosphere Packaging films for use as lidding materials or to produce packs on horizontal or vertical form-fill-seal machines are multi-layer structures that depend on the food to be packaged, could be made of materials such as PP, PET, EVOH, PE, etc.
MAP packaging films or pre-formed trays are often made from PP or PET/PE laminates.

1. Laminates — Two or more layers of material laminated via heat, adhesive, or tie layer.
2. Co-extruded — Two or more layers of material extruded at the same time.

Each process gives its own benefits and properties, to choose the MAP material that fits your products, the best choice is to consult a professional expert of MAP material supplier.

1. Semi-permeable and permeable films — Best MAP material for fresh fruit and vegetables, relatively high permeable films are often used in order that an Equilibrium Modified Atmosphere can be achieved by the respiring products. Films such as EVA or plasticized PVC have high gas transmission rates. An alternative way of achieving these high levels of transmission is to produce films with micro-perforations that have high but reasonably controllable levels of permeability. By matching the size and number of perforations to the respiration rate of the produce, a suitable film can be manufactured for most applications.
2. Specialist applications — The ever-growing use of the microwave is leading to the use of more PP trays or formings and PP-based lidding films. These kinds of films may also be utilized where a form of heat treatment is needed such as pasteurization or sterilization. Steam cooking in the microwave using PP or co-extrusions of PP, APET, and polycarbonate trays or formings is possible with various types of “venting” lids. Lids can include technology either in the film or actual valves/labels which will release the pressure build-up at a defined point. The use of susceptor (Die-Electric) layers in films can be used to create an ovenable effect in the microwave. Microwave energy is converted by the susceptor into radiant heat to give a browning/crisping to products such as bread or pastry. Specialist coatings are also available to improve the effect further. Preformed trays are also available as CPET, pressed foil, and ovenable board offering an option of dual ovenability to the customer.

Modified Atmosphere Packaging Machines

There are typically 5-6 types of modified atmosphere packaging machines for different MAP types: Premade pouches, thermoformed pouches, pre-made rigid trays, thermoformed rigid trays. Shandong Kangbeite Food Packaging Machinery Co., Ltd. offers professional MAP machines for rigid tray MAP packs.

Tray lidding type

A tray sealer uses premade rigid trays that are sealed by top lid films. The air in the plastic rigid trays is evacuated from the sealing die and protective gas is filled into the trays (Vacuum – Fill method). Based on automation grade and output capacity, Kangbeite Packaging Machinery offers 3 types of tray sealer MAP Modified Atmosphere Packaging machines: Vertical MAP machines KBT450 series, Inline MAP machine KBT1000, Ultra-fast speed MAP machine KBT550.

Thermoform fill seal type

Packaging material for the bottom forming film (base web) is unwound from the reel, then heated in the forming die and forming chamber, and formed into pockets or rigid trays. The thermoformed pockets/trays are loaded manually or automatically. The top sealing film (top web/lie film) covers the filled pockets/trays. The air is evacuated from the sealing die and sealing chamber, then protective gas is filled into the pouches/trays. Then the package is sealed by the application of heat and pressure. The finished packages are cut into individual packs, firstly cut by cross-cutting knives, then by longitudinal cutting knives.