Overview of Packaging Technology for Meat Products

Meat products are a kind of food with rich nutrition and high water content. Its shelf life may be as short as 3-4 days or as long as 6 months. Its shelf life mainly depends on the moisture content and processing method of meat products, as well as the operation and packaging technology after sterilization.

In recent years, with the development of economy and the change of consumption structure, supermarkets have increased year by year, and buying packaged meat products has become the mainstream of consumption. In order to meet the needs of consumption, various multifunctional Packaging Machines are first needed to realize batch mechanized production. In addition, novel packaging design is also indispensable, because packaged meat products are not only hygienic, but also improve their preservation. At the same time, packaging can also be used as advertising to attract customers. Novel and beautiful packaging can easily attract customers' attention, so the packaging of meat products should not be ignored.

Preservation and packaging of meat products

After meat products are packaged, they can avoid discoloration, oxidation, damage, and deterioration caused by direct sunlight, contact with air, mechanical action, microbial action, etc., thereby extending the shelf life. Due to the wide variety of meat products, a variety of packaging methods and suitable packaging materials are required.

1. There are many processes related to the preservation of meat products that will affect the packaging of meat products. Considering the relationship between the packaging and preservation of meat products, they can basically be divided into the following situations.

(1) The sterilization conditions of sterilized meat products are: the center temperature is 63, and the temperature is kept warm for more than 30 minutes. Under this sterilization condition, the bacteria that cause food poisoning are killed, but there are still some bacteria related to corruption such as Bacillus and heat-resistant lactic acid bacteria in the product. These residual bacteria will gradually multiply when encountering suitable conditions, causing food corruption.

(2) From sterilization to packaging, it takes at least a few hours and at most one day and night. During this period, contact with the operator's fingers, machines, etc. or microorganisms suspended in the ground and air, etc. will cause secondary contamination of food.

(3) Environmental conditions for packaging. After packaging, although external contamination is cut off, there is still a situation where internal contamination of the product continues. Oxygen will slowly enter through the film, so the oxygen partial pressure in the bag will gradually increase, and residual bacteria and contaminating bacteria will begin to multiply. The higher the storage temperature, the faster the bacteria multiply.

In view of the above situation, in order to prevent secondary contamination during packaging operations, the storage time after sterilization should be shortened as much as possible, and packaging should be carried out immediately after sterilization, and a film that can isolate light, water, and oxygen should be selected.

2. Packaging process The packaging of meat products adopts different packaging and operation processes according to whether it is sterilized again after packaging and whether the casing is breathable.

(1) Different processes are selected according to the type of casing used. When using a closed casing, the casing can keep its original appearance, and the process after filling is simple. This product is called a direct packaging product. The production method is as follows: put the prepared meat filling into a heat-resistant, airtight, and moisture-proof casing, then tie the two ends and seal them with an aluminum card, and then boil and cool them to make the finished product. The characteristic of this method is that the closed casing filled with meat filling is the outer packaging of the product, and there is no need to repackage the product. Because the casing is airtight, microorganisms cannot pass through. After sterilization, the inside of the product can remain in an oxygen-deficient state for a long time, and the product can avoid secondary contamination caused by contact with machines, fingers, etc. Post-filling can be avoided. Therefore, this method is a simple and effective way to improve the preservation rate. The ham sausage sold on the market now belongs to this type of packaging. The packaging material is mostly polyvinylidene chloride.

When using breathable casings, free juice, fat, water, etc. will flow out of the product during the drying, smoking and cooking processes. This free substance adheres to the surface of the product and becomes a nutrient source for microorganisms. After a period of time, the microorganisms on the surface of the product will multiply in large numbers, causing secondary pollution. If animal casings are used, the casings themselves will become a nutrient source, bringing microorganisms into the interior, causing the product to spoil. Even if animal casings are not used, it is often necessary to puncture the casings during operation, and it is inevitable that microorganisms will spread from the surface of the product to the interior for contamination. For such products, the following two methods can be used to prevent microbial contamination after sterilization. First, ordinary secondary packaging is performed, followed by secondary sterilization; second, aseptic packaging methods are implemented without secondary sterilization.

(2) Packaging methods Packaging methods can be divided into closed packaging and inflatable packaging. The difference between the two packaging methods is that the former keeps the shell and the product in a closed state, so that the air between the shell and the product can be excluded as much as possible, thereby preventing the product from deteriorating due to contact between oxygen and the product; the filler is the opposite of the above, and inert gas is filled to isolate oxygen. The purpose of these two methods is to reduce the impact of oxygen on product quality.

Tight packaging The purpose of this type of packaging is to reduce the impact of oxygen on the product by deoxygenation or vacuuming. The function of the packaging is to keep the product and casing in a vacuum state to inhibit bacterial growth and oxidation. In addition, when performing secondary sterilization, this type of packaging is easy to conduct heat, which can shorten the sterilization time and reduce the impact on product quality. This type of packaging can also fix the product in the packaging bag.

(2) Inflatable packaging This type of packaging uses an airtight film and is filled with an inert gas (such as nitrogen). When inflating, the oxygen in the bag should be removed before inflation. At this time, the replacement rate is very important. If the replacement rate does not meet the requirements, simple packaging should be used. This type of packaging must be carried out under sanitary conditions. Its characteristics are that the product is not affected by pressure and does not deform.

(3) Secondary sterilization. When using breathable casings to produce meat products, the product surface may be secondary contaminated from sterilization to packaging, and the inside of the product will change from anaerobic to aerobic, resulting in reduced preservation. In order to restore the product in this state to the microbial level immediately after sterilization, heating or secondary sterilization is required after packaging. The temperature, time and cooling conditions of secondary sterilization vary according to the degree of surface contamination of the product. If the entire surface of the sliced ​​product is contaminated, the secondary sterilization should be carried out after the core temperature reaches 63 for more than 30 minutes. If the product is in block form but the surface is contaminated, only the part a few millimeters below the surface needs to be sterilized at 63 for 30 minutes. In addition, necessary cooling treatment should be carried out. The sterilization or cooling conditions must be strictly set. If the setting is incorrect, there will be insufficient sterilization or cooling, and bacteria will grow at the appropriate temperature. If the heating temperature is too high, oil and water may appear, and these juices will become a nutrient source for bacteria and shorten the shelf life. For products that require secondary sterilization, the amount of starch and emulsifier added must be considered at the ingredient stage so that the juice and fat will not separate during the secondary sterilization. Generally, high-end products do not undergo secondary sterilization. During the second sterilization process, the product must be in contact with the heat medium, so it must be tightly packaged.

(3) The turnover date of the product and the appropriate packaging of the product must take into account issues such as quality, shelf life required by the market, and economy. Packaging that exceeds the market requirement standard is also unnecessary. With the popularization of meat products and the expansion of circulation, the turnover period required by the market is also different. According to market requirements, reasonable packaging must comprehensively consider manufacturing conditions, packaging methods and packaging materials.

Packaging materials and packaging methods

The purpose of packaging is to prevent bacteria from contaminating products, thereby ensuring product quality. Packaging can also serve as an advertisement to attract consumers' attention. In each stage of manufacturing, circulation, sales, and consumption, that is, from the factory to the hands of consumers, products come into contact with people, so contamination may occur at any time, so packaging is necessary to prevent bacterial contamination.

Most of the packaging materials used in meat products are plastics. Compared with packaging materials such as paper and metal, plastics have a wider range of packaging properties, and one packaging material can have several properties at the same time. Moreover, the lamination or coating technology of thin plastic capping can also supplement the deficiencies of single film performance, and lamination/coating technology can be used to develop multi-purpose films.

(1) Oxygen barrier is the permeability of isolating oxygen. Not only oxygen, but also other gases. The amount of gas passing through the plastic film has nothing to do with the molecular size of the gas. It is usually carried out in two steps. At first, the gas dissolves in the molecules of the film and then penetrates by diffusion. The oxygen barrier performance of the film is suitable for the packaging of all meat products except raw meat. Especially in Vacuum Packaging and inflatable packaging. Due to the action of oxygen, hemoglobin is converted into heme, resulting in product fading, fat oxidation, and the reproduction of aerobic microorganisms. Therefore, preventing the product from contacting with oxygen is extremely important for maintaining product quality and improving preservation.

(2) Moisture barrier is the property of preventing water vapor from passing through. When the molecules of the film do not contain hydrophilic hydroxyl and carboxyl groups, it is considered to have good moisture resistance. Moisture barrier performance varies greatly with temperature. The film's moisture barrier properties are suitable for all meat packaging. If product moisture penetrates from the inside of the packaging film in the form of water vapor, or if the product absorbs water vapor that penetrates from the outside, the flavor, texture, and content of the product will also change. This is especially important for packaging dry sausages with low moisture content to prevent the natural loss of quantitative products.

(3)Light blocking, especially light with a wavelength of 320 to 380 nm, has an optical effect in ultraviolet light. This property is very important for vacuum-packed sliced ​​products, colored products, and smoked products. Transparent films do not have the effect of shielding ultraviolet light. Although HDPE has some light blocking properties, the film is opaque. There are many ways to prevent ultraviolet light from penetrating, one of which is to add ultraviolet absorbers to the packaging material. However, in recent years, the use of ultraviolet absorbers in food packaging materials has been banned. Therefore, a method of shielding light by using the properties of light has been developed. This method is a method of using printing ink to absorb or reflect light, or a method of mechanically extruding a concave and convex pattern on the film surface by reflecting light using a satin processing roller. When using printing ink, black and white can absorb or reflect light. In addition, other inks, even if there is a difference in light and dark colors, cannot achieve the expected effect. Except for black, almost all light colors have no effect of absorbing light. Dark colors are black, blue, green, and yellow, and their shading becomes worse in turn, while red and purple have no effect. Generally, when printing, the film with a light-shielding effect is opaque, and the disadvantage is that the product in the packaging bag cannot be seen. In order to make up for the defects of opaque films, a method of micronizing ink has been recently developed. The interior of the film is shielded by short-wavelength ultraviolet scattering, allowing long-wavelength visible light to pass through, and the printed film of the product in the packaging bag can be seen.

(4) Impact resistance This property is applicable to all packaging. Especially for heavy things, tight packaging without gaps between the shell and the product is more important. The impact resistance of the packaging material can be guaranteed by the balance of tensile strength, tensile elongation and impact strength. Such films include polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, stretched nylon, etc.

(5) Cold resistance Even at low temperatures, the paint film will not become brittle and can still maintain its strength and impact resistance. Generally, there is no problem with storing meat products at -10 ~ 0, but if frozen meat products are stored at -15, the cold resistance of the film must be considered because it directly affects the sealing strength. Cold-resistant packaging includes polyamide resin, polyethylene (low density), polyester, polypropylene (stretched), polypropylene (unstretched), etc.

(6) Heat resistance refers to the property of high softening point and no deformation after heating (such as PVC). Because the product expands when heated, the heat resistance of the film must be guaranteed. This property is suitable for secondary sterilization packaging. Polyester, polyvinylidene chloride, polypropylene (unstretched), polypropylene (stretched) and polyethylene (high density) have good heat resistance.

(7) Formability refers to the performance of the film softened after heating by blowing with air (air pressure molding) or by air suction to form the film along the molding mold (vacuum molding) (the film is formed along the product when tightly packaged). Good formability means that the four sides of the heated film can be stretched evenly with very little force. Once the film is heated, it can stretch and become larger. When the heating temperature reaches a certain temperature, it will be in a stable state. The wider the stable temperature band, the easier it is to form the film and the easier the packaging operation. Films with good formability must also consider their barrier properties and sealing properties. Films with these comprehensive properties are called composite films. Most packaging films currently used in the market are composite films. The films are made of stretched nylon 6, unstretched polypropylene, polyvinyl chloride, polyvinylidene chloride, polyethylene, ethylene-acetic acid copolymer, etc., or may not contain these materials.

(8) Heat shrinkage refers to the property of the film to shrink when heated. This property is suitable for degassing shrink packaging and vacuum packaging. The heat shrinkage property of the film is used to fix the position of the product in the bag and improve the preservation effect. Shrinkage refers to the property of the thermoplastic film given by the moving molecules due to stretching when the thermoplastic film is heated above the softening point, that is, the elasticity of returning to the initial state. When the film is stretched, the film becomes thinner, but the molecules in the film are rearranged in the stretching direction. Therefore, its toughness, gas barrier and moisture resistance are also improved. Polypropylene, polyester, polyvinyl chloride and polyethylene have good heat shrinkage.

(9) Oil resistance is the property of preventing free fat precipitated from the product from penetrating to the outside of the film. The phenomenon of fat penetrating into the film may be caused by the following two situations: one is caused by membrane dissolution and the other is caused by fat penetration. Oil resistance also affects heat sealing. If the film dissolves at the seal and there is penetration, the film is considered unsuitable. The so-called oil-resistant film refers to a film that is not easy to dissolve or penetrate. Oil-resistant film is suitable for packaging meat products containing fat. For example, materials such as polyvinylidene chloride, polyamide resin, and polyester have better oil resistance.

(10) When heated below the decomposition temperature, the heat-bonded thermoplastic film softens, its fluidity increases, and becomes molten. At this time, the film is pressed tightly, and the molecules of the two layers of film diffuse with each other on the bonding surface. After cooling, it solidifies and bonds. This performance is affected by the melting temperature, viscosity, pressure and time of the film. According to these influences, the bonding method and conditions also change. Ionic resin, ethylene-vinyl acetate copolymer, etc. are all materials with heat bonding properties. According to the applicable temperature range, shrinkage rate and properties of the film, the bonding method is also different, generally divided into hot plate bonding (such as polyethylene, unstretched polypropylene, polyamide resin, polyvinyl alcohol, soft PVC, etc.), pulse bonding (such as unstretched polypropylene, polyester, polyamide resin, etc.) and high-frequency bonding.

(11) Slippery is the property of the film to have a small coefficient of friction with the contact and to slide easily. This property is closely related to the opening of the film and the ease with which the film can be fed into the machine. When the friction is large, it will cause obstacles to the film when the calendering film packaging machine is used for continuous packaging of products in bagging.

(12) Printing distance stability When the composite film is used, the film size can still maintain a relatively stable property when the temperature and humidity change. This property can ensure the consistency of the printing spacing, which is especially important for stretch packaging machines where the upper and lower film positions must be aligned.

(13) Charging film is easy to absorb dust when charging, so that there will be obstacles when applying the film. Almost all films with good insulation properties are charged on the surface. In order to prevent the film from being charged, an antistatic agent can be added, or a discharge device can be installed on the film, and a voltage of several thousand volts can be applied between the electrode and the ground wire to discharge from the needle to ionize the air between the film and the electrode, thereby achieving the purpose of eliminating static electricity. Films that are difficult to charge are generally films that are not easy to absorb water. Films that are not easy to charge include polyvinyl alcohol, polyvinyl chloride, cellophane, etc. Films that are easy to charge include polyethylene, polypropylene and polyester.

(14) Transparency The smaller the refractive index, the better the transparency of the film. The transparency of the film is expressed by turbidity. The smaller this value, the easier it is for light to penetrate. Transparent films include stretched polypropylene, stretched polypropylene, low-density polyethylene, high-density polyethylene, polyvinylidene chloride, etc.

(15) Films with high refractive index have strong reflectivity and good gloss.

(16) Anti-deformation is the property of the film to be hard and elastic. Even if the load is increased, the film will not stretch. Films with this property can be used in bag making machines and packaging machines because such films can meet the requirements of fast in and out of packaging machines. Films with high water absorption will weaken their anti-deformation ability in places with high relative humidity.

In short, the packaging of meat products requires the materials used to have various properties, but one film cannot meet all packaging performance requirements, so we compound films with various properties into laminated composite films to meet the requirements of meat product packaging.

2. Commonly used packaging materials for meat products

Due to the different types of meat and meat products, different preservation and storage conditions are required. Therefore, there are many kinds of packaging materials used. According to the type of product, meat packaging materials can be divided into fresh-keeping packaging materials, low-temperature storage packaging materials and room temperature storage packaging materials.

(1) Materials suitable for fresh-keeping packaging

① Cling film. Generally, it is an ultra-thin transparent film made of a single layer of polyvinylidene chloride. This film has high antioxidant, moisture-proof and heat-resistant properties and can be easily cut during the packaging process. At the same time, the film itself has strong adhesion and is easy to use. At present, traditional meat products, fresh meat, semi-finished products, cheese, vegetables, fruits, etc. are generally packaged with this film in supermarket freezers.

② Cooling meat film. This film is a multi-layer high-shrinkage composite film produced using a special co-extrusion technology. Polyvinylidene chloride (PVDC) is used as a barrier material in the center of the film, and polyolefin is used as the outer layer on both sides of the film. This film has a high low-temperature shrinkage rate and excellent transparency and gloss. The permeability of gases such as oxygen and water vapor is very small, so that the packaged goods can remain stable for a long time; it has excellent hot water shrinkage, can fit tightly to the meat pieces, the meat juice is not easy to seep out, and the packaging process is easier; it is suitable for using punching and heat sealing packaging equipment. This film can be used to package chilled meat (such as chilled beef, chilled pork, chilled lamb, turkey, chicken, etc.), cooked meat products (such as barbecued pork, bacon, meat pie, sausage, ham, sausage), cheese, fresh fish, and aquatic products.

(2) Film for low-temperature storage. Low-temperature meat products refer to cooked meat products whose core temperature reaches 63 and lasts for 30 minutes during the cooking process. Although the pathogens in them have been killed, there are still some high-temperature resistant spores. Therefore, they must be stored at low temperatures. There are many packaging materials suitable for this product, such as natural casings, limb casings, fiber casings, cellulose casings, various plastic films, etc.

① Natural casings. Natural casings are made from the intestines of goats, sheep, pigs and cattle. This casing has good smoke permeability, air permeability and elasticity and can be eaten. It can be smoked, dried, and steamed, and it can show good color after smoking. Harbin sausage, Guangdong sausage, breakfast sausage, hot dog, Frankfurter sausage, etc. are all filled with this casing. The defects of natural casings are inconsistent specifications and poor mechanical adaptability. Since the casing itself is a good environment for the growth of microorganisms, it is easy to be contaminated.

② Collagen casing. This casing is generally made of bovine collagen. This casing is smoke-permeable, breathable, has good mechanical strength, uniform specifications, and a variety of varieties. It can be eaten, smoked, and steamed. The color is uniform during smoking, which is suitable for mechanized production and punching. This casing should be soaked in warm water for about 10 minutes before use, and then filled after rehydration. The filling should be firm, and any form of smoking and cooking process is acceptable. After drying and smoking, the maximum cooking temperature should be controlled below 80. After cooking, spray or water bath cooling can be used. This casing can be used to make various steamed sausages such as Vienna sausages, breakfast sausages, and hot dog sausages.

③ Cellulose casing is a casing made directly from cellulose gum. It is breathable, inhalable, has good mechanical strength, and is suitable for high-speed automated production. This casing is not edible. The casing does not need to be processed before use and can be filled directly. It is mainly used to make small-diameter sausages such as hot dogs and frankfurters.

④ The fiber casing is a product made of cellulose gum and a layer of paper. It has high mechanical strength and can be punched; it is permeable to cigarettes and impermeable to fat; it is not edible, but it can be smoked and printed; it shrinks during the drying process. This casing must be soaked before use (the soaking time for printing is longer) and filled (holes can be punched to exhaust when filling). The surface of the casing should be completely dry before smoking, otherwise the smoked color will be uneven, and it can be sprayed or cooled in a water bath after steaming. This casing is suitable for the drying processing of various cold-cut sausages, various dry or semi-dry sausages, smoked sausages, cooked sausages and spine hams.

⑤ The fiber-coated casing is pressed from cellulose viscose and a layer of paper, and a layer of polyvinylidene chloride is applied to the inner surface of the casing. The casing has good barrier properties, which can prevent the product from losing water during storage and strengthen the protection against microorganisms; it has a high shrinkage rate, a full and beautiful appearance, and can be printed; but it cannot be smoked or eaten. Soak it in warm water before use. Fill it firmly when filling (no holes can be made). It can be cooked to the required core temperature, and then cooled with cold water spray or water bath. Suitable for all kinds of steamed sausages. Products using this packaging do not need to be repackaged.

⑥ Plastic casings, including polyvinylidene chloride casings, nylon sleeves (polyamide casings), polymer casings (such as polyester), etc.

Polyvinylidene chloride casings: This casing is a tubular or sheet casing made of a copolymer film of vinyl chloride and vinylidene chloride. This casing can effectively block water and oxygen, can resist 121°C humidity and heat, is cold-resistant, acid-resistant, alkali-resistant, oil-resistant, fat-resistant, does not absorb water, and has a beautiful gloss. This casing is suitable for ham and sausages (such as ham sausage, fish sausage, etc.) and is made by high-frequency heat sealing and filling. Manufacturers of this casing include Taketama Chemical and Asahi Kasei in Japan and Dow Chemical in the U.S. This casing is also widely used for room temperature storage of high temperature sterilized products.

Polyamide 121℃: Also known as nylon 121℃, it is a single-layer or multi-layer 121℃ made of nylon 6. The single-layer product is air-permeable and water-permeable, and is usually used for smoked and peeled sliced ​​meat products. The multi-layer casing is waterproof, airtight, printable, and not corroded by acids, oils, greases, etc. It is not conducive to the growth of fungi and bacteria. It can also shrink during the cooking process, has strong mechanical strength and elasticity, and can withstand high temperatures and sterilization. Before use, it should be soaked in 30 water. Fill it firmly when filling (no holes can be made). After cooking, it can be cooled with spray or water bath. It is suitable for making various cooked sausages, black sausages, liver sausages, head sausages, quick-sliced ​​sausages, fish sausages, etc. Polyester casing: This 121℃ is airtight and water-tight; it can be printed; it has high mechanical strength; it is not corroded by acids, alkalis, greases and organic solvents; it is easy to peel. It can be divided into shrinkable and non-shrinkable types. Shrinkable casings can be well combined with the contents after heat processing, and can be used to package non-smoked, steamed sausages, poultry rolls, steamed ham, meat slices, fresh game, fish, etc. and deep-frozen foods. In addition, there are polyester films specifically used to package barbecue products, such as packaging films for roast chicken. Of course, this film can also be used to package microwave foods and semi-finished products. Polyester 121℃ does not need to be soaked in water before use. It should be filled firmly but not pierced; after filling, in order to ensure the shrinkage of the casing, the sausage should be placed in hot water above 95 for a few seconds. The cooking temperature is 80~85. After cooking, it should be cooled with spray or water bath. Non-shrink casings are mainly used to package fresh meat, raw sausages and other meat products that do not require heating.

Composite bags: There are composite films produced by co-extrusion technology of the same or similar plastics (ordinary co-extrusion between polyolefin plastics) and films produced by co-extrusion of different plastics (mainly co-extrusion of high-polarity nylon PA, ethylene-vinyl alcohol copolymer EVAI, polyvinylidene chloride PVDC and non-polar polymer compounds such as polypropylene PP, polyethylene PE and ethylene-vinyl acetate copolymer EVA). This composite film can be printed, waterproof, airtight, has high mechanical strength, a wide range of applications, and is low in price. It is suitable for secondary packaging of various meat products.

In addition, there are canned low-temperature meat products. After pasteurization, the product can be stored at low temperature for 6 months. This packaging is mainly used for processing meat products for export.

(3) Meat product packaging stored at room temperature. Meat products stored at room temperature refer to products that are packaged with airtight materials, sterilized at above 121, can be circulated at room temperature, and have a shelf life of more than 6 months. The materials suitable for this packaging must be waterproof and resistant to high-temperature disinfection. Commonly used meat product packaging materials include tin, aluminum foil, composite bags, glass jars, polyvinylidene chloride films, etc.

Tin cans are made of tinplate. They are mainly used for canned meat packaging, such as canned luncheon meat, canned fish, etc. Generally, the packaged products can be kept for more than one year at room temperature.

Aluminum foil cans are made of aluminum foil stamping. Mainly used for canned meat.

Composite bags are made of nylon (PA) and polypropylene (PP) as the base material, and are made of high-temperature resistant adhesive resin through co-extrusion process. Composite films for cooking, or composite bags made of aluminum foil, can withstand 121 sterilization, while preventing external oxygen from entering the bag, effectively preventing the material in the bag from deteriorating, and keeping meat products at room temperature for 6 months. Mainly used for packaging roast chicken, beef, etc. Store at room temperature. Polyvinylidene chloride film This film has been introduced before. It can be used for packaging low-temperature meat products as well as high-temperature sterilized meat products. For example, it is now widely used for packaging ham sausages.

At present, glass jars are mainly used for canned fruit packaging and rarely for meat packaging.

Meat packaging machine

(1) Vacuum packaging.

There are two methods of vacuum packaging: one is to directly insert the nozzle of the vacuum pump into the casing after the product is loaded to remove the air, which is called external vacuum packaging. The other is to put the product into a closed vacuum chamber and use a vacuum pump to evacuate the entire vacuum chamber, so that the product packaging reaches a vacuum state.

① Degassing shrink packaging refers to directly inserting the nozzle of the vacuum pump into the opening after the product is loaded into the casing to remove the air. Usually, aluminum cards are used to tie the casing, so it lacks sealing. The purpose of removing air is to make the product and the casing stick together tightly by exhausting air, thereby improving its preservation. Therefore, it is necessary to use heat-shrinkable casings. After packaging, they are placed in hot water or hot air to shrink the casings and stick them tightly to the product. The film used is shrinkable polyvinylidene chloride, and the equipment used mainly includes an opening machine for opening the casing and a degassing tying machine. Products using this casing mainly include thick-diameter smoked products (long-back ham, compressed ham, Bologna sausage, semi-dried small intestine) and barbecued pork, etc.

② Vacuum packaging The basic principle of vacuum packaging is: in order to make the product and casing close together, the air is completely removed in the sealed chamber, but when it returns to normal atmospheric pressure, the volume of the product shrinks, making the vacuum degree of the package lower than the vacuum degree in the sealed chamber. There are intermittent and continuous vacuum packaging methods.

Bag-making vacuum packaging machine: refers to a device that puts the product into a bag-shaped casing, then removes the air in the vacuum chamber, and then heat-seals it. The most widely used is the intermittent vacuum packaging machine, but there are also movable vacuum packaging machines with a conveyor belt installed at the bottom of the vacuum chamber and rotary mobile continuous vacuum packaging machines with two vacuum chambers.

Vacuum stretch packaging: The vacuum stretch packaging machine must use a forming mold to heat the film first, and then use the forming mold to punch it into the shape of the container before vacuum packaging. The film used for deep-drawn packaging is deep-drawn film, which is divided into soft film and hard film. This film has the characteristics of excellent formability, high transparency, oxygen barrier, heat resistance, adhesion, flatness, excellent anti-fogging, and easy opening. This film is equipped with a thermoforming packaging machine, which can not only package solids, liquids, soft objects, fragile items, etc., but also can be used for vacuum soft film packaging, hard film inflation packaging, blister packaging, etc. It is hygienic, efficient, labor-saving, and low-cost when used. Products suitable for deep-drawn packaging include block products, sliced ​​products, frankfurter sausage products, Vienna sausages, etc. This packaging has become the trend of food packaging in the future.

Vacuum skin packaging: This packaging form uses the product instead of the packaging mold, and the packaging shape is the actual shape of the product. This packaging has good vacuum degree and can also inhibit the juice from the product, so the preservation effect is better. This packaging has two types: continuous and intermittent. It is suitable for packaging ham, bacon, sausage, etc., and its advantages are more evident when packaging irregularly shaped meat products.

(2) Inflatable packaging

This packaging usually uses a non-air-permeable film and is filled with inactive carbon dioxide or nitrogen. The function of this packaging is to prevent oxidation and discoloration, delay the rise of redox potential, and inhibit the reproduction of aerobic microorganisms. The disadvantage is that when using this packaging form, since the product and the film are not tightly attached, there is a temperature difference between the inside and outside of the package, causing condensation on the packaging film, so that the product in the bag cannot be seen. If the contaminated product is packaged, the movement of the product in the bag will expand the scope of contamination, and the dew in the bag will help the reproduction of bacteria. This packaging is only suitable for meat products that are easy to precipitate fat and water on the surface. According to the gas replacement method, the air-filling packaging machine can be divided into two categories: the filling type packaging machine that fills the packaging bag with gas from the atmosphere, and the vacuum type packaging machine that first evacuates the packaging bag and then fills it with gas. The filling type has a lower gas replacement rate but a faster speed; the vacuum type has a slower speed but a higher air replacement rate, which is more ideal. Air-filling packaging is suitable for packaging Vienna sausages and frankfurters.

(2) Packaging with deoxidizers Degassing shrink packaging, vacuum packaging, and gas replacement packaging can all isolate oxygen. In addition, there is a method of putting oxygen-absorbing substances into the packaging bag, which has the same effect as the other methods mentioned above. During general packaging, even if the oxygen is removed, some oxygen will still penetrate from the surface of the film, so it is impossible to completely isolate oxygen. The function of the deoxidizer is to absorb the oxygen that penetrates into the packaging bag at any time to maintain the oxygen concentration in the bag below the desired limit concentration, thereby preventing fading and oxidation and inhibiting bacterial growth. The advantages of adding deoxidizers include low cost, no need for vacuum and air-filling facilities, and convenient and flexible operation.

Design of meat product packaging

The standard sequence for designing meat product packaging is as follows:

(1) Investigate sales conditions Investigate the display conditions and storage conditions of products similar to the products we plan to produce in the market to determine the sales method and sales location.

(2) Determine product specifications Clarify the specifications of the packaged products, such as the weight, size, number of roots, coloring, casing used, moisture content, fat content, etc. of the packaged products.

(3) Determine the turnover days of the product Determine the packaging benchmark based on the turnover days of the product in the market.

(4) Determine the packaging form Determine the packaging form based on market requirements and the turnover days required by the seller.

(5) Determine the packaging method Determine the packaging method based on the packaging benchmark and packaging form. When packaging tightly, the air barrier should be studied according to the degassing method and vacuum method. Impact resistance should be studied, and heat resistance and heat shrinkage should be studied according to whether secondary sterilization is performed; when packaging with air, the air barrier, oil resistance and thermal adhesion should be studied.

(6) Determine the type of packaging machine. The type of packaging machine to be used is determined according to different packaging methods.

① The determination of manual and automatic packaging machines depends on the research of the thermal adhesiveness and formability of the packaging material.

② The determination of intermittent and continuous packaging machines depends on the research of the thermal adhesiveness, formability, sliding property, spacing stability, anti-static property, and anti-deformation property of the packaging material.

(7) Determine the packaging material. When determining the packaging machine, you can choose the film that is suitable for it. In addition, you can also determine the performance of the packaging material according to the circulation conditions and sales display effects.

① In terms of circulation, impact resistance, cold resistance, and thermal adhesiveness.

② In terms of display, gloss, transparency, printability, anti-deformation, and light-shielding properties.

③ In terms of products, air barrier, oil resistance, and moisture resistance.

④ In terms of cost, the film thickness and packaging size of the selected packaging material should be considered, and the cost should be set within 10% of the retail price.

(8) Examine its social benefits. When starting to design packaging, you should pay attention to checking the safety of the packaging material to ensure the safety of food.

In short, with the improvement of people's living standards, lifestyles are also developing in a diversified direction, and people's requirements for meat products such as ham and sausage are also diversified. This trend of diversified consumption has brought new challenges to packaging materials, packaging methods and packaging systems. In order to meet such challenges and meet the requirements of consumers, it is necessary to continuously research and innovate the packaging technology of meat products.