Sausage products is one of the main part of processed meat products, there are hundreds of types of sausages products all over the world. In order to meet the needs of consumption, first of all, various types of sausage packaging machines are required to achieve massive production capacity. In addition, novel packaging design is also indispensable, because the packaged sausage is not only hygienic, but also can improve its preservation. At the same time, packaging can also be used as an advertisement to attract customers. It is easy to attract customers’attention to packaging novel and beautiful things. Packaging can not be ignored.
Sausage is a kind of food with rich nutrition and high moisture content. Its shelf life may only be 3 to 4 days for a short time and 6 months for a long time. The duration of preservation mainly depends on the moisture content and processing method of sausage, as well as the operation and packaging technology after sterilization.
Sausage Preservation and Packaging
Sausage packaging can avoid discoloration, oxidation, damage and deterioration of products caused by direct sunlight, air contact, mechanical and microbial effects, thus prolonging the shelf life. Because there are many kinds of sausages, it is necessary to adopt a variety of packaging methods and appropriate packaging materials.
Preservation and Packaging of Sausage Products
1. Processes related to sausage preservation
There are many processes that affect the packaging of sausages. Considering the relationship between the packaging and preservation of sausages, there are basically the following situations.
(1) The sterilization conditions of sausage were as follows: the central temperature was 63 C and kept for more than 30 minutes. Under such sterilization conditions, the bacteria causing food poisoning are killed, but there are still some bacteria and heat-resistant lactic acid bacteria in the products which are related to deterioration. When these residual bacteria meet the appropriate conditions, they will gradually proliferate and cause food deterioration.
(2) The period from sterilization to packaging takes a few hours at least and a day and a night at most. During this period, contact with the operator’s fingers, machines, or suspended microorganisms in the ground and air can cause secondary contamination of food.
(3) After packaging, although the external pollution is cut off, the internal pollution of the products is continuing, and oxygen will enter through the film slowly, so the partial pressure of oxygen in the bag will gradually increase, and the residual bacteria and contaminated bacteria will begin to multiply. The higher the temperature of preservation, the faster the bacterial proliferation.
In view of the above, in order to prevent the secondary pollution of packaging operation, it is necessary to shorten the storage time after sterilization as far as possible, pack immediately after sterilization, and choose a film with isolation effect on light, water and oxygen.
2. Packaging Technology
The packaging of sausage is based on different packaging and operation process according to whether it is sterilized after packaging and whether the casing is breathable.
(1) choose different processes according to the type of casing used.
When using the airtight casing, the casing can keep its original appearance, and the later filling process is simple. This product is called the direct packaging product. The method is as follows: fill the cooked meat stuffing into heat resistant, non air permeability and moisture proof casing, then seal and seal the two ends with aluminum card, then boil and cool it to make the finished product. The characteristic of this method is that the non air permeable casing filled with meat is the outer packing of the product, and there is no need to pack the product two times. As the casing is non-permeable and microorganisms can not pass through, after sterilization, the product can be maintained in a long-term hypoxic state and avoid secondary contamination caused by the product contacting machines and fingers after filling, so this method is a simple and effective way to improve the preservation. Ham sausages sold on the market now belong to this kind of packaging.
When using a breathable casing, the product dries, smoked and steamed when it dries, smoked and steamed. The free juice, fat and water flow to the outside of the product. The free substance adheres to the surface of the product and becomes the nutrient source of the microorganism. After a period of time, microorganisms on the surface of products will multiply and form secondary pollution. If the animal casing is used, the casing itself becomes a source of nutrition, bringing the microorganism into the interior, resulting in spoilage of the products. Even if the animal casing is not used, it is often necessary to pierced the casing, so it can not avoid the diffusion of microorganisms from the surface of the product to the internal pollution. For such products, the following two methods can be used to prevent microbial contamination after sterilization. One is to carry out ordinary secondary packaging, and then to carry out secondary sterilization; the other is to implement aseptic hygiene operation packaging method without secondary sterilization.
(2) Packaging method
Packaging methods can be divided into vacuum packing and gas filling packaging. The difference between the two packaging methods is that the former is to keep the casing and sausage in a close state, to eliminate the air in between as far as possible, so as to prevent the deterioration of the product caused by the contact of oxygen and the product; the gas filling packaging (modified atmosphere packaging)is to fill the inert gas in order to isolate the oxygen. The purpose of both methods is to reduce the effect of oxygen on product quality.
① Vacuum packing. The purpose of this kind of packing is to reduce the influence of oxygen on products by deoxidation or vacuum. The effect of vacuum is to keep the casing and sausage in a vacuum and inhibit the proliferation and oxidation of bacteria. In addition, when the second sterilization is carried out, the packaging form is easy to conduct heat, which can shorten the sterilization time and reduce the impact on product quality. This kind of packaging can also play a role in fixing the product in the packaging bag.
(2) Inert gas filling packaging, which uses an airtight film and fills it with inert gases (e.g. nitrogen). When filling gas, the oxygen in the bag should be removed before filling. At this time, the replacement rate is very important. If the replacement rate does not meet the requirements, simple packaging should be adopted. This kind of packing must be carried out under hygienic conditions. Its characteristics are that the product is not subject to pressure and does not deform.
(3) Secondary sterilization
If breathable sausage casing is used, during the period from sterilization to packaging, the surface of the product may be contaminated twice, and the interior of the product may be changed from anaerobic state to aerobic state, resulting in a decrease in preservation. In order to restore the product in this state to the level of microorganisms just after sterilization, heating or secondary sterilization is needed after packaging. The temperature, time and cooling conditions of secondary sterilization vary according to the degree of surface contamination. For example, if the whole surface of the sliced product is contaminated, the second sterilization should be maintained for more than 30 minutes after the central temperature reaches 63 C; if the product is massive, but the surface is contaminated, only 63 C and 30 minutes sterilization is needed for the parts below the surface in a few millimeters. In addition, necessary cooling procedures should be carried out. Sterilization or cooling conditions must be strictly set. If the setting is not correct, inadequate sterilization or cooling will occur, instead, the growth of bacteria will be given the appropriate temperature. If the heating temperature is too high, and oil and water may appear, these juices will become the nutrient source of bacteria, resulting in shorter shelf life. The amount of starch and emulsifier should be taken into account in the batching stage of products requiring secondary sterilization, so that juice and fat can not be separated during the second sterilization. Generally high-grade products do not undergo secondary sterilization. In the second sterilization, the product must be in contact with the thermal medium, so it must be vacuum package.
(4) Turnover Date and Appropriate Packaging of Products
The packaging of products must consider the quality, the shelf life required by the market, economy and other issues. Packaging above market requirements is also unnecessary. With the popularization of sausages and the expansion of circulation scope, the turnover period required by the market is also different. In order to pack properly according to market requirements, we must consider the three aspects of manufacturing conditions, packaging methods and packaging materials comprehensively.
Sausage packaging materials and methods
The purpose of packaging is to prevent bacteria from contaminating the products, so as to ensure the quality of products. Packaging can also play an advertising role and attract consumers’attention. In all stages of manufacturing, circulation, sales and consumption, i.e. from factory to consumer, products always have to contact people, so pollution may occur at any time, so we need to prevent bacterial contamination through packaging.
Properties of Packaging Materials
As the packaging of sausage, it must meet certain requirements. Most of the packaging materials used for sausages are plastic. Plastics have a wider range of packaging properties than paper and metal packaging materials. One kind of packaging material can have several properties at the same time. Moreover, lamination or coating technology of thin plastic glands can supplement the insufficient properties of single film, and lamination/coating technology can be used to develop films for various purposes.
(1) oxygen isolation
Isolate oxygen permeability. 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. Usually it is done in two steps, first by dissolving the gas in the molecules of the film, and then by diffusing and penetrating into it. The film’s oxygen resistance is suitable for all sausages except raw meat. Especially in vacuum packaging, inflatable packaging is more important. Because of the effect of oxygen, hemoglobin is transformed into high iron hemoglobin, which causes the fading of products, promotes lipid oxidation and the proliferation of aerobic microorganisms. Therefore, it is very important to prevent the product from contacting with oxygen in order to maintain product quality and improve its preservation.
It is the property of preventing water vapor from passing through. When there are no hydrophilic hydroxyl and carboxyl groups in the film molecules, it is considered that the film has good moisture resistance. The humidity resistance varies greatly with temperature. The moisture resistance of the film is suitable for all sausage packaging. The flavor, organization and content of the product will also change if the moisture of the product passes through the inside of the packaging film in the form of water vapor or the product absorbs the water vapor from the outside. Especially for the packaging of dry sausages with little moisture content and the prevention of natural wastage of quantitative products are extremely important.
(3) Light proof
Especially for the 320-380 nanometer wavelength light with optical effect in ultraviolet radiation, it has shielding property. This property is very important for vacuum packaged slice products, colored products and smoked products. Transparent film has no effect of shielding ultraviolet rays. High density polyethylene (HDPE) film is opaque although it has some shading properties. There are many ways to prevent ultraviolet transmission, one of which is to add ultraviolet absorbents to packaging materials. But in recent years, the use of ultraviolet absorbents has been banned in food packaging materials. Therefore, a new method of shading by using the nature of light has been developed. This method is to use printing ink to absorb light or reflect light, or to use Satin processing drum to mechanically extrude concave and convex patterns on the film surface to produce reflection of light. When printing ink is used, black and white can absorb or reflect light. In addition, other inks, even if there is a shade difference, can not achieve the desired effect. Except for black, all light colors hardly absorb light. Dark colors are black, blue, green and yellow, and their shading becomes worse in turn. Red and purple have no effect. Generally, when printing, the film with shading effect is opaque, but the disadvantage is that the products in the package can not be seen. In order to remedy the defect of opaque film, a method of ultrafine ink granulation has recently been developed, which uses ultraviolet scattering with shorter wavelength to shield the film from the visible light of longer wavelength as well as the printed film of products in packaging bags.
(4) Impact resistance
This property applies to all packaging. Especially for heavy items, tight packaging with no gap between sausage and products is more important. The impact resistance of packaging materials can be guaranteed by the balance of tensile strength, tensile elongation and impact strength. The films include polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride and stretched nylon.
(5) Cold Tolerance
Even at low temperatures, the film is not brittle, but can maintain its strength and impact resistance. Generally, it is not a problem to preserve sausages at – 10 – 0 (?) C, but if the sausages are preserved at – 15 (?) C, 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), polypropylene (stretching), polypropylene (non-stretching) and so on.
(6) Heat resistance
It refers to the property of high softening point, even without deformation after heating, such as PVC. As the product expands during heating, the heat resistance of the film must be guaranteed. This property is suitable for packaging of secondary sterilization. Polyvinylidene chloride, polypropylene (non-stretching), polypropylene (stretching), polyethylene (high density) have good heat resistance.
It refers to the property of blowing-moulding (pneumatic forming) of a film softened by heating with air or forming along a forming die (forming along a product during compact packaging) by inspiration (vacuum forming). Good formability means that the heated film can be stretched evenly on all sides with very little force. As soon as the film is heated, it can be stretched and enlarged. When the heating temperature reaches a certain temperature, it will be in a stable state. The wider the stable temperature band, the easier the film will be formed and the easier the packaging operation will be. Thin films with good formability must also be considered for their barrier and sealing properties. Thin films with these comprehensive properties are called composite films. At present, the packaging film used in the market is mostly composite film. Formed films include stretched nylon, non-stretched polypropylene, polyvinyl chloride, polyvinylidene chloride, polyethylene, vinyl acetate copolymer, etc.
(8) Heat shrinkage
It means the shrinkage of the film when heated. This property is suitable for degassing shrinkage packaging and vacuum packaging. It can fix the position of the products in the bag and improve the preservation effect by using the shrinkage property of the film when it is heated. Shrinkage is the property of the film which is given by stretching between moving molecules when the thermoplastic film is heated to the temperature above the softening point, i.e. the restoring property of the film. When the film is stretched, it is thinned, but in the direction of stretching, the molecules in the film are rearranged. Therefore, its toughness, air insulation and moisture resistance are also improved. Polypropylene, polyester, polyvinyl chloride and polyethylene have better thermal shrinkage.
(9) Oil resistance
It is to prevent the free fat from the product from permeating to the outside of the film. The infiltration of fat into thin films may occur in two ways: one is due to the dissolution of thin films, the other is due to the infiltration of fat. Oil resistance also has an effect on heat seal. If the film is dissolved at the seal and permeation occurs at the same time, the film is considered inappropriate. The so-called oil-resistant film refers to the film that is not easy to dissolve and penetrate. Oil-resistant film is suitable for packaging sausages containing fat. For example, polyvinylidene chloride, polyamide resin, polyester and other materials have good oil resistance.
(10) Thermal bonding
When the thermoplastic film is heated below the decomposition temperature, it softens and its fluidity increases to a melting state. At this time, the film is compressed, and the molecules of the two films diffuse on the next surface. After cooling, the film solidifies and bonds. This property is affected by the melting temperature and viscosity, compaction force and time of the film. According to these influences, the bonding method and conditions also change. Ionic resins and ethylene-vinyl acetate copolymers are all materials with thermal bonding properties. According to the temperature range, shrinkage and properties of the films, the bonding methods are different. They are generally divided into hot plate bonding (e.g. polyethylene, non-stretching polypropylene, polyamide resin, polyvinyl alcohol, soft polyvinyl chloride, etc.), pulse bonding (e.g. non-stretching polypropylene, polyester, polyamide resin, etc.), and high frequency bonding.
(11) Sliding property
That is, the friction coefficient between the film and the contact material is small and easy to slide. This property is closely related to the openness of the film and the ease of machine feeding. When the friction force is high, the film will be obstructed when the product is packed in bags and when the film is packed continuously by a calendered packaging machine.
(12) Spacing stability
When the temperature and humidity of the composite film change, the size of the film remains relatively stable. This property ensures that the printing spacing is consistent, especially when the position of the upper and lower film must be aligned, such as the thermoforming packaging machine – the fully automatic version of sausage packaging machines.
(13) Static dissipative
The film with capacitance sucks dust easily, so that the film will have obstacles in bonding. The surface of the film with good insulation is almost charged. In order to prevent the film from being charged, it is possible to add an anti-charger or install a discharge device on the film, add thousands of volts between the electrode and the ground wire, discharge from the needle, and ionize the air between the film and the electrode, so as to eliminate static electricity. Thin films that are difficult to charge are generally thin films that do not absorb water easily. Thin films that are not easily charged include polyvinyl alcohol, polyvinyl chloride and cellophane. The easily charged films are polyethylene, polypropylene and polyester.
The smaller the refractive index, the better the transparency of the film. The transparency of the film is expressed by turbidity. The smaller the value, the easier the light will penetrate. The films with good transparency include extended polypropylene, extended polypropylene, low density polyethylene, high density polyethylene and polyvinylidene chloride.
Thin films with high refractive index have good reflectivity and luster.
(16) Deformation resistance
It is the hard and elastic property that the film does not elongate even when the load is increased. The film with this property can be used in vacuum sealing machine and thermoforming packaging machine, because the film can meet the fast feed requirements of sausage packaging machines. Where the relative humidity is higher, the deformation resistance of the film with high water absorption decreases.
In a word, the materials used in sausage packaging are required to have a variety of properties, but one kind of film can not meet all the packaging performance requirements, so we compounded the film with various characteristics to make laminated composite film, which can meet the requirements of sausage packaging.