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Suggestions on the selection of meat products packaging (I)

packaging materials and methods of meat products

the purpose of packaging is to prevent bacterial contamination of products, so as to ensure product quality. Packaging can also play an advertising role and attract consumers' attention. In all stages of manufacturing, circulation, sales and consumption, that is, from the factory to the hands of consumers, products always have to contact hands, so pollution may occur at any time, so we should prevent bacterial pollution through packaging

1. The performance of packaging materials as the packaging of meat products must meet certain requirements

most of the packaging materials used in meat products are plastic. Plastic has a wider range of packaging properties than paper, metal and other packaging materials. A packaging material can have several properties at the same time. Moreover, the lamination, pasting or coating of plastic film requires replacing the tubing layer with higher strength. The technology can also supplement the insufficient performance of a single film, and the lamination/coating technology can be used to develop a variety of films

(1) oxygen isolation

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. Usually, it is carried out in two steps. At first, the gas is dissolved in the molecules of the film, and then infiltrated through diffusion. The oxygen resistance of the film is applicable to the packaging of all meat products except raw meat. Especially in vacuum packaging and inflatable packaging. Due to the role of oxygen, hemoglobin is changed into heme, causing product discoloration, promoting fat oxidation and the proliferation of aerobic microorganisms. Therefore, preventing the product from contacting with oxygen is extremely important for maintaining product quality and improving preservation

(2) moisture resistance

is the property of blocking the passage of water vapor. When the film molecules do not contain hydrophilic hydroxyl and carboxyl groups, it is considered to have good moisture resistance. Moisture resistance changes greatly with temperature. The moisture resistance of the film is applicable to all meat products packaging. If the moisture of the product penetrates from the inside of the packaging film in the form of water vapor, or the product absorbs the water vapor from the outside, the flavor, organization and content of the product will also change. Especially for the packaging of dry sausages with little moisture, and to prevent the natural loss of quantitative products is extremely important

(3) shading

especially for the 320 ~ 380 nm wavelength light with optical effect in ultraviolet light. This property is very important for vacuum packaged sliced products, colored products and smoked products. The transparent film has no effect of blocking ultraviolet rays. Although HDPE has some shading properties, the film is opaque. There are many ways to prevent ultraviolet transmission, one of which is to add ultraviolet absorbent to packaging materials. However, in recent years, the use of UV absorbers in food packaging materials has been banned. Therefore, a method of shading by using the properties of light has been developed. This method uses printing ink to absorb or reflect light, or satin processing roller to mechanically extrude concave convex patterns on the film surface to reflect light. When printing ink is used, black and white can absorb or reflect light. In addition, other inks, even with light and dark color difference, can not achieve the desired effect. Except for black, all light colors have almost no effect of absorbing light. Dark colors, according to black, blue, green and yellow, have poor shading in turn, while red and purple have no effect. Generally, when printing, the film with shading effect is opaque, and the disadvantage is that the products in the packaging bag cannot be seen. In order to make up for the defects of opaque films, a method of ultra micronization of ink has been developed recently, which uses the scattering of ultraviolet light with relatively short wavelength inside the film to block light, so that the longer wavelength visible light can pass through, and the printed film of the products in the packaging bag can be seen

(4) impact resistance

this property is applicable to all packages. Especially for heavy things, tight packaging without gaps between casings and products is more important. The impact resistance of packaging materials can be ensured by the balance of tensile strength, tensile elongation and impact strength of materials. Such films include polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, stretched nylon, etc

(5) cold resistance

even at low temperature, the film remains brittle and can still maintain its strength and impact resistance. Generally, there is no problem in preserving meat products at -10 ~ 0 ℃, but if frozen meat products are preserved 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 (tensile), polypropylene (non tensile), etc

(6) heat resistance

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

(7) formability

refers to the property that the heated and softened film is blow molded (pneumatic forming) with air, and the orders of China's plastic extruder enterprises rise sharply or form the film along the forming die (forming along the product during compact packaging) by suction (vacuum forming). Good formability means that the four sides of the heated film can be stretched evenly with a small force. Once heated, the film can be stretched and enlarged immediately. When the heating temperature reaches a certain temperature, it will be in a stable state. The wider the stable temperature band is, the easier the film will be formed and the easier the packaging operation will be. For films with good formability, the influence of their barrier and sealing properties must also be considered. Films with these comprehensive characteristics are called composite films. Now the packaging films used in the market are mostly composite films. The forming film pays attention to and supports domestic experimental machine manufacturing enterprises with development potential, such as stretch nylon 6,

stretch free polypropylene, polyvinyl chloride, polyvinylidene chloride, polyethylene, vinyl acetate copolymer, etc

(8) heat shrinkability

refers to the property that the film shrinks once heated. This property is suitable for degassing shrinkage packaging and vacuum packaging. By using the heat shrinkable property of the film, the product position in the fixed bag can be achieved and the preservation effect can be improved. Shrinkage refers to the property of the film given by stretching between moving molecules when the thermoplastic film is heated above the softening point temperature, that is, the restitution of the original state. When the film is stretched, the film is stretched thin, but the molecules in the film rearrange in the stretching direction. Therefore, its toughness and gas isolation make the temperature influence minimum; Property and moisture resistance have also been improved. Polypropylene, polyester, polyvinyl chloride and polyethylene have good thermal shrinkage. (1) (II) (III) (IV)

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