The hottest soft canned food packaging cooking bag

2022-08-21
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Cooking bags for soft canned food packaging (II)

cooking bags

cooking bags are different from other food packaging materials. Because cooking bags need to be sterilized at a high temperature of ℃ in hot water or steam, they must have good heat sealing, heat resistance, water resistance and barrier properties. There are three requirements in terms of heat resistance:

1 The composite part and sealing part shall not peel off and reduce strength due to heat treatment

2. There shall be no adhesion between the sealing surfaces in the bag

3. The size should be stable, etc

in addition, the limiting temperature of inner film adhesion is 110 ℃ for medium density polyethylene, 120 ℃ for special polyethylene, 125 ℃ for polypropylene and 140 ℃ for special polypropylene

in terms of water resistance, nylon has a hydrophilic base. Although there is a risk of whitening after water absorption, the composite part will not be layered. As for barrier materials, there are ethylene vinyl alcohol polymers, polyvinylidene chloride, and special nylon; However, PVDC is different from other raw materials. Although white turbidity also appears, it will return to normal after a period of time. During this period, the barrier property remains unchanged

the composition, mechanical adaptability and physical properties of cooking bags are described in the following four types, namely:

1) transparent ordinary type

2) transparent isolated type

3) aluminum foil isolated type

4) high temperature sterilization bag

1. Transparent ordinary

transparent ordinary cooking bags are used by most food processing plants because they can see the contents. In particular, this type of packaging material is mostly used in the packaging of pickles, rice and hamburger patties sold at low temperatures. The outer layer of these transparent ordinary packaging materials is nylon or polyester film, and the inner layer is polyolefin film such as polypropylene and polyethylene. Table 2 shows the composition and physical properties of transparent ordinary cooking bags

from these results, we can see that the sealing strength of 20mm is kg, the heat sealing range is ℃, and the adhesion temperature is 124 ℃. Secondly, the barrier property of these two materials. The oxygen permeability of rp-t is 118 ml/m for 2.24 hours At atmospheric pressure, the water vapor permeability is 3 g/m for 2.24 hours, and the oxygen permeability of rp-n is 55 ml/m for 2.24 hours At atmospheric pressure, the permeability of water vapor is 3 g/m for 2.24 hours. The barrier difference between the two packaging materials may be due to the inherent barrier difference between polyester and nylon film

the composite packaging material factory that manufactures cooking bags has tested the composition of this transparent ordinary cooking bag and produced many types of cooking bags. Table 3 shows the composition and physical properties of representative cooking bags

it can be seen from the table that the inner layer, namely the sealing layer, of cooking bags suitable for use below 120 ℃ adopts special high-density polyethylene (there is no such product in China, and copolymer grade polypropylene can be used), while cooking bags that can sterilize at 135 ℃ must use special polypropylene as the sealing layer

transparent isolation type

protein is designed to neutralize the sterilization of meat processing products and fish processing products with high fat content in the design of China's 20 large transport aircraft and C919 large passenger aircraft. Transparent isolation type packaging materials are required. These packaging materials are sandwiched with high barrier polyvinylidene chloride (k-flex). The high barrier polyvinylidene chloride (PVDC) film compounded by coextrusion method is used as the intermediate layer. Table 4 is about the physical properties of high barrier polyvinylidene chloride composite film. According to this table, the cooking bag composed of polyester (12 microns)/high barrier polyvinylidene chloride (15 microns)/non stretched polypropylene blown film can also be used as food preservation and other utilization technologies (50 microns), and its oxygen transmission is 14 ml/m for 2.24 hours Atmospheric pressure (temperature 30 ℃, relative humidity 60%). In contrast, the oxygen permeability of biaxially oriented polypropylene (20 microns)/ethylene vinyl alcohol copolymer (17 microns)/polyethylene (60 microns) is 10 ml/m for 2.24 hours Atmospheric pressure (30 ℃, relative humidity 60%)

high barrier polyvinylidene chloride composite film has very good characteristics as a packaging material for soft cans. Figure 1 shows the relationship between sterilization temperature and oxygen transmission of high barrier polyvinylidene chloride composite film. It can be seen from the figure that for the three barrier composite films, the oxygen transmission was measured before sterilization and after sterilization at 120 ℃ and 130 ℃. The results showed that the oxygen transmission of the high barrier polyvinylidene chloride composite film still changed little after sterilization at 120 ℃ and 130 ℃, while the oxygen transmission of the other two packaging materials was very low before sterilization and increased sharply after sterilization

Figure 2 shows the change of oxygen transmission of high barrier polyvinylidene chloride composite film with time after sterilization. It can be seen from the figure that the oxygen transmission of high barrier polyvinylidene chloride composite film is still fixed after sterilization at 120 ℃ for 20 minutes and storage at 30 ℃ and 80% relative humidity for 15 days

3. Most of the aluminum foil insulated

soft cans are curry, stewed food, meat and high-grade cooking food. Among these food packaging materials, aluminum foil is the basic material to prevent aroma from escaping and has shading property

to make this kind of bag, firstly, the printed polyester film should be dry compounded with aluminum foil, and then compounded with polyethylene or polypropylene film

it can be seen from this table that the composition of this kind of film varies with the sterilization temperature. The film sterilized at 120 ℃ is composed of polyester/aluminum foil/special high-density polyethylene or copolymer grade polypropylene; The film, which can resist sterilization at up to 135 ℃, is composed of polyester/aluminum foil/special polypropylene. The oxygen permeability and moisture permeability of these films are almost zero. As long as there are no pinholes caused by the bending of packaging materials, the barrier index number can be close to zero

when using aluminum foil insulated cooking bags, pay attention to the corrosive effect of acidic food on aluminum foil and the deterioration of contents caused by pinholes caused by bending

in addition to these shortcomings and invisible contents, aluminum foil can be said to be a very excellent packaging material for soft cans

4. High temperature short-time sterilization bag

high temperature short-time sterilization food cooking bag, referred to as HTST (high temperature short time). Sterilization at high temperature for a short time not only does not affect the flavor of food, but also kills bacteria, which gives birth to soft cans with high temperature sterilization

first of all, let's understand the conditions that kill microorganisms

in the standard for packaging sealed pressurized heating sterilized food in cans and containers with cover with colorform surface and sealing support below at the same time, it stipulates that the parts in the food need to be heated at 120 ℃ for more than 4 minutes, and the heating sterilization conditions at 120 ℃ for 4 minutes, which means that the heat-resistant Bacillus botulinum can be completely killed

see Table 5 for the heat resistance of Botox. According to the data in the table, the spores of botulinum toxin are heated in phosphate buffer (pH7) at 100 ℃ for 330 minutes and 115 ℃ for 10 minutes. If they are sterilized at 120 ℃, they can be completely killed after 4 minutes

it can be seen from table 5 that the spores of Botox can be completely killed after heating at 120 ℃ for 4 minutes. However, canned food is a mixture of protein, fat, carbohydrates, etc., which form a protective layer on the spores of bacteria. Therefore, heating at 120 ℃ for 4 minutes sometimes may not kill the spores of bacteria. For the sake of safety, the food industry now adopts high temperature and high pressure sterilization with the central temperature cut off and the power supply degree heated at 120 ℃ for minutes

in order to completely kill spore bacteria, high temperature above 120 ℃ is also used for short-term sterilization. In addition, when high temperature and short-term sterilization are used, the flavor of food will not escape and the browning reaction of food will not deepen

high temperature and short-time sterilization can not only maintain food quality, but also greatly improve productivity. The reason is very simple. The shortening of sterilization time means the shortening of processing and production time. In this way, the equipment operation rate can be greatly improved, thus greatly improving the production efficiency

the main composition and physical properties of cooking bags for high temperature short time sterilization (HTST) are shown in Table 6. It can be seen from the table that the composition of the aluminum foil bag is polyester/aluminum foil/special layer/polyolefin, and its oxygen transmission and water vapor transmission are zero. Relatively speaking, the transparent bag has two compositions: Nylon/special layer/polyolefin and polyester/special layer/polyolefin, and its oxygen transmission is 30 and 47 ml/m for 2.24 hours respectively Atmospheric pressure (27 ℃ relative humidity 65%), water vapor permeability is 10, 6 g/M 2.24 hours, respectively. Compared with other cooking bags, these high temperature short time sterilization (HTST) bags have a higher adhesion temperature of 137 ℃, the heat sealing temperature is 190~250 ℃ for aluminum foil bags, and 180~220 ℃ for transparent bags

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