Anti-oxidation packaging technology (I)

Oxygen-proof packaging is a method of sealing and packaging products with good airtightness, low moisture permeability and low oxygen permeability packaging materials or packaging containers. Its main feature is to vacuum or vacuum the inert gas or place an appropriate amount before sealing. The oxygen scavenger and oxygen indicator reduce the oxygen concentration in the package to less than 0.1%, thereby preventing product mold, rust, or oxidative aging. At the beginning, oxygen-proof packaging was mainly used in the packaging of foods, precious herbs, and rubber products. In recent years, oxygen-proof packaging has also been extended to precision-machined parts, electronic components, radio communication equipment, precision instruments, mechanical equipment, and agricultural and sideline products. Other aspects of packaging. There are three main methods of oxygen-proof packaging: vacuum packaging, air-packing, and oxygen-free packaging of deoxidizers.
Vacuum and Inflatable Packaging Vacuum packaging is a packaging method in which a product is packed into an airtight packaging container and a vacuum is applied before sealing so that the sealed container reaches a predetermined degree of vacuum. The inflated packaging is filled with contents. A packing method in which an airtight container is filled with an inert gas (such as N2, CO2, etc.).
Vacuum and inflatable packaging are two different approaches taken to solve a common problem. They also use a high degree of oxygen barrier material, most of the packaging line equipment is the same, and are controlled by the air inside the packaging container does not delay the deterioration of the product.
Vacuum and inflatable packaging technology has been used in glass bottles and canned metal cans for more than 100 years. However, due to the complexity of the canning process and equipment, and the heavy packaging materials, it takes up a lot of space in the process of storage and transportation. Glass bottles are easy to use. Damaged, metal cans tend to rust, so its development and application have been limited. Until recent years, the emergence of plastics and containers of some composite materials, vacuum and inflated packaging have been able to flourish.
(1) Characteristics of vacuum packaging and air-packing (1) Reducing the oxygen in the container can reduce or prevent food oxidation in terms of food, and can inhibit the growth and survival of molds and pests, maintain the original color and flavor of the food, and extend it. Shelf life; for metal, it prevents rust; for bulky items, vacuum packing reduces volume.
(2) Vacuum packaging, because the heat conduction can be strengthened after the air is removed from the packaging container. If high temperature long bacteria are used, the sterilization effect can be improved. However, in vacuum-packed packages, the internal and external pressures are not balanced, and the mouth of the packaged object is subjected to certain pressure. The easily agglomerated powdery foods are likely to stick together or shrink into a clump; crisp and fragile items, such as fried potato chips , fried shrimp, etc. will be smashed; irregularly shaped items will wrinkle the surface of the package, affecting the appearance; sharp-angled items will puncture the bag, these items can not be vacuum-packed.
(3) Inflatable packaging is to fill a certain amount of inert gas immediately after the package is evacuated, or not to evacuate the air. Instead, the air is replaced with inert gas. As a result, oxygen is removed inside the package, and the internal and external pressures are also Towards a balance, it can overcome the deficiencies of vacuum packaging.
(B) the vacuum and inflatable packaging mechanism Vacuum and inflatable packaging function is the same, the process is slightly different, the essence of the mechanism can be attributed to three aspects: oxygen, gas barrier, inflatable.
1. The main reason for the deterioration of the detoxified foods is the presence of microorganisms, followed by the chemical deterioration of foods that come into contact with oxygen in the air. Microorganisms are anaerobic and anaerobic. Molds and yeasts belong to the genus Oxygen. When the oxygen concentration in the package is less than 1%, their growth and reproduction rate will rapidly decline. When less than 0.5%, most bacteria will be inhibited and stop breeding. Of course, the growth of microorganisms is also affected by temperature, moisture and nutrients.
Oxygen and grease or foods containing more than a long time exposure to fat, especially in the sun, oxygen and unsaturated fatty acids which make oil or food taste deteriorating.
Oxygen is in contact with steel products, especially in the case of high relative humidity, which can easily cause metal corrosion.
There are two ways to remove oxygen from the package: one is the mechanical method, that is, vacuum or inert gas replacement; the second is chemical method, that is, various oxygen scavenger. The vacuum and air-packed packages are deoxygenated using mechanical methods, sometimes supplemented by chemical methods.
2. Gas barrier is the use of different gas barrier packaging materials such as plastic film and plastic paper, foil and other composite materials, to prevent the gas inside and outside the package from infiltrating each other.
Use a variety of plastics in vacuum and inflatable packaging. Gas permeability to plastic films varies. For the same film, the transmittance ratio of several common gases is N2:O2:CO2=1:3:15-30.
In some films, the CO2 transmittance is about 30 times that of N2. For this reason, when inflating and packaging, part of the gas inside the package will be absorbed by the food, and the rest will diffuse and circulate according to the partial pressure difference between the inside and outside pressure of the package, and will change until the internal and external gases form an equilibrium state.
3. Inflatable The package is filled with inert gas, commonly used N2 and CO2, in addition to Ar and other special gases.
CO2 gas is extremely effective in preventing the growth and reproduction of mold. When the concentration in the package reaches 10% to 40%, it has an inhibitory effect on microorganisms. If the concentration exceeds 40%, it has the effect of sterilizing bacteria; CO2 gas Fruits and vegetables and other foods with respiratory performance can play an effective role in preservation, such as fresh fruit storage environment when the concentration of CO2 gas reaches 7% to 10%, can prevent fruit mold, reduce the intensity of respiration, extend its shelf life; CO2 on water The solubility is high, and the combination of the two produces weak acidity. Therefore, foods with high water content will have slight acidity after charging CO2 gas; CO2 has strong adsorption effect on oil, cereals and other foods, and can inhibit fat and vitamins in food. With the oxidation and decomposition of oils and fats, food oils are in a state of “hibernation”, thereby prolonging the shelf life.
The air inside the package is pumped out and filled with 99.5% of N2 to prevent metal corrosion and aging of non-metallic materials. After filling N2 in the package, the color, fragrance and taste of the food can be preserved, and oxidation of grease and discoloration of meat can be prevented. . N2 and foods generally do not have a chemical effect and are not absorbed. The permeability of plastic films is lower than that of O2 and CO2. It is an ideal gas for inflatable packaging.
The inert gas itself has the effect of inhibiting the growth and reproduction of microorganisms. Recently, the tea and the stains are often packed with argon (Ar) gas. In addition, dry air can be charged, and the relative humidity in the package is guaranteed to be below the critical relative humidity of the product, which can prevent metal corrosion.
(III) Vacuum and Inflatable Packaging Process The mechanical extrusion method is shown in Fig. 13-1. After the bag is filled, the air in the bag is removed from both sides of the bag with a sponge and sealed. This method is very simple, but the effect of degassing and deoxygenation is poor, and it is limited to applications where the requirements are not high, such as the degassing and deoxygenation of bagged raw noodle pasteurization. This method is sufficient. For cooking foods, when the food temperature is above 60°C, if this method is used, the bag is filled with water vapor, so that a vacuum package close to full vacuum can be obtained.
This method cannot be air-packed.

2. The straw insertion method is as shown in Fig. 13-2. The straw is inserted from the opening of the pouch, the valve 2 is opened, the air is evacuated by the vacuum pump, and the heat sealer is used to seal the straw. If you want to inflate, you can close valve 2 after vacuum, open valve 1 and inflate. There is also a similar method, called breath packaging, the principle is to fill the bag into a bag with a special breathing mouth, and then seal the bag, remove the air inside the bag through the breathing tube, fill with inert gas, and finally Breathing tube sealed.

3. The chamber method is shown in Figure 13-3. There is a vacuum chamber. The entire packaging process is performed in the chamber except filling. The filled packaging bag was placed in the chamber, and then the chamber was closed and the vacuum pump was used to start pumping. After the pumping was completed, the heat sealer was used to seal the container. If it is inflated, it will be filled with inert gas and then sealed after pumping. In order to facilitate the opening of the chamber, it is necessary to fill the chamber with air, and finally open the chamber to take out the package. The chamber method has a low productivity. In order to increase the productivity, a double vacuum chamber may be used to operate in turn, or a multi-position multi-chamber automatic continuous vacuum packaging machine may be used. Chamber method can get a higher degree of vacuum, suitable for packaging high quality products. Modern high-efficiency high-speed vacuum and pneumatic packaging machines use this method.

(4) Design points for vacuum and air packaging In the design of vacuum and air packaging, the following points must be noted:
(1) The first thing to understand is the performance of the packaged items and the main protection requirements. According to the different performance of the product, select the appropriate gas gas, in order to achieve the purpose of inflation, food packaging inflatable species see Table 13-1.
Table 13-1 Variety of Food Inflatables and Functions