There is much food that wraps with food packaging (as shown below) once we step into the market. Although we are not familiar with flexible packaging, it often appears in our life. Flexible packaging has many different functions, one of the functions is heat tolerance. The flexible packaging that can tolerate heat is called a high-temperature retort pouch. The definition of a high-temperature retort pouch is through the high temperature sterilization (121℃-135℃) inside the retort pouch, this process can prolong the food durability period and keep the original flavor of the food. Let the customers can enjoy the food within the durability period. Next, we’re going to introduce what is the high-temperature retort pouch.

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The origin of high-temperature retort pouch

Starting from ancient times, people keep thinking about how to make meat products have a longer durability period. Until modern times, there are two normal ways to preserve the meat, which are high temperature and autoclave sterilization and pasteurization. High temperature and autoclave sterilization have a longer durability period because it would kill all the viruses during the process, including the virus that causes the food easily to rot. The food with high-temperature sterilization can preserve with resistant packaging, and it can prolong the food durability period. The transportation and usage would be much more convenient and meet the customers’ needs. These advantages are the origin of a high-temperature retort pouch. Responding to the relative needs of food industries, packaging industries started to involve and introduce the relative products of high-temperature retort pouches.

Developmental history

Before the high-temperature product appears, people used cans and glass bottles made with SPTE as food packaging to store food. Because these two materials have high-temperature tolerance and high resistance, the food durability period can be almost two years. The disadvantages are that SPTE has bad chemicals and corrosion resistance, it would affect the food flavor when we put sour food in it. Plus, the can itself is a hard packaging, the volume is too big to carry. As the result, this kind of hard packaging is only used in specific kinds of food. In the 60s, the U.S developed the aluminum-plastic composite film to solve the food packaging problem of outer space. The food wrapped with aluminum-plastic composite film through high-temperature sterilization can be stored at normal temperature, and the food durability period can be one year. The function of the aluminum-plastic composite film is similar to cans, so it can also be called a flex can.
 

The advantages of high-temperature retort pouch

1. Keep the original flavor of food
The retort pouch is thinner, so it can reach to high temperature in a short time and has the effect of sterilization to keep the original flavor of food.

2. Easy usage of food packaging
During the eating, you can eat the food as long as you put the retort pouch in the hot water or microwave oven to heat the food. It’s easy to use for customers.

3. It can save energy during the process of high-temperature sterilization
Because the retort pouch is thinner than cans, it can heat to sterilization temperature in a short time. The total energy waste is less than 30-40% than cans.

4. Easy to sell to customers
The retort pouch can pack based on the food category, the top layer can be color-printing. Plus, the packaging is light and convenient, easy to attract customers to buy the products.

5. Long food durability period
Because the food has the process of high-temperature sterilization, this process can prolong the food durability period. No need to freeze the food that is in the retort pouch.

The category of retort pouch transparence

The retort pouch can be divided into a transparent retort pouch and aluminum foil retort pouch (non-transparent retort pouch), and a transparent retort pouch can be divided into a transparent resistant retort pouch and transparent non-resistant retort pouch. A transparent retort pouch has three constructions, such as PET, BOPA, and CPP lamination or PET, PET, and CPP lamination. This kind of laminating material normally tolerant heat to 135℃, usually are the packaging of sauces or meat products. Besides these three laminating materials, these also have the method of coating a layer of PVDC on PET or NY. The heat tolerance is below 121℃ and has great resistance to gas and moisture. As for the transparent non-resistant retort pouch, it usually is the double layer of the construction, such as PET (BOPA) laminates with CPP. The heat tolerance is below 135℃, usually used in normal food packaging like dried tofu.
 

The characteristic of retort pouch substrate

1. PET
It has great printing function, high mechanical strength, and great stiffness. Also have better resistance to moisture, gas, heat, and cold. The disadvantage is the ability of puncture-resistant is bad.

2. AL
It has the advantage of preserving the flavor of food because the resistance of gas and moisture is good. Also, have a strong protecting function, it can make the packaging item away from the invading of virus and mold.

3. BOPA(Nylon or NY)
Has higher resistance to normal gas and smell, and has the advantage of puncture resistance, abrasion resistance, and a wide range of usage temperature (-60℃-150℃). The disadvantage is the bad resistance to moisture. Once it gets moisture, the resistance function would drop dramatically.

4. CPP
Because the CPP is the inner material of the retort pouch, it has high demand of this material and needs to reach the level of high-temperature retort pouch. It requests to have good flatness, tensile strength, heat seal strength, and impact strength. The only disadvantage is don’t have the ability of resisting freeze.

PUA(Polyurethane Adhesive for Flexible Packaging Lamination)

Coating P Materials provides PUA (Polyurethane Adhesive for Flexible Packaging Lamination) can tolerant heat to 135℃. There are two kinds of adhesives, which are solvent-free type and general type.

1. Solvent-free type (More product information)
The solvent-free adhesive is eco-friendly adhesive. During the process, there is no VOCs emission. At the same time, the advantages are the low cost, complex velocity fast, automation degree high, and low energy cost. (Chart 2/Coating PUA high-temperature solvent-free type product characteristic)

2. General type (More product information)
The general type adhesive has the advantages of transparency, flexibility, and heat resistant. It has higher initial adhesion, and possesses higher peel strength for aluminum-plastic packaging products.
  (Chart 3/Coating PUA high-temperature general type product information)
  (Chart 4/Coating PUA high-temperature general type product characteristic)

In the food packaging history, food packaging provides many conveniences to people. A high-temperature retort pouch has many advantages, including ease to carry and a long durability period. Coating P. Materials provides PUA (Polyurethane Adhesive for Flexible Packaging Lamination) with good chemical resistance and heat resistance. It can be used in print aluminum high-temperature sterilization. If you want to know more about product information, welcome to contact us.​。
 
Referances：
1. 百度百科-高溫蒸煮袋。檢自https://baike.baidu.com/item/%E9%AB%98%E6%B8%A9%E8%92%B8%E7%85%AE%E8%A2%8B/10949057
2. 中文百科-蒸煮袋。檢自https://www.newton.com.tw/wiki/%E8%92%B8%E7%85%AE%E8%A2%8B