Plastic cups, plastic bags, plastic shoes, plastic chairs, plastic plates, etc., these plastic products surround every corner of our side and plastic packaging is closely related to our lives. Whether you like it or not, plastic packaging has become an indispensable ingredient in the food system.
China is a big country in the world of packaging manufacturing and consumption. The proportion of plastic packaging in the total output value of the packaging industry has exceeded 30%, which has become a vital force in the packaging industry. It plays an irreplaceable role in the fields of food, beverage, and daily necessities. For us to bring convenience, many plastic packaging allows us to eat while walking, or to taste the easily degraded cookies and the other side of the earth to keep fresh fish, behind them are hidden a lot of scientific principles and inventions.
Aaron Brody is a food packaging consultant and associate professor of food science at the University of Georgia. According to him, the plastic revolution in food packaging began in the 1960s because plastic is used because it is lighter than glass. Strong and cheaper.
The bags we contact are made up of different types of food packaging plastics. Plastics can be divided into two categories according to their own properties: a thermoplastic which can be repeatedly subjected to melt molding processing to substantially maintain its characteristics, and a thermosetting plastic which can be melt-molded only once. According to its use, it can be divided into general-purpose plastics with wide surface area, low price and good comprehensive performance, such as PE, PP, PVC, PS, and amine-based plastics. It has good physical and mechanical strength and may be used instead of metal on construction machinery. Engineering plastics such as: ABS, nylon, polyester, POM, TPX-1, etc.
Potato chip bag
In the case of a potato chip bag, its main ingredient is a plastic called “oriented polypropylene.” Brody explained: “It is a moisture barrier on the top. "In the packaging of potato chips, moisture protection is very important," because the potato chips will absorb water vapor and will begin to deteriorate. The wet potato chips won't be liked. For further reinforcement, many potato chip bags also have a thin layer of aluminum on the inner layer.
The product name and nutritional information are printed on the outer layer, and a layer of polyethylene (the material used to make the plastic shopping bag) is placed between the inner and outer layers. Brody also revealed that most companies inject nitrogen into the bag before it is sealed. "This will prevent the potato chips from crushing." Oxygen will oxidize the fat in the potato chips, producing a strange smell, while nitrogen does not cause any chemical reaction that destroys the taste.
Brody also said that food companies often spend a lot of time designing packaging in order to preserve every product they sell. This is also the practice of the team. In a previous report, Lu used a package to extend the shelf life of the sandwich to two years (more reading: sandwiches for two years, tastes good).
Like the potato chip bags, ready-to-eat vegetable salad bags are also made from poly, and a pack of nitrogen is also injected. Unlike potato chips, salad leaves need to breathe a little oxygen, which is why there are small holes in the salad bag. Brody pointed out: "The small holes allow oxygen to enter and the carbon dioxide can be discharged."
He added that the interior of these bags often has a thin layer of anti-fog, "so that condensation will not occur, and consumers will see beautiful green leaves."
When making many plastic packages, manufacturers are not only worried about how to isolate the air, but also how to keep the water vapor. For example, Brody said, this is very important in the packaging of ice cream. A bucket of ice cream must be easy to open and close, but it must also have a tight seal that locks in moisture to maintain a smooth mouthfeel.
When stored in a refrigerator, sublimation sometimes occurs, that is, the phenomenon that water directly changes from a solid to a gaseous state. “If the water of sublimation is lost, it cannot be recovered, and if the ice cream loses moisture, it will sand and agglomerate.” He also pointed out that this is the reason why a layer of polyethylene is added to the paper bucket containing ice cream. The advanced ice cream bucket is made of thick and strong material.
Of course, as food expert Herbert Stone said, even after various research and development, most plastic packaging still can't preserve food in extreme environments. Stone is a food industry consultant and a predecessor to the Food Technicians Society. He pointed out: "Food companies must ensure that they do not change the taste of food when using plastic containers." Plastics are not an inert material that reacts with other chemicals. And unlike many glass or metal products, it also allows air to pass through.
Have you ever put a plastic water bottle in a hot car for too long? It is mostly strange to drink it. But the reason is different from what you think: this is not because the chemicals in the plastic have penetrated into the water.
Stone explained that a small amount of air can penetrate the plastic, and when the temperature rises, the movement of the air will also speed up. Heat also accelerates the chemical reaction. When the chemicals in the bottle react with each other or react with substances in the external environment, the water in the bottle will smell strange. Leave a bottle of soda in the hot car and the carbonic acid will quickly escape from the bottle. "The rest is the soda that has no bubbles." Stone said, "Plastic is really convenient, but it is not."
In addition to technical limitations, all of the plastic packaging we use today produces a lot of trash. In 2012 alone, the United States produced 14 million tons of plastic waste that used to be bags and containers. Plastics cannot be easily biodegraded, so they sometimes enter the ocean, which not only harms the creatures in the sea, but also pollutes the seafood.
Although many types of plastics are already recyclable, bright packaging containing multiple layers of plastic is difficult to recycle because different types of plastic are treated separately in the recycling station. But Stone revealed that we are also increasingly good at making plastics that are both easy to use and environmentally friendly. We are even trying to convert waste products like whey protein into plastic.
The plastic packaging market is gradually on the right track, and the development prospects are expected to be broad. As a part of the plastic application field, its development speed has grown stronger than other packaging materials such as cardboard and metal. As an industry with good development prospects, the plastic packaging market should be valued. For the plastic packaging market, banks should lower their thresholds and support them in a timely manner, so that the plastic packaging market has more open prospects.