How to strengthen dairy product packaging?

Dairy products are rich in nutrients and easy to be digested and absorbed by the human body. It is an ideal food. With the improvement of people's living standards and the deepening of their understanding of dairy products, the consumption of dairy products is increasing day by day. Dairy products are no longer special food for infants and patients and have become a kind of daily food in people's diet. Especially in recent years, with the development of science and technology, the types of dairy products have gradually increased, the shelf life is longer, and they are more convenient to carry or drink, and they are deeply loved by the public.

There are many types of dairy products, different properties and different compositional components, so the packaging requirements are different. The purpose of dairy packaging is to select suitable packaging materials according to the requirements of different types of dairy products, to extend the period of preservation of dairy products, ensure the quality of dairy products, and at the same time be conducive to storage and transportation, which will facilitate sales.

In the past few decades, due to the limitation of living standards and technical conditions, raw milk consumption has occupied a large share of dairy products. The packaging operation of raw milk is simple. After the milk has been filtered and disinfected, it is put into a glass bottle and sealed with a metal lid or filled with a plastic bottle. Some products are also packed in polyethylene plastic film bags. Since the raw milk is very difficult to preserve and can easily degenerate, the circulation and sale time does not exceed one day at most, and it is sold in the form of market retail or home reservations.

The raw milk after the acceptance of the sterilized milk must be purified in order to remove the mechanical impurities in the milk and reduce the amount of microorganisms, which can be filtered or centrifuged. The purified raw milk is heat-sterilized in three forms: low-temperature long-time sterilization, high-temperature short-time sterilization, and ultra-high-temperature instantaneous sterilization. At present, most manufacturers use a plate heat exchanger ultra-high temperature instantaneous sterilization method to sterilize the raw milk, and almost no microorganism survives the sterilized fresh milk.

The packaging of sterilized milk is critical and is one of the most important aspects affecting the length of its shelf life. With the development of the age, the packaging of disinfected milk has gone through several different stages, from the initial packaging of glass bottles and single-layer polyethylene plastic film bags to the use of three-layer composite packaging film or carton packaging, which is currently popular. Packaging boxes made of multilayer composites are packed in sterile jars of sterilised milk.

The single-layer polyethylene plastic film has great air permeability, and it can only be stored for 1 to 2 days when it is stored under 10°C, and can only be stored for several hours at higher temperatures; it is made of two layers of polyethylene material. A composite container (one of which is formed by adding a black pigment to form a light-shielding layer) is used to package milk and can be stored for 3 to 4 days below 10° C., but it cannot be stored at room temperature.

Low-pressure polyethylene blown hollow containers for packaging liquid milk have the advantages of convenience, light weight, low cost, good impact resistance, shatterproof, leak-proof, lid reopenable and recyclable, and the bottle itself can be recycled and used. .

In addition to polyethylene, milk packaging containers made of polystyrene have recently developed. A new milk package consists of three layers of polystyrene, the middle layer is foamed polystyrene, and both sides are covered with the same kind of non-expanded polystyrene. Because the middle layer of styrofoam is filled with air, this packaging structure has excellent thermal insulation properties. In addition, the middle layer can also increase the strength and rigidity of the material, and it also minimizes raw materials. Since the surface of polystyrene is white and smooth, it is possible to carry out color printing of fine patterns.

Foreign countries are mainly used for packaging and disinfecting milk in three-layer composite carton (polyethylene/paper/polyethylene) and paper-pressure polyethylene blown hollow container. The former is used for half-pound small packaging, and later mainly

For large packaging. At present, China has used "house-shaped" paper packaging boxes to package disinfected milk, and the fresh-keeping period can reach 10 days.

The above packaging methods have their own characteristics, but they are generally only suitable for low-temperature storage below 10°C, and the production of milk has obvious regional and seasonal conditions. During the high tide of dairy production in pastoral areas in summer, a large amount of fresh milk cannot be packed and shipped. It is impossible to store so many cold storages. Except for a part of milk powder, a large part of it is wasted due to deterioration and waste of resources. Therefore, it is very necessary to explore the method of normal temperature preservation of milk.

To solve the problem of normal temperature storage of milk, in addition to using packaging materials with good barrier properties and strong light-shielding properties, the key is to reduce or avoid secondary pollution of milk during packaging. The emergence of aseptic filling technology has solved this problem. After the milk is sterilized by the ultra-high temperature instantaneous sterilizer, the aseptic filling machine is filled directly through the pipe, and the entire process is carried out in a sealed state. Aseptically filled, sterilized milk is packaged in bags (boxes) made of multi-layered composite materials consisting of PE/PE/AL/PE/paper/PE, PE/ET/AL/PE/paper. /PE. The use of this packaging material in conjunction with an automatic filling machine, completed on the filling line, can reduce the chance of contamination. Therefore, aseptically filled sterilized milk can be stored at room temperature for six months to one year.

There are many types of milk powdered milk powder, which vary depending on the composition of raw materials, processing methods, and excipients and additives. There are mainly whole milk powder, skimmed milk powder, whey powder, prepared cheese, and specially formulated milk powder. Progress in science and technology, there have been various types of milk powder, such as instant milk powder, cream powder, ice cream powder, buttermilk powder, cheese powder, fat-free desalination whey powder, fat-removed salt whey powder and malt milk, etc. .

Although there are various types of powdered milk products, their common feature is that the raw milk is dried to produce a powdered product. Milk powder products have the characteristics of reducing product volume, reducing quality, preserving nutrients, being resistant to storage, and being easy to use.

Because milk powder products are rich in protein, fat and other nutrients, such as full-fat milk powder milk fat content of up to about 26%, so susceptible to sunlight, chlorine and other effects and changes. In addition, due to the porous nature of the milk powder particles, the surface area is large, and the moisture absorption is strong. Once damp, it will agglomerate and cause the proliferation of bacteria. When mixed with other items, the airtightness of the package is not good. It is easy to absorb the odor of other objects and affect their own smell. Under the irradiation of ultraviolet rays, milk powder and other products will also be decomposed, so we must pay full attention to the weighing of milk powder products, packaging operations and the types of packaging containers, mainly to prevent moisture, oxidation, to prevent the proliferation of bacteria, to avoid UV Irradiation. Milk powder factory packing room should take air humidity control cooling measures, room temperature is generally controlled at 18 °C ~ 20 °C, the relative humidity of the air is less than 75% is appropriate. Milk powder products that need long-term preservation should be vacuum-packed or nitrogen-filled. Full-fat milk powder is preferably packaged in 500g tin cans and sealed in nitrogen for a period of up to 3 to 5 years.

1. The packaging of milk cans in metal cans is generally packed in vacuum nitrogen-filled packaging. The nitrogen-filled packaging uses semi-automatic or fully automatic vacuum nitrogen-sealing and canning machines. After weighing and filling, vacuum is drawn to eliminate milk powder and cans. The air was then immediately filled with nitrogen with a purity of 99% or more and then sealed. This is one of the best ways to pack whole milk powder. Experiments show that when filled with nitrogen-filled whole milk powder stored at 24 °C, after 9 months of storage, its flavor does not change; without filling with nitrogen filled whole milk powder, after 4 months storage, its flavor Changes will occur and the quality will decline significantly.

2. The plastic bag packaging uses 500g single-layer polyethylene film bag packaging is lower than the bottled cost, low labor intensity, and a certain degree of moisture-proof effect, but has a certain influence on the preservation of dairy products, poor insulation properties, milk powder is easily spoiled Can only meet the needs of short-term storage, and plastic film is brittle and easy to break, easily lead to damage. Using double-layer sandwich paper with a layer of polyethylene film sandwiched with aluminum foil or three-layer composite film bags, and sealing with high-frequency electric welding, light, moisture, and gas penetration can be substantially avoided. Composite film packaging materials are widely used in milk powder packaging. Although the current cost is high, it is one of the promising packaging materials. Currently used three-layer composite materials are: K-coated hard paper / AL / PE, BOPP / AL / PE, paper / PVDC / PE and so on.

3. Large packaging Large packaging products are generally supplied to special users, such as export or food factories for making industrial raw materials such as candy, bread, and ice cream. Canned products have 12.5kg round and square cans. Polyethylene film can be used as an inner bag when bagged, three layers of kraft paper bagging outside, divided into two kinds of 12.5kg and 25kg.