What is Vacuum Packaging?
Vacuum packaging seems to be just as the name suggests, but in fact, the word "vacuum" is worth discussing, which will help to understand the fresh-keeping technology. Firstly, a misconception must be corrected. Vacuum in physics refers to the physical space where no or no gas molecules and atoms exist. It is a field space where only particles of various energies exist. It is generally used for theoretical research. Practical technology is still unable to pump out all the gases in an environment. In other words, there are still gas molecules in the vacuum package, that is, the vacuum is not empty. Secondly: 1) Vacuum in the actual industrial production application (vacuum packaging machine, vacuum cooler) refers to the gas state less than one atmospheric pressure in a specified space collectively referred to as the vacuum state, which can be understood as a space where the gas is relatively thin. 2) The degree of vacuum is a numerical index used to measure the degree of gas thinning in the vacuum state, usually expressed by the pressure value. 3) In order to classify different vacuum degree values in the vacuum state, the concept of vacuum area is introduced, which is divided into five levels according to a certain pressure value interval and the corresponding pressure value and gas molecule density interval.
To sum up, the essence of vacuum technology is to make the inside of the container in a vacuum environment lower than an atmospheric pressure by means of pumping (exhausting), so it is also called decompression or exhaust packaging technology.
Vacuum Skin Packaging Technology
Nowadays, the application of traditional vacuum packaging technology in the field of fresh food has been fully popularized and accepted by consumers, so the product form presented in the sales process will not be repeated. However, another form of vacuum packaging - vacuum skin packaging technology has attracted more attention from consumers.
Vacuum Skin Packaging——vacuum skin packaging: The key to the forming of this technology lies in the performance of the packaging film (such as thermoforming stretchability, puncture resistance, etc.), and it also has extremely high requirements for the vacuum degree of the vacuum pump in the machine. The process flow is shown in the figure below. Firstly, thermoform the bottom film into a box or use a prefabricated box and complete the fresh filling inside; secondly, realize the skin-fitting process. Cover the top of the box with fresh food and enter the sealing mold. After the top film is heated and softened, the cavity between the film and the bottom box is vacuumed. At this time, the top film is due to the pressure difference between the upper and lower sides It moves downward and gradually adheres to the fresh product to adapt to its shape, and then adheres to the surface of the bottom box by relying on the colloid in the molten state on the surface of the body-fitting film; again, the punching process is carried out to complete waste recycling, and the packaging form at the time of sale is obtained. Regardless of traditional vacuum or vacuum body-fitting technology, based on the above correct understanding of vacuum, you can see its true face in fresh-keeping.
How to keep fresh in vacuum packaging?
Compared with modified atmosphere preservation, the principle of vacuum preservation is relatively simple: no longer control the gas composition and concentration inside the packaging container, only the gas in the container is pumped out to reach the preset vacuum degree, and the interior is maintained at a high decompression state. Reduce the oxygen content to inhibit the growth and reproduction of microorganisms (mainly including bacteria, molds, yeasts, etc.), so as to extend the effective shelf life of fresh food inside. Generally speaking, when the internal oxygen concentration is less than 1%, the growth and reproduction speed of microorganisms show a sharp decline; however, it must also be admitted that this technology alone is by no means foolproof, for example, the vacuum environment cannot inhibit the growth of anaerobic bacteria Therefore, according to the characteristics of the food, it is necessary to combine it with auxiliary methods such as refrigeration (freezing), high-temperature sterilization, and pickling, which is the way to keep fresh.
The causes of corruption and deterioration are divided into three categories: biology, chemistry, and physics. The main factors are as follows:
1) The reproduction of microorganisms causes changes in fresh food quality;
2) Oxygen in the environment causes food oxidative rancidity, especially free unsaturated fatty acids in oils are more likely to be oxidized;
3) The role of oxidase, peroxidase, amylase, protease, etc. in fresh food promotes the metabolism of food to produce water vapor, carbon dioxide, and heat, resulting in deterioration;
4) Direct or indirect contact pollution with insects' infestation, reproduction, harmful substances, etc.;
5) Improper storage temperature;
6) Physical coercion or abuse.
Among the many reasons, the adverse effects and effects of microorganisms are the most significant, not only to the fresh food itself but also to the damage to those who eat it by mistake.
Post time: Sep-09-2022
