nitrogen, with the chemical formula of N2, is usually a colorless and tasteless gas, and generally nitrogen has a lower density than air. Nitrogen accounts for 78.08% (volume fraction) of the total atmosphere and is one of the main components of air. When cooled to – 209.8 ℃, the nitrogen turns into a colorless liquid under the atmospheric pressure of – 209.8 ℃. Nitrogen is chemically inactive and difficult to react with other substances at room temperature, so it is often used to make preservatives. However, under the condition of high temperature and high energy, it can change chemically with some substances to make new substances useful to human beings
because the three bond energy of nitrogen molecule is very large and is not easy to be destroyed, its chemical properties are very stable. Only under the conditions of high temperature and high pressure and the presence of catalyst, nitrogen can react with hydrogen to produce ammonia. At the same time, because the chemical structure of nitrogen molecule is relatively stable, the structure of cyanide ion CN – and C22 – in calcium carbide CaC2 is similar to that of nitrogen molecule
Yes. Because two nitrogen atoms in nitrogen form a nitrogen nitrogen triple bond with very large bond energy, it requires a lot of energy to overcome the nitrogen triple bond if nitrogen wants to have a chemical reaction under normal conditions. Therefore, the chemical properties of nitrogen are very stable and can be applied to modified atmosphere preservation technology
modified atmosphere storage technology refers to the technology of using inert bacteriostatic gases such as nitrogen and carbon dioxide to inhibit bacterial growth and reproduction, so as to delay the metabolic process of storage cells, so as to maintain freshness. Compared with other technologies such as temperature control, water removal, food preservative addition and ionizing irradiation, this method of food preservation has many advantages:
1 The use of inert gas to isolate the air can directly inhibit the growth and reproduction of bacteria, delay the metabolic process of food cells, and effectively prolong the preservation time
2. The temperature of the food fresh-keeping with nitrogen will not change and the moisture will not be lost, which maintains the original nutrition, texture, color and taste of the food to a great extent
3. Nitrogen preservation without preservatives, no acidification, no temperature change, no radiation, safety, environmental protection and no pollution
4. Nitrogen preservation technology is simple and feasible, with low operation cost and remarkable economic benefits
5. The inflatable packaged food is very convenient to transport, and it can also prevent extrusion and avoid food crushing and bonding, so as to maintain the appearance and shape of the food.
all foods can be kept fresh with nitrogen. Different foods have different preservation effects. Preservation principle: it blocks the oxidation reaction between food and oxygen, but it will also promote the reproduction of anaerobic bacteria
factors affecting the fresh-keeping effect of nitrogen:
1. Replacement rate. The higher the replacement ratio of packaging air into nitrogen, the better.
2. Purity. The higher the concentration of nitrogen itself, the better.
3. The lower the air permeability of packaging material, the better.
however, it is not enough for some foods to be directly filled with nitrogen, such as fruits, vegetables, raw meat, halogen products, seafood, etc. These foods need oxygen, carbon dioxide, nitrogen and other gases, The best fresh-keeping effect can be achieved by mixing a certain proportion of high-precision fresh-keeping gas with refrigeration. Filling only nitrogen is far from the desired fresh-keeping effect.