Research on gas fresh-keeping packaging technology

Research on gas fresh-keeping packaging technology of fruits and vegetables

gas fresh-keeping method is currently considered to be the safest one in fresh food or agricultural products fresh-keeping. 8. Steel bar bending experimental machine is strictly prohibited from setting a fixed one side standing technology method within the working radius of the bending steel bar and the fuselage. This method is also called modified atmosphere preservation method. Modified atmosphere preservation method can be divided into Ca and ma. CA air conditioning refers to the air conditioning of artificial gas to regulate the gas composition, such as the oxygenated packaging of cakes. Ma air conditioning batch natural air conditioning without manual adjustment, also known as spontaneous air conditioning. For example, the breathing of fruits and vegetables in plastic bags can realize the automatic adjustment of the air composition in the bag

gas packaging or modified atmosphere preservation is a method to extend the preservation period of products by adjusting and controlling the environment or the gas composition in the packaging. That is to change the composition ratio of normal air in the storage room or packaging, so as to reduce the respiratory intensity of fresh food, inhibit the growth and reproduction of microorganisms, slow down the speed of chemical changes in food, and finally extend its fresh-keeping period

gas preservation can fill different gases or a variety of mixed gases into the storage or packaging environment according to the physiological characteristics of different foods or fresh agricultural products, so as to significantly reduce their respiratory intensity and reduce their self consumption, inhibit the ethylene production rate that promotes the aging of fresh fruits and vegetables and other products, and reduce the occurrence of diseases. At the same time, it inhibits the changes of its internal physiological functions and chemical components

any gas will affect the life of fresh food or related products. There are many kinds of gases in the air, but there are mainly three kinds of gases, namely 21% oxygen, 78% nitrogen and 0.03% carbon dioxide. It is the existence of several different proportions of gases in the region that makes the life on earth survive. The use of mixed gas as modified atmosphere packaging or gas preservation should consider the following issues:

I. reasonable selection of gas and its mixing ratio

the gases commonly used for preservation are: nitrogen, carbon oxide, carbon dioxide, oxygen, sulfur dioxide, ozone and other gases. For fresh food, some only need a single gas to achieve fresh-keeping, while others need two or more gases to be mixed in a reasonable proportion to achieve fresh-keeping

second, the fresh-keeping effect of different gases

nitrogen is an odorless, odorless, insoluble inert gas. Replacing the air in the packaging bag with nitrogen can effectively prevent the oxidation of pigments, Oils and fats in the packaging bag. Because nitrogen has the advantage of not producing peculiar smell to food, nitrogen or the mixture of nitrogen and other gases are preferred in most modified atmosphere packaging

carbon dioxide has a strong inhibitory effect on the growth and reproduction of most aerobic bacteria and molds. Sulfur dioxide has good bacteriostasis, sterilization, insect prevention and mold prevention effects, and can slow down the respiration and metabolism of fresh fruits and vegetables. It is often used for fresh keeping of fruits and vegetables

oxygen is the main factor of food deterioration. However, fresh meat, fish, shellfish, etc. need a certain amount of oxygen to maintain their color, so a certain proportion of oxygen is also needed in the food packaging of fish, vegetables, meat and other food that needs color protection

in modified atmosphere packaging, gas mixed by two or more gases is often used to fill the packaging to achieve a modified gas environment, such as carbon dioxide and nitrogen. The proportion of mixed gas should be selected according to the different characteristics of different foods, and the best mixing proportion should be obtained through experiments and practices. It should be noted that the aerated gas used for food preservation packaging should have strict standards. For example, nitrogen and carbon dioxide are not all self connected to the aerated gas used for food preservation packaging, because these gases can contain many impurities harmful to human body. Therefore, the gas used in the inflatable packaging of food should be strictly limited, and the gas that meets the food grade standard can be used in inflatable packaging

the biological characteristics of ozone (O3) are strong oxidation and disinfection effect, which can kill bacteria and yeasts in the air, and also inhibit the growth of pathogenic microbubbles on the surface of fruit and vegetable agricultural products. But it has no penetrating effect and selective specificity. Some people believe that ozone can inhibit the enzyme activity and the formation of ethylene, reduce the release rate of ethylene, and oxidize the ethylene in the storage environment to reduce the unstable conflict activity, so as to delay the aging of fruit and vegetable products and reduce the decay rate. The effect of ozone on Postharvest Physiology of fruits and vegetables remains to be studied

III. factors affecting the effect of gas preservation

proportion of mixed gas

different gas proportions are required for gas preservation of different foods. For example, the mixture of carbon dioxide and nitrogen is enough for the packaging of fish, while the mixture of carbon dioxide, nitrogen and oxygen is suitable for the fresh-keeping packaging of fruits and vegetables

gas barrier of plastic packaging materials

the barrier of this seat has two meanings. First, the external oxygen is blocked, making the packaged food free from oxidation; Second, the gas in the packaging bag can escape. For example, when packaging fruits and vegetables for consumption, it is necessary to meet the requirements of breathing until it is broken

effect of storage temperature on gas preservation effect

regardless of the gas preservation of any food, low-temperature storage can achieve a long shelf life. When the storage temperature is high, the bacteriostatic effect of gas filling will be greatly reduced. Foreign countries generally require the storage temperature of gas preservation food to be about 0 ~ 5 ℃

impact of food hygiene indicators on shelf life

if the hygiene condition of food before packaging has exceeded the standard, and its bacterial reproduction rate has reached a stable level, then filling gas will be difficult to inhibit the growth of bacteria, but will lead to food corruption and deterioration

IV. related problems

air pressure and sealing

at present, gas preservation uses gas generators or existing gas filled packaging or containers. This method will increase the volume of the package or generate a certain amount of air pressure in the package, so it is required to be highly sealed. Once the air is exposed, the fresh-keeping effect will be lost

have selectivity for fresh-keeping food

generally processed food does not need to be stored at low temperature, but for fruit and vegetable food, it must be combined with low temperature to achieve fresh-keeping effect. This is also the problem of gas promoting the freshness of fresh fruits and vegetables

seek new methods of gas preservation

seek to use two kinds of chemical substances to be directly sealed in the package, and the food in the package will produce some ingredients (such as water), so that the chemical substances react to produce fresh-keeping gas to achieve fresh-keeping, which will bring great convenience to the packaging operation. This is still a technology to be studied for gas preservation

the problem of packaging speed

generally speaking, gas preservation can be called a green packaging technology, which has a bright future, but improving the packaging speed and convenience is a problem that needs to be studied and solved

it's like a collision waiting for further research

the fresh-keeping effect of various gases needs to be studied. At present, there are still many gases whose fresh-keeping effect has not been studied and applied. (end)