Introduction:
However, for fresh fruits and vegetables, vacuum packaging may cause them to be squeezed and deformed, which also has a certain impact on the taste, and living in a "small house" full of special gases will not cause similar problems.
"Black technology" in fruit and vegetable preservation.
When the sun is hot, many people like to take fresh fruits and vegetables for a meal when they have no appetite. Fortunately, there is a fresh food e-commerce home delivery service, so that we do not have to go out against the scorching sun. However, have you ever wondered that fresh fruits and vegetables are not as frozen as meat, and how do merchants keep them fresh in hot weather?
To understand the preservation of fruits and vegetables, we must first understand why fruits and vegetables deteriorate and spoil.
The first reason lies in the fruits and vegetables themselves. After picking, the fruits and vegetables do not end their lives, but continue to breathe. During respiration, fruits and vegetables produce ethylene, a gas that has a ripening effect. I believe that everyone has such experience, the kiwi fruit that I just bought home is very hard, and it will become soft and sweeter when left at room temperature for a few days, which is the credit of ethylene. However, if ethylene is continuously released, fruits and vegetables will be "overcooked" or even spoiled. Especially in summer, the respiration of fruits and vegetables will be more vigorous, producing a large number of "ripening agents", which is why in summer, if fruits and vegetables are not put into the refrigerator in time, it will be very easy to spoil.
Preservation for long time:
Another common cause of spoilage comes from external microorganisms, such as various bacteria and molds. Their effect is independent of the ripeness of the fruit and vegetables, even fresh fruits and vegetables, they can make them taste and spoil.
In order to retain that mouthful of freshness, people have designed various preservation methods for the reasons for the spoilage of fruits and vegetables.
Method of freshness preservation:
The most common method of freshness preservation is low temperature refrigeration. When we receive fresh goods, we often see ice packs, in fact, these ice packs are not ice cubes, but a special cold storage material, colorless transparent gel, the cold capacity of this material is several times that of ice cubes, the cooling speed is slow, and can be used repeatedly. Before use, it needs to be frozen in the refrigerator in advance, and after freezing, it can be put together with the goods to achieve the effect of freshness.
Another way to preserve freshness is to solve the ethylene gas released by fruits and vegetables. This is divided into two methods: physical and chemical. The physical method is to absorb ethylene gas through some special preservation equipment, which usually place some active substances with high adsorption to ethylene, such as activated carbon, minerals, etc. The chemical method is also similar, except that the adsorbed substance is replaced with other substances that can react with ethylene or weaken the ripening effect of ethylene on fruits and vegetables. The advantage of these methods is that they do not have any effect on the fruits and vegetables themselves, but only on the gases they emit.
Latest technology for preservation:
Recently, a very interesting preservation technology has emerged, which customizes a "small house" containing special gas for fruits and vegetables that need to be preserved, so that fruits and vegetables can sleep in it at ease, and use the dormant state to reduce respiration. This technology is called modified atmosphere preservation, that is, artificially adjusting the gas composition around fruits and vegetables, mainly by reducing oxygen content, increasing the content of carbon dioxide, nitrogen and other gases, and inhibiting respiration and oxidation under the premise of ensuring the vitality of fruits and vegetables. The familiar vacuum packaging is actually a modified atmosphere preservation technology. However, for fresh fruits and vegetables, vacuum packaging may cause them to be squeezed and deformed, which also has a certain impact on the taste, and living in a "small house" full of special gases will not cause similar problems.
For the preservation problem caused by microorganisms, chemical preservatives are often used in the past, that is, we often call preservatives, its main role is bacteriostasis, which can inhibit the activity of microorganisms by steaming, spraying or soaking chemical agents.
Chemical preservatives, while effective, are not safe enough, and a newer preservation tool is becoming increasingly popular today – bio preservatives. This method uses natural substances with bacteriostatic functions, which is safe and convenient. It mainly uses the anti-antagonism of beneficial microorganisms to fight harmful microorganisms, such as lactic acid bacteria have an inhibitory effect on a variety of pathogenic bacteria, and many foreign companies are studying the application of lactic acid bacteria in the field of preservation.
Blue LEDs can also be used for fruit and vegetable preservation.
In addition, there is a "light preservation" technology, through the use of light combined with nutrient solution, fruits and vegetables can continue to grow slowly after being picked, on the one hand to ensure freshness, on the other hand will not grow too fast and become old. Remember the blue LED that won the 2014 Nobel Prize in Physics? The researchers found that it can kill Listeria, E. coli and Salmonella, and are further studying its application in the field of freshness. There are also some light technologies that can not only keep fresh, but even change the taste and nutritional content of plants, which is really a boon for foodies!
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