- May 26, 2018 -
Many consumers believe that freshly slaughtered animal foods are fresh, freshly picked plant foods are fresh, and processed and stored canned foods are no longer "fresh." This is true on the basis of the definition of "new", but not entirely true on the basis of "fresh". In fact, some fish, such as tuna, stay fresh while they are alive and lose nutrients quickly when they die. Usual, alive, it's hard to find this kind of food cans factory post-harvest processing into canned immediately, but will catch to the processing cycle is shortened, thus more keep its nutrients. In addition, some fruits are not just picked and eaten best. If pineapple contains strong bromelain, eating immediately will hurt the mucous membrane and gastric mucous membrane on the surface of the tongue, and yellow peach will be more delicious after being "ripe later" for a period of time. When canned, bromelain is deactivated by high temperature sterilization, and a large amount of plant fiber in the flesh is softened to make it more palatable, but there is no reduction in nutrients. The main source of human vitamin intake is food. Vitamins are sensitive to oxidation, light and high temperatures, such as asparagus losing 40 percent of its vitamin C during 24-hour storage and transportation, spinach losing 30 percent, and green beans losing 20 percent. The short time high temperature heat treatment technology used in modern canning food processing technology makes up for this deficiency. Studies show that modern canning foods improve the nutritional value of food, and the loss of vitamins in canning processing is less than family cooking techniques such as frying, frying, cooking and frying. In addition, the materials used to process cans come from the normal growing season, with better nutrition and flavor quality, and less lack of flavor than the fruits and vegetables of the opposite season.
Actually, the reason for canning is quite simple. First, the contents were heated sufficiently to kill all the microbes in them. Meanwhile, the packaging can/bottle/bag shall be fully heated to sterilize. Then put the sterile food into the sterile container. Don't overfill it. After cooling, the air volume in the top slot of the container shrinks, resulting in negative pressure. The sealed bottle cannot be opened, and the bacteria outside cannot enter.
In this way, the microbes inside are killed by the high heat, the microbes outside cannot find their way in, and the food will certainly not rot. If the sterilization is thorough enough and the seal is strong enough, do not say two years, three years will not be bad, there is no need to add any preservative.
You have to heat the food twice to make a can, and you're bound to lose some nutrients. But what's the point of canned nutrition if it's all lost? Since people have been canning for 200 years, people who work in the field also rely on canning to survive, proving that it still contains nutrients.