Opacity
In addition to triggering a deterioration reaction in food, light can also cause changes in proteins and amino acids. Vitamin C is more likely to interact with other food ingredients when exposed to light, resulting in a large loss. According to research analysis, the loss of vitamin C in transparent glass bottles of milk is 14 times higher than that of dark bottled milk, light will also cause milk to produce oxidative odor, and nuclide, methionine and other cleavage and loss of nutritional value, the opacity of tinplate cans makes the preservation rate of vitamin C the highest.
Good sealing
The barrier of packaging containers to air and other volatile gases is very important for the preservation of nutrients and sensory qualities. Comparing various juice packaging containers shows that the oxygen transmittance of the container directly affects the browning of fruit juice and the preservation of vitamin C. Metal cans, glass bottles, aluminum foil laminates and cartons with low oxygen transmission rate have better preservation of vitamin C, among which iron cans are the best.
The reducing effect of tin
The tin on the inner wall of tinplate will interact with the oxygen remaining in the container during filling, reducing the chance of oxidation of food ingredients. The reduction effect of tin has a good preservation effect on the flavor and color of light fruits and juices, so the juice cans packed in unpainted iron cans are better nutritious than the juice cans packed in other packaging materials, the brown change is slight, the acceptance of flavor quality is better, and the storage period is extended.
Source
Tinplate canned food, except for a few light-colored fruits and fruit juices, mostly use empty cans painted inside to improve the corrosion resistance of the container; Due to the electrochemical action of metals, painted canned food will have a small amount of iron dissolution in storage, which is present in the form of divalent iron in sealed canned food, which is easily absorbed by the body at a content of about 1 to 10 ppm. In terms of fruit and vegetable products, the raw material itself does not contain much iron, and iron can products can provide 1.75mg of iron per can of 350 ml of beverage can, with an iron content of 5 ppm, which is about one-tenth of the daily intake of 18mg of the human body. If the above fruit and vegetable juice beverage cans are rich in vitamin C, iron is easier to be absorbed, so iron canned food and beverages are a good source of iron, and the significance of providing nutrition for iron canned food is more far-reaching.
Because of these properties, tinplate cans provide a closed system that completely isolates environmental factors in addition to heat, color-avoiding food deteriorates due to light, oxygen, moisture, and does not become lighter due to aroma penetration or odor through pollution and taste, food storage stability is better than other packaging materials, vitamin C has the highest preservation rate, and nutrients are also the best preserved.
