Recently, some media interviewed the following questions:
How do some imported instant noodles have a shelf life of up to 12 months? Why are domestic preservative-free instant noodles marked with a shelf life of 6 months?
Similarly, the shelf life of domestic boxed pure milk is 6 months, and imported milk is 12 months. Why is it so long? There are also many foods with a shelf life of at least 12 months. Is this kind of thing worth buying?
Actually, what’s wrong with the longer shelf life of food?
The transportation time is abundant, the sales range is large, and the manufacturer is happy; the risk of selling is small, and the merchant is happy; there is peace of mind at home, and the consumer is also happy. Especially when stockpiling during the epidemic, who wants food to expire at home?
However, when it comes to food that doesn’t go bad for a year or two, there are always people who worry: can it really last that long? Why isn’t it always bad?
People worry about the shelf life of food because they are worried that the food will spoil before the shelf life, or the quality of the food will deteriorate.
The most common reasons for food spoilage are two: one is spoilage caused by microbial activity, and the other is spoilage caused by chemical reactions such as fat oxidation.
First, let’s talk about spoilage caused by microorganisms.
After the microorganisms multiply, there may be three problems:
First, it will produce various enzymes, which will change the smell and taste of food, and lose its edible value. After a long time, the daily food becomes rancid, sour, and smelly. This is the result.
The second is that some pathogenic microorganisms proliferate, which may cause bacterial or viral food poisoning. For example, if someone eats food that does not seem to have a noticeable change in taste, but suffers from loss of appetite, vomiting, diarrhea, abdominal bloating or cramps, or even weakness, fever, etc., there is a high probability that this type of food poisoning has occurred.
Third, the activities of pathogenic microorganisms produce various toxins, which may cause acute or chronic poisoning. For example, “eating sour soup caused the whole family to die”, “eating foamed fungus and entering the ICU”, “eating leftover noodles and entering the ICU”, “the life is dying after eating homemade tempeh”, etc., are mostly caused by toxins produced by microorganisms. .
The easiest way to control microbes is to deprive them of the water they need to function. Or make the food extra dry; or add a lot of sugar and salt to the food, and let the salt and sugar rob the microorganisms of the water they need for activity.
Of course, there are other methods, such as adding a lot of alcohol to the food, or adding preservatives to help inhibit the activity of microorganisms; or placing the food in the freezer and letting the low temperature inhibit the Microbial proliferation.
Instant noodles are very dry, and microorganisms cannot proliferate in large quantities. Therefore, as long as the instant noodles are not damp, there is no need to worry about food safety problems caused by microorganisms.
However, why do instant noodles have to be marked with an expiration date? Since microorganisms can’t reproduce, they can always be preserved, so why should the shelf life of 6 months be marked?
This is because, there is a second cause of food spoilage, and that is chemical reactions that are detrimental to food quality, such as the most common fat oxidation response.
Here we focus on fat oxidation.
As long as natural fats are placed in the presence of oxygen, oxidation reactions will occur automatically. It’s called “auto-oxidation” and it lives up to its name.
Autoxidation reactions are initiated by free radicals. Due to the effects of light, heat, rays, singlet oxygen, metal catalysts, etc., a very small number of unsaturated fatty acid molecules become restless, and they remove hydrogen atoms and become free radicals.
These free radicals are like the new coronavirus. Although the amount is very small, they are highly “infectious” and will make those healthy fatty acids “infected” and become free radicals. Then, slowly, “community spread” began, until a large area of fatty acids fell, and the spark became a prairie prairie, as we have seen in South Korea and Hong Kong.
Fatty acids captured by free radicals will absorb oxygen atoms and become “hydroperoxides”. When it accumulates to a certain extent, it will break down to produce some small molecules with unpleasant odors. Then we feel that the food “smells”. As the saying goes, “hala flavor”, “oil consumption flavor”, “artemisia flavor”, “old oil flavor”, etc., all refer to the taste produced by fat oxidation.
When this taste is evident, the food is unfit for consumption.
Oxidatively spoiled food not only tastes bad, but also contains many substances that are prone to free radicals, as well as toxic and harmful oxidative decomposition products. At the same time, most of the vitamin E and essential fatty acids that are useful to the human body will be lost.
Eating into the body, they also contribute to disease and aging in the body.
It can be said that after oxidative deterioration, food loses its health value. If you are not extremely hungry and need a little calories to survive, don’t eat these spoiled foods.
Instant noodles, cookies, potato chips, fried foods, peanuts, melon seeds and nuts, cooking oil and sesame paste… As long as it is a food containing fat, it may be captured by the “virus” of fat auto-oxidation, and then go bad.
Unfortunately, fat auto-oxidation is an intractable problem. Drying or freezing doesn’t stop it completely, it only slows its progress.
If you want to keep it longer, you have to think of various ways to delay the automatic oxidation of fat.
How to extend the shelf life of fatty foods?
On the one hand, choose fats that are less prone to oxidation. In general, saturated fatty acids are less prone to oxidation, and the higher the degree of unsaturation, the easier it is to oxidize.
For example, linseed oil has a particularly high degree of unsaturation, and it is easily oxidized and more easily oxidized when heated. This is the reason why it is not recommended to use it for cooking and stir-frying. In contrast, coconut oil, palm oil, cocoa butter, etc. are highly saturated and less prone to oxidation.
Therefore, many fried foods such as fried instant noodles, crispy rice chips, etc. like to use palm oil, because it is cheap, stable, and crispy when fried.
On the other hand, it is necessary to make fatty acids less accessible to oxygen, Oxygen can only result in oxidation after all. Therefore, it is necessary to work hard on packaging, airtight packaging, vacuuming or filling with nitrogen, and adding a pack of “oxygen scavengers” to create a relatively “safe” environment for fatty foods.
In addition, it is necessary to find a way to remove the metal ions that can catalyze the oxidation reaction.
Minimize the effects of light, radiation and temperature during storage as these all promote oxidation. In opaque packaging, it is wise to keep in a cool environment.
Finally, there is another big trick, which is to add “antioxidants”.
This additive can promptly “extinguish” a small amount of “free radicals” that appear in the early stage, preventing the spark from becoming a prairie prairie. Therefore, there are almost no foods with a long shelf life that are high in fat without added antioxidants. What variety to add, how much to add, or the combination of several antioxidants, there is a lot of knowledge.
Can the shelf life of instant noodles be extended from 6 months to 12 months?
Take the 12-month shelf life of imported instant noodles as an example. To the media’s question, it is said that the reply given by the manufacturer is: “This product has added antioxidants.”
It is true that antioxidants can delay the deterioration of instant noodles, but they cannot make the food have a “good golden body”. Given enough time, food will eventually oxidize.
So, even with the addition of antioxidants, instant noodles still need to be marked with an expiration date.
Most products are marked 6 months, and storage and sales practices have proved that this shelf life is no problem. So, 6 months has become the industry norm.
In general, product development involves various experiments to determine its quality standards and shelf life under specified conditions.
A product that is usually marked for 6 months can be marked for 12 months, which requires a shelf life experiment.
For example, if the shelf life of imported boxed milk is changed from 6 months to 12 months, the temperature and time of sterilization will need to be adjusted.
Instant noodles need to double the shelf life, and may also need to adjust the variety, amount of antioxidants and packaging conditions, etc., to ensure that all indicators are qualified after 12 months, and there is no detectable flavor. Variety. It’s better to get the data out and give consumers peace of mind.
If the raw materials are unchanged, the formula is unchanged, the packaging is unchanged, and the storage conditions are unchanged, and no shelf life experiment has been done, just write the shelf life for 6 months and bring it. Sell, this is not very reliable.
Would you like to buy food with a longer shelf life?
This question should be decided by consumers based on cost performance and personal needs.
For example, for boxed milk, a longer shelf life can ensure transportation across the ocean and be more assured in the process of selling it around the world, but more powerful sterilization Treatment also results in a reduction in vitamin content, as well as a reduction in flavor quality. Among them, proteins may generate a small amount of “isopeptide bonds”, reducing bioavailability; lysine content will decrease due to mild Maillard reaction, and sulfur-containing amino acids may be partially lost due to heating.
So, for those who care about the flavor and texture of milk, or the nutritional quality of milk, just buy fresh refrigerated pasteurized milk. But if you just want to use milk for cooking, for beverage making, or just want to add some calcium and protein, don’t care about vitamins, and care more about cost-effectiveness, then buying boxed milk is still very cost-effective.
Instant noodles have many products to choose from, and consumers can choose according to their own preferences. If I don’t need to store the instant noodles for a long time after I buy them, and eat them in ten days and a half or a month or two, then of course I don’t need to deliberately choose a product with a one-year shelf life. If it is just for emergency reserves, it may be more convenient to be longer.
I am more gratified that consumers are getting better at reading product labels and questioning product-related information. This shows that the level of consumers has improved, which is a good thing.