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Too long to look at
Food with a shelf life of up to several months to a year, just expired the problem is not big, basically can eat, and its own shelf life of less than a month of food, expired cautious eating.
Foods that are not stored in the correct way, or that have been opened and packaged with damage, should be careful, even if they have not expired.
Shelf life of this thing, we all know, but there are also many misunderstandings, may not know very clearly, today to talk about the shelf life of the topic.
Shelf life
What is it that is guaranteed?
In the National Standard for Food Safety And General Rules for the Labeling of Prepackaged Foods (GB 7718-2011), the shelf life is explained as the period during which prepackaged foods maintain their quality under the storage conditions specified in the labels. During this period, the product is fully fit for sale and maintains the unique qualities on the label that do not have to be stated or have been stated.
This "maintaining quality" not only includes whether it can be eaten, but also whether it is delicious or not, that is, whether it is safety, or taste, flavor, and appearance of food during the shelf life, it is to be guaranteed.
Additional conditions behind it
From the definition, you can also see an additional condition of the shelf life - a specific storage environment, if you change the environment, the shelf life will change, so when you buy food, look at the shelf life at the same time also depend on what the specified storage conditions are, such as room temperature or refrigeration, freezing.
Who sets the shelf life
Generally, the food manufacturers themselves formulate.
How to set
On the one hand, manufacturers can consult the relevant literature and refer to other similar products to obtain a rough shelf life range, on the other hand, it must also be determined by experiments.
There is an "accelerated destructive experiment", that is, deliberately placed in high temperature, high humidity, strong light and other conditions to see how long the food is bad, and then convert the shelf life at room temperature according to the formula.
There is also a "long-term stability test", which is to place it under the specified storage conditions and then test it every once in a while until the food deteriorates to determine the shelf life.
In addition, the shelf life should also take into account the actual problems of storage, transportation and sales.
Will the manufacturer "counterfeit" the shelf life?
It is not good for the manufacturer to have an unrealistic shelf life, because the "shelf life" is the same as the "warranty period", which is the manufacturer's responsibility period. Manufacturers promise consumers that the shelf life as long as the conditions of storage will not be bad, once broken they must be responsible, if the shelf life is set too long, it increases the probability of being claimed for compensation, set too short, but also will increase the pressure of transportation, sales, may not be sold out of the shelves.
Foods with longer shelf life are undoubtedly more convenient and less stressful for both manufacturers and distributors, but to extend the shelf life through technological means, rather than shelf life digital fraud.
The longer the shelf life
More preservatives?
Of course not.
It is undeniable that preservatives are indeed one of the ways to extend the shelf life, but they are not the only ones, they are not the best, the most reasonable cost, and there are many ways to extend the shelf life of food.
The two great enemies of food quality are "decay" and "oxidation".
Anti-corruption
Anti-corruption is anti-microbial, in addition to the addition of preservatives, common means are:
dry
Deprived of the moisture necessary for microbial life, it is difficult to rot, such as instant noodles, dried fruits, dried meat, biscuits and other foods are dried to preserve quality, not preservatives.
Add sugar and salt
The high osmotic pressure brought about by high sugar and salt content will also make it difficult for microorganisms to survive, so jams, honey, curd milk, pickles, sauces, salted meat and the like can also be left uncorrupted for a long time.
alcohol
Alcohol itself can kill microorganisms, so foods containing alcohol have a longer shelf life.
Eliminate microorganisms + seal
While completely eliminating internal microorganisms, sealing them to block the entry of external microorganisms, as long as the packaging is not damaged, it can maintain sterility and will not rot, such as canned and ambient box milk is this principle.
Refrigerate, freeze
Low temperatures do not kill microorganisms, but they can slow down their reproduction rate, so that they do not reach harmful amounts during the shelf life.
Antioxidant
In addition to spoiling, food also oxidizes. In the presence of aerobic presence, the fat in the food can begin to oxidize automatically, and this oxidation will also spread to the whole food, and light, heat, metal catalysts, etc. will accelerate this process.
Oxidation not only brings unpleasant taste (such as the "hara taste" of oils), but also leads to the loss of nutrients such as vitamins, but also produces substances that are harmful to health.
How to prevent oxidation? Sealing, protecting from light, heat these are useful, you can also add some antioxidants.
The same is milk
Why shelf life is so far apart
The same is fresh milk, some have a shelf life of only 2-7 days, and some can be put for half a year or more, why?
It is because the scope and extent of this step in the elimination of microorganisms are different.
Sterilized milk
The so-called "sterilization" is only to eliminate the most virulent "pathogenic bacteria" for the purpose of eliminating non-pathogenic bacteria, spore (bacteria dormant body, the ability to resist adversity) and other forms and other microorganisms can allow some of the remaining undead.
Specific to milk, according to the national standard, the microbial requirements of pasteurized milk are that Staphylococcus aureus and Salmonella cannot be detected, but the number of E. coli and the total number of bacteria is less than a certain value.
Therefore, during the placement of pasteurized milk, the remaining living microorganisms will still multiply, and once they are more than a certain extent, they can also make people vomit and diarrhea. Therefore, pasteurized milk is generally refrigerated and stored, with a shelf life of only 2-7 days, which can be seen on the low temperature shelves of supermarkets.
Sterilized milk
Although "sterilization" and "sterilization" are one word apart, the meaning is very different, and the goal of "sterilization" is to completely eliminate all microorganisms, including spores.
According to the national standard, sterilized milk should meet the standard of "commercial sterility", that is, it does not contain any microorganisms that can multiply at room temperature.
Therefore, the sterilized milk has a shelf life of up to 6 months, and it does not need to be placed in the refrigerator, which can be seen on the normal temperature shelves of supermarkets.
Incidentally, these room temperature milks also don't have as many preservatives as the rumors say, because there is no need to increase this cost.
Which to buy?
Just choose according to your actual situation.
Pasteurized milk due to the experience of low temperature, nutrient retention is slightly better, while the cost is a little lower, so the price will be lower, but buy must pay attention to refrigeration preservation, quickly drink, more suitable for having a refrigerator, out of the supermarket can go home, regular drink milk or family friends.
And sterilized milk, it is true that due to high temperature to destroy a little heat-intolerant ingredients, such as B vitamins and vitamin C, but these are not very much in milk, milk's main nutrition - calcium and protein is heat-resistant, so this nutritional loss is not very worthy of ordinary people's concern. Sterilized milk is generally more expensive, but it is much more convenient, it does not matter if it is put for a long time, it is easier to carry, and it is more suitable for busy student parties and commuter parties.
Some foods can never be bad?
First of all, according to the "National Standard for Food Safety, General Principles for The Labeling of Prepackaged Foods" (GB 7718-2011), the prepackaged foods that do not have to identify the shelf life are only: beverages and wines with an alcohol content of ≥ 10%, vinegar, edible salt, solid sugars and monosodium glutamate, which are indeed difficult to spoil.
As for the honey that everyone often hears, it is necessary to mark the shelf life, and the honey seen on the market is generally set for about two years.
Honey is indeed not easy to break, if it is mature honey, the water content is generally below 20%, most microorganisms in this hypertonic state are difficult to survive, and honey is very acidic in its natural state, pH is about 3 to 4.5, and there are certain oxidase and hydrogen peroxide in honey, which are not conducive to the reproduction of various types of bacteria.
However, honey is not absolutely bad, there is a type of "osmophilic yeast" can carry the harsh environment of honey to survive, resulting in honey rot.
What the case
Be careful during shelf life too?
As mentioned earlier, the shelf life is tied to a specific storage method, and if it is not stored according to the correct method, the shelf life is likely to be shortened.
So pay attention to whether the mall is saved in the right way.
For example, many of the promotional yogurts sold in supermarkets are about to expire, and they are removed from the freezer and sold at room temperature, and these yogurts will accelerate deterioration if the weather is hot.
In addition, there are frozen foods that are about to expire and sold at room temperature, which may be fast when you get them, and when you go home and freeze up, there may be a lot of bacteria.
In addition, once opened, the shelf life written on the packaging is no longer established, and it is necessary to eat and drink as soon as possible. If the food that can be stored at room temperature cannot be eaten for a while after opening, it can also be put into the refrigerator to extend the shelf life, such as oyster sauce and soy sauce should be put in the refrigerator after opening.
What the case
Can you also consider eating after expiration?
In principle, it is recommended that you do not eat after expiration, after all, there is no guarantee, and the manufacturer is not responsible for eating badly.
But you just want to save as much as possible, and you are not willing to throw it away, then you can also reduce the risk through analysis and judgment.
The original shelf life is long, and the problem of just expiring is not big
Dried meat, dried fruit, biscuits, and other foods with very low moisture
Dry grain products with a low fat content
Most of the bottled and canned beverages that can be stored at room temperature
Canned food
Sauce food
candy
These foods, which originally have a long shelf life (months or even a year), are not easy to rot, and if they expire soon, the safety problem is not big, and they can generally be eaten.
There is also frozen food that has been frozen and has not been repeatedly frozen and thawed, and it is not a big problem if it has just expired.
The original shelf life is short, and the risk is large after expiration
The original shelf life is short, such as only a week to a month of food, generally belongs to the water, protein, sugar and salt less food, easy to spoil, microbial exceeding the standard, expired or not according to the storage conditions after the risk is much greater, it is best not to eat.
Be wary of high-fat foods as well
In addition, foods with high fat are treated specially, because fat is most likely to be oxidized quickly, and even if the shelf life is long, it is not recommended to eat after expiration, such as cooking oil, high-fat meat products, nuts, etc. Especially if nuts are already bitter, don't eat them.
Also pay attention to the packaging status
If the package is well sealed and there is no air leakage, the risk is lower, while if the package has been defaced, the risk is greater.
Smell it, taste it
If there is already a taste of wine, sourness, smell, slimy brushing, mildew, bitterness after tasting, and spicy food itself, these should obviously not be eaten.
Resources:
[1] National Food Safety Standards General Rules for Labeling Prepackaged Foods (GB 7718—2011)
[2] National Standard for Food Safety Pasteurized Milk (GB 19645—2010)
[3] National Standard for Food Safety Sterilized Milk (GB 25190—2010)
[4] Food Microbiology Inspection Commercial Sterility Inspection (GB 4789.26—2013)
[5] "Liquid Food Ultra-high Temperature Instantaneous Sterilization (UHT) Equipment Acceptance Specification" (GB/T 22023-2008)
[6] General Guidelines for Food Shelf Life of China Food Industry Association Group Standards (T/CNFIA 001-2017)
Edit: Xiao Hui
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