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The nutrient loss of frozen meat and frozen vegetables is not large. In fact, the nutrition of fresh vegetables after 5 days of refrigeration may not be comparable to that of quick-frozen vegetables (see the text for the data)
“Quick freezing” is the key to quality assurance, commercial quick freezing temperature is lower, and the effect is better than self-freezing.
The recommended way to thaw frozen meat is to thaw it in the refrigerator overnight. Frozen vegetables do not need to be thawed, but can be directly steamed, grilled, or microwaved.
Figure | pixabay
Whether it is for daily life or stocking up during the epidemic, frozen food is a kind of convenient and durable good thing. When preparing frozen meat and vegetables at home, should you freeze them yourself or buy ready-made ones? Frozen or cooked? Let’s talk about it today
Frozen Meat
First question, if you want to stock up on meat, or if the meat you buy is not sure if it will be eaten soon, will you choose to buy chilled meat or frozen meat?
1. Buy frozen meat directly
2. Buy cold fresh meat and freeze it by yourself (if you don’t store it, you will freeze it when you buy it)
3. Buy cold fresh meat first and put it in the refrigerator, and then freeze it if you can’t finish eating it
4. Buy cold meat, cook it first and then freeze it
From the perspective of nutritional safety, 1>2>3 is recommended, and from the perspective of taste, 4 is not recommended
Is frozen meat nutritious?
The protein, fat, iron and other minerals in the meat will not be greatly affected by freezing. At most, the juice lost during thawing may take away a little B vitamins.The nutritional value of frozen meat is not much worse than that of fresh meat.
Figure | pixabay
Why is it better to buy ready-made than to freeze it yourself?
Because the conditions of commercial quick-freezing are better than their own, the meat can be “quick-frozen”.
Why flash freeze?
During quick freezing, all parts of the food quickly pass through the temperature zone (0°C to -5°C) where ice crystals are formed, and the juice freezes in place “before it can react”, and the whole food freezes in place. Numerous and fine ice crystals appeared uniformly without damaging tissue or cells. The frozen food does not see any large pieces of ice ballast, and the juice can be absorbed back in place when it is thawed.
In slow freezing, the food stays in the temperature zone where ice crystals are formed for a long time. In some places, the ice crystals are frozen first, resulting in the concentration of the remaining juice nearby. In order to “balance”, Moisture from other parts will continue to penetrate, allowing the ice crystals to grow, and finally form small and large ice crystals. These large ice crystals will squeeze tissue, puncture cells, and damage muscle fibers, resulting in no juice during thawing. It is absorbed again, and it is reflected in the meat that the taste is poor.
Figure | Reference [1]
Simply put, The lower the temperature, the faster the freeze.
So the industry mostly uses extremely low temperature to freeze, such as -30℃ below, or use some special technology to freeze food instantly. But ordinary families do not have this condition, and the freezer compartment of the refrigerator is only -18 ℃.
But also depends on storage and shipping conditions
In theory, commercial quick-frozen meat is better, but if the supermarket is not well-preserved, or the cold chain conditions are not good during transportation, it may be that the frozen meat you bought has experienced repeated freeze-thaw /strong>, nutrition and safety are compromised.
An easy way is to see if the meat is still small and uniform ice crystals.If there are large ice slugs locally, then Not so good anymore.
Figure | pixabay
What should I pay attention to when I freeze myself?
You can also freeze it when you buy it back, but you should pay attention to buying chilled fresh meat for home, start to freeze it directly, do not put it in, try to reduce the initial number of microorganisms, and the shelf life will be longer. long.
Another important thing is to refreeze in small pieces, ideally cut into thinner pieces and bag them separately Freeze afterwards.
This will not only allow all parts to cool down quickly during freezing, but also achieve the purpose of quick freezing. It is also convenient to take the amount on demand when eating, avoiding repeated freezing and thawing. In addition, thin frozen meat can be cut even if it is not thawed, which is more convenient.
Figure | pixabay
Frozen or cooked?
Some people asked if it was better to freeze the meat after it was cooked.
Frozen meat is fine if you can ensure that it is well heated before eating.
However, in terms of taste, cooked and frozen meat is basically impossible to be tender and juicy. After heating, the protein of meat is denatured and cannot absorb water itself, and the process of freezing, thawing, and reheating will further lose water, and finally the meat will become hard and woody. The taste is far better than that of raw frozen meat that is thawed and cooked.
Figure | pixabay
What should I pay attention to when thawing?
As mentioned earlier, it should be “quick frozen” when freezing, but the opposite is true when thawing, “slow down” is to give the juice enough time to absorb back into the tissue Go inside, try to restore the food to the juicy and elastic state before it was frozen.
But “moderation” takes a long time, and during the thawing process, the food faces the problems of microbial reproduction, protein and fat oxidation, discoloration under the action of enzymes, etc., so we have to let the food At a temperature where ice crystals melt but oxidation reactions and microbial growth are inhibited. This temperature is about 3℃-5℃.
So the most recommended way to thaw meat is directlymoving from the freezer to the freezer, and letting it thaw slowly.
Figure | pixabay
If you bought frozen meat in a package, you don’t need to unpack it in this step. If you put it in a fresh-keeping bag, you can also bring it with you to thaw it. It is recommended to take it out the night before and thaw overnight in the refrigerator. Even if you can’t handle it right away the next day, it’s fine to keep it in the refrigerator for a while.
Frozen Vegetables
Are frozen vegetables nutritious?
Everyone will automatically think that frozen vegetables are much less nutritious than fresh vegetables, but it’s not that exaggerated.
First, fresh vegetables will continue to lose nutrients if you buy them and store them at room temperature or in the refrigerator. This is because vegetables still have respiration after being picked, and many enzymes in vegetables are also triggering various chemical reactions, resulting in color change, nutrient loss, flavor changes, and so on.
Commercial frozen vegetables are blanched to inactivate enzymes before quick freezing, so they are stable during storage. However, the blanching step itself will also bring a certain amount of nutrient loss.
In general, the commercial quick-freezing process has little effect on dietary fiber, minerals, carotenoids, vitamin E in vegetables, and some polyphenols may even increase after frozen storage, but blanching before freezing and water loss after thawing may take away some of the heat-labile and water-soluble Vitamins (vitamin C and B vitamins).
Fresh vegetables that have been refrigerated for 5 days may not be as nutritious as quick-frozen vegetables
Studies have found that vitamins in broccoli, corn, kidney beans, peas, and strawberries that are refrigerated (4°C) for 5 days after being bought home C content is not as good as frozen dishes. And most people probably buy groceries once a week, so it’s normal to keep them at home for 5 days.
Figure | Reference [3]
However, this also includes vegetables. The vitamin C of spinach dropped from 25.2 to 14.5 after the quick-freezing process, which was nearly half of the loss. These losses are likely to occur mainly during blanching before freezing. Leafy vegetables such as spinach have a large surface area, and there are no factors that can protect VC (such as an acidic environment, such as starch), and the loss of vitamin C itself is very serious when heated. .
What should I pay attention to when I freeze myself?
Due to different conditions, commercially frozen vegetables are actually better than those frozen at home, but if you buy more vegetables one day, or want to stock up For the convenience vegetables you like, you can try to make your frozen vegetables better quality through some tricks.
Pick the right vegetables
First of all, you have to pay attention to choosing some vegetables that are suitable for freezing. Generally, it is recommended to choose peas, corn, broccoli, carrots, cauliflower, which are relatively stable.
Figure | pixabay
Blank before freezing
You can change the vegetable into a shape that can be put directly into the pot, and then put it into boiling water for a while (a dozen seconds to half a minute), which is equivalent to cooking to a blanching effect.
On the one hand, it can kill some bacteria, and on the other hand, it can make the color of vegetables better, and can kill enzymes, so that it is not easy to produce peculiar smell during storage (especially broccoli). type that is prone to special odors).
Figure | pixabay
Drain
Be sure to keep the water safe at home, and remember to drain the water on the vegetables at the end, you can gently squeeze out the excess Moisture to avoid quality deterioration after freezing.
Packaging
Be careful to use small packaging, enough for the family to eat a meal, to avoid the safety risk caused by repeated thawing.
At the same time, be alert to whether there are substances such as plasticizers in the packaging container, and choose a safer packaging bag.
The air inside should be exhausted as much as possible when packing.
Which layer?
It is generally recommended to lower the temperature of the freezer compartment as much as possible, or choose the coldest level, close to the Location.
You can go and check the information of the product of this refrigerator that you bought, to know the freezing technology it uses, and what temperature it can be frozen to. I have a good idea of what kind of location the refrigeration unit is probably in.
Figure | pixabay
What should I pay attention to when thawing?
Frozen vegetables are not the same as meat, in fact do not need to be melted and cooked, just thaw and cook together.
Frozen vegetables can be steamed, microwaved or oven ready,
Figure | pixabay
References
[1] Feng Xianchao, Zhou Guanghong. Effects of rapid freezing process on beef quality and tissue structure [J]. Food Science, 2016,37(19):1-7.[2] Hu Xin. Effects of different freezing and thawing methods on pork quality[D]. Nanjing Agricultural University, 201[3] Linshan Li, et.al, Selected nutrient analyses of fresh, fresh-stored, and frozen fruits and vegetables, Journal of Food Composition and Analysis, Volume 59, 2017, Pages 8-17
Editor: Xiaohui
This article is reproduced with permission from Nutritionist Gu Zhongyi (ID: yy4gz1). If you need a second reprint, please contact the original author.