Does frozen food lose its nutrients?

What is frozen food?

Frozen food, also known as quick-frozen food, is a type of food produced by rapidly freezing at low temperatures. Frozen food refers to the appropriate treatment of raw materials, which are rapidly frozen within 15 minutes, causing their temperature to quickly pass through the temperature range of -1℃ to -5℃ (also known as the maximum ice crystal formation zone) within 30 minutes. After freezing, the food crystallizes, and the storage and transportation temperature must also be below -18℃. In a super low-temperature environment, food is quickly frozen, and the structure and cell composition do not change, while the activity of microorganisms, enzymes, etc., is temporarily suppressed. It is then sealed and vacuum-packed (to prevent drying, oil loss, oxidation, etc.) and finally stored in an environment below -18℃ for long-term preservation, lasting 300 to 600 days. Many people often confuse quick-freezing with freezing, but in fact, the two concepts are completely different.

Will the nutritional components of frozen food be 'frozen' away?

Meat stored at lower temperatures can better retain its nutritional components. In particular, the content of protein and minerals generally does not change. It can be said that compared to fresh meat, frozen meat has not lost much in terms of nutrition, aside from a decline in taste. Compared to fresh fruits and vegetables, frozen fruits and vegetables may be inferior in taste, but their nutritional value is not necessarily lower. This is because, from the moment vegetables and fruits are harvested, their nutrients are continuously lost during transportation and storage, while frozen fruits and vegetables are quickly frozen at -18℃ right after harvesting, almost halting respiration and suppressing microbial activity, which is actually more beneficial for nutrient retention. For transportation and preservation, many vegetables are processed by quick-freezing, and there are many types of vegetables suitable for quick-freezing, such as leafy vegetables, stem vegetables, root vegetables, and edible fungi. Before quick-freezing, vegetables must undergo pre-treatment, which involves boiling, steaming, or microwaving.

An experiment comparing the nutritional components of eggplant, green beans, garlic sprouts, and cabbage under quick-freezing and room temperature storage conditions found that in the early stages of storage, the vitamin C content of quick-frozen vegetables was lower than that of room temperature stored vegetables. However, as the storage days increased, the vitamin C content of room temperature stored vegetables rapidly decreased, quickly falling below that of quick-frozen vegetables.

How to choose frozen food

First, choose frozen food that has been stored at temperatures below -18℃. If the store does not have a freezer or the freezer's temperature does not reach -18℃, the product quality cannot be guaranteed and should not be purchased. Choose frozen food that is closest to the production date.

Pay attention to the production date; the closer the food is to the production date, the higher its freshness and the less nutrient loss. If frozen food has not undergone thawing during production and transportation, there will be no water generated, and thus no frost or ice will appear. Only during repeated thawing will frost and ice occur, which can also cause varying degrees of damage to the food's nutrition. Therefore, we should prioritize frozen food that is frost-free and ice-free. Choose packaging that is undamaged, with intact frozen products that are not soft or stuck together, with little to no frost inside the packaging, and with a natural color that is not discolored or dull.