Which elements get bigger when they freeze

Frozen foods

What you should know about frozen foods:

  • What is deep freezing
  • Physical processes
  • Tips on how to freeze yourself
  • Shelf life of even frozen foods
  • What should be considered when purchasing frozen food
  • Shelf life of purchased frozen products
  • What is freezer burn
  • Tips for proper thawing
  • Storage of frozen goods at the entrepreneur
  • Marking of frozen food in stores
  • Legal provisions

Freezing (deep-freezing, freezing, ...) is a gentle technique for preserving food. The terms "Freezing"Or"Freezing"Are used for industrial processes, the cold preservation in the domestic freezer is called"Freeze" designated. Due to the removal of heat through product-specific, rapid shock freezing and the growth of microorganisms that is stopped as a result, frozen foods can be stored for several weeks, some even for a year. The loss of vitamins and nutrients is very low compared to other preservation methods, even after months.

Due to the low temperature of -18 ° C and below, the water in the food freezes and forms crystals. Microorganisms can no longer multiply at these temperatures, which leads to an extension of the shelf life. However, the oxygen in the air also causes spoilage in the freezer, so that frozen food unfortunately cannot be stored for indefinitely.

Shock freezing (-25 ° C and below) severely restricts the formation of larger ice crystals, which can break up the cell structures.

Especially when freezing slowly, as is the case with most conventional domestic freezers, large ice crystals form, which affect the cell structure of the frozen food. As a result, when meat is thawed, for example, a lot of juice escapes and microorganisms multiply much faster than with shock-frozen products.

During storage, the food must be hermetically sealed to avoid freezer burn.

Tips for Freezing Yourself:

  • If you freeze food and pre-cooked meals yourself, is Freshness is the top requirement. The longer the food waits to sleep in the cold, the greater the loss of quality. It is best to think about which foods should be preserved immediately after shopping.
  • Basically, the food should airtight and watertight in small portions be packed. Both freezer bags and frost-proof storage boxes are suitable for this. However, it must be ensured that as little air as possible remains in the respective container. A high proportion of air can easily cause freezer burn. The food can also be vacuum-sealed.
  • Now it's time to get the frozen food to cool down as quickly as possibleso that the smallest possible water crystals are formed. Some freezers have a so-called "Shock freeze“- function, this ensures a better quality of the frozen food and should in any case be used for larger pieces.
  • If too much food is placed in the freezer at once, the cooling process slows down and the food also loses its shelf life and quality.
  • What is important is the fresh frozen food not on bags and containers that are already frozeninstead of placing them flat in the freezer box, the freezing process can take place evenly.
  • who warm food If you want to freeze, this should first be outside the freezer Allow to cool in small portions. Due to the increased temperature of food that is still warm or precooked, food that has already been frozen could thaw for a short time and its shelf life could be impaired. The important thing is that Cool food quickly to room temperature and quickly and quickly in small portions in a clean container to close airtight and freeze, otherwise bacteria will multiply quickly.
  • For fresh food that you are freezing yourself, always have one with appropriate labels labeling make. Make a note of that on it too Date the food was frozen.

Shelf life of even frozen foods:

Here is a rough overview of the shelf life of some foods at an optimal storage temperature of -18 ° Celsius:

Vegetables: 3 - 12 months
Herbs: 3 - 4 months
Fruit: 9-12 months
Meat fish: 3 - 12 months
Sausage: 1 - 6 months
Bakery products: 1 - 3 months
Dairy products: 2 - 6 months
Home cooked: 1 - 3 months

In the case of fatty foods, they can be stored for a shorter period of time. The oxygen in the air causes fat to go rancid.

What should be considered when purchasing frozen food?

  • Vegetables, stir-fried vegetables or rice dishes must be individually frozen so that the taste, vitamins and minerals are optimally protected. Therefore do the "shake test". Are vegetables and rice frozen into large chunks, the cold chain was probably interrupted. Water has leaked from the vegetables and clumps together when they are frozen again. The result: the vegetables later taste tough and dry.
  • It should never "snow" in the pack be. This is also an indication that the cold chain has been interrupted and water has leaked. With transparent bags you can see the white ice crystals very clearly. In the case of printed bags, the damage can be determined using a simple trick: The bag must not crackle when you shake it!
  • For high-quality seafood (prawns, fish fillets, crabs, mussels) the Note "glazed" on the packaging. That means: These foods were sprayed with ice water before shock freezing. The thin layer of ice prevents oxygen from penetrating and thus spoiling fish or seafood more quickly. In addition, water cannot escape so easily, the meat does not dry out as quickly and remains nice and tender.
  • Stay away from Seafood and fish in clear packaging. This is especially true for high-fat fish products such as salmon. With lean products like scampi or cod, it doesn't matter that much. These products have been exposed to light for too long during storage. The result: if too much light comes in, the oil it contains becomes rancid faster. If you receive transparent fish packaging from frozen food suppliers, it is essential to inquire whether the packaging has always been stored and transported away from light.
  • Watch out for Freezer burn! Cakes, poultry and meat are particularly susceptible to this. You can recognize freezer burn by the fact that the products have gray spots around the edges. The food then usually tastes tough and bland, and the edges of the cake become mushy when thawed.
  • Important: Always pay attention to this Best before date! It should be valid for a few more months. This guarantees greater freshness.
  • Frozen goods may only be placed in the freezer up to a certain height. If it is stored at a higher level, the goods are no longer adequately cooled. You can use the Check the color marking in the chest. This is required by law. If the marking is clearly visible, the goods are properly cooled.
  • The temperature of frozen food in the supermarket must be at least -18 ° C. Customers can easily check whether the minimum temperature is being adhered to. Because it is required by law that a Thermometer on the freezer counter must be appropriate.

Shelf life of purchased frozen products:

In addition to the best-before date, the label also always states the period during which the food can be stored at the consumer's premises.

It must therefore be stated how long frozen food can be kept at home. This mainly depends on the freezer used. Freezer compartments are marked with a star, which indicates the temperature in the refrigerator compartment. The specified best-before date can only be reached at - 18 ° C (***).

The following shelf life information could be found on the label:

This would mean that the food can be stored at home at -6 ° C (*) for a maximum of one week and at -12 ° C (**) for a maximum of 2 weeks. Of course, it should preferably be stored at at least - 18 ° C (***).

So that the specified shelf life can be achieved at all, the Never interrupt the cold chain (example: transport from the supermarket to your home).

Star designation for freezer compartments:



Performance specification

<0 ° C

not suitable for storing frozen food (mainly for ice cubes)


≤ −6 ° C

suitable for short-term storage of frozen food (approx. 1 week)


≤ −12 ° C

suitable for medium-term storage of frozen food (approx. 2 weeks)


≤ −18 ° C

suitable for long-term storage of frozen food


≤ −18 ° C

suitable for long-term storage of frozen food
suitable for freezing without thawing frozen food that has already been stored

Freezer burn occurs when the frozen food is frozen with too much oxygen, or when parts of the food come into contact with the cold fresh air through leaky packaging. The affected areas dry out and take on a whitish-gray color.

Freezer burn significantly reduces the taste of the frozen food in these areas. The spots should therefore be removed generously. If the food is affected over a large area, consumption is completely discouraged from a taste point of view.

You can prevent freezer burn with an airtight envelope, but tight-fitting packaging, for example vacuum-sealed, works best.

Tips for proper thawing:

  • In order for the frozen food to survive its vitamin-preserving cold sleep well, it should thawed slowly and gently become. Many foods that are frozen directly into the hot pot lose their crispness and consistency. Only some vegetables, such as spinach, survive this procedure unscathed; tender fruits, such as raspberries, tend to become mushy if they are heated too quickly.
  • Meat, fish and particularly sensitive foods should be removed from the freezer the evening before and overnight thawed in the refrigerator because bacteria become active again after cold sleep and multiply particularly quickly in warm temperatures.
  • You should therefore thaw frozen goods never at room temperature on.
  • For this reason, raw foods that have already been frozen and that have been completely thawed should also be not frosted a second time - the number of bacteria and germs is so increased that the quality of the product cannot survive further storage times.
  • Place them Food to be thawed in a bowl, Defrosting juices should be discarded. Also, make sure that these juices do not contaminate other food in the refrigerator.
  • When thawing food that has already been cooked, the following applies: Do not defrost in the refrigerator or at room temperature, but heat it up quickly and eat it. The longer the already cooked food is stored at temperatures above zero, the more bacteria develop!

Storage of frozen goods at the company:

The temperature of frozen food must be constant during storage in retail establishments such as supermarkets or restaurants and must be kept at -18 degrees C or lower at all points on the product.

A short-term increase in temperature of 3 degrees C (up to a maximum of -15 degrees C) is permitted for shipping, local sales and in retail freezers.

Freezing equipment (also means of transport) over 10 cubic meters must be equipped with suitable recording devices to monitor the ambient temperature. The records must be kept for at least 1 year.

At Freezers with a capacity of less than 10 cubic meterswhich are used in retail stores to store reserve supplies, a simple, clearly visible thermometer is sufficient for temperature monitoring.

For open retail sales furniture, such as Chest freezers in supermarkets:

  • is the Line for maximum filling clearly mark the chest;
  • is this Thermometer at the level of this mark easily visible to attach.

Labeling of frozen food in stores:

In principle, frozen foods are subject to the Food Information Ordinance.

In addition, the following elements must be found on the label:

  • In addition to the item description, the note: "frozen'', „Frozen foods'', „frozen'' or "frosted'';
  • Period during which the food can be stored by the consumer (see also the item Shelf life of frozen products);
  • the note "Do not freeze again after defrosting''.

There are still deviations in the labeling for frozen products that are not intended for the end consumer or community supplies.

New label elements since the end of 2014

With the new food information regulation, the following additional labeling information must be provided since December 13, 2014:

  • The freezing date must be stated for frozen meat, meat products and unprocessed fish products.
  • The ordinance requires that the words "defrosted" be added to the sales description of the food for food that has been frozen before sale and is sold thawed.
    Exceptions: These include in particular foods for which freezing is a technologically necessary step in the manufacturing process or for which thawing does not have any negative effects on the safety or quality of the food.
  • Ordinance on frozen foods (Federal Law Gazette 201/1994 as amended)
  • Regulation (EC) No. 37/2005 for monitoring the temperatures of deep-frozen foods in means of transport and in warehousing and storage facilities.
  • Food information regulation LMIV (No. 1169/2011)

Compiled by Ing.Gerhard Wimmesberger (11/2012, supplemented 01/2015)

Please send your suggestions to [email protected]

Sources: de.wikipedia.org, www.chefkoch.d, www.hr-online.de