Everyday life would be unimaginable without frozen foods. The most popular products in the chest freezers of food retailers are frozen spinach, frozen vegetables and of course frozen pizza. However, homemade precooked meals, fresh vegetables, meat, fish and fruit also make their way into the freezer to preserve them. Here, we have compiled some answers to the main questions:
1. Frozen products from the food retailer
The frozen goods offered in the chest freezers of food retailers are subject to strict quality control. To date, this has covered the production processes and thus the product quality on the premises of the frozen food manufacturer as well as temperature control in frozen transport (generally by special refrigerated shipping). This path from packaging to chest freezer is called the cold chain, or in this case also the deep-freeze chain. Temperature control directly on the product is not yet performed at present – the LOOKICE® temperature indicator was developed to close this gap. This temperature label also registers short-term fluctuations of the temperature directly on the frozen product and changes colour if the cold chain is interrupted (and the quality endangered). More about the subject of frozen food and food quality can be found here.
2. Freezing correctly
Always freeze raw food such as meat, fish, vegetables and fruit in the way in which you wish to use it later. Place sensitive foods such as fruit on a board and shock freeze for a few hours – only then should they be placed in a freezer bag or freezer container. This preserves the shape and the pieces do not stick together. It also allows partial amounts to be removed again. Freeze meat and precooked meals in the desired portions. Always label frozen products clearly with the contents and date.
There is a loss of nutrients from fruit and vegetables even in the freezer compartment or chest freezer. Around 15 percent of the vitamins contained in them have disappeared after approx. four months of storage, and 55 percent after a year. The same applies for meat and fish.
The more modern the chest freezer, the lower the energy consumption. Regular defrosting ensures optimal cooling performance. The temperature of the chest freezer should be set to a minimum of minus 18 degrees Celsius and a maximum of minus 21 degrees Celsius. New freezers can be set precisely and often offer a special compartment for quick freezing.
So that it is already tender later for preparation, beef and pork should be bought from the butcher well hung if you wish to freeze it. If meat is defrosted or thawed (see also defrosting) then it should not be refrozen. Meat is particularly susceptible to freezer burn (see information) – so always pack well and tightly, never in the original packaging from the retailer! Always cook thoroughly when preparing defrosted frozen meat.
For how long can meat be frozen?
This varies depending on type. The fat content plays an important role here. Beef can be frozen for longest (approx. 3 – 4 months), as beef has relatively low fat content. Like pork, frozen mince can be kept for less time – it should be used within 4 – 6 weeks. Poultry such as chicken or turkey should be precooled in the refrigerator for around 24 hours before freezing. Lean poultry can be kept in the freezer for up to 10 months.
As fish – whether whole or as a fish fillet – is a very sensitive food, it should also be pre-frozen on a board to preserve the shape. It is particularly important here to have fresh, high-quality raw fish in order to achieve a longer shelf life (approx. 4 months) and exclude health risks.
Many types of vegetables can be frozen raw, thus preserving their colour, crisp quality and good flavour. With almost all types (other than asparagus, peppers, cucumbers and courgettes), the washed and portioned vegetable should be blanched – i.e. the vegetable is scalded briefly (the time varies depending on the type) in boiling water. More information about frozen vegetables at http://www.einfrieren.org/tipps-zum-einfrieren.php.
Which vegetables cannot be frozen?
Salad (everything from lettuce to leaf spinach), radishes, garlic, tomatoes (whole – diced or puréed tomatoes can be frozen then used for cooking).
Fresh, washed fruit should be frozen quickly and in perfect condition (no bruises, not overripe). Pre-frost individually on a board (see Basics). Fruit can of course also be processed into mush – slight sugaring increases the shelf life to 12 months (otherwise 8 – 10 months).
Which fruit is it better not to freeze?
Bananas, cherries, yellow plums (Kriecherl), green grapes, damsons (plums), watermelon. Papaya and apple should be frozen only when puréed.
3. Defrosting correctly
Defrosting meat and mince, poultry and fish: Always defrost meat (all types), fish and precooked meals in the freezer bag in the refrigerator (at approx. 5 – 7°C), preferably overnight. The cooled defrosting process limits the awakening of microorganisms. After defrosting, process and cook directly as quickly as possible. How long meat takes to defrost depends on the size of the frozen product – large pieces (whole poultry, for example a goose) can take longer than one night. A cold water bath speeds up the process (caution – packaging must be waterproof).
Frozen vegetables can be placed directly in boiling water – the cooking time is reduced by approx. 30% as a result of the previous blanching (see above).
Frozen fruit can also be processed frozen, for example for pastries or in smoothies and purées.
4. Refreezing defrosted products
In every food, there are naturally microorganisms – these multiply over time, then cause the perishing process. During freezing, these microorganisms are also “frozen”. However, as soon as the temperature rises again – i.e. on defrosting if the product is still frozen throughout – the microorganisms and bacteria (for example such as salmonella) become active again and restart the processes, often even accelerated. Food that is particularly perishable such as meat, fish and poultry must therefore always be defrosted in the refrigerator – then refreeze defrosted meat as quickly as possible (i.e. if only a few hours have passed and the appearance and smell have not changed). If it has left the refrigerator then it should not be refrozen but rather processed immediately. The same principle also applies for frozen vegetables and frozen fruit, albeit here primarily the consistency and good flavour are jeopardised by defrosting. Finished products containing yeast (this also includes defrosted pizza), milk, eggs, cream or cheese are equally as sensitive as meat.
More information about this from the German institute for frozen food at http://www.tiefkuehlkost.de/tiefkuehlwissen/tiefkuehllexikon/wiedereinfrieren.
5. What is freezer burn?
Whitish, grey or brown marks on the frozen product are called freezer burn. They are caused by temperature fluctuations, air or water in the packaging (unsealed packaging). Water droplets form on the product as a result of a rise in temperature, which then produce small ice crystals when refrozen and cause the discolouration. Poultry is particularly sensitive, and whitish fluffy marks can also be found frequently on vegetables. Freezer burn is not harmful to health but may indicate that the deep-freeze chain has been interrupted several times, which has a negative effect on product quality. Frozen products with the LOOKICE® temperature label offer a reliable check here. You can prevent freezer burn for yourself by ensuring that the products to be frozen are packed tightly in a way that is air and watertight (for example vacuum sealed).