Imagine this – instead of riding an elephant, you could be riding a mammoth! In the year 2000, for the first time in the history of archaeology, an almost complete mammoth carcass was discovered frozen solid and perfectly preserved in the permafrost of Upper Siberia. Scientists dated the mammoth at 20,300 years old. Due to the excellent state of preservation, there is even a possibility of cloning the carcass DNA to create a live mammoth.
Freezing works by lowering the temperature to a state that inhibits microorganism growth. As in the case of the mammoth in Siberia, it was perfectly preserved for 20,000 years. That is amazing. No chemicals or artificial preservatives. Absolutely 100% natural! Freezing in food preservation has been used for centuries in cold regions, and a patent was issued in Britain as early as 1842 for food preservation by immersion in an ice and salt brine. It was not, however, until the invention of mechanical refrigeration that the process became widely applicable commercially. In 1880, a cargo of meat shipped from Australia to Britain under refrigeration accidentally froze with such superior results that the process was at once adopted for long-distance shipments and other storage. There are many ways to preserve food, but why should we consider freezing as an option? Let’s have a look.
What can be frozen?
The key to this is not whether it can be frozen but the quality of such foods after defrosting. You can therefore freeze almost any food. But there are foods that simply don’t freeze well. Canned foods need to be taken out before freezing. Eggs in shells will not be of much use when defrosted. Others that also do not freeze well include lettuce, mayonnaise, and cream.
Is frozen food safe?
Although freezing does not eliminate microbes (bacteria, yeasts, molds) already present in food, they become inactive at temperatures -18°C and below. Therefore, these microbes are prevented from doing what they do – causing food spoilage and food borne illnesses.
What about the quality of frozen food?
Frozen foods reflect the quality of food at the point of freezing. If food is frozen at its peak quality, it will be better tasting when thawed compared to food frozen near the end of useful life. Garbage in, garbage out. To retain vitamin content, color, flavor, and texture, store all foods at -18°C or lower.
Aren’t nutrients destroyed during the freezing process?
Nope, in fact, there is insignificant change in nutrient value during freezer storage in meat and poultry products.
Do enzymes stop working when food is frozen?
No. Enzymes are tough little proteins. Vegetables need to be blanched (cook in boiling water for about 30 seconds before plunging them in ice water) prior to freezing. If not, the enzymes will continue with their chemical reactions, albeit at a slower pace, and you’ll end up with lower quality vegetables.
What is the best way to freeze food?
Normal freezing creates undesirably large, six-sided snowflakes within food. These ice crystals with their sharp pointed edges will create unwanted cavities in food, which upon thawing, will leak and lose their juiciness. Large institutional kitchens such as hotels and restaurants use the Cook-Chill method to produce safe and massive quantities of quality food. They do this by using blast chillers/freezers to maintain the quality of their cooked product, maximise food hygiene and reduce wastage. Blast chillers/freezers are needed to comply with Food Health guidelines that require the chilled temperature of cooked food to be reduced from +70ºC to +3ºC or below within 90 minutes. The temperature of food to be frozen needs to be reduced from +70ºC to –18ºC in no more than 240 minutes. Normal freezers are unable to comply with these requirements. How do we then freeze food in normal freezers? If your fridge has “quick freeze” shelfs, use them. If not, try to freeze food in single layers and not one on top of the other. That will quicken the freezing process. You can then stack them after they are frozen.
How critical are storage temperatures for chilled/frozen food?
Although the speed of freezing is important, it is even more critical to maintain the temperature at storage. If food is frozen at -18°C, then it must be transported and stored at the same or lower temperature. One of the most important items to have in the kitchen is a refrigerator thermometer (the other being an oven thermometer). It tells you about the actual temperature (depending on the quality of thermometer) in your chiller (not > than 4°C) and freezer compartments (not > than 0°C).
How long can you keep food safely frozen?
Indefinitely. Recommended freezer storage times for different foods are for their quality only. Discard items that are rancid or don’t smell good if frozen for too long.
How is the best way to thaw frozen food?
Frozen food is best thawed in the chiller, so plan your thawing process properly. Bulky foods will take longer to thaw (one to two days). In general, overnight thawing is sufficient. You can also use the defrosting function in a microwave to thaw foods but do remember that they could be slightly cooked too.
Can you refreeze thawed food?
Yes, you can safely refreeze thawed food, but the quality may suffer due to loss of moisture during the thawing process.
Is freezing the best food preservation option?
Freezing is one of the most convenient, safe, and natural methods of food preservation. Other methods involve the extensive use of heat and chemicals, and these methods have been shown to adversely affect quality, flavor, appearance, and texture of food. They are also more expensive requiring the use of sophisticated technology, such as pasteurisation and retort cooking. Freezing methods, although not perfect, provide you with a more viable alternative, and this is evidenced by the discovery of intact animals and plants frozen in ice for thousands of years.
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