Why does Frozen Food keep well?
Frozen food keeps for a long time because the freezing of the water inside the food forces the bacteria, which cause it to decompose, into inactivity. Like all living things, bacteria need water in order to thrive.
Bacteria are microscopic organisms, or forms of life which occur in air, water and soil all over the world. But they flourish and multiply particularly wherever organic matter is present. Some may cause disease, others are harmless, or even beneficial, but their activity causes organic matter, including food, to decompose.
Modern discoveries have enabled sub-zero temperatures to be obtained by cooling air to about—300 degree C (—508 degree F) by compressing it and passing it into low pressure chambers through fine nozzles. The result is a sudden and violent expansion, causing the air to be drastically cooled. In home refrigerators Freon-12 gas is used instead of air, and the temperatures are much less drastic.
The temperature in the freezing compartment of a domestic refrigerator is about -4 degree C or 25 degree F and that of a deep freezer about -15 degree C or 5 degree F.
Preserving food has an ancient history. The salting and smoking of fish and meat have been carried out for centuries. Another long used method of preserving food is to change its form, for example turning milk into butter and cheese, and grapes into wine. More recently preservation has been affected by canning, heat being used to kill bacteria, or dehydration.
Most fresh food contains 75 to 90 percent of water. When this liquid is removed, great savings in packaging, storage and transport are made. Potatoes, milk, eggs, tea and coffee are among the well- known products now sold as dry powders that need only the addition of water to reconstitute them.