Freezing or solidification is a phase change in which a liquid turns into a solid when its temperature is lowered below its freezing point. The reverse process is melting....
food preserves it from the time it is prepared to the time it is eaten. Since early times, farmers, fishermen, and trappers have preserved their game and produce in unheated buildings during the winter season. Freezing food slows down decomposition by turning water to ice, making it unavailable for most bacterial growth. In the food commodity industry, the process is called IQF or Individually Quick Frozen.
Frozen product don’t require many preservatives because the process of preparing the food for freezing kills most of the bacteria living on the food. Carboxymethylcellulose (CMC) is used as a stabilizer in frozen foods because of its tasteless and odorless properties.
Beginning in 1929, Clarence Birdseye
Clarence Frank Birdseye II was an American inventor who is considered the founder of the modern method of freezing food.- Early work :...
offered his quick-frozen foods to the public. Birdseye got the idea during fur-trapping expeditions to Labrador
Labrador is the distinct, northerly region of the Canadian province of Newfoundland and Labrador. It comprises the mainland portion of the province, separated from the island of Newfoundland by the Strait of Belle Isle...
in 1912 and 1916, where he saw the natives use freezing to preserve foods. Modern attempts at refrigeration began in the early 20th century in the meat packing industry. More advanced attempts include food frozen for Eleanor Roosevelt
Anna Eleanor Roosevelt was the First Lady of the United States from 1933 to 1945. She supported the New Deal policies of her husband, distant cousin Franklin Delano Roosevelt, and became an advocate for civil rights. After her husband's death in 1945, Roosevelt continued to be an international...
on her trip to Russia. Other experiments, involving orange juice, ice cream and vegetables were conducted by the military near the end of World War II.
Frozen food packaging must maintain its integrity throughout machine filling, sealing, freezing, storage, transportation, thawing, and often cooking. As many frozen foods are cooked in a microwave oven, manufacturers have developed packaging that can go straight from freezer to the microwave.
In 1974, the first differential heating container (DHC) was sold to the public. A DHC is a sleeve of metal designed to allow frozen foods to receive the correct amount of heat. Various sized apertures were positioned around the sleeve. The consumer would put the frozen dinner into the sleeve according to what needed the most heat. This ensured proper cooking.
Today there are multiple options for packaging frozen foods. Boxes, cartons, bags, pouches, heat-in-bag pouches, lidded trays and pans, crystallized PET
Polyethylene terephthalate , commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination...
trays, and composite and plastic cans.
Scientists are continually researching new aspects of frozen food packaging. Active packaging offers a host of new technologies that can actively sense and then neutralize the presence of bacteria or other harmful species. Active packaging can extend shelf-life, maintain product safety, and help preserve the food over a longer period of time. Several functions of active packaging
The terms active packaging, intelligent packaging, and smart packaging refer to packaging systems used with foods, pharmaceuticals, and several other types of products. They help extend shelf life, monitor freshness, display information on quality, improve safety, and improve convenience.The...
are being researched:
- Oxygen scavengers
- Time Temperature Indicator
A time temperature indicator is a device or smart label that shows the accumulated time-temperature history of a product. Time temperature indicators are commonly used on food, pharmaceutical, and medical products to indicate exposure to excessive temperature .-Technology:There are a large number...
s and digital temperature dataloggers
- Carbon Dioxide controllers
- Microwave susceptor
A susceptor is a material used for its ability to absorb electromagnetic energy and convert it to heat . This energy is typically radiofrequency or microwave radiation used in industrial heating processes, and also occasionally in microwave cooking...
- Moisture control: Water activity
Water activity or aw was developed to account for the intensity with which water associates with various non-aqueous constituents and solids. Simply stated, it is a measure of the energy status of the water in a system...
, Moisture vapor transmission rate
Moisture vapor transmission rate , also water vapor transmission rate , is a measure of the passage of water vapor through a substance....
- Flavor enhancers
- Odor generators
- Oxygen-permeable films
- Oxygen generators
- Validation of cold chain
A cold chain is a temperature-controlled supply chain. An unbroken cold chain is an uninterrupted series of storage and distribution activities which maintain a given temperature range...
With these new technologies, food may last longer and our knowledge about its safety will increase.
Vitamin content of frozen foods
- Vitamin C: Usually lost in a higher concentration than any other vitamin. A study was performed on peas to determine the cause of vitamin C loss. A vitamin loss of ten percent occurred during the blanching phase with the rest of the loss occurring during the cooling and washing stages. The vitamin loss was not actually accredited to the freezing process. Another experiment was performed involving peas and lima beans. Frozen and canned vegetables were both used in the experiment. The frozen vegetable were stored at -10 °F and the canned vegetables were stored at room temperature (75 °F). After 0, 3, 6, and 12 months of storage, the vegetables were analyzed with and without cooking. O'Hara, the scientist performing the experiment said, "From the view point of the vitamin content of the two vegetables when they were ready for the plate of the consumer, there did not appear to be any marked advantages attributable to method of preservation, frozen storage, processed in a tin, or processed in glass."
- Vitamin B1 (Thiamin): A vitamin loss of 25 percent is normal. Thiamin is easily soluble in water and is destroyed by heat.
- Vitamin B2 (Riboflavin): Not much research has been done to see how much freezing affects Riboflavin levels. One study found an 18 percent vitamin loss in green vegetables while another found a 4 percent loss. It is commonly accepted that the loss of Riboflavin has to do with the preparation for freezing rather than the actual freezing process itself.
- Vitamin A (Carotene): There is little loss of carotene during preparation for freezing and freezing of most vegetables. However, there is a danger of losing the vitamin during a long-continued storage period.
Freezing is an effective form of food preservation because the pathogens that cause food spoilage are killed or do not grow very rapidly at reduced temperatures. The process is less effective in food preservation than are thermal techniques, such as boiling, because pathogens are more likely to be able to survive cold temperatures rather than hot temperatures. One of the problems surrounding the use of freezing as a method of food preservation is the danger that pathogens deactivated (but not killed) by the process will once again become active when the frozen food thaws.
Foods may be preserved for several months by freezing. Long-term frozen storage requires a constant temperature of -18 °C (0 °F) or less. Some freezers cannot achieve such a low temperature. The time food can be kept in the freezer is reduced considerably if the temperature in a freezer fluctuates; small ice crystals thaw as the temperature moves up, and refreeze onto larger crystals as the temperature declines. Fluctuations can occur by a small gap in the freezer door or adding a large amount of unfrozen food.
According to a study, an average American consumes 71 frozen foods a year. The largest category of these frozen foods is frozen dinners, which many consumers purchase for a convenient and quick meal. Many food critic
The terms food critic, food writer, and restaurant critic can all be used to describe a writer who analyzes food or restaurants and then publishes the results of their findings. While these terms are not strictly synonymous they are often used interchangeably, at least in some circumstances...
s have devoted a show to the tasting and reviewing of frozen food, such as the web show Freezerburns
Freezerburns is a frozen food review web show hosted by Gregory Ng. Calling himself the "Frozen Food Master," Ng eats and reviews various brands of frozen food, and assigns it a rating based on his opinion...