g new ideas for keeping things like foodcold. Up until the early 20th century ice was the best method for cooling perishable items, but
then we figured out a more efficient and affective way of keeping items cold. It was called the
refrigerator. Soon after the introduction of the refrigerator we developed something called
cryogenic freeing, which is freezing with very low temperatures.
Cryogenic freezing is the study mater that is colder than temperatures that occur naturally
on earth. The air in the cryogenic temperature range becomes a liquid or even a solid. The
lowest possible temperature is -459.69 degrees F, and the highest temperature in the cryogenic
range is somewhere around -100 degrees F. The most common matter in cryogenic freezing is
liquid nitrogen. Liquid nitrogen is most commonly used at temperatures from -100 degrees F to
-320 degrees F. Cryogenic freezing is mostly used in food processing plants to freeze small items
like patties, prepared meals, pizza, pasta, baked goods, appetizers, and confectioneries. Although
there are some systems that are designed to freeze large items like turkey breast, pork, and beef,
but because the cost of liquid nitrogen and the amount of liquid nitrogen it takes to freeze large
items it is not economically feasible. However for freezing small items cryogenic freezing is a
reasonable choice since a cryogenic freezing unit is two thirds less than a conventional system, but
you still have to add the cost of the nitrogen which will put you at over one and a half as much as
ac conventional unit.
Under natural conditions a substance is cooled by placing something cooler next to it. In
cryogenic freezing a substance is made cooler by a substance that is colder than anything in
nature. For this to happen work must be done to remove heat and then insulation must be
provided to maintain temperature. First you must compress the gas in a system so that it releases
all of its heat and then insulate the system so that it has to allow the gas to expand by using up the
remaining heat energy and cooling the system below the temperature of its surroundings. Now to
reach even colder temperatures you have to the second law of thermodynamics which states that
disorderly atoms within a system may be made more orderly only if outside energy is applied to
the system. This is accomplished by demagnetization. In demagnetization you apply a strong
magnetic field to the system which causes the molecules of paramagnetic to line up. Then remove
the magnetic field and the system will use up more energy inside the system to move back into a
disorderly arrangement. By using the demagnetization process you can achieve temperatures of
-459.69 degrees F.
Conventional freezing is cheaper and is used in almost every house, restaurant, grocery
store, and food plants. Most places use a compression system which is composed of four
different elements: a compressor, a evaporator, a compressor, and a expansion valve. The
refrigerant is vaporized in the evaporator then the vapor goes to the compressor and is
pressurized and heated. After that it goes on to a water cooled condenser were it is condensed
into liquid. Now the refrigerant moves on to the expansion valve, in which its temperature and
pressure are maintained. The same system is used in refrigerators and freezers only the freezers
have bigger tubes and more insulation. In a compression system the refrigerant never has to be
replaced unless the system fails. The most common refrigerant is called R-12.
If only cryogenic freezers werent so expensive we could have frozen food in just seconds.
Instead of waiting on those slow conventional freezers. We will just have to wait until the price
of nitrogen goes down.
The first thing that I for my experiment is take two pieces of turkey breast meat and
made them weigh the same weight.(5lbs.) After that I took one piece of meat and put it in a
freezer. Then I took the other piece of meat and soaked it in liquid nitrogen until it was frozen
and then put it in a conventional freezer over night. Next I took both pieces of meat and thawed
them out by putting them in a tub of water. When the two pieces were thawed out I weighed
them and the piece that was froze by liquid nitrogen weighed more than the one that was froze
conventionally. Now I gave the pieces of meat to our inspector and he took them and ran a some
test to check the bacteria count. Again the one froze with liquid nitrogen had less bacteria than
the piece that was froze conventionally. After that I ran the two pieces of meat through a
machine that injects the meat with all the ingredients. The piece frozen with liquid nitrogen
picked up more solution and held it longer than the meat that was froze in a conventional freezer.
Also the physical appearance of the two pieces was dramatically different. For instance the piece
froze with liquid nitrogen had a more brighter and fresher look, while the piece that was froze
conventionally looked paler and not quite as plump. So as you can very well see cryogenic
freezing is much more efficient but not quite as economical.