Yes, that's correct. And the reason for choosing nitrogen is twofold: first, it's a very cheap byproduct of liquefying oxygen which has lots of uses; and second, because it does not change the pH of whatever it's packaged with.
As Read-Only states, air is liquified to extract liquid Oxygen, leaving the liquid Nitrogen as a byproduct. It is the same food-grade as ordinary air. It is often used to displace Oxygen, such as when grains are placed in large containers. This prevents their slow oxidation over time (spoilage). It is also used in processes where it is undesirable to have ambient CO2, which can dissolve into water, so a nitrogen blanket is laid down, excluding both CO2 and O2. For instance, manufacture of dissolved NaOH can be effected by absorption of CO2, so the solid NaOH is dissolved into CO2 free water that has a nitrogen blanket over it.
Thanks for all the replies. One of the risks I project is oxygen contamination. If oxygen contamination is possible, it will make the Nitrogen not a food grade. :shrug:
there is only one way i can think of to get enough nitrogen for the food industry and that would be liquification. the act of liquifying nitrogen would purify it. oxygen contamination? are you serious? trust me, you definately want to be oxygen contaminated, you really should be swimming in it. but not too much oxygen though, about 28 or so percent, you can pad the rest with nitrogen.
Oxygen contamination when Nitrogen is extracted by fractional distillation isn't an issue. Liquid Oxygen has a BP of 90.2K, Liquid Nitrogen has a BP of 63.15k. If you hold the container at 89k, the Oxygen will condense out, leaving a Nitrogen rich atmosphere, which can be cooled further. IF contamination of Liquid Nitrogen by Liquid Oxygen does occur, it's easy to spot, because Liquid Oxygen is clear, and blue in colour, whereas Liquid Nitrogen is clear and colourless.
True. In commercial application, contamination never occurs because the O is removed long before the N even begins to condense. The industrial process takes full advantage of that temperature differential - it's a very simple matter to keep them well-separated.
They only need a mostly non-reactive pure gas (in terms of food). Nitrogen is used not only because of its abundance but because it is one of the last gases in common air to condense, so it is relatively easy to purify. The only other gas that would be left is hydrogen which there would only trace amounts. As for the food grade part, people need to stop thinking that the guy is an idiot for asking when there is an issue with what "type" of nitrogen is used. As anyone should know, there is really no such thing as a truely pure sample. When nitrogen is stored there is two ways of doing it, liquid and gas. Though you may not you buy it liquid, some companies origanally stored it that way. The problem is that when companies "boil" it back to a gas, they usually use tanks that have a chemical coating on the inside to prevent re-condensing. These chemicals would then be released in small amounts when the nitrogen is released. These chemicals are also not the kind of thing you want to eat!
