Someone once said that every conceivable flavor combination has already been tried. They may be correct; we’ve been cooking for a long time and nature hasn’t come out with many new items for us. One thing that has changed, though, is the way that we prepare nature’s ingredients now.
Last year we purchased our first dewar of liquid nitrogen for the kitchen. While we had played with dry ice when items came packed in it, we’d never had the opportunity to use it in its liquid form.
Liquid nitrogen is nitrogen in a liquid form that is -321 degrees Fahrenheit. It’s a cryogenic fluid that can instantly cause frostbite if it comes into contact with living tissue, so you’ll want to make sure that you always take the necessary precautions when handling it.
This is a dish that our Executive Pastry Chef, Bill Hallion, created. On it we see what appear to be pomegranate seeds, but are actually shattered raspberries. Before liquid nitrogen came into the kitchen this would be an almost impossible feat to accomplish…separating the hundreds of buds on a single raspberry without breaking them.
Liquid nitrogen is also useful in the pastry kitchen to make quick ice creams, slowly adding it to ice cream base while spinning in a stand mixer. If you’re using a pacojet then it can also greatly reduce the amount of time it takes to freeze a beaker solid.
Another great application for liquid nitrogen is freezing and preserving foods. Any time a product is frozen, the water in the product crystallizes at a rate dictated by the temperature. The higher the freezing temperature (the closer it is to thirty two degrees Fahrenheit), the larger the crystals. Conversely, the lower the temperature is the smaller the crystals will be. When the crystals form they destroy the cell walls of the product, making it seem “mushy”. You can almost always tell when fish or similar proteins have been previously frozen. The great thing about liquid nitrogen is that crystallization is absolutely minimal. Not only that, but if you have a cryovac machine then you can bag your product close to the surface of the liquid nitrogen before sealing it, ensuring that no oxygen has been trapped in the bag at all. Now you can enjoy blueberries in the dead of winter, frozen at their peak during the summer months.
We purchase our liquid nitrogen here in Charlotte at Airgas. The initial investment was $800 for the dewar, then $50 for each refill. I recommend just purchasing the liquid nitrogen when you intend to use it, as the liquid sublimates as it sits.
Here’s a video of a high school teacher giving a pretty informative talk on the properties of liquid nitrogen.