Nitro Cold Brew Coffee and Why Nitrogen Forms a Small Bubble
Imagine a beverage that energizes. A beverage that is served cold, is creamy and slightly sweet, yet is only one calorie, and does not contain artificial
sweeteners or creamers? Sounds too good to be true, doesn’t it? Well that is exactly what nitro cold brewed coffee delivers. The cold brewing process
simply uses time to take the place of heat in the brewing process. Brewing methods vary, but in general, coffee is put into a cloth bag and it
is steeped in cold water, the brew is then refrigerated for 18-24 hours. Here is reference to a system used
by many commercial coffeehouses. Without the heat to burn the coffee’s oils, the resulting beverage is somewhat free from the bitterness of coffee
(low acid) and imparts a mellow sweetness to the drink.
The creaminess comes from the infusion of nitrogen into the beverage. Most of us are familiar with Nitro beers like Guinness which is infused with
nitrogen to give a creamy finish to the beer. So, much like Nitro beers, Nitro coffees are pressurized with nitrogen so that a small amount of
nitrogen dissolves into the coffee. At the dispense head a special aerator helps to release the dissolved nitrogen so that when the coffee is poured,
you get that beautiful nitro cascade and lovely crema head on top.
But why is the head creamy? The creamy head on nitro cold brew coffee comes from the small bubbles (about 60 microns)
formed by the dissolved nitrogen as it comes out of solution. Those small bubbles give a creamy feel on the tongue that gives the illusion that
there is cream in the coffee. That raises an interesting question – why are nitrogen bubbles smaller than say the bubbles formed by carbon dioxide
in a beverage? A quick google search yielded nothing substantive. Asking some of my fellow engineers did not help either, so I’ll give my thoughts
with the caveat that I may be totally wrong.
According to the engineeringtoolbox.com, we know that nitrogen has
a water solubility of .019 g/kg vs CO2 at 1.7 g/kg at 20C. Almost 100 times more CO2 than N2 is dissolved in the beverage. Therefore, there is
100 times less nitrogen available to form a bubble than there is for CO2. So, when the nitrogen bubble is formed, dissolved gases near the bubble
must come out of solution. Since there is so little nitrogen available, a stable small bubble is quickly formed and is all that can be formed.
Unlike a CO2 bubble that actually grows as it rises due to the abundance of CO2. That’s my opinion and without finding more evidence, it’s all I’ve got. What do you think?
I’m serving Nitro Cold Brew, but where do I get my nitrogen from? Nitrogen from a small nitrogen generator is an excellent choice for a coffeehouse.
Delivered gas from a local welding supply shop or gas company can pose issues for a coffeehouse. Typically, coffeehouses and café’s are small with
little space to store cylinders. These cylinders need to be handled by baristas that are often not trained in safe cylinder handling. Since the
cylinders are small, running out of gas in the middle of a pour is common and serving coffee is interrupted. Also, delivery from a fossil fueled
truck is harmful to the environment. A Parker gas generator eliminates the problems of safety, inconsistent supply, and needless truck deliveries.
Parker has been making nitrogen gas generators for the beverage market for over 35 years. Contact us and let us know your needs.