Back in season 2 of Top Chef, one of the contestants routinely experimented with molecular gastronomy through the use of unorthodox equipment and chemicals. This naturally caught my interest and I remembered how Marcel would use a Nitrous Oxide injector to “foam” components into his dishes. Though I’ve yet to experience the taste of airy coconut, I’d imagine the texture to be similar to the foam on my expresso. More so, I remember Freddy, Carlo, and Brian talking about achieving the perfect head back in the days of Ebar, so I thought..
Why is the Head so important?
[Source: http://beerbeer.org/image/2009/beer/beer-head.jpg]
Let’s begin with why beers bubble. During one of the manufacturing processes, yeast is added to the barley and hops to do an important chemical reaction. What the yeast does is eat up Glucose to create three by-products, Ethanol (the alcohol), Carbon Dioxide, and Released Heat.
Glucose - > [2]CH3-CH2-OH + [2]CO2 + Energy
Yeasts gradually release Carbon Dioxide gas as they nomnomnom on the barley and hops, sorta like humans (they’re Eukaryotic too!). Though some of this CO2 is removed during manufacturing, some of this gas dissolves into the beer and remains there throughout the bottling process. As a person begins to pour the brew, the movement of beer from bottle/keg to glass (or red cup) causes some of this gas to escape. As expected, more gas is released with increased disturbance and vigorous pouring pisses off even Mr. Bubble.
The bubbly, white foam is a gas-liquid-protein interaction that holds everything together. This interaction includes hydrophilic ends that associate with the liquid, while hydrophobic proteins cling to the side of your glass. These two types of proteins work together to increase the stability in the Head and their effectiveness can change due to many reasons. These include the species of cereals used, the acidity of the hops, and temperature at which the alcohol is held at. I wonder how many people I put to sleep with this paragraph.
Beer enthusiasts look for this head because the escape of carbon dioxide helps prevent some of the “prickliness,” described as undesirable flavor aromas. There’s even a term called lacing, qualifying the foam’s ability to stick to the glass. Of course, lacing can be manipulated due to confounding factors, such as temperature and the presence of other chemicals. For example, oils and soap interfere with foaming and you’ll end up with a “flat” beer. They do so because they contain hydrophobic ends that pull apart the hydrophobic proteins. This prevents the creation of new bubbles.
Likewise, if you’re a neophyte at pouring beer and it begins to “foam over,” you can prevent this by touching the rim of the glass with your fingers. The natural oils in your skin work in the same manner described above. Or you can just stop the foaming with any other part of your body.
[You made the blog Ms. Tang!]
Due to the increased demand for Head, many breweries and restaurants now inject beer with Nitrogen gas to prolong its foamy duration. The bubbles that form due to Nitrogen (as opposed to Carbon Dioxide) release at a slower rate because it is less soluble in water than CO2. This means your Head won’t deflate as quickly as you quest for 30 bars within 30 days. In addition, Nitrogen gas doesn’t carry that tart bite that Carbon Dioxide can carry as it is converted to Carbonic Acid.
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