Day 385

In Rock & Roll History, we discussed why 1950s society was such a fertile ground for rock & roll music: a much simpler time in some respects, with no computers, internet, portable music, battery-powered watches, cell phones, microwave ovens, CDs, VCRs, PVRs, surround sound, or even Tang. America feared Communist infiltration and atom bombs. Baby boomers were just starting school or being born, father was the breadwinner, mother was the housewife, an economic boom was spurring prosperity, the suburbs were growing, boys’ hair was short, girls’ hair was long, consumerism was on the rise, pressure to conform was uppermost, sex was a never-spoken three-letter word, and everyone wore good shoes everywhere.

Since I’m a baby boomer–yes, the only one in the class–I still think I’m under-dressed if I wear running shoes in public.

In FCF (Filtration, Carbonation and Finishing, remember?), it was all about fining agents. That’s the stuff that’s added to wort or beer to reduce haze issues. A fining agent does that by glomming onto yeast and small bits of protein, creating matrices of stuff that gravity can then drag down to the bottom of the vat.

How quickly this happens depend on the variables in Stoke’s Law:

Vs = 2/9 [(þpþf) x g x R²]

¯¯¯¯¯¯¯

µ

where

  • Vs = velocity of a settling particle
  • þp = density of the particle
  • þf = density of the fluid
  •  g = acceleration due to gravity
  •  R = radius of the particle
  •  µ = viscosity of the liquid

Essentially, if the density of the particle, the force of gravity, or the radius of the particle increases, the particle will fall to the bottom faster, but if the density or viscosity of the liquid increases, the particle will fall more slowly. However, density of the particles can’t be changed without changing your beer; likewise the density and viscosity of the liquid can’t be decreased without changing the quality if the beer. Gravity is fairly constant around the world. That means the only positive change we can make is to increase the radius of the particles. The good thing about this is that as we increase the radius of the particle, the falling velocity of the particle increases by the square of the radius. So if we double the radius of the particle, its falling velocity increases four-fold.

The easiest way to increase the radius of particles is to glue several of them together. We do this with fining agents, which have a positive charge, and can pull the negatively-charged particles together into a larger clump.

There are several types of fining agents, the most commonly used being isinglass, made from the swim bladders of certain fish like sturgeons, and Irish moss, made from a certain type of seaweed. We also covered silica gels and a compound called PVPP.

I was particularly fascinated by the way that Irish moss works. Its active ingredient is k-carrageenan, which normally is coiled into a helix shape. When it is heated, it unwinds into a long straight strand. Negatively charged particles are attracted to various positively-charged sites along this strand. Then when the molecule is cooled down, it snaps back into its helix shape, trapping the particles in its coils.

However, with a number of tests and projects coming up, I have little time to admire molecular structures: an on-line test in FCF tomorrow, a Business Ethics class presentation and 8-page report due next week, a completely costed Sensory Evaluation menu also due next week, a recipe and grist bill for an IPA also due next week, a class presentation in History of Beer in two weeks, and a Rock & Roll project proposal also due in two weeks. Better get typing.

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