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Basic Chemical Reactions in Roasting

25/04/2009

I have some spare time over the coming weeks so I will go into more detail of what we think is happening when we roast and how we perceive some of these reactions in the cup.  Let’s start with some information I learned from Carl Staub, on basic chemical reactions in roasting.

Staub says, “Many thermal/ chemical reactions occur during the roasting process, decarboxylation, dehydration of quinic acid moiety, fractionization, isomerization, polymerization, and complex sugar reactions. The principal thermally reactive components are monosaccharides and sucrose, chlorogenic acids, free amino acids and trigonelline. Both arabinose and Gollactose of polysaccharides are split off and the basic sulphur containing and hydroxyamino acids decompose. Carbohydrates both polymerize and degrade, liberating thermally unstable mono saccharides, decomposing 15 to 35% of the polysaccharides, depending on the degree of roast.”

Some meanings that I could not find links too

Hydroxyamino-acid (a protein constituent in coffee)

What does that mean to us? Well, like some of the Irish roasters that I used to work with would say, “when it’s brown, feck it out!”.

Soon I will post about sweetness and what it means to me when evaluating coffee.

In other news I am contemplating a trip up to Seattle and Portland this week, contemplating…

Deaton

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