From the HBD Archive
From: Len Reed <>
Subject: no subject (file transmission)
Date: 1990-05-22 01:37:49 GMT

Subject: Invert Sugar (Time to get out the old textbooks)

Eric Pepke(, in #421, writes:

>Invert sugar (sometimes labelled CORN SUGAR or DEXTROSE) can be regarded
>as the standard brewing sugar. Ready made invert comes in the
>form of a crystalline mass containing approximately 10 per cent water.

I don't think so. But we're both computer experts, not organic chemists.

From my wife's organic chemistry book[1], I gather the invert sugar is
a di-saccharide consisting of D-(+)-glucose and D-(-)-fructose. The
first of these is dextrose (dextrorotary glucose); the second is
levorotary fructose. So what we have is right-handed glucose plus
left-handed fructose.

Common table sugar (sucrose) is similar; it is dextrose + dextrorotary

Honey is mostly invert sugar; the bees supply the invertase, which is
the enzyme that inverts the fructose. Yeast also can generate invertase.
They will do this if you put sucrose in your beer. The yeast will make
invertase to convert sucrose into invert sugar.

So if you add invert sugar instead of sucrose, you'll save the yeast a
step. There is an ongoing argument over whether the inversion process
creates unhappy byproducts.

In any event, invert sugar is not dextrose. Dave Line, in the Big
Book of Brewing [2], describes a process to invert sucrose with citric
acid. He dances around the issue a big, but it's pretty clear that he's
talking about a left-handed di-saccharide.

However, my Webster's, while noting that the above definition of invert
sugar is #1, lists "dextrose obtained from starch" as a number two
definition! This can't be what Dave Line intended, though, as it
conflicts with his writing.

[1] Organic Chemistry, Morrison and Boyd, 3rd ed., (c) 1973, p. 1118.

[2] Dave Line _The Big Book of Brewing_, p. 61.

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