Yupo, yucca paste and emulsion

For those who don't know, yucca paste is the creamy stuff made from
starch of yucca, mainly served with rice and stew in Brazil.
(Brazilian people - feel free to elaborate)

From: Sandy King <sanking@clemson.edu>
Subject: Re: Yupo, was Re: Temperaprint & Gum
Date: Sat, 31 Jan 2004 00:10:46 -0500

> I may try Pete's suggestion and add a bit of colloid to the
> sensitizer and try again. Would this make the coating an emulsion?

I guess you and most people know this, but the term "emulsion" used in
silver gelatin process is entirely a misnomer. It's just that everyone
knows silver gelatin emulsion is actually a dispersion, it just
doesn't matter what it's called, and the misnomer never got fixed
(though I occasionally persist in saying dispersion, or at least being
reluctant in using the term emulsion). Mayonnaise is an emulsion, some
salad dressing are emulsion, the real hollandaise sauce is an
emulsion. Silver gelatin sensitizer, yucca paste, the liquid part of
the Chinese egg drop soup or sweet and sour soup, thickened sauce of
stews made with connective tissue rich cuts cooked near boiling point
for hours (collagen breaks down to gellatin in such a condition), many
fake hollandaise-like sauces are dispersions, not emulsions. Emulsion
involves tiny droplets of fats, water, or both. Aquaous phase of
gelatin or starch may give thickened texture but does not involve
droplets of fat or water.

Many silver gelatin literatures use term "emulsification" to mean what
is correctly called precipitation. This is clearly also a
misnomer. There is no emulsification going on. You have to stir the
reacting vessel during precipitation stage, and you'll get an instant
milky appearance as soon as you let the jet (buret or any apparatus
providing one of the reacting agent, usually silver nitrate) flow, but
it's just the appearance, and the amount of stirring is nothing
compared to the vigorous stirring needed to make hollandaise
sauce. Real emulsification would typically need a lot more vigorous
stirring. (You could make hollandaise emulsion much easier if you
added Kodak PhotoFlo 200 and antifoamer before adding lemon juice, but
it's probably considered inedible)

Ok enough on another piece of useless information that doesn't let you
do anything new. As long as it is clearly understood that it's a
misnomer and people know what's right, one can call anything an
emulsion but that would void the word. I personally think it's
sensible to avoid incorrect use of emulsion altogether in a small
attempt to break the chain of nomenclature misuse.

--
Ryuji Suzuki
"Reality has always had too many heads." (Bob Dylan, Cold Irons Bound, 1997)