glace or “half-glace,” which is stock
simmered down to 25–40% of its original
volume, often with some tomato puree or
paste to add flavor and color, and with some
flour or starch to supplement its lower gelatin
content (10–15%). The tomato particles and
flour gluten proteins cloud the stock and are
removed by skimming the stock as it reduces,
and then by a final straining. The starch in
demi-glace, around 3–5% of its final weight,
is largely an economy measure — it gives a
greater thickness with less stock reduction and
loss of volume to evaporation — but it also
has the advantage of sparing some of the
stock’s flavor from being boiled off, and
avoiding the sticky consistency of very
concentrated gelatin.
Demi-glace is the base for many classic
French brown sauces, which are given
particular flavors and nuances with the
addition of various other ingredients (meats,
vegetables, herbs, wine) and final enriching
barry
(Barry)
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