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Re: Quick Rise vs Regular Yest

Cavan asked about yeast. The following is from the web site of Cook's
Illustrated. It is written from the perspective of a baker, who would use
yeast to proof dough but it does give some idea of what to expect in our use
for yeast.
Despite indications to the contrary - created by the commercial largesse of
the yeast companies - there remain to this day only these three types of
yeast: fresh, active dry, and instant. All are derived from the powerful
brewer's yeast known as Saccharomyces cerevisiae, but each is processed from
a slightly different strain of this protypical yeast.

The original commercial yeast, known as fresh or compressed, is about 70
percent water by weight and is composed of 100 percent living cells. It is
soft and crumbly and requires no proofing - fresh yeast will dissolve if it
is simply rubbed into sugar or dropped into warm liquid. Owing to qualities
associated with its strain, fresh yeast will produce the most carbon dioxide
of all three types of yeasts during fermentation. Fresh yeast is considered
fast, potent, and reliable, but has somewhat of a drawback: it is perishable
and must be refrigerated.

Active dry and instant yeasts arrive at their granular state by undergoing
processes that reduce them to 95 percent dry matter. Traditional active dry
yeast is exposed to heat so high that many of its cells are destroyed in the
process. Because the spent outer cells encapsulate living centers, active
dry yeast must first be dissolved in a relatively hot liquid (proofed) to
slough off dead cells and reach the living centers.

Instant yeast, on the other hand, is subjected to a gentler drying process.
As a result, every dried particle is living, or active. This means the yeast
can be mixed directly with recipe ingredients without first being dissolved
in water. It is in this context that the yeast is characterized as
"instant." With one-third less instant yeast than active dry yeast required
for the purposes of most recipes, instant yeast has earned a reputation as a
 stronger yeast. It combines the potency of fresh yeast with the convenience
of active dry, and it is considered by some to have a cleaner flavor than
active dry because it contains no dead cells. (In our months of testing, we
found this to be true when we made a lean baguette dough but could detect no
difference in flavor when using the two yeasts in doughs made with milk,
sugar, and butter.)

Though instant yeast was not developed to create a quicker rise, it is often
marketed and used as such in the United States. This is because it is more
potent than active dry. When recipes call for yeast without distinguishing
instant from active dry, the instant will rise more rapidly. But it is best
used in judicious amounts, as we discovered in our kitchen tests.

James Purchase