bake - May 2015 - 18

equipment

The Science of
Fermentation
As dough ferments, heat is generated, raising the dough

Monitoring proper dough temperatures is vital to the bread baking process.

temperature and accelerating the yeast activity. This temperature increase can be monitored and indicates the progress

to work best. A pH ranging from 4.5 to 6.0 gives the best

of fermentation. At the end of a standard fermentation time,

results. Bread doughs are generally in the region of pH 5.5.

higher temperatures than expected may indicate an excess of

Some ingredients used in the bakery, such as mold inhibitors in

fermentation has been accomplished.

some bread improvers, lower the pH of the dough and do have
a retarding effect on yeast fermentation. This effect is usually

The optimum temperature range for yeast activity is between

taken into account when deciding on the yeast level to use in

32° to 40°C. Temperatures higher or lower than this range

a given formula. There are other ingredients which can retard

will slow yeast metabolism. The general practice in bakeries,

yeast activity such as spices or raisins.

depending on the dough system used, is to ferment doughs
between 23° to 30°C, so as to maintain proper dough handling

Carbon dioxide cannot form a gas bubble on its own. In ﬁzzy

through production. One must also bear in mind that the

drinks, microscopic projections on the side of the bottle

quantity and the type of aromatic substances will vary with the

provide those sites, which is why when you release the pres-

temperature.

sure as you open the bottle you see "streams" of gas running
from the sides. In bread dough the nucleating sites are

The initial pH of a dough should range between 4.0 to 6.0.

provided by the nitrogen gas bubbles, trapped in the dough

However, if the pH is higher or lower than this range a slower

during mixing. The yeast has used up the oxygen from the air.

yeast activity is seen. As a dough is fermenting the pH will
begin to drop because of acid production. A freshly made

During proof stages the carbon dioxide goes into solution

dough will have a pH slightly above 6, but the pH will drop

until the solution is saturated and then any more, which is

during fermentation (due to the formation of lactic and acetic

generated, makes its way into the nitrogen gas bubbles, which

acid).

grow in size, and the dough expands. The more yeast and the
warmer the temperature the faster the expansion; bakers get

Salt is one ingredient that should be mentioned because of the

oven spring because the maximum gassing rate occurs at

strong retarding effect it has on yeast fermentation. As salt in

40° - 45°C.

a formulation increases by as little as 0.2 percent, the yeast
activity will slow. Normal salt ranges for most breads are 1.75 to

In bulk fermentation stages bakers also get dough expansion

2.25 percent, based on ﬂour weight.

from carbon dioxide generation but most of that is lost when
the dough is knocked back and divided, so the yeast has to

Prooﬁng Stages

start over again. Yeast also contributes to dough maturity/

The primary function of yeast is to produce carbon dioxide gas,

development. Though its role is minor compared to improvers

which expands the dough during proof and the early stages of

in no-time doughs, it is more signiﬁcant in bulk fermentation

baking (oven spring). Yeast prefers slightly acidic conditions

where the enzymes play a signiﬁcant role.

18 < MAY 2015 | bakemag.com

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bake - May 2015

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