Name: Libbie C.
PLease could you explain how dough rises and why? Aso why
does it rise faster when heated? Another thing that I don't uderstand is
how enzymes work. Please help me, Thank-you
The yeast mold consumes sugars present in the bread dough. One of the
products of this digestion is CO2, which forms (usually) microscopic
bubbles. The CO2 gas occupies a larger volume, but cannot escape the dough
because the viscosity of the dough is too high. Hence the dough swells
(rises). Other things are going on but the above is the simple answer. Dough
rises faster when heated (slightly) because the yeast molds propagate faster
when the temperature is somewhat higher than say 25 C.
However, if the dough is heated too much the yeast mold is killed and the
dough rises less or not at all.
As to how enzymes work. That is a very complicated. Different enzymes work
What they have in common is that they accelerate (or retard) the speed at wh
ich some chemical reaction occurs, but the specific mechanisms may be
complex, and in a lot of cases is not known.
Dough rises because of production of carbon dioxide, a
gas that has no color or taste. When dough contains
yeast (a micro-organism) it is the yeast that produces
the carbon dioxide while it eats away from the sugars
in the dough. Alternatively, the gas can be produced
by enzymes and chemicals. This may sound unattractive,
but the production of gas by baking powder is
Yeast has a faster metabolism at higher temperatures
but would die when it becomes too hot. So by the time
your bread is baked it no longer contains alive cells.
The chemical processes caused by baking powder are
also faster at higher temperatures.
Enzymes are proteins that have a specific function.
This can be practically anything. Enzymes can degrade
large molecules into small ones (for instance, degrade
fat or other proteins: this is how enzymes help
destain fabrics in washing powders) or they can build
large molecules from small ones (for instance when
they build the proteins, DNA, and fats that are
constituents of all cells from smaller building
blocks). The function of an enzyme is determined by
its composition and structure. I hope this information
answers your question
Dough rises because of the yeast metabolizing the starch (sugar) in the
flour. Yeast ferment glucose to alcohol and carbon dioxide. It's the CO2
gas that expands in the dough and causes it to rise. The process is stopped
when the oven is turned up. These higher temperatures kill the yeast. When
you look at a slice of bread, all the little holes were actually trapped gas
bubbles. This process occurs faster at a slightly warm temperature. Enzymes
are catalysts that make biochemical reactions occur at a faster rate. These
reactions may occur without the enzyme but at rates that are biologically too
slow. Enzymes are proteins and they have a unique 3 dimensional shape.
Their substrates (the substance they work upon) are also 3 dimensional. They
fit together like a "lock and key". Each chemical reaction has its own
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Update: June 2012