|
Making simple syrup is an exercise in chemical reactions
When you make simple syrup, you boil equal parts of granulated sugar and
water-and add a pinch of cream of tartar. The end result is invert syrup, a
mixture of equal parts of glucose and fructose.
When yeast cells in a dough begin their digestion of the formula's
granulated sugar, they activate an enzyme called invertase. Result: the
sucrose is broken down into its simple components, glucose and fructose.
Both you and the yeast cells have conducted essentially the same chemical
reaction-hydrolysis of sucrose into its constituent sugars, glucose and
fructose. You, of course, want to use the invert syrup for its hygroscopic
properties. The yeast cell wants to eat. Yeast can't digest sucrose, so the
yeast cells must convert it to simple sugars, which they can digest.
An increase in solids
Both simple syrup and commercial invert syrups have long been known for
their hygroscopic properties-the ability to attract and retain moisture.
This ability helps products to stay moister longer, increasing their shelf
life and keeping qualities in a consumer's home. Invert syrups usually are
incorporated into formulas before baking, while simple syrup is used to thin
fondants or icings and can be brushed onto cake layers for additional
moisture before icing is applied.
Chemically, invert syrup and simple syrup are the same, and both are
produced by acid hydrolysis. Hydrolysis is a chemical reaction during which
a molecule is split (lysis). H2O or water (hydro) splits into its ions, the
H+ (positive hydrogen atom) and OH- (negatively charged oxygen/hydrogen
atoms), and these ions become part of the new components. (To learn more
about water as a chemical compound, click here)
In acid hydrolysis, an acid is used to speed up the conversion process.
When you added a pinch of cream of tartar or some lemon juice to your
sugar/water solution, you added tartaric or acetic acid, respectively, which
act as a catalyst in the reaction that converts sucrose to glucose and
fructose. (A catalyst is an ingredient or element that speeds up a chemical
reaction, but does not become part of the finished product.) The yeast
cell's conversion of sucrose into glucose and fructose also speeds up as
dough pH drops and dough acidity increases during fermentation.
In the conversion of sugar and water to invert syrup, the sucrose molecule
splits; the glucose segments acquire the oxygen (O) that connected the two
halves and the H+ ion of the water (H2O) molecule; the fructose segment gets
the OH- ion.
The reaction looks like this:
C12H22O11 (sucrose) + H2O (water) in the presence of an acid =
C6H12O6 (glucose) + C6H12O6 (fructose) or invert syrup
If you add up all the carbon (C), oxygen (O), and hydrogen (H) atoms in
invert syrup, you'll see that they equal the sum of all the C, O, and H
atoms in sucrose and water. In other words, the segments of the water
molecule have become a chemical part of the new glucose and fructose
molecules. That's why invert syrup stays a syrup, instead of settling out or
crystallizing as a simple sugar/water mixture might. As a result, the total
solids in the newly created invert syrup are about 5% higher than the total
solids of the sugar/water mixture you started with!
The reaction increases the number of H+ and OH- sites from 13 on the sucrose
molecule to 18 on the glucose and fructose molecules. These sites attract
the H+ and OH- ions of water. The positive H+ ions are attracted to the
negative OH- sites on the sugar molecules, and the negative OH- ions are
attracted to the positive H+ sites on the sugar molecules. Because there are
more sites on the molecules in invert syrup, you can see why invert or
simple syrup is more hygroscopic than sucrose alone.
In addition to increased moisture retention ability, converting sucrose to
invert syrup has two other interesting results: increased sweetness and
better solubility. On a sweetness scale where sucrose is set at 100, invert
syrup ranks about 130. So, using invert syrup in formulas can allow you to
cut back on the total amount of sugar used and still maintain the same
sweetness in the finished product.
Carol Meres Kroskey is the award-winning former senior baker editor of Bakery Production and Marketing magazine, a trade magazine that covered the entire bakery industry. Her baking experience includes stints at various retail, hotel and supermarket bakeries as baker and pastry cook. She also spent several years as an experimental baking technician for the American Institute of Baking, and as a test baker at The Long Co., a co-op for independent wholesale bakers.
You can reach her at carol@bakers-exchange.com
|
