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Part 3 The Preparation of Food
on starch causes the dark crust of baked goods, toast, and some ready-to-eat breakfast
cereals.
Mixing starch granules with water and heating them causes them to become soluble.
They absorb water and swell. As starch granules swell, the starch mixture thickens.
As heating continues, the starch mixture becomes thicker until it reaches a maximum
thickness. This process is called gelatinization. It is basic to cooking all starches.
During cooling, bonds form between the starch molecules. Because of this bonding,
most starch mixtures form gels. The spaces of the gel network hold water. If you cut the
gel, or if it stands too long, water may leak out. This is called syneresis. You may have
seen this leakage in a lemon pie fi lling.
Cooking Cereal Products
The relative low cost and high energy value of cereals make them an important part
of the diet. Cereals are popular as breakfast foods. However, you can serve a variety of
cereal products at meals throughout the day.
Factors Affecting
Starch-Thickened
Mixtures
The temperature,
time, agitation, and
mixing method used
when cooking with starch can all affect the outcome
of the mixture. These factors must be controlled
during cooking.
The temperature used to cook starch mixtures
must be warm enough to make the starch molecules
swell uniformly (the same amount). It should not be so
hot that it causes uneven swelling or lumping. When
lumping occurs, the molecules in the middle of the
lump do not swell. They stay small and dry. Cooking
starch mixtures in a double boiler or in a heavy pan
over moderate heat will help prevent lumping.
The time needed for gelatinization to be completed
depends on the kind of starch and the cooking
temperature. Once gelatinization occurs, cook the
starch mixture for a short time longer to thoroughly
cook the starch. This will prevent a raw starch fl avor
in the fi nished product.
The amount of agitation a starch mixture receives
can affect its texture. Gentle stirring during cooking
will help keep the starch mixture smooth. If you stir
the mixture too rapidly or for too long a time, the
starch granules may rupture (break down). As a
result, the cooked starch mixture will be thinner.
A recipe will usually tell you which mixing method
to use when adding starch to a hot liquid. If you add
starch directly to a hot liquid, the starch granules
usually will lump. To prevent lumping, you must
separate the starch granules from one another before
you add them to the hot liquid. You can separate
starch granules by using one of three techniques:
• coating with fat
• combining with sugar
• mixing with a cold liquid to form a paste
©2011 Wisconsin Milk Marketing Board, Inc.
Cornstarch was mixed with cold half-and-half to
separate the starch granules before being added as a
thickening agent in this soup.
Food Science