Baking & Snack - May 2004 - 138

STARCH

Bakers know that selecting the right starch for their applications can be a complex task. The variety of starches
available - wheat, corn, waxy, potato, tapioca - and
their range of functionality provides unlimited options.
A few similarities can be found among the different
types of starch. For instance, all starches consist of
granules ranging in size from 1 micron to 100 microns,
and all starch granules contain chains of two glucose
molecules: amylopectin and amylose. Amylose chains,
which are straight, are less viscous and more soluble
than amylopectin chains, which are more branched.
High-amylose starches impart the crispy crunch of
snacks and cereals. Because they are slow to hydrate,
high-amylose starches can extend the bowl life of cereal.
Granular starches are insoluble in cold water, but
when heated to approximately 140°F to 158°F (60°C
to 70°C), the granules begin to swell and gelatinize.
As the granules begin to hydrate, they become thicker
and more viscous, developing a paste-like texture.
During storage, the solubility of the gelatinized
molecules decreases, and they begin to crystallize or
retrograde. Retrogradation contributes to the firming
of crumb structure in bread.
It is here that the similarities end, and the characteristics of individual starches take over. Because each
starch has a different crystalline organization in its
granules and vary in their amylose content, they swell
in different ways and offer various forms of viscosity.
Corn starch can withstand high levels of heat and
stress and has strong adhesive properties, making it
well suited for snack products.
Waxy starches, which resemble hard, opaque
wax, consist mostly of amylopectin. They form clear,
thick and tacky pastes.
Waxy maize starch is noted for its good expansion
properties. It is well suited for puffed cereals, baked chips
and cakes. In filling applications where boil-out and heat
stability are issues, waxy maize starch is recommended
because it is thicker than other starches, which helps
reduce boil-out. Using a modified waxy maize starch in
snacks yields a crunchy texture and eliminates the risk of
starch breakdown during processing.
Tapioca starch is glossy and more brittle. In
products where a bland flavor is required, such as
creme-based fillings, tapioca starch is recommended.
Waxy rice starch is preferable in all-natural
products, especially if the product will be frozen or

STARCH BASICS

there is a risk of starch retrogradation. Rice starch is
also being used in extruded applications, where it
reduces moisture migration, improves batter viscosity and imparts a crisp texture to snack foods.
Modified wheat starch imparts rapid meltdown,
or a melt-in-your mouth sensation, and provides a
better flavor release.
Potato starch is often used in potato-based
extruded snacks because it provides high expansion
during extrusion, imparts a crisp texture to the
finished product and acts as a shelf life extender.
TERMINOLOGY
Unmodified starch. Also known as native starches,
unmodified starches are not chemically altered and
therefore can be labeled in their generic terms: corn
starch, wheat starch or tapioca starch. Unmodified
starches may be physically altered to produce the
desired effects and are used in applications that require
little shear, low baking temperatures or short bake times.
As the interest in clean labeling increases, suppliers are trying to find ways to use starch to get the
same functionality as modified starches or those that
have been chemically altered.
Modified starch. Modified starches have
undergone chemical modification to yield desired
characteristics not found in native starches.
Modification can stabilize a starch, preparing it for
activities such as freezing and shearing.
Fruit fillings and icings often require a modified
starch that can impart high viscosity to hold fruit pieces in position. Since fruit fillings have a low pH level,
modified starches that have a tolerance for a low pH
environment, process shear and high temperature
stability are well suited for filling applications.
Too, in baked products with a high moisture
content, moisture migration is a common problem,
leading to an over-saturated crust. In such applications, modified starches are used to provide a sheen
to the filling, bind and retain moisture and deliver a
short paste texture, which eliminates tailing.
Instant starches. Instant starches, which can be
either modified or unmodified, disperse easily in
baking applications. They impart stability and act as
shelf life extenders in fillings for pies, toaster pastries
and cereal bars. Instant starches are also used in cake
mixes, muffins and quick bread. Because they go di-

rectly into a system, shear and breakdown are avoided.
Instant starches are often used in baked snacks
where oven temperatures increase slower than with
other cooking equipment. These starches also produce
a crispy, crunchy texture and can eliminate the drying
time before or during the production process. They are
better suited for foods baked at low temperatures, such
as in a microwave.
Pre-gelatinized starch. Pre-gelatinized starch,
often referred to as a pre-gelled or cold water swelling
starch, is processed to swell in cold water, unlike regular starch. A starch paste is heated to its gelatinization
temperature, dried on a drum dryer and ground into a
powder. When added to water, this pre-cooked starch
is thinner than other starches and gels more easily.
Many low-moisture products require pre-gelled
starches. For example, cake mixes use finely ground
waxy maize starch for its rapid hydration and
viscosity-building characteristics. According to one
supplier, the pre-gelled starch at a 1% to 3% usage
rate yields a more uniform cell structure, bake and a
higher volume in the final product.
Pre-gelled starch contributes moisture retention among other functions and is typically used in
applications that require rapid hydration or room
temperature preparation, such as instant fruit fillings,
cream fillings, cake mixes, bread, muffins, icings,
cookies and reduced-fat baked foods.
Cook-up starch. Cook-up starches require additional heat to reach their full functional temperature.
They are often used in products that will reach 180°F
for at least 10 minutes. In fresh and frozen applications, cook-up starches add viscosity, are resistant to
acid, heat and shear, increase overall stability, provide
clarity and remain stable in cold storage.
Resistant starch. Resistant starches act like fiber in
that they resist to digestion in the small intestine and
fermentation in the large intestine. While they have
fiber contributions, these starches do not have the
typical off flavor or negative effect on baking as fiber.
Resistant starches are used mainly in low- to
moderate-moisture products, such as high-fiber bread,
bran muffins and breakfast cereals. According to
studies conducted by one starch supplier, resistant
starch yields a better product appearance, texture
and mouthfeel than conventional fiber and increases
expansion and crispness.

STARCH RETROGRADATION: THEORIES
Staling describes changes in baked foods other than
microbial spoilage, notably the progressive deterioration in
crumb texture, that take place over time. Bakery researchers
have proposed several theories to explain staling.
The most commonly held theory blames staling on
starch retrogradation. The crumb of baked foods firms
because of the collapse of swollen starch molecules as
they lose their bound water and recrystallize. Branched
and unbranched molecules, both inside and outside the
starch granule, are involved. Long chains recrystallize, or
retrograde, faster than short ones.
For the most part, retrogradation is a one-way street,
as is moisture loss from protein. Baked bread can be refreshed by heating at temperatures as low as 140°F (60°C).
But ultimately, any activity that drives free water out of
the system speeds staling. Once total system moisture falls
below 30%, heat no longer returns bread to a fresh state.
The newest theory of staling proposes that firming
138 / BAKERS PRODUCTION MANUAL / May 2004

within the crumb takes place because gluten and
starch, which are both polymers of considerable
size, become increasingly entangled as the system
loses bound water. The intertwined polymers result in
insoluble moieties that stiffen the crumb.
Although better known as emulsifiers, surfactants
can complex, or combine, with starch fractions.
The effect of adding lecithin, lactylates, mono- and
diglycerides or polysorbates at low levels is to
soften the crumb over an extended period of time.
There is good evidence that monoglycerides, for
example, complex with the outer linear chains of
the branched amylopectin starch fraction within the
swollen granule. The surfactant, thus, interferes with
the recrystallization of this starch fraction.
Surfactants are also thought to coat starch granules
during mixing, reducing their capacity to absorb water.
More dough water is thus available to hydrate the glu-

ten for softer fresh bread. In addition, surfactants inhibit the
diffusion of amylose from the swollen granule to restrict
the formation of an insoluble retrograded starch gel.
Emulsifiers can also complex with gluten. One study
found that during mixing, the surfactants associated mostly
with the protein but, after baking, were strongly bound to
starch and its amylose and amylopectin components.
Enzymes, specifically amylases, are the latest ingredients to be recruited to fight the baker's war on staling.
Amylases cleave long-starch chains, raising the proportion of short-chain starches in the crumb. Short-chain
starches retrograde more slowly than long-chain starches.
Because the heat of baking deactivates enzymes, these
ingredients don't remain active after baking. They need
not be included in ingredient statements.
Enzymes and emulsifiers are not interchangeable as
anti-staling ingredients. Rather, they synergistically support
each other in softening crumb texture.

Baking & Snack - May 2004

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