Extrusion applied in the food processing industry serves for upgrading carbohydrate- and protein-based raw materials. In the field of carbohydrate-based raw materials, starch by far accounts for the largest share.

1. Digital Re-print - July | August 2012
Generating added value by Extrusion
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2. FEATURE
Generating added value by
EXTRUSION
by Christopher Rubin, Head of Product Management and Marketing,
Pasta and Extruded Products business unit, Bühler, Switzerland
E
xtrusion applied in the food process- If the correct amount of thermal and
ing industry serves for upgrading mechanical energy is introduced into the Bühler presents new
carbohydrate- and protein-based product in the extrusion process, this will twin-screw extruder
raw materials. In the field of carbohy- enable end products to be made which are
drate-based raw materials, starch by far soluble either in cold or hot water and have “The goal of our development efforts
accounts for the largest share. a certain bandwidth of viscosities. was to offer an extruder which would
Swelling flours are used as binders, fill- satisfy customers’ needs in the respec-
Grain-based foods are staples throughout ers, or freshness extenders in baked goods. tive segments they are engaged in while
the world. Day in, day out, millions of tons The extrusion process is particularly suited still being a much simpler solution than
of grain are processed in food production to the modification of flours because it the comparable all-rounder PolyTwin,”
plants. In addition to baking flour, dark flour does not require the use of any chemi- explains the development engineer in
and bran are also obtained during grain cals whatever. These flours are therefore charge.
processing, especially with wheat. suitable also as ingredients in products
Extrusion technology is a possible way of subject to a ‘clean label policy’. When using
further processing flour and the by-products extruded swelling flours, it is enough to
obtained in the process. Extruders are used declare wheat flour on the ingredient list.
in a wide variety of flour processing applica-
tions. The most important resulting products Extrusion as an alternative The PrioTwin has been designed for
are breakfast cereals, baby food, bread- Another possible use is the production of continuous production with few prod-
crumbs, croutons, plus modified flours and breadcrumbs. Extrusion technology enables uct changes. Thanks to its new modules
starches used, for example, as soup or sauce breadcrumbs to be produced on the basis and its leaner design, it is particularly
binders or in the bakery industry. of a wide variety of raw materials. Whereas easy to operate. It combines proven
high-protein flours such as wheat or rye processes using simplified modules,
Modified and still a clean label flours are needed for developing a gluten which reduces the capital investment
Modified flours are also called swelling framework in the traditional production proc- cost. In developing this new design,
flours. Swelling flours are characterised by ess, it is basically possible to apply all starch- careful attention was also paid to inte-
their modified water absorption capacity and containing products in the extrusion process. grating the extrusion process optimally
their solubility properties. The viscosity of This also allows the use of lower-grade wheat in the upstream and downstream proc-
flour-and-water suspensions can be adjusted flours or corn (maize), rice, or potato flours. ess stages in order to offer integral solu-
to the specific applications by selection of the In this case, the dough is caused to rise on tions with a high customer value.
suitable extrusion parameters. the one hand due to its expansion at the die.
16 | July - august 2012 Grain &feed millinG technoloGy

3. FEATURE
Extruded Bran Sticks – a by-product transformed into flours as well as wheat bran are
valuable food as a rule sold at low prices to
the feed manufacturing industry.
The extruder enables also such
‘by-products’ to be upgraded
into high-grade foods. Both
by-products can be processed
into breakfast cereals, but are
also used in a modified form
as ingredients in other foods.
Bran flakes are highly popular
today. Extruded wheat bran,
for instance, can fetch double
the price of wheat bran in its
native form. The opportunities
that wheat bran presents as a
high-grade food are significant.
The high dietary fiber content of
wheat bran gives the product an
‘aura of health’.
The basis for making all the
products mentioned above is
grain flour. This is what the extru-
sion process has in common
with conventional bakery proc-
esses. The difference however
lies in the dough texture. The
dough framework of conven-
tional bakery goods is based on
proteins such as gluten and pen-
tosans. The texture of extruded
products is based on starch. The
raw material must have a starch
content of at least five to ten
percent in order to ensure a
stable end product texture. The
protein content may be low, that
is, below ten percent. Flours with
such protein contents are typi-
On the other hand, dough rising can also be a capacity of two metric tons per hour – are cally unsuitable for baking. As the flour price
controlled through specific chemical or physical twice as high in the traditional process as in is – among other factors – also influenced by
agents. Fluctuations in the raw material quality the extrusion process. In addition, the extruder the protein content, low-protein flours are
are easier to balance in the extrusion process. offers the flexibility required to produce related less expensive than high-protein ones. The
In addition, it is possible to accurately adjust the products such as baking peas and croutons or extruder therefore allows also inexpensive
texture, colour, and particle size. even bread chips on a given processing line by flours to be processed.
Moreover, extrusion is a highly energy-effi- selecting an appropriate configuration.
cient process. The much lower water contents More InforMatIon:
in the product formula in comparison to tra- Extrusion increases value
Christopher Rubin, Bühler AG
ditional production, in conjunction with short generation Tel: +41 71 9551111
retention times, ensures low energy costs, Even very dark flours (low-grade flours) Fax: +41 71 9553851
especially during subsequent drying. The energy and wheat bran are suitable as raw materials Email: christopher.rubin@buhlergroup.com
costs per ton of finished product – based on for processing by the extruder. Low-grade Website: www.buhlergroup.com
Grain &feed millinG technoloGy July - august 2012 | 17

4. Innovative extrusion processes without limits. Bühler is the global technology
partner for companies producing breakfast cereals, snack foods, or food in-
gredients on a commercial scale. With its extensive extrusion know-how and
its passion for customized solutions, Bühler is always in a position to generate
added value and success for any product idea. Bühler offers an integral range of
products and services for all process stages – from correct raw material handling,
cooking and shaping through extrusion to drying of the extruded products. And
this for all market segments – from breakfast cereals and snack foods to modified
flours and starches, texturized proteins, or vitaminized rice. In short: extrusion
processes without limits.
extrusion@buhlergroup.com, www.buhlergroup.com/extrusion
Innovations for a better world.

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Milling Technology magazine.
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