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Digital Re-print - January | February 2010 Feature title: Generating added value through extrusion in the flour mill

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Grain & Feed Milling Technology is published six times a year by Perendale Publishers Ltd of the United Kingdom.All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies, the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis of information published. ©Copyright 2010 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1466-3872

Extrusion serves the food industry as an upgrading process on the one hand

for carbohydrate-based and on the other hand for protein-based raw materials.

With carbohydrate-based raw materials, starch occupies by far the most important place. Other polysaccharides such as cel-lulose and glycogen are especially used in the production of confectionary and in encapsu-lating processes.

Making additional productsGrain-based foods are staples throughout

the world. In the grain year of 2007-08, 2.1 billion

tonnes of grain was harvested around the globe. The production plants of the food industry process millions of tonnes of grain every day. The most important intermediate product in this connection is flour.

In addition to baking flour, grain process-ing also produces dark flour and bran, espe-cially when wheat is processed.

Extrusion technology is one of the numerous possibilities of further processing flour as well as the by-products obtained in grain grinding. It offers especially flour mills the possibility of increasing the value added that they generate. The most important products made by the extrusion process include breakfast cereals, breakfast flakes, baby foods, extruded breading

(crumbs), croutons and modified flours and starches. These are used, for example, as binders in soups and sauces or in the baking industry.

Modified and ‘clean label’ as well

Modified flours are also called swelling flours. They are applied as binders, fillers, or freshness extenders in bakery products.

Swelling flours are characterised by their modified water absorption capac-ity and their solubility characteristics. It is possible by suitable selection of the extru-sion parameters to adjust the viscosity of flour-and-water suspensions to the needs of customers or the requirements of a particular application.

When the correct amount of thermal and mechanical energy is introduced into the extruder, end products will be obtained which are soluble in either cold or hot water and which possess a certain bandwidth of viscosities.

The extrusion process is especially suita-ble for modifying flours because it completely eliminates the need for using chemicals.

Therefore, modified flour can be excel-lently applied as an ingredient in products to which the ‘clean label policy’ applies (no use of ingredients with e-numbers). When extruded swelling flours are used, it is enough to declare wheat flour on the ingredients list.

Alternative to traditional processes

Another field of application for extrud-ers is the production of breading (bread crumbs). Extrusion technology allows bread-ings to be made on the basis of a wide variety of raw materials. Whereas the tradi-tional production method requires the use of high-protein flours such as wheat or rye flours for developing the gluten framework, all starch-containing materials can basically be applied in the extrusion process. This also enables the processing of lower-grade wheat flours or flours made from corn (maize), rice, or potatoes. Raw material quality fluctuations are easier to smoothen out in the extru-sion process. In extrusion, dough leavening is achieved on the one hand through the expansion of the dough at the die, but on the other hand can also be controlled through chemical or physical raising agents.

Reduction of the energy costsIn addition, the extrusion process also

allows different types of breading flours to be made (American bread crumbs, Japanese bread crumbs, cracker meals, etc.) without requiring any modification of the extrusion line.

Moreover, it is possible to accurately adjust the texture, colour, and particle size of the product. In terms of energy efficiency, extrusion is a process excellently suited for producing bread crumbs. Much lower water contents in

Extrusion technology is one of the numerous possibilities of further processing flour as well as the by-products obtained in grain grinding. It offers especially flour mills the possibility of increasing the value added that they generate. The most important

eliminates the need for using chemicals. Therefore, modified flour can be excel-

lently applied as an ingredient in products to which the ‘clean label policy’ applies (no use of ingredients with e-numbers). When extruded swelling flours are used, it is enough to declare wheat flour on the

bread crumbs, cracker meals, etc.) without requiring any modification of the extrusion line.

Moreover, it is possible to accurately adjust the texture, colour, and particle size of the product. In terms of energy efficiency,

products made by the extrusion process include breakfast cereals, breakfast flakes, baby foods, extruded breading

it is enough to declare wheat flour on the ingredients list.

extrusion is a process excellently suited for producing bread crumbs. Much lower water contents in

The Buhler POLYtwin™ extruder is configurable flexibly and is well suited for the processing of milling by-products in premium food ingredients.

The extrusion of grain-based, starch containing raw materials is a process allowing all but boundless applications. Christopher Rubin, extrusion specialist in the Buhler Pasta and Extruded Products Business Unit, explains the possible value generation and benefits associated with the application of extruders.

Generating added value through extrusion in the flour mill

by Christopher rubin, product marketing manager - Extrusion, buhler, Switzerland

Grain&feed millinG technoloGy16 | January - february 2010

FeatureExtrusion

GFMT10.01.indd 16 29/01/2010 15:17

the product recipe and short retention times ensure low energy costs, especially in the downstream drying stage.

Thus, with a capacity of two tonnes per hour, the energy costs per tonne of finished product are twice as high for the traditional process than for the extrusion process.

Furthermore, with a suitable setup, the extruder offers the flexibility of also allowing related products such as baking beans and croutons and even bread chips to be made on the same line.

By-products as a raw materialExtrusion offers additional advantages. It can also process raw

materials such as very dark flours (low-grade flours) and wheat bran. Both are typically made available at low cost to the feed manufacturing industry.

With the aid of the extruder, these by-products can be trans-formed into high-grade foods.

They are extruded into breakfast cereals or are applied in a modified form as ingredients for other foods. Bran flakes are highly popular today. And extruded wheat bran may fetch a price that is double that of native wheat bran.

The opportunities for wheat bran as a high-grade food are vast. The high dietary fibre content of wheat bran gives the product a ‘healthy image’.

Utilisation of lower-price raw materialsThe basis of all the products mentioned up to now, which can

be made by the extrusion process, is grain flour. This is one characteristic that extrusion shares with the conven-

tional baking processes. The basic difference resides in the dough texture. The dough framework of conventional baked products is based on proteins (gluten or pentosans).

On the other hand, the texture of extruded products is based on starch. The raw material used for extrusion must have a starch content of at least five to 10 percent to ensure that the end product will have a stable texture.

But the protein content can be low, that is, below 10 percent. Flours with such a low protein content are normally unsuitable for baking purposes. As the flour price is determined, among other things, by the protein content, low-protein flours are less expen-sive than high-protein ones. The extruder therefore also allows low-price flours to be processed.

ExtrusionIn the extrusion process, a material is forced through a defined

aperture. In order to ensure that this opening (die hole) is not choked,

the material must be either completely or at least partially liquefied by subjecting it to the action of pressure and temperature.

But in practice, the extruder fulfils many more functions: conveying, melting, mixing (dispersion and homogenisation) and proportioning.

In addition, the material undergoes chemical and physical modifications during extrusion, for example starch gelatinisation or protein texturising. At the end of the extrusion process, the product is cut to size and thus shaped by a cutting device.

The raw material and the extrusion parameters deter-mine the product characteris-tics such as texture, bulk den-sity, colour, taste, water solubil-ity and others of the extruded products.

more inFormation:Christopher RubinProduct Marketing Manager ExtrusionBuhlerUzwilSwitzerland

Tel: +41 71 9551317Fax: +41 71 9553388Email: christopher.rubin@buhlergroup.com

Grain&feed millinG technoloGy January - february 2010 | 17

Feature Extrusion

We could talk all day about our quality and productivity.

But we’d rather

talk about yours.

Lafe Bailey, Vice President of Sales and Services

SABETHA, KANSAS USA 785-284-2133 INFO@WENGER.COMWWW.WENGER.COM

USA BELGIUM TAIWAN BRASIL CHINA TURKEY

Superior Technology. Unparalleled Service.

You see, the real story is the customer solutions we deliver,

and the lifelong business relationships

we cultivate by continually

surpassing expectations.

Wenger will offer you more

knowledge and skill in all

aspects of extrusion and drying

than anyone, anywhere.

Talk to Wenger today, and surround

yourself with unrivaled resources for

exceeding your processing goals.

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The solution behind the solution.

Fatten up your bottom line. Buhler high-performance animal and aqua feed production systems are used by leading companies around the world. These producers know they can rely not just on the technology itself, but also on the support that accompanies it. A service combining local presence with global expertise both lowers feed mill operating costs and increases capacity utilization. So the question is not whether you can afford to choose Buhler – it’s how a solution from Buhler will feed your profits. To find out more, visit www.buhlergroup.com.

Bühler AG, Feed & Biomass, CH-9240 Uzwil, Switzerland, T +41 71 955 11 11, F +41 71 955 28 96

fu.buz@buhlergroup.com, www.buhlergroup.com

Visit us at Victam Asia 2010 in Bangkok, Thailand,3-5 March 2010, www.victam.com

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February 2010

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In this issue:

• Learning & Development

- Is it a waste of money?

• Switzerland, training institutes

to service the milling sector

• Global Grain & Feed market report

• Extrusion Generating added

value through extrusion in the flour mill

• Learning & • Learning & • Learning & • Learning & • Wheat

Preparation Cleaning, conditioning

& colour sorting

GFMT10.01.indd 1 29/01/2010 15:16

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