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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

Digital Re-print - July | August 2010 Added value by Flour Heat Treatment

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The physical and chemical properties of flour depends on the original grain quality.

However, the grinding process allows the baking characteristics to be controlled to a certain extent.

Thermal and hydrothermal treatment modifies flours in such a manner that they can be applied not only for baking, but also in numerous other areas of food processing. Thermally-treated flours are a response to the issues of recipe optimisation, enhance-ment of convenience and product safety, which are omnipresent in today’s food processing industry.

In addition, such flours do not have to be declared.

Flour Heat Treatment (FHT) allows the physical, rheological, microbiological, enzy-matic and chemical flour properties to be selectively modified.

During thermal treatment, the flours are exposed to the action of heat in order to strengthen the gluten and to reduce the water content. The purpose of hydrothermal treatment is to partially gelatinise the starch and to inactivate enzymes and microorgan-isms.

A very wide range of applications exist for such thermally and hydrothermally modi-fied flours. Generally speaking, they can be

divided into the following groups: bakery products, binders, coatings, and carriers:

Bakery productsThermally-treated flours with a strength-

ened gluten structure are used for making high-ratio cakes, where high proportions of sugar and fat are applied.

To obtain a long shelf life of fresh doughs, raw materials are required which have a low level of microbiological contamination. The heat treatment hygienizes the flour by inacti-vating a large portion of the microorganisms. The high temperature denatures part of the enzymes, making them incapable of reaction. This also has a positive effect on the shelf life.

Certain proportions of FHT flour may

The Flour Heat Treatment (FHT) process provides modified grain-based milling products with specific characteristics for a wide range of applications in the food industry. Heat-

treated flours are opening up new market segments for the grain milling industry

by Urs Schwendener, Process Engineer, Bühler AG, Uzwil, Switzerland

Added value by Flour Heat Treatment

Grain&feed millinG technoloGy22 | July - august 2010

FeatureHeat Treatment

increase the water absorption capacity of the bread dough.

BindersThe hot viscosity of flour can be selective-

ly increased by the FHT process. Such flours are used as thickeners in soups and sauces.

The action of the heat dries the flour. Flours used in instant soups must have a low water content to prevent them from releas-ing moisture to the other ingredients.

Microorganisms and enzymes are inacti-vated by the process heat. This increases the shelf life of the products.

Hydrothermally modified flours with an increased cold viscosity and water absorp-tion capacity can be applied for making sausages or instant desserts.

CoatingsHydrothermally-treated flour is excellent-

ly suited as a batter (liquid dough) for coating fish, meat, and vegetables with breading.

The optimised cold viscosity allows wet panadas to be uniformly applied to the product virtually without dripping. Such bat-

ters serve as binders between the meat or fish and the dry panada. Their purpose is to ensure that the bread crumbs will adhere permanently to the meat. It is not allowed to rupture or blister, even when deep-frozen or deep-fried.

The higher the cold viscosity, the thicker the wet panada coating that can be applied.

CarriersUntreated flours are hardly ever used

as carriers for flavorings, spices, or enzymes because the flour component substances might affect the actual product.

FHT flours, on the other hand, can be applied as carriers. The reactivity of their component substances is minimised, for the gluten has been denatured and the enzy-matic activity and the microorganism count have been reduced. The water content of such carriers must be low to ensure that no water will diffuse from the carrier into the actual product.

Other applicationsIn the FHT process, it is possible to stabi-

lise bran and germ (for example of wheat). This extends the shelf life to a significant extent. The thermal action largely inactivates the enzymes, which appreciably slows down the rancidity process.

In addition, microbially induced spoilage is reduced because a large part of the micro-organisms has been inactivated by the heat. Stabilized bran and germ are characterised by their nut-like taste. They can be used in bread, breakfast cereals, cereal bars, etc.

Grain&feed millinG technoloGy July - august 2010 | 23

Feature Heat Treatment

Grain&feed millinG technoloGy July - august 2010 | 7

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obtained. With in a medium degree of gelatinisation, the FHT and extrusion proc-esses overlap to some extent. The extrusion process allows a starch gelatinization degree up to 100 percent to be achieved.

Flours that are subjected solely to thermal treatment will to some degree retain their baking properties and therefore differ funda-mentally from extruded flours.

FHT is the optimal process for modifying flours on a customer-specific basis. Such flours open up a wide range of applications in the most diverse fields of the food produc-tion industry.

Buhler is a global leader in the supply of process engineering solutions, especially technologies for grain processing plants and nutrition solutions. Buhler is present in over 140 countries and has some 6600 employ-ees worldwide.

stream of product flowing at a rate up to 2500kg/h.

In a conditioner, steam and – depend-ing on the type of treatment – water are injected into the flour. Then the flour is transferred to the retention screws, where the actual “cooking process” takes place.

Thermopneumatic conveying systems dry the moist product to the required water content. Agglomerated product is removed

by sifting, reduced to a defined particle size, and returned to the flour. After the end product has passed through the metal detector, it is conveyed to the finished-product bins, from where it is bagged or loaded out in bulk into trucks.

The most important process parameters are the through-put rate, the steam and water quantity, the temperature, the retention (dwell) time, and the drying temperatures. These parameters are permanently controlled and monitored by a PLC control system. They are visualised and recorded online, enabling the entire process to be carefully logged.

FHT process versus extrusion

Frequently, the question aris-es as to the difference between the FHT process and extru-sion. The two processes do not compete with each other.

Unlike extrusion, where the flours are exposed to the very powerful action of heat, mois-ture and mechanical forces, the flour in the FHT process is treated only hydrothermally or thermally.

Hydrothermal treatment allows a low to medium starch gelatinisation degree to be

A new field of application is the stabiliza-tion of rice polishings as a preliminary stage to subsequent oil extraction from rice hulls.

Flour heat treatment processThermally and hydrothermally treated

flours can be produced on the same system when the Buhler FHT process is used. A loss in weight dosing scale sup-plies the system with a constant, defined

More inforMation:Urs SchwendenerProcess EngineerBühler AGUzwilSwitzerland

Tel: +41 71 9552259Email: urs.schwendener@buhlergroup.comWebsite: www.buhlergroup.com

Related companies

Cimbria A/SFaartoftvej 22 PO Box 40Thisted, DK-7700 DK

Tel: +45 96 17 90 22Fax: +45 96 17 90 19Email: jyn@cimbria.comWebsite: www.cimbria.com

John Staniar & Co.34 Stanley Road WhitefieldManchester, M45 8QX GB

Tel: +44 161 767 1500Fax: +44 161 767 1502Email: sales@johnstaniar.co.ukWebsite: www.johnstaniar.co.uk

Grain&feed millinG technoloGy24 | July - august 2010

FeatureHeat Treatment

The solution behind the solution.

Bühler AG, Grain Milling, CH-9240 Uzwil, Switzerland, T +41 71 955 11 11, F +41 71 955 66 11

milling@buhlergroup.com, www.buhlergroup.com

Back in 1900, a Swiss man invented muesli. Our passion for the finest flakes and

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Milling_2010.indd 1 23.02.2010 10:56:10

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