Using A+S BioTec products in the cereals industry

A+S BioTec products have a whole range of uses within the cereals industry, including:

- the use of micronised bran (and low-fat oat bran) to increase the amount of fibre in cereals

- the use of micronised fruit powders to colour the cereal constituents

- the use of micronised flour to improve extruder performance

- the special use of wheat gluten to improve extruder performance

These products are largely used to produce extrudates, which are then used as ingredients in various types of muesli and muesli bars.

Extruder technology:

Applications: Extrusion is used in food technology to produce snacks, breakfast cereals, instant flour and breadcrumbs, flat breads, liquorice, starch gels for soups, puddings, doughs and textured vegetable protein as a meat substitute.

Technology: During extrusion, a substance is pressed through a nozzle. This is performed using one or several worm shafts which transport material from one end of the shaft to the other within tightly-fitting housing (as in a meat grinder). The transported material is pressed through a nozzle fitted to the other end of the housing. This process is pressurised and takes place at varying temperatures depending on the application. The material movement and production of a mass take place in different areas within the shafts. There is a transport section and a shearing section. In the transport section the material is mixed and transported. In the shearing section the starch is agglutinated and the protein puffed.

In food technology, the extruder combines several conventional production methods in a single process (1):

> A doughy mass made of cereal flour is produced     > The dough is mixed, cooked, kneaded and sheared

> Starch expulsion (agglutination)                             > Protein sources (structuring) 

> Build up pressure, temperature and viscosity

> Forming (formation of a strand followed by cutting)

> Poss. addition of other masses (co-extrusion)

> Drop in pressure with water evaporation at the nozzle outlet

> Poss. cutting of the extrudate at the nozzle

> Expansion of the extrudate after passing through the nozzle

Extruder types:

There are various types of extruder: a single-screw extruder, a twin-screw extruder, and a co-extruder. The shafts’ respective pressure, temperature, water content and RPM settings are of vital importance to the end product. Extruders from the firm Schaaf only process semolina; all other extruder types such as those from Bühler, Werner & Pfleiderer, APV, etc. can benefit from using A+S BioTec products.

How A+S BioTec products work in extruder technology:

1. Micronised bran products (and low-fat oat bran)

Flour with a high fibre content has a negative effect on expansion and process stability during extrusion. “If I want to produce a loose, voluminous product, it should not contain too much fibre or moisture”. (2).This undesired effect can be reduced by using micronised whole-wheat flour or by adding micronised bran.

2. The use of micronised fruit powders to colour the cereal constituents

Finely grinding fruit produces a well-mixed end product together with the desired colouration due to the increase in surface area.

3. The use of micronised flour to improve extruder performance

As micronised flour has a large surface area, meaning that starch can be agglutinated faster, the extruder used can return performance increases of up to 15%. To achieve this, tests must be performed for the respective recipe to determine what percentage of the flour used needs to be replaced with micronised flour (e.g. micronised wheat flour d90<100µm).

However, the shearing parts in the extruder shaft have to be adjusted to the modified conditions, i.e. the shearing power has to be reduced.

4. The special use of wheat gluten to improve extruder performance

In the case of special wheat gluten, the gluten itself is denatured. The wheat starch structure is not destroyed, however, as the high-molecular wheat proteins are reduced to low-molecular ones during the extrusion process (2), meaning an increase in performance can also be achieved by using the denatured gluten. To this end, depending on the recipe, 10 - 30% of the wheat flour should be replaced with the special wheat gluten. The shearing parts of the extruder shaft also need to be adjusted for this purpose, i.e. the shearing power should be reduced.

Sources: (1) (2) Breakfast cereals: Neue und bekannte Getreideprodukte, Arbeitskreis für Ernährungsforschung 2004 (New and existing cereal products, study group for food research 2004)


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