Question and Flour Problems (Extensograph and Alveograph; Guten Index and Glutomatic)




1.What is measured in an Extensograph and an Alveograph?
These instruments measure the resistance of a dough to extension under controlled conditions. The shape of the curve shows the energy input (E in the Extensogram, W in the Alveogram). Different dough properties (short, normal, soft) and different protein levels (low, normal, high) are recorded.

2. How can the effect of flour improvers be measured rheologically?
Of course baking tests are the analytical method for determining the nature and amount of the flour improvers to be added in the long term.

But extensogram data, especially, react extremely sensitively to all additives whose effects result from reactions with the proteins in the gluten. It was on the basis of such data that the theory of the Rheological Optimum was established and became acknowledged throughout the world. It gives concrete information on which flour improvers can be used to achieve which changes in the properties of the dough.

3. What is the difference between the Extensograph and the Alveograph?
So far the Alveograph method assumes the addition of a constant amount of water, which naturally results in doughs with different consistencies. The Extensograph method is based on doughs of equal consistency, since the optimum amount of water to be added has to be determined previously in the Farinograph. In the Alveograph the rheological effects of doughs can only be determined to a very limited extent under the present standard conditions.

But by extending the dough resting times it is possible to acquire as much valid information as with the Extensograph.

4. Can the effects of vital wheat gluten be detected with the Extensogrpah?
Since vital wheat glutens from different sources may have a noticeable influence on the viscoelastic properties of wheat doughs, their effect is also visible in the Extensogram. However, it must be taken into account that the behaviour of an isolated wet gluten and a rehydrated dried gluten is different when they are used alone from their behaviour in a natural combination with starch, pentosans, lipids and other constituents of the dough.

5. What shape should the Extensogram have to indicate good bread baking properties?
The area below the curve should be high, the ratio of resistance to extensibility should be approx. 1.5 – 3.0.

6. Can the correlation between the Alveogram and the baking results be improved?
Yes, within certain limits. The water addition rate should be flexible, i.e. according to the needs of the flour.

Furthermore, a pressure-relaxation test has been recommended, where the airflow suddenly stops and the relaxation of the bubble is measured.

Guten Index and Glutomatic
1.What information does the Gluten Index provide?
The more residue is left in the sieve of the centrifuge, the firmer is the gluten. Firm glutens usually result in more stable doughs with a high volume yields a Gluten Index > 85 is desirable.

2. Although we find 36% wet gluten with the Glutomatic, the baking properties are not satisfactory. How is this possible?
Several reasons should be considered :
.There are wheat varieties, for instance feed wheat, that contain quite a large amount of gluten but have poor baking performance.
.A lack of enzymes can be another reason. Check the Falling Number.
.Also check for insect or heat damage by gluten extraction and/or rheological tests, e.g. Extensogram.

3. Our in-house test results by Glutomatic wash meet the bare minimum specification. However, customers using the hand wash method have found the gluten quality to be too low and to cause greater wastage and thus a smaller quantity. What may the reason be?
Depending on whether the gluten washed out by hand is
a.Short and crumbly, or
b. rather weak and even slimy,

you may be facing a problem of heat damage or bug damage. Both seem to be fairly common with Indian wheat at times. As you know, heat damage would also be indicated by rather high Falling Numbers, while bad cases of bug damage would yield a terrible Farinogram with the curve decreasing more sharply than it would even with most standard protease.


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