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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