Bubbles in bread - Endo-xylanases as bread improver
10 important questions on Bubbles in bread - Endo-xylanases as bread improver
How do carbohydrates contribute to the loaf volume?
What does endo in endo-xylanases mean?
What does exo- in exo-xylanases mean?
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To which family do the most well-studied endo-xylanases belong to?
What is the difference between Aspergillus GH10 and GH11 endo-xylanases?
- GH10: can cut many positions along the xylosyl backbone, and is not hindered much by arabinosyl branches. Has difficulty in cleaving directly next to branched xylosyl residues at the reducing end side (right)
- GH11: much less tolerant to branching
How are arabinoxylans divided considering water extractability?
- Linear/low degree of branching --> water-unextractable (WU-AX)
- Highly branched --> water-extractable (WE-AX)
What can water-unextractable polysaccharides do?
- They can easily bind to other WU-AX molecules or to cellulose (also a linear polysaccharide)
- Often associated with cell wall materials such as cellulose
- Inert material, which does not contribute to dough viscosity or air bubble stabilization
What can water-extractable polysaccharides do?
Which endo-xylanases should be added to obtain an increased loaf volume?
- Aspergillus GH11. They have a low tolerance to branching, and consequently release fairly large chunks of WE-AX from WU-AX, whereas the WE-AX originally present will not be cleaved to a large extent. It redistributes arabinoxylan from water-insoluble materials into solution.
- The WE-AX increases dough viscosity, and a larger surface area around gas bubbles can now be covered.
What happens if Aspergillus GH10 would be added?
- Decrease in loaf volume
- Tolerant to branching
- It will degrade both WE-AX and WU-AX to small oligosaccharides, as a result of which dough viscosity decreases.
- AX oligosaccharides are too small to assist in coating gas bubbles.
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