These are flashcards an notes made by students on topics like 'gluten', 'evaporation' and 'tg', originating from:

Study material generic cover image
- Wageningen University
ISBN-13 9990002019708
665 Flashcards & Notes
  • This + 400k other summaries, also in PDF!
  • A unique study and practice tool
  • Never study anything twice again
  • Get the grades you hope for
  • 100% sure, 100% understanding
Remember faster, study better. Scientifically proven.
Trustpilot Logo

Study Cards on gluten, evaporation, tg

Can you think of other plasticizers that influence the Tg of gluten and starch, apart from water?
Other plasticizers could be glycerol, glucose, or even soluble proteins. A plasticizer is a small molecule with good interaction (e.g. similar polarity) with the biopolymer.
Describe in your own words why the glass transition temperature is decreasing with increasing water content.
Water makes the starch molecules more mobile and less closely packed. More mobility means that the temperature should decrease further to immobilize the molecules (i.e. to create a glass). Therefore, Tg will decrease.
Why would the Glutenins be more important for baking performance than the Gliadins?
Gliadins “melt” at a lower temperature. So at a certain temperature/moisture content, only glutanins account for solid-like behaviour. Gliadins will not be able to make or stabilize a structure.
The authors state that the glass transition is partially reversible, which seems not in line with theory. The Glass rubber transition in conventional thermoplastic polymers is completely reversible. What the authors probably mean is that during the initial stages of the baking process, the rubbery gluten might become (partly) glassy again. How could that happen knowing that the temperature is not going down and the water content is not yet decreasing?
At Tr, the gluten become reactive, forming additional disulphide bridges. Below the Tr, the amount of crosslinks is fairly low, meaning that the gluten phase in the dough behaves elastic. With an increased number of crosslinks, the gluten behaviour will shift in the direction of a thermoset material that lost its elasticity. After the reaction, the Tg of the gluten will increase, but it might be questionable whether the gluten phase will become a real glass given the high moisture content.
The state diagrams do not contain the lines for the freezing and evaporation of water. At medium and high water content, the Tm and Tvap for the bread are 0° and 100°C respectively. How do they deviate at low water content? Sketch them in fig 4.
The state diagram should look like this.
The upper arrow indicated the transformation from dough to crust. The material at the outside of the bread is not able to follow the path indicated by the arrow though. Sketch a more likely route.
The temperature of the crust during baking will be controlled by evaporation temperature of water at that Aw. See diagram below.
During storage at ambient temperature, the crumb will become stale. Why is this not possible for the crust?
The crumb will become stale due to evaporation of the water to the environment. The water content of the crust is too low, and possible the starch is chemically altered in the crust preventing starch crystallisation.
  • Higher grades + faster learning
  • Don't study anything twice
  • 100% sure, 100% understanding
Discover Study Smart