Bubbles in bread Flashcards
What are the steps involved in bread making from the wheat
- milling 2. mixing the flour 3. Fermentation and baking
T or F : the hard wheat will give more starch damage than soft wheat
true
T or F : hard wheat is better because it has higher than 9% damaged starch
false it is not better because over 9% wheat damage you have sticky bread
T or F : bread from sprouted wheat are better quality
false, they lesser the quality because of the presence of a-amylase which doesn’t let the starch ferment during the doug fermentation step
Yeast will convert ___ to CO2 and ___
maltose will be converted to CO2 and ethanol
what is the goal of the milling step?
making the starch available for the enzymes amylase for breaking them down into sugar for fermentation by the yeasts
What are the 4 class of proteins identified by the osborne fractionation?
- Albumin 2. Globulin 3. Prolamin 4. Glutelin
Albumins are soluble in :
water
Globulins are soluble in :
water with dilute salts
Prolamins are soluble in :
70% ethanol
Glutelins are soluble in :
soluble in dilute acids or base
Glutenins are responsible for the ___ of the bread while gliadins are responsible for the ___
glutenins : strenght gliadins : viscosity
gluten is a mixture of two class of proteins :
- gliadins 2. glutenins
The ___ creates disulfide bridges in the bread
glutenins-HMW
What are the two types of glutenins?
LMW and HMW
T or F : the gliadins will be responsible for the disulfide bridge
false, it is the glutenins
T or F : disulfide bridge can also be found in LMW-glutenins
True, the disulfide bridge are also found int he LMW glutenins but less. the disulfide bridge are covalent bonds.
Glutenins/ or gliadins are more present in gluten?
they are present 50% /50%
The network formed by the gluten (gliadin and glutenin) is due to what type of interactions ?
- hydrophobic
- s-s (covalent) by the glutenins
- hydrogen bonds
What can you do to know if you will have good baking behaviour from a cultivar?
you can separate the proteins by SDS page and some bands will indicate good baking behaviour while others will be predictive of bad baking behaviour
which part of the HMW glutenins are responsible mostly for the disulfide bridges?
the n terminal contains most of the thiol groups
the disulfide bridge are intermolecular or intramolecular between the glutenins?
both
How can you measure the elasticity of a bread ?
using the micro-mixograph : t is a spoon that measures the mixing over time, at first the dough is watery and over time it becomes a dough and it becomes harder for the spoon to move around. There is also something that measure the resistance of the bread mixture to the spoon.
What are two ways you can access the quality of flour?
- Separate the proteins from the cultivar using SDS page
- Look at the mixing behaviour using the micro-mixograph
what does the area under the curve represents in the micro-mixograph?
it represent the work require to mix a dough
how do you read the micro-mixograph ?
you can see that good flour will develop resistance quickly and can maintain it while the poor flour will develop resistance quickly but will not be able to maintain it.
which enzyme is used for the volume enhancement of dough
transglutaminase
what are the enzymes seen in class used in the bread development
- transglutaminase
- xylinase
what is the reaction catalysed by the transglutaminase?
can make a cross-link (peptide bond) between the peptide chains by connecting the lysines and glutamine
what is the enzyme used that targe the proteins inside bread to improve the loaf volume ?
transglutaminase
what is the enzyme that target the carbonhydrates in bread ?
the xylanase
What are the two kinds of arabinoxylans?
highly substituted or less branched
What is the backbone of arabinoxylan and the side chains?
the backbone is beta 1-4 linked residues and the side chains are arabinosyl side chains
which of the arabinoxylan is water. soluble?
the highly branched because the unsustituted can link water-insoluble cellulose and form an unsoluble polymer
both xylose and arabinose are pentoses, and therefore arabinoxylans are sometimes referred to as ____
pentosans
at which position is the arabinosyl side chains connected to in the xylose reside
o2 or o3
GH enzymes are xylinase and the GH stands for
glycoside hydrolase
GH__ are more tolerant to branching than GH__
GH10 are more tolerant to branching than GH11
what is the proposed mechanism for the use of xylanase as a bread improver ?
which one of the xylanase is best for increasing the loaf volume?
the less tolerant to branching because it converts the WU-AX into WE-AX and WE-AX. The coating at the air bubble interphase remains more or less the same but the viscosity of the dough increases which reduces the coalescence rate of the bubbles
why are xylanase tolerant to branching not good for the loaf volume ?
because you need a minimum lenght of the AX to be able to coat the bubble and when it is tolerant, then you will convert some of the WE-AX into smaller chains that will not prevent the coalscence
why does the GH10 increases coalescence and reduced the air volume
because it will be tolerant to the branched AX that is found at the air bubble interphase and will reduce the film of the air bubbles.
____ xylanase are isolated from bacterium pseudoalteromonas and have their best acitivty between 0-60˚C
psychrophilic
psychrophilic have their best activitiy between ___ and __˚C
0 and 60
T or F : the increased activity of the psychrophilic GH8 enzymes at lower molecule mobility is due to a bigger groove of the enzyme
false, it is due to the flexibility of the groove because here you can see that the groove is the same size.
exam. ** what is the difference between the psychrophilic and thermophilic enzyme ?
- thermophilic enzymes have a lot of cross-links that make the structure less flexible and psychrophilic have less of the disulfide and salt bridge
- the a.a. in the groove are hydrophobic and flexible and so this helps at catching the substrates
T or F : GH8 (psychrophilic) is even better at increasing the loaf volume
true
T or F : the loaf volume enhancement effect of GH8 (psychrophilic) is due to its psycrhophilic nature
false, here the GH10 is also psychrophilic and the loaf volume not enhanced
What are the wheat inhibitors we saw in class ?
- TAXI
- XIP inhibitor
Why would you need to increase the dose of xylinase you use in some wheat ?
because there arre multiple isoform of TAXI-type and XIP-type inhibitor of xylinase and so this will reduce your activity
What are the advantages of using GH8 endo-xylanase for the bread baking
- acitivity at room temperature (during dough rising)
- supposed to be sensitive to the brnaching like the GH11
- it is not inhibited by the endo-xylanase inhibitors endogenous to wheat.
- it is rapidely inactivated at baking temperautre
