Atoms and Molecules Flashcards
What is crucial to create inflated gas cells in bread dough?
A gas cell nucleus. Without one it takes an infinitely high pressure to inflate the gas cell bubble
Is the pressure needed to inflate a gas cell proportional or inversely proportional to the radius of the gas cell?
Inversely proportional. It will take more pressure to inflate a small gas cell than it will a larger one
What are the valencies (how many covalent bonds will the following atoms make?
- Hydrogen
- Oxygen
- Nitrogen
- Carbon
- 1
- 2
- 3
- 4
Which one of the following does not take part in hydrogen bonds? C-H N-H O-H =O
C-H
Describe atoms, molecules and colloids. Say which are constituents of the others.
An atom is the smallest entity of any chemical element. A molecule is the smallest entity of any substance. A molecule is made up of atoms. A colloid is a substance dispersed throughout another one. It consists continuous and dispersed phases. The phases in colloids are made up of molecules and atoms.
What happens to amylopectin when a bakery product goes stale?
It recrystallises
What happens to atoms, hydrogen bonds and hydrophobic interactions when something is heated in an oven?
Atoms vibrate increasingly violently, hydrogen bonds start to break and hydrophobic interactions get stronger.
What are the two chemical groups in every amino acid that can take part in hydrogen bonds?
- Carbonyl (C=O)
* Amide (N-H)
What forms do amino acid side chains come in and which one cannot take part in hydrogen bonds?
- Polar
- Non polar- cannot take part in hydrogen bonds
- Charged
What type of chemical bonds hold the secondary structures of proteins (α-helix, β-sheet and β-turn) in their characteristic shapes?
Hydrogen bonds
In which type of secondary structure does the polypeptide chain to turn through 180° and so double back on itself?
Β-turn
Where are these chains found in protein?
- Polar
- Non polar
- Charged
- On the surface of the protein
- Inside the protein
- On the surface of the protein
What do charged and polar amino acids contribute to in the protein molecule?
- They contribute to the solubility of the protein in water
* They form binding sites for charged molecules.
Which type of bond is a disulphide bond?
Covalent bond
What structure do the gluten proteins form in developed dough?
Sheets that can envelope gas and hold bubbles.
Are prolamins the storage proteins of all cereals or just wheat?
All Cereals
What are the three amino acids that are most abundant in prolamins?
Proline, glutamine and glycine
What do you get when you mix the prolamins of wheat with water?
Gluten
Which class of proteins is responsible for dough viscosity?
Gliadins
Hot water pastry is best refrigerated for 24 hours after moulding but before baking. What sort of bonds between what molecules are strengthened by doing so?
Hydrogen bonds between starch (amylose and amylopectin) molecule
What feature of the quaternary structure of glutenins is important for the elastic properties of dough?
Intermolecular disulphide bonds create extremely large molecules.
What type of secondary structure comprises the repetitive domain of wheat prolamins?
Linked β-turns.
What type of bond dominates the intermolecular interactions in wheat prolamins
Hydrogen bonds
Low molecular weight glutenins are similar to α and γ-gliadins. Why are they glutenins?
They contain a cysteine that takes part in intermolecular disulphide bonds with other glutenins.
What do oxidising improvers do during breadmaking?
They strengthen dough by remaking intermolecular disulphide bonds between glutenins that have been broken during dough development.
Which of the following does not take part in the Maillard reaction?
Glucose
Lactose
Maltose
Sucrose
Sucrose
Will acid make the Maillard reaction go faster or slower?
Slower
What is falling number a measure of, and what would you expect to go wrong in a plant bakery if it uses flour with falling number >300 seconds?
It is a measure of amylase, and nothing should go wrong
what do the Amylograph and the Rapid Visco Analyser give you information on relating to the flour?
Starch
