Chapter 1

Question 1

What is the difference between anisotropic and isotropic structures?

Answer 1

Anisotropic structure properties depend on direction while isotropic structure properties do not depend on direction.

Question 2

Water has high or low heat capacity and heat evaportation.

Answer 2

Both high

Question 3

Lipids - what leads to lower melting points?

Answer 3

Shorter chains and presence of unsaturated groups.

Question 4

Can fat form crystals

Answer 4

Yes

Question 5

How does Aw change at low moisture content? (Sorption Isotherm)

Answer 5

At low/intermidiate moisture content, Aw changes significantly with a slight change in moisture content. At high moisture content, Aw changes very little with change in moisture content.

Question 6

What are humectant and plasticizers and name some?

Answer 6

Humectants are moisture controllers e.g sugar and salt and bind to water while plasticizers soften material e.g. water, glycerol and glucose.

Question 7

Henry Model explain

Answer 7

The amount of water absorbed is linear with Aw

Question 8

Langmuir model explain

Answer 8

The amount of absorbed water levels off at higher Aw as no more water can be absorbed.

Question 9

BET and GAB model explain

Answer 9

At higher Aw more water is absorbed as also the matrix absorbs water.

Question 10

Differences between Henry, Langmuir and BET/GAB

Answer 10

Henry is for liquid systems, Langmuir is for porous and some glassy polymers and BET/GAB is for mixed systems and food matrixes.

Question 11

At eutectic point what happens and what is it?

Answer 11

The eutectic point is the theoretical chemical composition and temperature corresponding to the lowest melting point of a mixture of components. This occurs at equilibrium of the two components. However food is not in equilibrium.

Question 12

What is a glass

Answer 12

Hard, crispy and brittle. Molecule cannot move and no crystal can be formed

Question 13

Is a glass in thermodynamic equilibrium

Answer 13

No

Question 14

How can glass form

Answer 14

Very fast cooling which does not allow crystals to be formed.

Question 15

What does glass transition temperature depend on?

Answer 15

The biopolymer and chain length. Higher molecular weight products have higher Tg.

Question 16

What is the effect of a plasticizer e.g. water?

Answer 16

Reduce intermolecular forces, increase flexibility and lower Tg

Question 17

What is the driving force for crystallization

Answer 17

Difference in temperature, lower difference in temperature will lead to a higher rate of crystallization.

Question 18

Filler can have effect on rheological properties. What does the effect depend on?

Answer 18

Viscosity and volume fraction of both phases. Equation in formula sheet for low and high volume fractions.

Question 19

According to the CDS formalism, oil, water and proteins are abbreviated as O, W and P, respectively. The denotation for an oil-in-water emulsion stabilised by proteins is therefore

Answer 19

(O@P)/W

Question 20

At low water content, proteins tend to form crystalline structures

Answer 20

No

Question 21

How is the diffusion of acid and bases in water

Answer 21

It is fast and protons can be exchanged.

Question 22

Is energy released or absorbed when fats form crystals?

Answer 22

Released

Question 23

What is Aw?

Answer 23

Water activity equals relative humidity in case product is in thermodynamic equilibrium

Question 24

What can be the role of sugar in food products and why substituting is not easy

Answer 24

It has bulk, softening and preservation properties.

Question 25

How are kinetics influence in the phase diagram?

Answer 25

By solidification rate and flow conditions.

Question 26

What do this symbols illustrate: /, @, +, I, c

Answer 26

/= dispersed into, @= included into-encapsulated by, += mixed with, I= in parallel with ( for co-continuous structures), c= superimposed on (indicating macrostructure e.g. crispy fry and inner is soft).