3. Physical Properties

Question 1

Do fats have a sharp melting point? why or why not?

Answer 1

No because fat is a complex mixture of TG that each has its own melting point

Question 2

What is a broad melting range?

Answer 2

composite of individual melting points of all TG in a fat

Question 3

• fat appears to be solid at room temp but in fact consist of oil trapped in a ___________ ____________
• there can be as little as 10% “solids” in a fat that still retains a ________ (solid or liquid) character

Answer 3

• crystalline matrix
• solid

Question 4

Why can fat have plasticity or spreadability?

Answer 4

because it is made up of a liquid in crystalline matrix

Question 5

What are the forces that hold fat crystals together? (2)
- forces can be broken by shear and reformed? –> hence gives fat ?

Answer 5

• van der Waals & hydrophobic bonds
• yes! hence, gives flat plasticity

Question 6

What is plasticity?
IMPORTANT!
- Plasticity is a function of what? (2)

Answer 6

• ability to be shaped or molded
• function of the solid to liquid ratio, which in turn is a function of temperature

Question 7

The plastic range of a fat is a function of (2?)
VS solid fat content is a function of (1)

Answer 7

• a function of the FA composition of TG and distribution of FA on their glycerol backbones
• SFC –> function of temperature

Question 8

How can solid fat content be determined? (2)
IMPORTANT!

Answer 8

• dilatometry
• nuclear magnetic resonance (NMR) measurements

Question 9

Dilatometry is a technique based on what?

Answer 9

• measurement of change in specific volume (inverse of density) per unit temperature
• amount of shrinkage/expansion is measured

Question 10

solid fat index vs solid fat content?

Answer 10

index –> determined by dilatometry
content –> determined by NMR

Question 11

What does it mean that fats have polymorphism?

Answer 11

• they are able to change from one crystal form into another (of the same product)

Question 12

3 most common polymorphic forms

Answer 12

• alpha
• beta prime
• beta

Question 13

How to determine FA crystal structure?

Answer 13

by crystallography

Question 14

• Tuning fork form –> which 2 FA are parallel to each other/which one is pointing out?
• Chair form: which 2 FA are on top of each other?

Answer 14

• 1 and 3 –> 2 is pointing out
• 2 and 3

Question 15

Stearic acid: what groups are facing each other to form a dimer?
- is it angled?

Answer 15

• carboxylic group
• angle at 63°

Question 16

4 analytical methods for study of polymorphism?

Answer 16

• x-ray diffraction analyses (crystallography)
• microscopic analyses
• infrared spectroscopic analyses
• thermal analyses

Question 17

How to convert beta form to beta prime form for lard? (4 ways)

Answer 17

• interesterification
• winterization (destearinization)
• addition of cottonseed oil
• addition of tallow flakes (beta prime)