Size reduction

Question 1

What are the advantages of size reduction?

Answer 1

1 - increases surface:volume
2 - creates uniform particle size for better mixing

Question 2

Name some methods of size reduction + examples

Answer 2

1. Chopping
2. Milling (powders or pastes - flour, sugar, starches)
3. Emulsification and homogenization (liquids, milk, butter, margarine, ice cream)

Question 3

What is an example of a shearing force

Answer 3

Cutting

Question 4

When is Kick’s law used

Answer 4

(course grinding nand change in dimension)

Question 5

When is Rittinger’s law used

Answer 5

Fine grinding and change in surface area

Question 6

When is bond’s law used

Answer 6

Between coarse and fine grinding

Question 7

Function of pulper and finishers

Answer 7

Pulper = macerate whole fruit (crush)
Finisher = smaller refining screens

Question 8

Size reduction for fiberous foods examples

Answer 8

Slicing, shredders, pulpers, finishers

Question 9

Size reduction for dry foods examples

Answer 9

Ball mills, disc mills, hammer mills, roller mills, centrifugal mills, granulator

Question 10

Hammer mill

Answer 10

Particle collision

Question 11

Granulator

Answer 11

Cuts into granules

Question 12

Size reduction for liquid foods

Answer 12

High speed shear mixer; pressure homogenizer; colloid mill; ultrasonic homogenizer; hydro-shear homogenizers

Question 13

What is the function of a homogenizer

Answer 13

Reduce the size of droplets

Question 14

What is the function of a stablilizer

Answer 14

Increase viscocity of the liquid + prevent colescence

Question 15

What law do you use for homogenizers?

Answer 15

STOKES LAW - see example on slide 25

Question 16

Effect of homogenizers on food:

Answer 16

increase viscosity
creamy mouthfeels
decrease separation
colour change (reflectance and scattering)