Size Reduction

Question 1

Grinding

Answer 1

Reduction of size by fracturing
Pressure exerted along the weakness causes a fracture where heat is released
Only minimum energy should be exerted to see the rupture

Question 2

First crushing

Answer 2

At beginning size of granule is varied considerably but a dominant size appears
Very large surface area which can cause instability explosive oxidation

Question 3

Specific surface

Answer 3

Surface area per mass unit

Question 4

Hammer mills

Answer 4

2 hammers rotating at high speeds
Used for croaste brittle materials

Question 5

Rotor mills

Answer 5

2 rollers at different speeds milling flour

Question 6

Plate mills

Answer 6

One fixed one rotating
Material enters the axis of rotation and is crushed
Often horizontal

Question 7

Edge runner mill

Answer 7

Trough round a circular barrel
Used to grind cocoa and chocolate

Question 8

Ball mill

Answer 8

Milled with steel balls

Question 9

Cutting

Answer 9

Knives in a particular direction that chop up material
Knives are hard to ensure they are sharp to make sure they are cutting not tearing

Question 10

Bowl cutter

Answer 10

A vertical knife with material spinning underneath

Question 11

Emulsification

Answer 11

Stable suspension of one liquid in another
Continuous and dispersed phases
Stability dependent on
Surface area
Size of dispersed phase
Emulsifying agents added

Question 12

High pressure for nozzle

Answer 12

7x10^3kPa

Question 13

Atomisation

Answer 13

Increase surface to mass ratio in which evaporation will take place

Question 14

Pressure nozzles

Answer 14

Milk is pushed through a small gap at very high pressure to ensure emulsion
Must overcome surface tension

Question 15

Centrifugal nozzles

Answer 15

Droplets are centrifuged at 100-200m/s
Quickly breaks into droplets

Question 16

Colloid mill

Answer 16

Used for medium and high velocity liquids
Coarse emulsion is fed into colloid mill
More efficient
Secondary homogenisation

Question 17

Ultrasonication

Answer 17

Ultrasonic waves transmitted through a liquid
Acoustic cavitation
Nuclear ion and gas bubbles collapse
High energy event
Energy efficient
Reduced droplet size

Question 18

Pros of ultrasonication

Answer 18

Help in development of new flavoured milk with nutritional contents
Pasteurisation and emulsifying dairy technique with minimal processing and heat treatment