COLLOIDS

Question 1

What is a colloidal system

Answer 1

Give structure/ texture/ mouthfeel to different products
jam/ ice cream/ mayo

formed when one substance is dispersed through another but doesn’t combine to form a solution

substance which is dispersed is the dispersed phase and is suspended in the continuous stage

are stable but could separate over time - change in temperature/ physical force/ frozen/ heated

Question 2

Foams

Answer 2

gas - disperse phase
liquid - continuous phase
(solid foam)

gas - disperse phase
solid - continuous phase
(meringue)

Small bubbles of gas dispersed in a liquid - as liquid egg is whisked air is added
mechanical action causes albumen proteins to unfold forming a network - trapping air

if egg white is heated proteins coagulate and moisture driven off - solid foam (meringue)

Question 3

Emulsions

Answer 3

Liquid - disperse phase
Liquid - continuous phase
(mayo/ milk)

liquid - disperse phase
solid - continuous phase
(butter)

emulsion of oil and water are unstable and would separate

stable emulsion formed when two liquids held stable by emulsifying agent
made up of two parts - hydrophilic (water loving) and hydrophobic (oil loving) each part attaches to the part it likes
emulsifier holds disperse phase within continuous phase - stable

Question 4

Gels

Answer 4

liquid - disperse phase
solid - continuous phase
(jelly)

when solution cooled the sol turns into a gel - solid not liquid

protein and starch used in the formation of sol/ gel

Question 5

Sols

Answer 5

solid - disperse phase
liquid - continuous phase
(unset jelly)

liquid colloid where solid particles are dispersed in a liquid phase
disperse phase attracted to molecules of continuous phase

protein and starch used in formation of sol/ gel