Emulsions 1

Question 1

define an emulsion

Answer 1

dispersion made up of two immiscible liqud phases

Question 2

name the two phases of an emulsion

Answer 2

continuous
dispersed

Question 3

what is the internal phase

Answer 3

dispersed

Question 4

what is the external phase

Answer 4

continuous

Question 5

describe a water-in-oil emulsion

Answer 5

water in the dispersed phase and oil is continuous

Question 6

descirbe and oil in water emulsion

Answer 6

oil is the dispersed phase and water is the continous phase

Question 7

examples of water in oil emulsions

Answer 7

mayo, butter

Question 8

examples of oil in water emulsions

Answer 8

salad dressing, ice cream, milk

Question 9

importance of emulsions in food science (4)

Answer 9

stabilise lipid components
mouthfeel
formation of food structures
reservoirs for flavours or bioactives

Question 10

descirbe texture of low fat cheese

Answer 10

hard and crumbly

Question 11

effect of fat in mouth/mouthfeel

Answer 11

lubricates (reduces friction in mouth)

Question 12

foods application of emulsifiers

Answer 12

marge, mayo, sausages, beverages

Question 13

food application of dispersion

Answer 13

chocolate, peanut butter

Question 14

food application for aeration

Answer 14

whipped cream
cake

Question 15

food application of anti-foaming

Answer 15

sorbet, jellies, pudding, brewing

Question 16

food application of solubilisation

Answer 16

flavour

Question 17

food application of cleaning

Answer 17

food grade cleaning agent

Question 18

food application of starch complexing

Answer 18

bread, pasta

Question 19

food application of crystal modification

Answer 19

marge, shortening, chocolate

Question 20

food application of creaming ability

Answer 20

margerine, shortening

Question 21

food application of gluten modification

Answer 21

dough conditioner

Question 22

food application of plasticising

Answer 22

chewing gum

Question 23

food application of viscosity modification

Answer 23

chocolate

Question 24

food application of lubrication

Answer 24

pasta, noodles, pet food

Question 25

food application of processing aids

Answer 25

pharmaceutical excipient

Question 26

Define emulsification

Answer 26

process of creating an emulsion from two immiscible liquids

Question 27

define surfactant

Answer 27

substance that can reduce the surface tension of a liquid

Question 28

define emulsifying agent/emulsifier

Answer 28

a surfactant that concentrates at the interface of the two immiscible liquid phases, decreases the interfacial tension.

Question 29

how does an emusifer create an emulsion

Answer 29

stabilising of droplets in dispersed phase by providing a barrier around the droplet as they form in the emulsion

Question 30

describe interfacial tension

Answer 30

molecule at the surface are more attracted to themselves which forms droplets

Question 31

two theories used to describe interfacial tension

Answer 31

continuum molecular

Question 32

what is the continuum theory

Answer 32

straight line across water/oil

Question 33

what is the molecular theory

Answer 33

highly dynamic interfacial region, molecular structure image oi{water

Question 34

stability of an emulsion

Answer 34

thermodynamically unstable

Question 35

Why are emulsions unstable

Answer 35

the surface energy (Gibbs energy) of oil-water interface -emulsions will seek to minimise the interfacial tension by reducing the interfacial area (contact) as small as possible

Question 36

role of surfactant

Answer 36

make an emulsion sufficiently stable over time (kinetically stable) -increase shelf life

Question 37

two requirements for a stable emulsion

Answer 37

-dispersed phse droplets should be so small they stay suspended -suffciciently viscous film surronds each droplet to prevent coalescnese

Question 38

what dictates emulsion appearance and translucency

Answer 38

particle size

Question 39

at what size will the emulsion be transparent

Answer 39

<0.05um

Question 40

stages of transparency

Answer 40

>1um: milky white 0.1-1um: blue white 0.05-0.1: grey, semi transparent <0.05: translucent

Question 41

types of emulsifiers

Answer 41

small molecule surfactants detergents/soap phospholipids proteins

Question 42

properties of a good emulsifer

Answer 42

small molecular mass flexible conformation migrates to the interface quickly amphilic soluble in continuous phase

Question 43

what is HLB

Answer 43

hydrophile-lipophile balance -measure the degree to which a surfactant is hydrophillic or lipophillic

Question 44

How is HLB calculated

Answer 44

calculate values for different regions of the moelcule

Question 45

HLB scale

Answer 45

1: lipophillic 20: hydrophillic

Question 46

what are low HLB emulsifiers good for

Answer 46

water in oil -oil continous phase

Question 47

what are high HLB emuslifers good for

Answer 47

oil in water -water continous phase

Question 48

HLB >7 means

Answer 48

water soluble emulsifier

Question 49

HLB<7 means

Answer 49

oil soluble emulsifier

Question 50

HLB ~7 means

Answer 50

equal solubility

Question 51

examples of small molecule surfactants

Answer 51

monoglycerides, sorbitan esters of fatty acids, polyoxyethylene sorbitan esters of fatty acids, and phospholipids

Question 52

structure of small molecule surfactant

Answer 52

long chain fatty acid that provides a hydrophobic group

Question 53

HLB range of small molecule surfactants

Answer 53

3-10

Question 54

examples of surfactant materials

Answer 54

vegetable oils: palm, sunflower, soy bean, rapeseed -one or two fatty acids will have been cleaved off lactic acid esters

Question 55

hydrophillic components of surfactant materials

Answer 55

glycerol, derived from vegetable oil -propylene glycol -lactic, tartaric, succinic, citric, acetic acids

Question 56

most studied proteins

Answer 56

milk easily prepared soluble and realtively well-behaved in solution extenisve literature on emulsiifcation with milk proteins

Question 57

types of proteins used as emulsifiers

Answer 57

milk egg gelatin

Question 58

why are proteins good emulsifiers

Answer 58

amphipatic -amino acid chain -can rearrange and adhere to another surface

Question 59

important factor to conisder when using protein

Answer 59

can be slower to rearrange and coat a surface -need to prevent coalescence