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FOSC301 > Emulsions 1 > Flashcards

Emulsions 1 Flashcards

1
Q

define an emulsion

A

dispersion made up of two immiscible liqud phases

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2
Q

name the two phases of an emulsion

A

continuous
dispersed

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3
Q

what is the internal phase

A

dispersed

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4
Q

what is the external phase

A

continuous

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5
Q

describe a water-in-oil emulsion

A

water in the dispersed phase and oil is continuous

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6
Q

descirbe and oil in water emulsion

A

oil is the dispersed phase and water is the continous phase

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7
Q

examples of water in oil emulsions

A

mayo, butter

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8
Q

examples of oil in water emulsions

A

salad dressing, ice cream, milk

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9
Q

importance of emulsions in food science (4)

A

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

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10
Q

descirbe texture of low fat cheese

A

hard and crumbly

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11
Q

effect of fat in mouth/mouthfeel

A

lubricates (reduces friction in mouth)

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12
Q

foods application of emulsifiers

A

marge, mayo, sausages, beverages

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13
Q

food application of dispersion

A

chocolate, peanut butter

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14
Q

food application for aeration

A

whipped cream
cake

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15
Q

food application of anti-foaming

A

sorbet, jellies, pudding, brewing

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16
Q

food application of solubilisation

A

flavour

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17
Q

food application of cleaning

A

food grade cleaning agent

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18
Q

food application of starch complexing

A

bread, pasta

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19
Q

food application of crystal modification

A

marge, shortening, chocolate

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20
Q

food application of creaming ability

A

margerine, shortening

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21
Q

food application of gluten modification

A

dough conditioner

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22
Q

food application of plasticising

A

chewing gum

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23
Q

food application of viscosity modification

A

chocolate

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24
Q

food application of lubrication

A

pasta, noodles, pet food

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25
Q

food application of processing aids

A

pharmaceutical excipient

26
Q

Define emulsification

A

process of creating an emulsion from two immiscible liquids

27
Q

define surfactant

A

substance that can reduce the surface tension of a liquid

28
Q

define emulsifying agent/emulsifier

A

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

29
Q

how does an emusifer create an emulsion

A

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

30
Q

describe interfacial tension

A

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

31
Q

two theories used to describe interfacial tension

A

continuum
molecular

32
Q

what is the continuum theory

A

straight line across
water/oil

33
Q

what is the molecular theory

A

highly dynamic interfacial region, molecular structure image
oi{water

34
Q

stability of an emulsion

A

thermodynamically unstable

35
Q

Why are emulsions unstable

A

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

36
Q

role of surfactant

A

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

37
Q

two requirements for a stable emulsion

A

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

38
Q

what dictates emulsion appearance and translucency

A

particle size

39
Q

at what size will the emulsion be transparent

A

<0.05um

40
Q

stages of transparency

A

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

41
Q

types of emulsifiers

A

small molecule surfactants
detergents/soap
phospholipids
proteins

42
Q

properties of a good emulsifer

A

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

43
Q

what is HLB

A

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

44
Q

How is HLB calculated

A

calculate values for different regions of the moelcule

45
Q

HLB scale

A

1: lipophillic
20: hydrophillic

46
Q

what are low HLB emulsifiers good for

A

water in oil
-oil continous phase

47
Q

what are high HLB emuslifers good for

A

oil in water
-water continous phase

48
Q

HLB >7 means

A

water soluble emulsifier

49
Q

HLB<7 means

A

oil soluble emulsifier

50
Q

HLB ~7 means

A

equal solubility

51
Q

examples of small molecule surfactants

A

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

52
Q

structure of small molecule surfactant

A

long chain fatty acid that provides a hydrophobic group

53
Q

HLB range of small molecule surfactants

A

3-10

54
Q

examples of surfactant materials

A

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

55
Q

hydrophillic components of surfactant materials

A

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

56
Q

most studied proteins

A

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

57
Q

types of proteins used as emulsifiers

A

milk
egg
gelatin

58
Q

why are proteins good emulsifiers

A

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

59
Q

important factor to conisder when using protein

A

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

60
Q
A

FOSC301 (17 decks)

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