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Water and Food Dispersions Flashcards

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1
Q

What are 3 common roles of water in food systems?

A
  1. A carrier of nutrients and wastes
  2. A reactant and a reaction medium
  3. A stabilizer of biopolymer configuration (poteins and COHs)
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2
Q

Water makes up what % of tomatoes and lettuce?

A

95

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3
Q

Water makes up what % of apple juice/milk?

A

87

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4
Q

Water makes up what % of potatoes?

A

78

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5
Q

Water makes up what % of meats?

A

65-70

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6
Q

Water makes up what % of bread?

A

35

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7
Q

Water makes up what % of honey?

A

20

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8
Q

Water makes up what % of rice/wheat flour?

A

12

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9
Q

Water makes up what % of shortening?

A

0

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10
Q

The amount of water, its location and its interaction with the chemical components in a food product is extremely important from the standpoint of _________and ________.

A
  1. acceptability

2. STABILITY

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11
Q

What is texture often associated with? Example?

A

Moisture

Ex: freeze-dried orange vs. fresh orange

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12
Q

Because water is a major reactant and serves as a reaction medium, many of our food processing and preservation methods involve the control of water content to:

A

slow down deteriorative reactions

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13
Q

What 3 factors all reduce the water activity (Aw) of a system?

A
  1. Freezing
  2. Concentration
  3. Dehydration
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14
Q

What is one of the most abundant molecular species on Earth?

A

Water

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15
Q

Water is the only _____ liquid and the most _______ solid.

A
  1. common

2. abundant

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16
Q

Comparing water (hydrate of oxygen) to the hydrates of other atoms:

a) Across the periodic table (CH4, NH3, HF - all ____ at room temp)
b) Down the periodic table (H2S, H2Se, H2Te - all _____)

A

Gases

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17
Q

How many electrons does H2O have? How many are valence? How many electrons does each Hydrogen have?

A

8, 6, 2

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18
Q

The __ __ orbital(s) and the __ __ orbital(s) of the oxygen atom are combined to form __ __ _____ orbitals.

A
  1. three 2p
  2. one 2s
  3. four sp3 hybrid
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19
Q

How many of oxygen’s 6 valence electrons are used up in the two covalent bonds that form between H and O? What is the net result?

A

2

Net result: there are 2 oxygen lone electron pairs left in two of the sp3 orbitals

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20
Q

What makes oxygen highly electronegative in a water molecule?

A

Its 2 lone electron pairs

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21
Q

Water molecules can be viewed as having two ________ regions and two ________ regions situated ________.

A
  1. electron-rich
  2. electron-poor
  3. tetrahedrally
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22
Q

In the presence of other water molecules, the electron-rich/poor regions of H2O will associate in order to do what?

A

To minimize the overall free energy of the system.

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23
Q

What is hydrogen bonding?

A

The associations due to differential electron density between hydrogen and other electronegative atoms

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24
Q

The tetrahedral nature of the spatial arrangement of these regions of electron density in H2O molecules promotes the ability to form a _________________.

A

3D association/network

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25
Q

How strong are hydrogen bonds? Is this strong?

A

~10 kcal/mol

Not very strong

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26
Q

Hydrogen bonding is the basis for what in the atmosphere? What does this lead to?

A

Water vapor accumulation. Leads to the accumulation of clouds

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27
Q

What is capable of forming due to waters ability to hydrogen bond in 3D?

A

local regions of structure

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28
Q

What structure does water have in the liquid phase? What is this termed?

A

“Transitional” structure

Termed: “flickering clusters”

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29
Q

What do flickering clusters do?

A

They continually form and break up

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30
Q

What is the lifetime of flickering clusters?

A

10^-10 to 10^-11 seconds

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31
Q

What happens to the # of flickering clusters as the tempurature of water increases? What is simultaneously happeing to the number of molecules per cluster?

A

Increases

Decreases

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32
Q

Do flickering clusters still exist at the boiling point of water?

A

yes

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33
Q

What have flickering clusters been postulated to explain?

A

The relatively normal (low) viscosity of water.

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34
Q

All ______ affect the “structure” of water to some exten

A

solutes

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35
Q

What happens when ionic compounds are dissolved in water? What is this due to?

A

The ionize into their respective ions.

Due to the very polar nature of water molecules

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36
Q

Is the polarity of water sufficient enough to break covalent bonds?

A

No

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37
Q

The polarity of water molecules can dissociate ____ bonds by allowing multiple water molecules to act as ______ for opposing charged ionic species

A
  1. ionic

2. counterions

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38
Q

What happens to the ions of NaCl as it is dissolved in water?

A

Each ion is hydrated by water

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39
Q

When NaCl dissolves in water, what is attracted to the chlorine anions? The sodium cations?

A

Slightly + hydrogen

Slightly negative oxygen

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40
Q

When NaCl is dissolved in water, what forms around each ion? What does this do?

A

A hydration shell.

This NEUTRALIZES the charge of the respective ions.

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41
Q

What does the formation of hydration shells around the solute do? What does this do to the normal structure of water?

A

It forces water into a specific orientation around each ion. This disrupts the normal structure of water.

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42
Q

How does the formation of bulky hydrates affect viscosity of the system?

A

Increases viscosity

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43
Q

How does the formation of bulky hydrates affect the freezing pt. of the system?

A

Depresses the freezing pt.

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44
Q

Hydrogen bonding compounds are capable of __________ the structure of water.

A

Disrupting

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45
Q

Water around a hydrogen bonding site on a molecule will associate in a manner that disrupts what?

A

the natural tetrahedral geometry of water.

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46
Q

Can hydrogen bonding solutes disrupt the structure of water?

A

yes

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47
Q

Which macromolecules have a large number of hydrogen bonding sites?

A

polypeptides, proteins, carbohydrates, and polysaccharide

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48
Q

What can happen to water when exposed to macromolecules that have a large number of H-bonding sites? Under what condition?

A

The water can be completely/extensively immobilized by hydrogen bonding if the amount of water present is limited.

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49
Q

When ____ concentrations of non-polar substances (hydrocarbons, FAs, or nonpolar side chains of proteins) are dissolved in water, ______ are thought to be formed.

A
  1. low

2. ice-like inclusions

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50
Q

How does the formation of ice-like structures around a non-polar group/molecule affect free energy? Why?

A

Minimizes the free energy state of the system. Because symmetric electron-neutral constituents (hydrophobic) and asymmetric electron-rich hydrophilic materials are forced to associate.

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51
Q

What form does an ice-like inclusion produce? What is another term for this? Is it structurally identical to ice?

A

Semicrystalline.

Clathrate hydrates

No

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52
Q

What is the definition of Clathrate compounds?

A

Compounds not formed by the action of valence bonds but by molecular imprisonment

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53
Q

Clathratehydrate structures are important in stabilizing ________ structure around ________ moieties

A

Protein

Hydrophobic

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54
Q

Overall, the presence of any solute will tend to have a ______ effect on the structure of water.

A

disruptive

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55
Q

In all cases, the activity of water (its freedom of movement) is ______ when a solute is added

A

Reduced

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56
Q

When does the freezing or crystallization of water take place?

A

When the kinetic energy of the molecule is reduced to such an extent that a flickering cluster is able to become large enough to form a MINUTE CRYSTAL OR NUCLEUS.

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57
Q

What happens to water at 0 degrees celcius?

A

There is an equilibrium between crystal nucleation and liquid water.

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58
Q

In ultrapure water, what is difficult and does not readily take place? What can occur?

A

Nucleation

SUPERCOOLING

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59
Q

What is supercooling?

A

When the water stays liquid well below 0 degrees C

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60
Q

Supercooled water will freeze almost instantly if _______ or if an ________ is thrown in.

A
  1. Disturbed

2. Ice crystal

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61
Q

In normal water, what aids the start of nucleation?

A

Impurities such as dust or container wall surface

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62
Q

The nucleation process is a function of _________.

A

the rate of cooling

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63
Q

What is the result of a slow freezing rate of water? A rapid freezing rate?

A

A few large ice crystals

Many small ice crystals

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64
Q

How does slow freezing affect meat?

A

Larger ice crystals form, which can become large enough to burst the cell walls, causing physical damage that reduces water holding capacity and activates enzymes previously contained

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65
Q

How does rapid freezing affect meat?

A

Small ice crystals form uniformly through the product

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66
Q

Solutes interfere with the ________ process and also _________ the rate of diffusion of water to the ice crysta

A

nucleation

slow down

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67
Q

What happens to the solutes as the freezing process takes place?

A

They become more concentrated as the water diffuses to the surface of the crystal.

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68
Q

As the solutes become more concentrated, a _______ temperature is required for the ice to form.

A

lower

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69
Q

What is the eutectic point? What temperature range does it occur at?

A

When the temperature is low enough that the solution can become concentrated to a point at which the remaining water co-crystallizes with the solute crystals to start to grow and form.

-55C to -70C

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70
Q

When the eutectic point has been reached, what happens to all the water in the system?

A

immobilized

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71
Q

What are the conventional frozen storage tempuratures?

A

0F or -18C

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72
Q

Is total stability attained in a frozen food product?

A

No, only ~98% is immobilized

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73
Q

What becomes disrupted in cells when large ice crystal form?

A

Organelles

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74
Q

What concentrates in cells when large ice crystal form? Why does this concentrated solution not freeze totally?

A

Salts, ions, enzymes, and other solutes.

Because the temperature is well below the eutectic point.

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75
Q

What is interesting about water when large ice crystals form in cells and salts, ions and enzymes all concentrate?

A

Water is still available to act as a REACTANT and the REACTION MEDIUM is very concentrated.

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76
Q

Can reactions still take place when large ice crystals form in cells?

A

Yes, all types of reactions can still take place. Enzyme and substrates that are usually kept apart are mixed due to tissue disruption.

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77
Q

What can denature proteins in cells that have formed large ice crystals? Net result?

A

Ionic strength and pH changes . Deterioration

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78
Q

Do frozen foods have an infinite shelf life?

A

No b/c of large crystal formation which leads to a high solute in water concentration where many reactions can take place which ultimatly leads to deterioration

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79
Q

Because enzymatic reactions carry on under conditions of frozen storage, fruits and vegetables have to be ______ before being frozen.

A

blanched

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80
Q

What is blanching/

A

mild heat treatment

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81
Q

All reactions speed up when the _______ process is started.

A

thawing

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82
Q

During what step is a lot of a food’s quality lost relative to frozen storage?

A

Thawing

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83
Q

In what two ways can water be present in foods?

A

Bound or free

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84
Q

Free water vs bound water

A

Free: relatively mobile
Bound: effectively immobile

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85
Q

One way of assessing the mobility of water is to measure its ________.

A

Water activity

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86
Q 
What is the formula for water activity? (Aw)
...where...
P=
P0=
T=
A

Aw = P/(P0 x T)

P= partial pressure of the solution (or food matrix)...or...the vapor pressure above the solution. 
P0= partial pressure of pure water 
T= temp
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87
Q

What is the scale used to measure water activity?

A

0 to 1.0

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88
Q

What is the water activity of pure water?

A

1.0

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89
Q

A sealed container containing water comes to an equilibrium between what at any constant temperature?

A

Liquid water and its vapor form

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90
Q

What would happen if we measured the partial pressure of water vapor in the headspace over water?

A

We would obtain some constant value at a constant temp

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91
Q

Would the partial pressure (or RH) of a 25% NaCl solution be greater or higher than the partial pressure of a solely water solution? Why?

A

It would be reduced significantly because the salt, by being solvated, ties up some of the water, restricting its freedom of movement (activity) or mobility

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92
Q

The ratio of the partial pressures is a useful measure of the relative _____, _____, or _____of water.

A

mobility, activity, availablility

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93
Q

Any solute will _____ the activity of water.

A

Reduce

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94
Q

We can classify the water in foods based on their _____________.

A

Water activity ranges

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95
Q

What is Type IV water?

A

Pure water

Aw = 1.0

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96
Q

Does pure water exist in food systems?

A

No

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97
Q

What is the water activity of Type III water?

A

Aw = 0.99 - 0.80

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98
Q

Where can Type III water be found in animals/meat? Present in what? Diameter?

A

Trapped in the tissue matrix. (the water present in macrocapillaries > 1um in diameter)

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99
Q

How many solutes does Type III water contain?

A

Contains some solutes but not enough to immobilize the water in any major way.

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100
Q

In Type 3 Water activity range, many _________ are capable of growth, with some ________ and _______ inhibited at the lower end of the range

A

Microorganisms

Bacteria & yeasts

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101
Q

What 3 type or reactions proceed readily in Type III water activity range?

A

Hydrolytic, oxidative, enzymatic

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102
Q

Is the freezing point much lower in Type III water than in normal water?

A

no its not really that much lower

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103
Q

What is the water activity of type II water?

A

Aw = 0.80 - 0.25

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104
Q

What is the broad range of Type II Water?

A

From water in microcapillaries (<1 um in diameter) to outer layers of “bound water” (water hydrogen-bounded to solutes)

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105
Q

What is the microbial growth in Type II Water? What about molds?

A

Most microbial growth is halted, with the exception of some molds at the upper end of this range.

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106
Q

What is the freezing point of Type II Water relative to normal water?

A

significantly reduced

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107
Q

What happens to most enzymatic reactions requiring water in Type II Water?

A

Slowed significantly

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108
Q

Discuss non-enzymatic browning at both ends of the Type II Water range.

A

Non-enzymatic browning takes place readily with heat at the upper end of this range – it also occurs without heat but over time at the lower end of this range.

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109
Q

What is the water activity of Type 1 Water?

A

Aw = 0.25 - 0

110
Q

What is Type 1 Water?

A

Bound monolayer of water directly hydrogen-bonded to molecules (proteins/COHs).

111
Q

Type I Water is very strongly hydrogen-bonded to the molecules and an ______ part of the molecular structure - essentially _______.

A

integral

immobile

112
Q

Type 1 water can not be what?

A

Frozen

113
Q

What type of reactions can take place in type 1 water?

A

Autoxidation

114
Q

________ occurs when a “wet” food is placed in a dry environment.

A

Desorption

115
Q

What does desorption imply?

A

That the food is moving toward equilibrium with the environment

116
Q

What is dehydration?

A

The permanent loss of water from a food

117
Q

What happens to the Aw in both desorption and dehydration?

A

Decreases

118
Q

Does desorption happen slowly or rapidly?

A

Slowly, with moisture gradually decreasing until the food is in equilibrium with its environment

119
Q

_______ occurs when a “dry” food is placed in a wet environment

A

Absorption

120
Q

What happens as foods gain moisture?

A

Aw increases

121
Q

What is the term “hygroscopic” used to describe?

A

Foods or chemicals that absorb moisture

122
Q

How do hygroscopic foods pose a problem in the food industry?

A

Lumping, clumping, increased rxn rates

123
Q

What does water activity tell a food scientist?

A

Potential stability

Loss/gain of moisture as a function of relative humidity

124
Q

How man food scientists determine the water activity profile of a food product?

A

By deriving a moisture sorption isotherm

125
Q

How is a moisture sorption isotherm derived? What happens once the samples have come to an equilibrium?

A

Dry the food product completely, then place it in an enclosed HERMETICALLY SEALED chamber above a saturated salt solution of known ERH at a constant tempurature. The salt solution contains a wide variety of salts which generate a specific Aw.

They are weighed to determine the amount of moisture adsorbed (g H2O/g dry weight) = the equilibrium moisture content (EMC)

126
Q

What is Aw directly related to which is much easier to measure?

A

Equilibrium relative humidity (ERH)

Aw = P/P0(T) = ERH at a constant tempurature

127
Q

A plot of what provides the moisture sorption isotherm? What does this plot illustrate?

A

Equilibrium moisture content EMC vs. Aw

Illustrates how the food product would behave as a function of relative humidity in terms of water absorption or loss at a given temperature

128
Q

Moisture sorption plots are ________ dependent.

A

Temperature

129
Q

What is a phenomenon that commonly occurs in Plots of water content vs water activity?

A

Directional hysteresis

130
Q

What is directional hysteresis?

A

When a curve on a water content vs activity plot is different depending on whether the product started out dry or moist. So the same product could have a different curve depending on its initial Aw

131
Q

What can permanently change the moisture sorption behavior of steak?

A

Drying it, which causes irreversible chemical and physical reactions to take place

132
Q

Except in very simple systems, the moisture sorption curves will show _________.

A

hysteresis

133
Q

What does moisture sorption information define?

A

How a product picks up or loses moisture under specific conditions (relative humidity)

134
Q

What can moisture sorption data be helpful for determining?

A

the final moisture content that can be obtained in a drying operation based on temperature and relative humidity (RH) of the drying air

135
Q

Moisture sorption data provides important information about the relative stability of a product in regards to what two factors?

A
  1. the type of microbial growth possible

2. The type of reactions that may predominate in a food system

136
Q

What 5 factors are of major concern with reguards to water activity?

A
  1. Enzymatic reactions
  2. Lipid oxidation
  3. Hydrolytic reactions
  4. Non-enzymatic browning
  5. Various forms of microbial growth
137
Q

What does the fact that most reactions are exponential functions of water activity imply?

A

That even en a slight reduction of water activity will have a significant effect in reducing the rate of a reaction

138
Q

A break point for many reactions lie around Aw = ?

A

0.80

139
Q

Aw has to be reduced down to what value to reach a minimum for most of the deteriorative reactions?

A

0.3-0.4

140
Q

What is the water activity value/region where all reactions are stopped?

A

There is none

141
Q

What is the optimum Aw?

A

0.3-0.4

142
Q

What are 3 ways to control water activity?

A
  1. Remove water (dehydration or concentration)
  2. Convert the free water to bound water
  3. Freeze the food
143
Q

How does the removal of water affect the physical nature of the food?

A

Alter its color, texture, and/or flavor

144
Q

How can free water be converted to bound water?

A

Addition of sugars, salts (water soluble agents)

145
Q

What does freezing food to to the water?

A

Immobilizes it and lowers the Aw

146
Q

What is the hurdle concept?

A

Control Aw, pH, ionic strength, modification of atmosphere as “hurdles” the pathogen has to overcome if it is to remain active in the food

147
Q

What two general categories can food systems be divided into?

A
  1. Intact edible tissues

2. Food dispersions

148
Q

What are intact edible tissues?

A

Natural biological systems - plant and animal tissues - very complex

149
Q

What are food dispersions?

A

Complex systems - man made

150
Q

What is a dispersion?

A

A system consisting of one or more discontinuous phases (dispersed) in a continuous phase

151
Q

What is an example of a colloidal system?

A

Addition of acid to whey protein

152
Q

What 3 general classes can we classify solutions into?

A
  1. True solutions (or molecular dispersions)
  2. Colloidal dispersions
  3. Suspensions
153
Q

What are the 5 characteristics of true solutions?

A
  1. The molecules and ions are present in their lowest subdivision.
  2. The particles are <0.1 μm in diameter.
  3. The solution formed is transparent.
  4. The solution has high osmotic pressure
  5. The solution passes through parchment membranes
154
Q

What allows a solution to be considered collodial?

A

If it does not pass through a parchment membrane but does not settle under the force of gravity

155
Q

A colloidal material is usually which of 2 things?

A
  1. macromolecule

2. an aggregate of a smaller molecule

156
Q

What is the size range of colloidal dispersions?

A

0.1-1 micrometers

157
Q

Colloidal solutions have significantly reduced ____________.

A

osmotic pressure

158
Q

What is the color of colloidal solutions?

A

May be transparent but is often translucent - scatters light

159
Q

What do true colloids not do? What might they do?

A

They do not settle out of solution and may aggregate to form gets

160
Q

What are the particle sizes in suspensions?

A

> 1 micrometer

161
Q

What color are suspensions?

A

Opaque

162
Q

Can the suspended material be filtered out in suspensions?

A

Yes

163
Q

How do suspensions settle out of solutions?

A

By gravity with time

164
Q

How much osmotic pressure do suspensions show?

A

negligible / no measurable osmotic pressure

165
Q

What happens to ungelatinized starch solutions when stirred?

A

Form suspensions but then soon settle out

166
Q

What do gelatinized starchs form?

A

Colloidal solitions
or
Gel (depends on [])

167
Q

What are true solutions considered to be?

A

uniphasic

168
Q

What are colloidal solutions considered to be?

A

biphasic

169
Q

What are suspensions considered to be?

A

biphasic

170
Q

The conversion of a true molecular solution to a colloidal solution often takes place when _______ are involved.

A

macromolecules

171
Q

What does charge repulsion depend on?

A

pH

172
Q

Under what circumstances can macromolecules associate?

A

Via electrostatic interactions, hydrophobic interactiions, & hydrogen bonding if the overall charge repulsion is not too great

173
Q

What does wastewater from food processing plants often contain?

A

Colloidal material

174
Q

What is a common method of wastewater treatment?

A

Convert colloidal solutions into suspensions that will settle out by adding salts to neutralize the charge of the colloids

175
Q

In food dispersions ranging from simple biphasic to multiphasic, the formation of colloids is the combined result of what 4 reactions?

A
  1. Electrostatic interactions
  2. H-bonding
  3. Hydrophobic interactions
  4. Hydrophobic/hydrophilic associations
176
Q

Which reaction which results in the formation of colloidal solutions is the basis of many food dispersions?

A

Hydrophobic/hydrophilic associations

177
Q

What are the 4 types of common food dispersions?

A
  1. Liquid in liquid - emulsion
  2. Gas in liquid - foam
  3. liquid in solid - solid emulsion
  4. Gas in liquid - solid foam
178
Q

________ and ________ involve the dispersion of a hydrophobic material in a hydrophilic material and vice versa.

A

Emulsions, foams

179
Q

Are foams and emulsions favorable or unfavorable from a free energy standpoint?

A

unfavorable

180
Q

What is a surface-active agent? AKA?

A

Any compound that has both hydrophilic and hydrophobic groups in its molecular structure. More commonly termed surfactant.

181
Q

Surfactants have the property to do what? What does this cause? What can be formed?

A

Reduce the surface tension of water significantly. This causes foaming and can form emulsions

182
Q

Surfactant is a term used in what application? Example?

A

Non-food applications

Ex: soap is a good surfactant and foams readily

183
Q

Where is the location of the lowest free energy state for emulsifiers and surfactants?

A

the air-water interface which is why they start off there

184
Q

Molecularly, why are hydrophobic compounds attracted to the air-water interface when added to a hydrophilic medium?

A

The hydrophobic ends of the molecule orient themselves toward hydrophobic air, and the hydrophilic ends of the molecule orient themselves into the water

185
Q

What is the net effect of the air-water interface formed when a hydrophobic material is placed in a hydrophilic medium?

A

Reduction of the surface tension of the water

186
Q

Emulsifiers and surfactants not only reduce the _________ of water but are capable of forming structures called _______ in solution

A
  1. surface tenstion

2. micelles

187
Q

What are micelles?

A

Colloid-like particles which are produced by hydrophobic-hydrophilic head-to-tail association

188
Q

When are micelles formed in solutions?

A

When the concentration of an emulsifier or surfactant added to a solution is increased beyond the surface-covering capacity

189
Q

Micelles form so as to reduce the ________ of the solution after the air/water interface has been ________.

A

Free energy

Saturated

190
Q

Micelles serve as a reservoir of what?

A

Surfactant molecules capable of migrating to the new surfaces that are created by mixing

191
Q

What does the hump in a Surface Tension vs. Concentration (or surfactant) plot mean?

A

Micelle formation

192
Q

How much does the surface tension of a solution increase if you keep adding surfactants after the micelles have already formed?

A

Barely

193
Q

What types of molecules are amphipathic and act as emulsifiers?

A

Phospholipids and monoglycerides

194
Q

What are the 3 reasons to make emulsions?

A
  1. To incorporate oil into a food system without imparting an oily sensation
  2. To develop a unique texture, enhance the viscosity of the system or obtain plastic properties
  3. To change the optical characteristic of a product
195
Q

The opacity of an emulsion is a function of _______________________, which is a function of _____________________.

A
  • the droplet size of the dispersed phase

- the energy put into the system

196
Q

What is the droplet size of emulsions in which you can distinguish the phases?

A

Macrogobules (>1 micrometer)

197
Q

What is the droplet size of emulsions that appear milky white?

A

~ 1 micrometer

198
Q

What is the droplet size of emulsions that appear bluish white?

A

1 micrometer - 0.1 micrometer

199
Q

What is the droplet size of emulsions that appear gray-semitransparent

A

0.1 micrometer - 0.05 micrometers

200
Q

What is the droplet size of emulsions that appear clear?

A

< or = to 0.05 micrometers

201
Q

What are the two basic categories of emulsifiers?

A

Non-ionic, ionic

202
Q

Which category of emulsifiers is the most important and widely used group? Why?

A

Non-ionic because they are insensitive to pH

203
Q

What are non-ionic emulsifiers?

A

Emulsifiers based on glycerol esters (mono- and diglycerides) and their non-charged derivatives

204
Q

What is the estimated consumption of monoglycerides in pounds/annum?

A

~250 million pounds/annum

205
Q

Nowadays, pure monoglycerides/diglycerides are manufactured by __________ followed by ____________ to obtain relatively pure fractions.

A

Interesterification

Fractional distillation

206
Q

What is the plasticity of monoglycerides controlled by?

A

overall IV

207
Q

What is the IV of dry powdered monoglycerides?

A

19-36

208
Q

What is the IV of plastic emulsifiers?

A

65-67

209
Q

How are acetylated monoglycerides formed?

A

By reacting the monoglyceride with acetic acid?

210
Q

How are polyoxyethylene monoglycerides produced? What does this lead to?

A

By treating monoglycerides with ethylene oxide - leads to polymerization of ethylene oxide as well as the connection of the polymer to the hydroxyl group at either the 2- or 3-position on the glycerol backbone

211
Q

How long is a polyexyethylene chain?

A

~20 ethylene units

212
Q

What is the main application of polyexylethylene monoglycerides in food chemistry?

A

cake production for emulsification & air incorporation

213
Q

What are 2 other derivatives of non-ionic emulsifiers?

A
  1. lactylated monoglycerides

2. propylene glycol esters

214
Q

What are sorbitan derivatives?

A

Sugar alcohols esterified to FA

215
Q

How is sorbitan monostearate produced?

A

by reacting sugar alcohol with stearic acid in the presence of a catalyst

216
Q

How can sorbitan derivatives be further modified?

A

by reacting with ethylene oxide to form polyoxyethylene derivatives

217
Q

What are esters of polyhydric compounds?

A

Polyglycerol derivatives and sugar esters

218
Q

How is polyglycerol formed? What is the average degree of polymerization normally controlled to be?

A

polymerization of glycerol by reacting glycerol with an alkaline catalyst, then esterified with a FA

n=2 to n=10(decaglycerol)

219
Q

What is an example of a sugar ester?

A

Olestra

220
Q

What is olestra?

A

A non-caloric fat substitute. Sucrose esterified with 6-8 FAs

221
Q

What are the 3 types of ionic emulsifiers?

A
  1. Anionia (-)
  2. Amphoteric (+/-)
  3. Cationic (+)
222
Q

What are anionic (-) emulsifiers?

A

charged monoglyceride derivatives

223
Q

What is the most important anionic monoglyceride? How is it produced?

A

succinylated monoglyceride (SMG)

Produced by reacting monoglyceride with succinic anhydride

224
Q

What is an example of a non-glycerol-based anionic emulsifier?

A

stearoyl-2-lactylate

225
Q

stearoyl-2-lactylate form very stable ___________ emulsions which are resistant to ____________ and is therefore good for ________.

A

oil-in-water

freeze/thaw cycles

frozen foods

226
Q

What type of emulsifier is sodium lauryl sulfate? What is its main use? How are they created?

A

Anionic

Whipping aid for egg white

Produced by the reduction of coconut oil fatty acids (~C12) to their alcohols followed by sulfonation of the alcohols produced

227
Q

Why are cationic (+) emulsifiers not used as food additives?

A

Because they are bacterial/toxic

228
Q

What are cationic (+) emulsifiers extensively used as? Why?

A

Cleaning compounds - they lift and emulsify food residues - very strong surface-active agents

229
Q

What is your typical example of cationic (+) emulsifiers? Such as?

A

Quatrenary ammonium compouds –> cetyltrimethylammonium bromide

230
Q

What is an example of an amphoteric (+/-) emulsifier? This compound is commonly produced as a by-product from what?

A

lecithin (phospholipid) - byproduct from soybean, corn, safflower oil processing

231
Q

What is the majority of lecithin made up of? What may it contain?

A

Phosphatidylcholine and phosphatidylethanolamine

May contain phosphatidylinositol

232
Q

Lechithin is usually treated with __________ and/or __________ to bleach the product.

A

hydrogen peroxide

benzoyl peroxide

233
Q

What does bleaching of lecithin produce?

A

hydroxyl groups at the sites of FA unsaturatoin

234
Q

What is beneficial about hydroxylated lecithin?

A
  • More dispersible in cold water

- a more effective emulsifier than lecithin

235
Q

Proteins fall under the heading of being ________ emulsifiers, but whether they function as such depends on their ________and __________.

A

Ionic

Structure and AA composition

236
Q

What is the role played by proteins in sausage emulsions?

A

Form a protein film around the oil droplets, preventing coalescence of the fat

237
Q

Proteins often partially ____________ at the phase interface and orient themselves in relation to the respective phases.

A

denature

238
Q

What is an example of a type of protein that has good foam-forming properties?

A

egg albumin

239
Q

Ionic emulsifiers have the ________ of being relatively sensitive to _____ and the presence of _______.

A

Disadvantage

pH

other ions

240
Q

What group of compounds are often used in conjunction with emulsifiers?

A

Hydrocolloids

241
Q

What type of compound are hydrocolloids? such as?

A

polysaccharides - starch and gums

242
Q

Hydrocolloids are not considered true _________ but are termed ________ _______.

A

emulsifiers

stabilizing agents

243
Q

What is the major contribution of hydrocolloids?

A

They increase the viscosity of the hydrophilic phase (usually the continuous phase) which makes it more difficult for the oil droplets to coalesce

244
Q

What one stabilizing mechanism of hydrocolloids?

A

Formation of a light gel which traps the oil droplets

245
Q

What can gums form around oil emulsion droplets? Which 2 gums do this?

A

Film

Gum arabic and gum ghatti

246
Q

How are emulsifiers assessed?

A

HLB (hydrophilic-lipophilic balance)

247
Q

What do HLB systems do? What type of emulsifiers is this system mainly applicable to?

A

They help people select emulsifiers. Mainly applicable to non-ionic emulsifiers

248
Q

What does the HLB value represent? Example:

A

The weight percentage of hydrophilic groups in a non-ionic emulsifier molecule divided by 5

Ex: if 50% of the molecular weight of a molecule is hydrophilic HLB=50/5=10

249
Q

What is the HLB of a molecule that is completely lipophilic?

A

HLB = 0

250
Q

What is the HLB of a molecule that is completely hydrophilic?

A

HLB=100/5=20

251
Q

What is the HLB of glycerol monooleate emulsifiers?

A

2.8

252
Q

What is the HLB of lechitin emulsifiers?

A

4.2

253
Q

What is the HLB of polyoxyehylene sorbitan strearate emulsifiers?

A

10.5

254
Q

What is the HLB of polyoxyehylene strearate emulsifiers?

A

16.9

255
Q

What HLB range do hydrophobic molecules fall under? What type of emulsions do they promote?

A

1-6

water-in-oil (w/o)

256
Q

What HLB range do hydrophilic molecules fall under? What type of emulsions do they promote?

A

12-20

oil-in-water (o/w)

257
Q

What HLB range do intermediate molecules fall under? What type of emulsions do they promote?

A

7-11

either w/o or o/w

258
Q

The HLB system provides ______ in selecting and blending emulsifiers to obtain a specific HLB.

A

guidance

259
Q

HLB systems can include assessment under what kind of conditions? Such as?

A

stress

freezing, high temp, agitation

260
Q

What is the HBL range for water in oil emulsifiers?

A

4-6

261
Q

What is the HBL range for wetting agents?

A

7-9

262
Q

What is the HBL range for oil-in-water emulsifiers?

A

8-18

263
Q

What is the HBL range for detergents?

A

13-15

264
Q

What is the HBL range for solubilizers?

A

15-18

265
Q

In what 3 ways are emulsifiers used as conditioners?

A

Bread doughs
Dehydrated potatoes
Processed cereals

266
Q

Emulsifiers as conditioners increase ________ and have the ability to improve the _____ and ________ strength of proteins such as ________.

A
  1. water absorption
  2. cohesive
  3. film foaming
  4. gluten
267
Q

Emulsifiers that are used as conditioners improve what? And allow more use of wat type of protein?

A
  1. tolerance to mixing

2. non-wheat

268
Q

The uses of emulsifiers as conditioners results in improved _______ _______ and ____ _______ and greater resistance to ________.

A
  1. loaf volume
  2. crumb texture
  3. resistance to staling
269
Q

What are 4 ways that emulsifiers can be used as wetting agents?

A
  1. Gelatin dessert mixes
  2. dry beverage mixes
  3. Cocoa powder
  4. pudding mixes
270
Q

What are 3 benefits of the use of emulsifiers as wetting agents?

A
  1. Provide better hydration characteristics
  2. Increase rate of dispersion
  3. Minimize clumping
271
Q

What is the primary role of emulsifiers? Why is this important?

A

Formation and stabilization of complex dispersions. Important in terms of obtaining desired sensory and textural characteristics of a food product

272
Q

Why do we need a wide range of emulsifiers?

A

to maintain product characteristics for long periods of time & under stress conditions (thermal processing, freezing, baking, freeze/thaw stresses)

Food Chemistry (2 decks)

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