Ice cream

Question 1

T or F : the size of the bubbles determine the sensory properties and will influence the shelf-life

Answer 1

True

Question 2

there is only one temperature at which there is ice crystals and salt crystals at the same time and this is at the __

Answer 2

eutectic point.

Question 3

Why do you want your ice cream serum phase to be at an almost supersaturated state?

Answer 3

because this results in having the serum phase extremly concentrated and so you would have a high viscosity

Question 4

T or F : sugar alcohol are smaller and so have a bigger effect on the Fp depression.

Answer 4

true, and monosaccharide will also have a larger effect on the Fp depression than sucrose

Question 5

T or F : the largest differences in ice content is at larger temperatures and at lower temperatures the ice content doesn’t change that much.

Answer 5

true

Question 6

How can you control the amount of sweetness and the Fp depression

Answer 6

by a combination of sugar

Question 7

What is this graph

Answer 7

it is showing the critial radium for crystal growth

Question 8

The iciness sensory property is related to the ____

Answer 8

size of the crystals

Question 9

The hardness sensory property is related to the ___

Answer 9

amount of crystal and size

Question 10

smoothness of an ice cream is related to the ____ of crystals

Answer 10

size

Question 11

Coldness of ice cream is related to the ___ of the crystals

Answer 11

melting profile (depends on the collapse of ice cream which depends on multiple factors) and the size/amounts

Question 12

the size and the amount of crystals can be controlled by :

Answer 12

1. the freezing point depression
2. the temperature difference of freezing

Question 13

T or F : the fat coalescence is unwanted in ice cream

Answer 13

false

Question 14

whey proteins are found ___ in ice cream

Answer 14

at the air interphase

Question 15

casein proteins are found ___ in the ice cream

Answer 15

at the interphase as well as at the fat globule

Question 16

why are polysobarte 80 (surfactant) used in ice cream formulations?

Answer 16

they compete with the casein molecules for the fat globules and so they will induce the partial coalescence which is wanted for air bubble stability.

Question 17

what is the downside of surfactant?

Answer 17

they compete with the proteins for the air bubble interphase which as a destabilizing effect for the air bubbles and can lead to collpase of ice cream if too much is used

Question 18

What is the role of stabilizers ?

Answer 18

1. water-binding and so less ice
2. Create smoothness in texture because increased viscosity
3. reduction of the melting rate
4. Slowing down moisture migration
5. Masking detection of ice crystals
6. Incorporation of air

Question 19

what kind of ice cream stabilizer are mostly used

Answer 19

polysaccharides (alginates, pectins, locust bean gum, guar gum, carrageeenans)

Question 20

what are the downsides of using stabilizers

Answer 20

1. supersaturation :cthere is one bad effect of the stabiliser, because they bind the water, they increase the sugar content that is already increased by the freezing so you can go into a state of supersaturation (not enough water to bind the sugar) and the sugar will crystalise (concentration higher than the crystalisation concentration) and so this leads to the crystalisation and so white spots on the ice cream.
2. phase separation of polysaccharide and proteins because of the binding of water

Question 21

what is accretion?

Answer 21

when two crystals touches and they will form a neck and a consequently a bigger crystal will be formed

Question 22

T or F ; the thawing and freezing cycle do not get a decrease in the crystal surface area but a change in the number of crystals present.

Answer 22

true because the small crystal melts faster and the bigger one will grow back when freezing again

Question 23

what are the two effect that leads to re-crystalization ?

Answer 23

1. accretion
2. ostawald ripening

Question 24

What are the way to reduce the crystallization?

Answer 24

1. addition of polysaccharides
2. ice structuring proteins
3. Increasing the viscosity

Question 25

t or f : You need to keep your icecream for a very long time to be able to see the ostawal ripening and the accretion.

Question 26

t or f : smaller crystal melts faster

Question 27

how does polysaccharides reduce the crystalization?

Answer 27

increasing the viscosity reduces the water mobility ot the syrface of the crystals

Question 28

how does ice structuring proteins reduces the crystalisation?

Answer 28

the proteins sits on the ice crystals and prevent them from growing. This is related to the icephobocity. They will change the curvature of the ice crystal

Question 29

The freezing will determine :

Answer 29

1. Size of crystals
2. Size of air bubbles
3. Over run: (ratio of volume of gas/volume of liquid)

Question 30

What are the functions of the scraper in ice cream making?

Answer 30

1. Subject the mix to high shear
2. Beating shears and breaks bubbles into smaller ones
3. Causes the fat dropplet to coalesce

Question 31

What are the steps involved in ice cream making?

Answer 31

1. mixing
2. aging
3. Continuous freezing and churning

Question 32

What is the role of the aging step in ice cream making?

Answer 32

give time for the emulsifiers to go at the fat interphase for the fat dropplets to crystallise

Question 33

Storage modulus (G’) is measured the ___ like properties of ice cream

Answer 33

elastic like

Question 34

The loss modulus (G”) is measuring the ___ like properties of ice cream

Answer 34

liquid like

Question 35

Are fat particles related to the G’ or G” ?

Answer 35

Both depending where the fat is within the ice cream.
Fat inside the continuous phase : Contribute to the solid-like (G’) behaviour
Fat at the air interphase : Contribute to the softeness of the ice cream so more related to the liquid-like (G”)

Question 36

The serum phase is more related to the ___ (G’ or G”)

Answer 36

G” because it creates viscosity so it is more related to the viscous properties (liquid-like : G”)

Question 37

Ice crystals are more related to the ___ (G’ or G”)

Answer 37

They are related to both but more the G”.
G” (solid-like) : because they are hard and increase the solid behaviour
G’ (liquid-like / viscous properties) : because they increase the viscosity of the serum phase

Question 38

Air bubbles are more related to the ____ (G’ or G”) ?

Answer 38

G” : Air bubbles are soft particles so they are more related to the viscous behaviour / liquid like

Question 39

Which ingredients present in ice cream are related to both the G’ and the G” of rheological measurments ?

Answer 39

1. Fat particles depending on where they are (serum phase (G’ : solid like) or air interphase (G” : viscous like))
2. Ice crystals because they increase the hardness (G’ : solid like) and the viscosity (G” : viscous like)

Question 40

What does the rheology graph looks like ?

Answer 40

The are three zones :
Zone I : Related to the ice crystal structure (solid-like behaviour) and the viscosity of the serum phase (viscous like behaviour)
Zone II : Related to the melting behaviour
Zone III : molten state : related to the viscosity / liquid like properties (G” ) which dpends on the stabilizers, air. Also related to the solid-like behaviour if fat is present

Question 41

In zone 3 of the rheology graph, ___, ____, and __ in the matrix increases the G”

Answer 41

G” is related to the viscous like / liquid - like behaviour and so more air, stabilizers and water in the serum phase would increase the G”

Question 42

The slope of the rheology graph is related to the ____ and can give information on the ___, ___ and ___

Answer 42

rate of melting
Overrun, Air crystals size and viscosity

Question 43

The more inclined the slope is in zone II, the ___ the crystals are

Answer 43

smaller because they cover more surface area

Question 44

Higher is the viscosity of the matrix and the ___ inclined the slope is in zone II

Answer 44

less because it will slow down the rate of melting

Question 45

in zone I, higher is the amount of ice and higher is the ____

Answer 45

G’

Question 46

In zone I, lower is the G” and the more there is ___

Answer 46

air

Question 47

In zone III : - Higher overrun and more stable air bubbles: ___ G” and more fat leads to a ___ G”

Answer 47

higher
more viscous: higher

Question 48

Sandiness refers to the perception of ____

Answer 48

lactose crystals

Question 49

T or F : gelatin has a small effect on the freezing point

Answer 49

true because it is a large molecule but it can lower the FP by increasing the viscosity and binds water (stabilizer)

Question 50

alcohol will lead to denaturation of proteins for 2 reasons :

Answer 50

1- loss of the hydration layer

2-hydrogen bonds in the core of the proteins between the core