Ice cream Flashcards
T or F : the size of the bubbles determine the sensory properties and will influence the shelf-life
True
there is only one temperature at which there is ice crystals and salt crystals at the same time and this is at the __
eutectic point.
Why do you want your ice cream serum phase to be at an almost supersaturated state?
because this results in having the serum phase extremly concentrated and so you would have a high viscosity
T or F : sugar alcohol are smaller and so have a bigger effect on the Fp depression.
true, and monosaccharide will also have a larger effect on the Fp depression than sucrose
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.
true
How can you control the amount of sweetness and the Fp depression
by a combination of sugar
What is this graph
it is showing the critial radium for crystal growth
The iciness sensory property is related to the ____
size of the crystals
The hardness sensory property is related to the ___
amount of crystal and size
smoothness of an ice cream is related to the ____ of crystals
size
Coldness of ice cream is related to the ___ of the crystals
melting profile (depends on the collapse of ice cream which depends on multiple factors) and the size/amounts
the size and the amount of crystals can be controlled by :
- the freezing point depression
- the temperature difference of freezing
T or F : the fat coalescence is unwanted in ice cream
false
whey proteins are found ___ in ice cream
at the air interphase
casein proteins are found ___ in the ice cream
at the interphase as well as at the fat globule
why are polysobarte 80 (surfactant) used in ice cream formulations?
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.
what is the downside of surfactant?
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
What is the role of stabilizers ?
- water-binding and so less ice
- Create smoothness in texture because increased viscosity
- reduction of the melting rate
- Slowing down moisture migration
- Masking detection of ice crystals
- Incorporation of air
what kind of ice cream stabilizer are mostly used
polysaccharides (alginates, pectins, locust bean gum, guar gum, carrageeenans)
what are the downsides of using stabilizers
- 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.
- phase separation of polysaccharide and proteins because of the binding of water
what is accretion?
when two crystals touches and they will form a neck and a consequently a bigger crystal will be formed
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.
true because the small crystal melts faster and the bigger one will grow back when freezing again
what are the two effect that leads to re-crystalization ?
- accretion
- ostawald ripening
What are the way to reduce the crystallization?
- addition of polysaccharides
- ice structuring proteins
- Increasing the viscosity
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.
t or f : smaller crystal melts faster
how does polysaccharides reduce the crystalization?
increasing the viscosity reduces the water mobility ot the syrface of the crystals
how does ice structuring proteins reduces the crystalisation?
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
The freezing will determine :
- Size of crystals
- Size of air bubbles
- Over run: (ratio of volume of gas/volume of liquid)
What are the functions of the scraper in ice cream making?
- Subject the mix to high shear
- Beating shears and breaks bubbles into smaller ones
- Causes the fat dropplet to coalesce
What are the steps involved in ice cream making?
- mixing
- aging
- Continuous freezing and churning
What is the role of the aging step in ice cream making?
give time for the emulsifiers to go at the fat interphase for the fat dropplets to crystallise
Storage modulus (G’) is measured the ___ like properties of ice cream
elastic like
The loss modulus (G”) is measuring the ___ like properties of ice cream
liquid like
Are fat particles related to the G’ or G” ?
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”)
The serum phase is more related to the ___ (G’ or G”)
G” because it creates viscosity so it is more related to the viscous properties (liquid-like : G”)
Ice crystals are more related to the ___ (G’ or G”)
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
Air bubbles are more related to the ____ (G’ or G”) ?
G” : Air bubbles are soft particles so they are more related to the viscous behaviour / liquid like
Which ingredients present in ice cream are related to both the G’ and the G” of rheological measurments ?
- Fat particles depending on where they are (serum phase (G’ : solid like) or air interphase (G” : viscous like))
- Ice crystals because they increase the hardness (G’ : solid like) and the viscosity (G” : viscous like)
What does the rheology graph looks like ?
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
In zone 3 of the rheology graph, ___, ____, and __ in the matrix increases the G”
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”
The slope of the rheology graph is related to the ____ and can give information on the ___, ___ and ___
rate of melting
Overrun, Air crystals size and viscosity
The more inclined the slope is in zone II, the ___ the crystals are
smaller because they cover more surface area
Higher is the viscosity of the matrix and the ___ inclined the slope is in zone II
less because it will slow down the rate of melting
in zone I, higher is the amount of ice and higher is the ____
G’
In zone I, lower is the G” and the more there is ___
air
In zone III : - Higher overrun and more stable air bubbles: ___ G” and more fat leads to a ___ G”
higher
more viscous: higher
Sandiness refers to the perception of ____
lactose crystals
T or F : gelatin has a small effect on the freezing point
true because it is a large molecule but it can lower the FP by increasing the viscosity and binds water (stabilizer)
alcohol will lead to denaturation of proteins for 2 reasons :
1- loss of the hydration layer
2-hydrogen bonds in the core of the proteins between the core
