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Exam 1 > Ice cream > Flashcards

Ice cream Flashcards

1
Q

Characteristics of fat globules in ice cream

A

Partially coalesced globules and clumps
5-80 microns
Discrete phases in the serum or stabilising air cells
Used for aeration, retention and meltdown properties

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2
Q

What is in the serum phase of ice cream?

A

Water containing dissolved sugars, salts, proteins and stabilisers

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3
Q

What happens to the concentration of components after freezing?

A

Increases due to ice crystal formation

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4
Q

How does serum phase hold the ice cream structure together?

A

By interacting with other phases

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5
Q

How does serum phase prevent phase separation?

A

Reducing the growth of ice crystals

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6
Q

What is the perfect range for the size of ice crystals for a smooth ice cream?

A

30-50 microns

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7
Q

How large are air cells in ice cream?

A

20-25 microns

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8
Q

What are air cells stabilised by?

A

Destabilised fat globules
Milk protein
Viscosity in the serum phase

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9
Q

Why is the mixing stage important?

A

To disperse and hydrate ingredients

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10
Q

What is the step after mixing?

A

Pasteurisation at 80C for 30 seconds

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11
Q

Why is pasteurisation of ice cream important?

A

Destroy pathogens
Melt fat
Solubilise solids

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12
Q

What is the step after pasteurisation?

A

Homogenisation

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13
Q

Why is homogenisation important?

A

Disrupts phases causing droplet deformation, emulsifier adsorption and droplet collision

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14
Q

What is the role of emulsifiers in ice cream?

A

Allow milk membrane to coat the droplets as surface area has increased

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15
Q

What step is after homogenisation?

A

Cooling at <5C for 4-24 hours

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16
Q

Why is fat crystallisation important during cooling?

A

Fat destabilisation

17
Q

What is fat destabilisation?

A

Rearrangement of milk fat globule interface with surfactants displacing proteins

18
Q

What are crystalline fat globules formed by in the cooling stage?

A

Casein micelles in a solution of sugar, salt, whey and stabilisers

19
Q

What is used for the cooling phase?

A

Scraped surface heat exchanger (SSHE)

20
Q

What occurs in the SSHE?

A

Air is injected
Air cells are formed but reduce during whipping
Air cell size reduction is affected by viscosity

21
Q

How does the SSHE limit the coalescence of globules?

A

Destabilisation of emulsion droplets and crystalline fat globules

22
Q

How is the stability of fat globules reduced during cooling?

A

Displacement of proteins from the fat globule interface

23
Q

What do partially coalesced fat globules do during cooling?

A

Stabilise air bubbles and form a network in the serum phase

24
Q

What is hardening?

A

Process after cooling to reduce temperature from -6 to -18

25
Q

What occurs during hardening?

A

Static cooling causes growth of ice crystals and change in air cell size

26
Q

What causes change in air cell size during hardening?

A

Disproportionation, coalescence and drainage

27
Q

What are colligative properties?

A

Properties that depend on number of solute particles

28
Q

What are non-colligative properties?

A

Properties that depend on identity of dissolved species and solvent

29
Q

How do solutes effect freezing?

A

Makes ice cream harder to freeze as the liquid is less ordered

30
Q

What does temperature abuse cause?

A

Ice crystal and air cell changes
Loss of volume
Lactose crystallisation (sandy texture)

31
Q

Why is temperature increase a problem?

A

Ice melts and diffuses in serum phase and drains through the product

32
Q

What is meltdown rate?

A

Mass that drips through the product

33
Q

What is meltdown rate affected by?

A

Overrun
Air cell stability
Fat destabilisation
Ice crystal size
Viscosity of serum phase

34
Q

What increases recrystallisation?

A

Initial size
Insufficient freezing

35
Q

What decreases recrystallisation?

A

Fat globule network
Ingredients with WHC
Serum phase viscosity
Proteins preventing water molecule exchange

36
Q

How does ice cream shrink?

A

Loss of air cells
Formation of channels
Temperature fluctuations

Exam 1 (13 decks)

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