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I c e - C r e a m Food Facts & Fallacies YSCN0006 I scream You scream We all scream for ice-cream What is ice-cream? 1 Cool Smooth Yummy What is ice-cream? 2 Water Fat Carbohydrate Protein Air What is ice-cream? 3 Solid (at low temp) Liquid (at room temp) A colloid Emulsion

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i c e c r e a m

Ice- Cream

Food Facts & FallaciesYSCN0006

slide2
I scream

You scream

We all scream for ice-cream

what is ice cream 1
What is ice-cream? 1
  • Cool
  • Smooth
  • Yummy
what is ice cream 2
What is ice-cream? 2
  • Water
  • Fat
  • Carbohydrate
  • Protein
  • Air
what is ice cream 3
What is ice-cream? 3
  • Solid (at low temp)
  • Liquid (at room temp)
  • A colloid
  • Emulsion
  • Frozen foam
what is a colloid
What is a Colloid ?
  • Physical states
  • Solids, Liquids, Gases and….
  • Stable mixtures of them are colloids
  • Emulsion, solid dispersed in a liquid
  • Foam, gas dispersed in a liquid
sizes
Sizes
  • dissolved sugars, polysaccharides, proteins
  • fat globules 1 to 5 µm
  • ice crystals 30 to 50 µm
  • air bubbles 50 to 100 µm
making ice cream
Making ice cream
  • Ingredients
  • Mixing
  • Freezing
  • Hardening
ingredients
Ingredients
  • Sucrose 15%
  • Milk fat 15% (legal min. 10%)
  • Non-fat milk solids 10% (lactose & casein)
  • Corn syrup 5% (fructose & dextrins)
  • Stabilisers 0.4% (polysaccharides)
  • Emulsifier 0.2% (mono or di-glycerides)
  • Water
making ice cream13
Making ice-cream
  • Mixing of ingredients and homogenisation to give small fat globules.
  • Pasteurisation to cook and sterilise the mix
  • Cooling, allows crystallisation of fat in globules
after homogenisation
After homogenisation
  • Addition of liquid flavours
  • Colouring
  • Fruit puree
freezing
Freezing
  • Uses a scraped barrel freezer
  • Simultaneous beating and freezing
  • Beating to
    • destabilize fat emulsion
    • incorporate air
not enough air
Not Enough Air
  • a solid lump of ice?
  • Too cold
  • Too hard
  • Too rich, percentage fat too high
too much air
Too Much Air
  • Dry texture
  • Melts too quickly
  • Correct quantity around 50% of volume
  • = overrunof 100
  • overrun is used to control the texture of ice-cream
after freezing
After Freezing
  • about 50% water frozen
  • Sot texture =
  • Soft serve ice-cream as used for cones
  • Particulate addition, eg. nuts, biscuit crumbs, chocolate chips
  • Packaging
freeze concentration
Freeze concentration
  • dissolved solutes depress the freezing point of a liquid
  • the higher the concentration the greater the depression
  • as the ice-cream water freezes the concentration of sugars increases
  • even at very low temperatures there will be a small amount of unfrozen water present
hardening
Hardening
  • Continuous blast freezer or batch freezer
  • -40 °C
  • remaining water frozen
  • ice-cream stable if kept below -25°C
ice crystals
Ice crystals
  • essential to stabilise air bubbles
  • too big give a gritty texture
  • small crystals formed by
    • good nucleation
    • rapid freezing
  • ice crystals grow if temperature fluctuates
emulsifiers stabilisers
Emulsifiers & Stabilisers
  • Emulsifiers
    • help fat globule breakdown
    • essential to stabilise air bubbles
  • Stabilisers
    • reduce ice-crystal growth
sugar crystals
Sugar crystals
  • formation of lactose crystals detectable as gritty sandiness in texture
  • avoided by fast freezing and rapid formation of glass
other ices
Other Ices
  • Sorbet & water ices (no milk fat, high fruit)
  • Sherbets (added citric acid)
  • Frozen yoghourt (fermented milk solids)
  • Ice-milk (3-5% milk fat)
ice bars novelties
Ice Bars & Novelties
  • Formed by moulding or extrusion
  • Moulding requires a stick!
  • Centre filling possible with moulded bars
  • After freezing products can be coated and enrobed
dr ramsden s special hku chocolate ice cream
Dr Ramsden’s special HKU chocolate ice -cream
  • Chocolate 60g
  • Milk 200ml
  • Cream 400ml
  • Sugar 150g
  • Vanilla 10ml
  • Egg yolk x 3
preparation method
Preparation method
  • melt chocolate & mix with milk
  • mix egg yolks with sugar
  • add cream and vanilla to chocolate milk and bring to boil
  • allow to cool & then add egg sugar
  • mix at low heat for 15 min
  • 4°C for 4 hours
  • freeze for 30 min
  • harden at 30°C 12 h