I c e - C r e a m

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Ice- Cream Food Facts & Fallacies YSCN0006

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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 - PowerPoint PPT Presentation

Transcript of I c e - C r e a m

Page 1: I c e -  C r e a m

Ice- Cream

Food Facts & FallaciesYSCN0006

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I scream

You scream

We all scream for ice-cream

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What is ice-cream? 1

• Cool

• Smooth

• Yummy

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What is ice-cream? 2

• Water

• Fat

• Carbohydrate

• Protein

• Air

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What is ice-cream? 3

• Solid (at low temp)

• Liquid (at room temp)

• A colloid

• Emulsion

• Frozen foam

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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

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Milk ~ Fat in water emulsion

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Butter ~ Water in fat emulsion

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Ice-cream

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Sizes

• dissolved sugars, polysaccharides, proteins

• fat globules 1 to 5 µm

• ice crystals 30 to 50 µm

• air bubbles 50 to 100 µm

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Making ice cream

• Ingredients

• Mixing

• Freezing

• Hardening

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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

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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

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After homogenisation

• Addition of liquid flavours

• Colouring

• Fruit puree

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Freezing

• Uses a scraped barrel freezer

• Simultaneous beating and freezing

• Beating to destabilize fat emulsion incorporate air

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The Importance of Air

- 40°C- 5°C

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Not Enough Air

• a solid lump of ice?

• Too cold

• Too hard

• Too rich, percentage fat too high

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Too Much Air

• Dry texture

• Melts too quickly

• Correct quantity around 50% of volume

• = overrun of 100

• overrun is used to control the texture of ice-cream

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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

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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

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Hardening

• Continuous blast freezer or batch freezer

• -40 °C

• remaining water frozen

• ice-cream stable if kept below -25°C

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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

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Emulsifiers & Stabilisers

• Emulsifiers– help fat globule breakdown– essential to stabilise air bubbles

• Stabilisers– reduce ice-crystal growth

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Sugar crystals

• formation of lactose crystals detectable as gritty sandiness in texture

• avoided by fast freezing and rapid formation of glass

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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)

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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

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Dr Ramsden’s special HKU chocolate ice -cream

• Chocolate 60g

• Milk 200ml

• Cream 400ml

• Sugar 150g

• Vanilla 10ml

• Egg yolk x 3

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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