Presentation on theme: "C1b 5.3 Everyday Emulsions. What happens if you let ice cream melt and then re-freeze it? Separates into crunchy ice crystals and a buttery oily part."— Presentation transcript:
C1b 5.3 Everyday Emulsions
What happens if you let ice cream melt and then re-freeze it? Separates into crunchy ice crystals and a buttery oily part
Made from two runny liquids! Egg yoke stops the oil and water from separating out Egg yoke is an emulsifier Oil, water
mayonnaise milkice cream salad dressing What do these substances have in common? They are all…… OK – so what is an emulsion?
Emulsions are foods made from a mixture of oil and water and they are important foods as they are smooth and creamy. But, oil and water don’t mix (immiscible) so we need a special substance which stops the water and oil separating out. Oil droplet Water We need an EMULSIFIER
Emulsifiers stop oil and water from separating out, but how do they work? _ An emulsifier molecule This end is attracted to water (Hydrophilic) This end is attracted to oil (Hydrophobic)
_ _ _ _ _ _ _ _ oil droplet The charged oil droplets repel each other (like charges repel), keeping them spread throughout the water. water
_ _ _ _ _ _ _ __ _ _ _ _ _ _ __ _ _ _ _ _ _ _ The negative charges repel each other which stops the oil droplets from coming together and forming bigger drops.
Observing an emulsion (milk) with a microscope Put a drop of one type of milk in the centre of the microscope slide. Place a cover slip at the edge, and support it with the mounted needle. Gently, lower onto the liquid in order to minimise air bubbles getting trapped underneath. Put the slide onto the microscope stage, and adjust for the lowest magnification and bring into focus. Repeat for other milk. Draw diagrams of what you see.