CarbohydratesCarbohydrates

Aims of today’s lesson:Aims of today’s lesson:

To develop knowledge of To develop knowledge of carbohydrates, sources, functions carbohydrates, sources, functions and structureand structure

CarbohydratesCarbohydrates

Carbohydrates are an important MACRO Carbohydrates are an important MACRO nutrient because they:nutrient because they:

Carbohydrates are our primary source of Carbohydrates are our primary source of energy.  energy. 

Supply energy for activitySupply energy for activity Supply energy to maintain normal body Supply energy to maintain normal body

temperaturetemperature Supply indigestible fibrous materials to aid Supply indigestible fibrous materials to aid

digestiondigestion

How are they broken down?How are they broken down?

The two different types of The two different types of carbohydrates affect the production carbohydrates affect the production of insulin differently.of insulin differently.

Simple carbohydrates (sugar), are Simple carbohydrates (sugar), are used up more quickly for energy. used up more quickly for energy.

Complex carbohydrates (starch) take Complex carbohydrates (starch) take longer to digest, resulting in longer longer to digest, resulting in longer lasting energy.lasting energy.

What if we eat too many carbs?What if we eat too many carbs?

When the body takes on When the body takes on carbohydrates, its stored in the liver carbohydrates, its stored in the liver and muscle cells as glycogen, to be and muscle cells as glycogen, to be used for when the body needs an used for when the body needs an extra burst of energy. extra burst of energy.

Any leftover, not used for energy, is Any leftover, not used for energy, is stored as fat. stored as fat.

Cellulose - FibreCellulose - Fibre

Fibre is a unique type of carbohydrate because Fibre is a unique type of carbohydrate because it contains zero calories, zero vitamins and it contains zero calories, zero vitamins and cannot be digested.  Therefore, it does not cannot be digested.  Therefore, it does not provide your body with any energy.  provide your body with any energy. 

Insoluble Fibre vs Soluble FibreInsoluble Fibre vs Soluble Fibre Insoluble fibre absorbs water in your intestine Insoluble fibre absorbs water in your intestine

to form a bulky mass which then helps clear to form a bulky mass which then helps clear waste materials from your digestive tract.  waste materials from your digestive tract. 

Soluble fibre dissolves in the water in your Soluble fibre dissolves in the water in your intestine to form a thick gel which then holds intestine to form a thick gel which then holds food in your digestive tract for longer.food in your digestive tract for longer.

Types of starchTypes of starch

Starch is obtained from cereals such as

wheat and maize.

Wheat flour contains a high percentage of starch

Cornflour and arrowroot are pure starch

GelatinisationGelatinisation

Starch particles do not dissolve in liquid, instead they form something

called a suspension.

If liquid is not stirred the starch granules sink to the bottom, stick together and start to form lumps.

GelatinisationGelatinisation

When heated at 60oC, the starch granules begin to absorb the liquid

and swell

At 80oC the particles will have absorbed about five times their volume of water until they burst

open and release starch, thickening the liquid.

This process is Gelatinisation

GelatinisationGelatinisation

Gelatinisation is complete when the liquid reaches boiling point 100oC When the sauce cools it goes even

thicker, going into a Gel.

Heat starch granules in liquid

Starch granules become swollen

Starch granules burst

The liquid thickens and gelatinizes

Starch gelatinizes when heated in a liquid, producing a thickened liquid

Examples of GelatinisationExamples of Gelatinisation

White Sauce for Lasagne

Cheese Sauce

Sweet & Sour Sauce

Modified StarchModified Starch

This is starch that has been altered to perform additional functions to react to

different processes.These are sometimes called SMART

starches.

Modified starch is used to thicken food when boiled water is added e.g. Cup a

soup,dried custard or Pot Noodle.

Food & Drink: Food for thought - What is modified starch? Food & Drink: Food for thought - What is modified starch? Roy Ballam, British Nutrition Foundation Roy Ballam, British Nutrition Foundation

The starch in some canned soups is bonded with phosphate, which allows it to absorb more

water and so the soup from does not separate. Fish batter contains an oxidised starch to make

it "stickier" to adhere to the sides of the fish better.

Instant desserts, such as blancmange, use a pre-gelatinised starch which has been thickened

by heat, then dried and added to the product. Pizza, to stop the tomato sauce spilling off

during baking, a starch treated with a chlorine solution is often added to the topping. This

produces a gel that thickens during cooking, but goes runny when cooled.

Task:Task:

Design and make a macaroni Design and make a macaroni cheese product suitable for cheese product suitable for

children.children.

Specification;Specification; Suitable for children – high in calciumSuitable for children – high in calcium It must have a garnishIt must have a garnish Increase the fibre contentIncrease the fibre content Have a sauce – using the roux methodHave a sauce – using the roux method

What is a garnishWhat is a garnish

To enhance a dish before serving To enhance a dish before serving with an edible decoration or with an edible decoration or

accompaniment, which is accompaniment, which is appealing to the eye and appealing to the eye and

complements the flavours of the complements the flavours of the dish.dish.

Roux SauceRoux Sauce

Milk is added to the roux and the Milk is added to the roux and the sauce is cooked until thick and sauce is cooked until thick and glossy.glossy.

BBC - Food - Techniques : ThickeningBBC - Food - Techniques : Thickening a roux to make béchamel sauce a roux to make béchamel sauce