Carbohydrates

Question 1

Classify carbohydrates according to their structure and give two examples in each class?

Answer 1

Monosaccharides
A simple sugar that contains one simple sugar unit . It is the smallest unit of carbohydrates
Eg glucose and fructose

Disaccharide
Formed when two monosaccharides join resulting in the lose of a water
Eg maltose and sucrose

Polysaccharide
Formed when three or more monosaccharides join together resulting in the loss of a water molecule with a new link . Chains can be straight or branched
Eg starch and pectin

Question 2

Write a brief note on a)pectin b)cellulose

Answer 2

Pectin.
Naturally present in plant cells and the walls of fruit and vegetables. It is used as a setting agent and has the ability to absorb water and from a gel. For pectin to be abstracted it needs heat and acid eg lemon juice

Cellulose
Insoluble in water. Cannot be digested by the body. Absorbs water as it passes through intestinal tract and stimulates peristalsis . This feeds up passage of food and waste and prevents bowel disease

Question 3

What are 6 properties of sugar

Answer 3

Caramelisation 
Crystallisation 
Hydrolysis 
Inversion 
Solubility 
Sweetness

Question 4

What is caramelisation and culinary application

Answer 4

On heating sugar melts and carmalises.
This occurs over ten gradual stages between 104 degrees to 177 degrees
Normally occurs at 160 degrees resulting in brown colour and sweet taste
Culinary application: caramel squares

Question 5

What is crystallisation and culinary application

Answer 5

When a liquid has dissolved as much sugar as it can it is saturated
If more sugar is added crystals form in the solution and solidify when cool

Culinary application. Fudge

Question 6

What is inversion and culinary application

Answer 6

When a liquid sucrose solution is heated in the presence of an acid or enzyme it causes the disaccharide to split to monosaccharides
Also know as an invert sugar

Culinary application. Jam-making

Question 7

What is hydrolysis

Answer 7

The reverse of the condensation reaction occurs during digestion
Water and enzymes split disaccharide into two monosaccharides e.g lactose in glucose and galactose

Question 8

What is soluabilty and culinary application

Answer 8

Sugar is a white crystalline compound
Soluble in water
A syrup if formed when a large amount of sugar is dissolved in a small amount of water

Culinary application. Canned fruit

Question 9

What are the 6 properties of starch

Answer 9

Soluabilty 
Flavour 
Hydroscopy
Gelatinisation 
Hydrolysis 
Dextrinisation

Question 10

What is the rda of fibre

Answer 10

25-35g per day

Question 11

Effects of dry heat on carbohydrates

Answer 11

Dextrinisation eg toasting bread
Carmalisation eg creme caramel
Mallard reaction eg roast beef

Question 12

Effects of moist heat on carbohydrates

Answer 12

Syrup formation eg tinned peaches
Gelatinisation eg white sauce
Cellulose softens eg tomatoes
Pectin extraction eg jam

Question 13

What are the 4 biological functions of carbohydrates

Answer 13

Supply the body with heat and energy. Keep body at 37 degrees and supply energy for all activity’s

Protein-sparing function. Protein can fulfill their primary function of growth and repair of cells rather than being used to produce energy

Fibre absorbs water as it passes through the intestinal tract which stimulates peristalsis. Speed up passage of food and water and prevent bowl diseases

Excess carbohydrates converted to glycogen and store in the liver and muscle as a long term energy reserves . Can be converted to fat and stored in adipose tissue to insulate the body

Question 14

What is the energy value of carbohydrates

Answer 14

1g provides 4 kcal of energy

Question 15

Absorption of carbohydrates

Answer 15

After digestion the monosaccharides are ready to be absorbed by the small intestine .
Pas through wall of villi and into the bloodstream
Hepatic portal vein transports monosaccharides to the liver
In the liver fructose and galactose be converted to glucose
Glucose is oxidised to produces heat and energy
Converted to glycogen and stormed in liver and muscle as a long term energy reserve

Question 16

Digestion of carbohydrates in mouth
Pancreas
Small intestine

Answer 16

During digestion water and enzyme break carbohydrates into monosaccharides

Mouth. Food is chewed into small pieces by the teeth. Salivary glands secrete saliva which contains the enzyme salivary analyses which breaks down starch to maltose

Pancreas . Secretes pancreatic juices contains the enzyme amylase into the duodenum. Continues break down of starch to maltose

Small intestine. The ileum secretes intestinal juices containing the enzyme maltase which breakdown maltose to glucose and the enzyme sucrase which breaks down glucose to fructose and enzyme lactase which breaks lactose down to galactose

Question 17

What is hyrdroscopy and culinary application

Answer 17

Starch has the ability to absorb moisture from the air
Can cause uncovered food to soften and lose crunch

Culinary application keeps cakes from drying out

Question 18

What is dextrinisation and culinary application

Answer 18

When starch food is dry heated short chained polysaccharide called dextrins form
Further heating theses combine and form pyrodextrins
Causes colour change on food surface

Culinary application. Browning of bread to make toast

Question 19

Assimilation of carbohydrates

Answer 19

Monosaccharides can be oxidised to produce energy

Monosaccharides are changed to glycogen and stored in the liver and muscle as an energy reserve

Excess carbohydrates are changed to fat and stored in the adipose tissue under the skin

Question 20

What is gelatinisation

Answer 20

Starch is heated in the presence of water
Starch grains swell and burst and absorbs water
Results in thickening of the liquid

As temperature rises mixture become viscous forming a sol
On cooking this becomes a gel

Eg using flour to thicken soups

Question 21

Two properties of non-starch polysaccharides

Answer 21

Pectin

Cellulose