Properties Of Starch

Question 1

List the properties of starch

6

Answer 1

Solubility 
Flavour 
Hygroscopy 
Gelatinisation 
Hydrolysis 
Dextrinisation

Question 2

Describe the solubility property of starch

2

Answer 2

Starch is a white non-crystalline powder

It in insoluble in cold water

Question 3

Describe the physical appearance of starch.

Answer 3

Starch is a white non-crystalline powder

Question 4

What is starch insoluble in?

Answer 4

Cold water

Question 5

Describe the flavour property of starch

Answer 5

Starch is not sweet in flavour

Question 6

Is starch sweet?

Answer 6

No

Question 7

Describe the hygroscopy property of starch

2

Answer 7

Starch has the ability to absorb moisture from the air

This can cause uncovered foods, e.g. biscuits, to soften and lose crunch

Question 8

What can starch absorb?

Answer 8

Starch can absorb moisture from the air

Question 9

What affect can hygroscopy have on foods?

Answer 9

This can cause uncovered foods to soften and lose crunch due to starch’s ability to absorb moisture from air

Question 10

What is hygroscopy?

Answer 10

The ability to absorb moisture from the air

Question 11

Give a culinary application of the hygroscopy property of starch

Answer 11

It helps to keep cakes moist and prevents them from drying out

Question 12

What is an advantage of hygroscopy?

Answer 12

It can keep cakes moist

Question 13

What is a disadvantage of hygroscopy?

Answer 13

It can cause biscuits to lose their crunch

Question 14

Describe the gelatinisation property of starch

3

Answer 14

When starch is combined with liquid and heated to 55-70 degrees the grains swell, burst and absorb the liquid around them, increasing the viscosity

As the temperature increases (above 85 degrees) it becomes even more viscous and forms a sol

When the mixture cools, water molecules become trapped, resulting in a gel

Question 15

What is the first step in forming a gel?

Answer 15

Starch must be combined with a liquid and heated to 55-70 degrees for the grains to swell, burst and absorb the liquid around them

Question 16

What affect does starch grains swelling, bursting and absorbing the liquid around them have?

Answer 16

It increases the viscosity of the mixture

Question 17

What must starch be mixed with to form a gel?

Answer 17

A liquid

Question 18

At what temperature do the starch grains burst?

Answer 18

Between 55 and 70 degrees

Question 19

What happens to the viscous liquid formed from the burst starch when it reaches 85 degrees?

Answer 19

It becomes even more viscous and forms a sol

Question 20

What temperatures are needed to form a sol?

Answer 20

85 degrees

Question 21

What happens when a sol cools?

Answer 21

Water molecules become trapped in the mixture which forms a gel

Question 22

Give a culinary application of the gelatinisation property of starch
(2/4)

Answer 22

Moist heat - roux sauce, lemon curd;

Dry heat -popcorn, pastry.

Question 23

Describe the hydrolysis property of starch

2

Answer 23

Hydrolysis (the reverse of the condensation reaction) occurs during digestion

Water and enzymes split starch (polysaccharide) into the disaccharide maltose

Question 24

What is hydrolysis?

Answer 24

The reverse of the condensation reaction

Question 25

What happens to starch during hydrolysis?

Answer 25

It is split into the disaccharide maltose by water and enzymes

Question 26

What two things are needed for hydrolysis?

Answer 26

Enzymes Water

Question 27

Describe the dextrinisation property of starch | 3

Answer 27

When starch foods are dry-heated, short-chained polysaccharides called dextrins are formed On further heating these combine to form pyrodextrins This causes a colour change on the surface of the food, resulting in an attractive brown appearance

Question 28

What is formed when starch foods are dry-heated?

Answer 28

Short-chained polysaccharides called dextrins are formed

Question 29

What are dextrins?

Answer 29

Short-chained polysaccharides formed from the dry-heating of starch foods

Question 30

What forms dextrins?

Answer 30

The dry-heating of starch foods

Question 31

What happens when dextrins are heated?

Answer 31

Pyrodextrins are formed

Question 32

What forms pyrodextrins?

Answer 32

The further heating of a starch food after dextrins have been formed

Question 33

What affect does the formation of pyrodextrins have on food?

Answer 33

This causes a colour change on the surface of the food, resulting in an attractive brown appearance

Question 34

Give a culinary application of the dextrinisation property of starch

Answer 34

The browning of bread to make toast