Unit 4 : Food Chemistry - Carbohydrates

Question 1

How many sugar molecules are in each of Monosaccharides , Disaccharides , Oligosaccharides and Polysaccharides ?

Answer 1

• Monosaccharides : 1 sugar molecule
• Disaccharides : 2 sugar molecules
• Oligosaccharides : 3-10 sugar molecules
• Polysaccharides : 100s of sugar molecules

Question 2

What are some examples of Monosaccharides ?

Answer 2

• Glucose
• Fructose
• Galactose

Question 3

What area some example of Disaccharides and what enzymes are used for digesting each of them?

Answer 3

• Sucrose - enzyme sucrase helps to digest it
• Maltose - enzyme maltase helps to digest it
• Lactose - enzyme lactase helps to digest it

Question 4

Compare Lactose Intolerance with Milk allergy
- name what they are classified as and where they occur and what the reaction it is to

Answer 4

• Lactose intolerance : A sensitivity, occurs in gastrointestinal system and its a sensitivity to lactose
• Milk allergy : An allergy , triggered by immune system , reaction to milk protein

Question 5

Sugars are hygroscopic and what does that mean ?

Answer 5

• It means they attract water and absorb water

Question 6

Sugars are Humectants, and what does that mean?

Answer 6

• It means that they hold moisture in food

Question 7

How does caramelization occur with sugar ?

Answer 7

• its dry heated at high temp, sugars melt and turn brown

Question 8

How does the Maillard reaction occur with sugar?

Answer 8

• A non enzymatic reaction between reducing sugar and an amino acid, when they are heated the sugar and amino acids undergo a series of reaction which lead to the production of a complex mixture of brown compounds called melanoidins

Question 9

How does sugar affect the freezing point?

Answer 9

• The higher the concentration of sugar, the lower the freezing point

Question 10

How does Crystallization occur in sugars?

Answer 10

• When the supersaturated sugar solution is cooled , the sugar starts to separate from the water and starts to recrystallize.
• this is how candy is made

Question 11

What are some examples of Oligosaccharides ?

Answer 11

• Raffinose
• Stachyose
• Verbascose

Question 12

How are Oligosaccharides digested ?

Answer 12

• Humans do not have enzymes to digest oligosaccharides
• so the normal intestinal bacteria ferments them to produces gases (methane, CO2, hydrogen)

Question 13

What are some examples of Polysaccharides ?

Answer 13

• Starches
• Fibres
• Glycogen

Question 14

What are some properties of Starch and how does the digestion work ?

Answer 14

• pure starch is a white, tasteless, and odourless powder that is insoluble in cold water
• Enzymes are produced to digest starch and when digest it is broken down into monomers of glucose

Question 15

What are 3 ways starch is used in foods

Answer 15

• as a thickener in foods
• as an excellent binder
• To form the gel like soft texture of baked goods

Question 16

How does Dextrinization occur in starch?

Answer 16

• Starch is heated in the absence of water, it turns brown and breaks down a little.

Question 17

How can starch be used as a sweetener ?

Answer 17

• Since starch is tasteless, it needs to be hydrolzued so the glucose molecules start to become free and can bind to our taste receptors , thus taste sweet.

Question 18

Where is glycogen stored in humans and what is it the storage form of and how is it digested ?

Answer 18

• Its stored in liver and muscles
• storage form of carbohydrates in human beings
• the human body produces enzymes to breakdown glycogen

Question 19

Do dietary fibre get broken down by enzymatic reaction?

Answer 19

• No , dietary fibre is resistant to it , as the. digestive system does not produce enzymes to break down fibres

Question 20

What is another name for water soluble fibres and what do they do ?

Answer 20

• Viscous fibres
• They dissolve in water and increase the viscosity of the water

Question 21

How do water soluble fibres impact our digestive system when consumed ?

Answer 21

• They increase the viscosity of chyme in our digestive system which leads to slow movement of chyme in the digestive system - aka peristalsis

Question 22

How is peristalsis impacting the body ?

Answer 22

• It keeps the stomach full for a longer period of time and slows down the absorption of nutrients through the wall

Question 23

What is another name for water insoluble fibres and what do they do ?

Answer 23

• Non viscous fibres
• They do not dissolve in water and thus have no impact on the viscosity of water

Question 24

What do water insoluble fibres help with?

Answer 24

• they bind minerals. phytochemical and some vitamin

Question 25

What are some ways the food industry uses fibres?

Answer 25

• For improving texture
• as a bulking agent in reduce sugar applications
• To manage moisture in the replacement of fat
• To add colour

Question 26

What are the two main types of pectic substances that are also soluble fibres and at what pH and how much sugar is needed for them to form gels ?

Answer 26

1. High methoxy (HM) pectins and they form gels below 3.5 pH and at least 55% sugar
2. Low methoxy (LM) pectins and they form gels between 2-7 pH and without sugar