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Carbohydrates Flashcards

1
Q

Formation of Carbohydrates

A

Carbohydrates are formed in plants by a process known as photosynthesis

Carbon dioxide is absorbed from the air through the leaves
Water is absorbed from soil through the roots
Energy is absorbed from sunlight by chlorophyll (green pigment)
This energy is used to create glucose from carbon dioxide (CO2) and water (H2O)
Oxygen is released into the air

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2
Q

Elemental composition of carbohydrates

A

Carbon
Hydrogen
Oxygen

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3
Q

Classification of carbohydrates

A

Monosaccharides
Disaccharides
Polysaccharides

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4
Q

Monosaccharides

A

Monosaccharides are simple sugar units. They are the basic units of all carbohydrates

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5
Q

Monosaccharide Formula

A

C6H12O6

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6
Q

Examples of monosaccharides

A

Glucose - fruit
Fructose - fruit, honey
Galactose - cheese

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7
Q

Disaccharides

A

Disaccharides are formed when two monosaccharides join together with the elimination of water (condensation reaction)

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8
Q

Disaccharides formula

A

C12 H22 O11

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9
Q

Examples of disaccharides

A

Sucrose (glucose, fructose) - sugar
Lactose (glucose, galactose) - milk
Maltose (glucose, glucose) - barley

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10
Q

Polysaccharides

A

Polysaccharides are formed when many monosaccharides join together with the loss of a water molecule each time (condensation reaction).
They may be in straight or branched chains.
Examples include starch, pectin, cellulose and glycogen.
Pectin, cellulose and glycogen are referred to as non-starch polysaccharides

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11
Q

Polysaccharide formula

A

(C6 H10 O5 )N

N - number of monosaccharides present

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12
Q

Examples of polysaccharides

A

Starch - potatoes, cereals
Cellulose - fruit, vegetables, whole grain
cereals
Glycogen - meat (stored animal starch)
Pectin - fruit

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13
Q

Sources of SUGAR Carbohydrates

A

Sugar
Biscuit
Cake
Honey
Sweets
Fruit

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14
Q

Sources of STARCH Carbohydrates

A

Breakfast cereals (Eg:) fruit and fibre
Potatoes
Rice
Pasta
Flour: bread and cakes

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15
Q

Sources of CELLULOSE Carbohydrates

A

Fruit and vegetables (skin on)
Whole grain breakfast cereal (Eg:) fruit and fibre
Whole meal bread and pasta
Brown rice
Nuts

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16
Q

Properties of SUGAR Carbohydrates
List

A

Solubility
Flavour
Maillard Reaction
Foam formation
Caramelisation
Crystallisation
Hydrolysis
Inversion

MIFFCCHS

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17
Q

Sugar - solubility

A

Sugars are white crystalline compounds that are soluble in water.
Solubility is increased when you heat the water.

Culinary Application
Combining sugar and water to form a syrup served with pancakes
Used as a preservative in canned foods (eg:) peaches

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18
Q

Sugar - flavour

A

Sugars vary in sweetness. For example sucrose is much sweeter than lactose. Sucrose has a relative sweetness of 170, lactose is 15

Culinary Application
Adding sugar to sweeten desserts and cakes

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19
Q

Sugar - Maillard reaction

A

Non-enzymic browning that occurs when sugars and amino acids react in dry heat, giving the food an attractive appearance and flavour.

Culinary Application
Crust forming on bread as it bakes in the oven
Roast potatoes
Shortbread biscuits

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20
Q

Sugar - assists aeration/foam formation

A

Sugar helps to denature egg protein. When eggs are whisked the heat produced by the friction coagulates the protein around the air bubbles, allowing aeration to occur.
Cooking further coagulates the protein forming a permanent foam.

Culinary Application
Aeration of meringues and sponge cakes

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21
Q

Sugar - caramelisation

A

When sugar is heated on its own, it melts and then caramelises - in other words, it changes to a brown syrup (caramel).
If caramel is overheated, it will carbonise its burn.
There are ten gradual changes in the sugar between melting and caramelisation.
These changes occur between 104°C - 177°C.
Caramelisation usually occurs at 160°C.
Resulting in an attractive amber brown colour and sweet taste.

Culinary Application
Caramel used in chocolate caramel slices

22
Q

Sugar - crystallisation

A

This occurs if more sugar is added than can be absorbed by a liquid.
Crystal particles are deposited from the solution

Culinary Application
Used in the confectionary, fudge and sweet industry

23
Q

Sugar - hydrolysis

A

Sugars (disaccharides) react with water and enzymes and break down into monosaccharides.

Culinary Application
Hydrolysis occurs during digestion

24
Q

Sugar - inversion

A

Sugars are capable of being inverted (changed back to monosaccharides).
Invert sugars are monosaccharides that result from the hydrolysis of disaccharides — for example, sucrose is hydrolysed, it is inverted to glucose and fructose.
Invert sugars are very sweet and do not crystallise.

Culinary Application
Used in jam making to produced a smoother texture

25
Q

Properties of STARCH Carbohydrates

A

Solubility
Flavour
Gelatinisation
Hygroscopic
Dextrinisation
Hydrolysis

HHDFGS

26
Q

Starch - solubility

A

Starch is a white powder that is insoluble in cold water

Culinary Application
Must be blended well before being used as a thickening agent

27
Q

Starch - flavour

A

Starch is not sweet in flavour

Culinary Application
Flour is used as a base ingredient in both savoury and sweet dishes

28
Q

Starch - gelatinisation

A

When starch grains are headed in liquid, they swell and burst and absorb the liquid, forming a thickens solution.
Upon cooling, this becomes a gel
(55°C - 70°C)

Culinary Application

Using flour or corn flour to thicken soups and sauces

Moist heat - roux sauce/ lemon curd
Dry heat - popcorn/pastry

29
Q

Starch - hygroscopic

A

Starch absorbs moisture - for example, biscuits soften and loose crunch if not stored in a sealed container

Culinary Application
Helps to retain moisture in cakes

30
Q

Starch - dextrinisation

A

When carbohydrate foods are heated short chains of polysaccharides called dextrins change to long chained polysaccharides called pydrodextrins, causing the surface of the food to brown, resulting in an attractive brown appearance

Culinary Application
Toasting bread

31
Q

Starch - hydrolysis

A

Starch may undergo hydrolysis

Culinary Application
Hydrolysis of starch occurs during digestion

32
Q

Pectin

A

Pectin is a non starch polysaccharides that occurs naturally between plant cells and in the cell walls of some fruit and vegetables.

33
Q

Pectin - property

A

Gel formation
Pectin is a gelling or setting agent found in varying quantities in ripe fruit.
(Only present in ripe fruits).
When heated it combines with sugar to form a gel.
Heat and acid, such as lemon juice, help to extract pectin from the fruit

Culinary Application
Used to set jam, jellies and marmalades

34
Q

Pectin extraction

A

Use a fruit rich in pectin, such as apples
Heat must be applied to extract the pectin
Acid, such as lemon juice, assists in pectin extraction from the fruit

35
Q

Dietary fibre/ Cellulose

A

Dietary fibre is found in the cell walls of plants.
It is indigestible but can absorb large amounts of water, which adds bulk to the diet without adding kilocalories.
It stimulates peristalsis, helping food to move quickly through the digestive system and thereby reducing the incidence of bowel disorders.
The recommended dietary allowance (RDA) is 25-35g

36
Q

To increase fibre intake

A

Choose whole grain bread, pasta breakfast cereals and rice
Reduce the intake of sugar and refined foods such as white bread
Increase the intake of fruit and vegetables (skin where possible)
Add nuts, seeds and bran to breakfast cereals and homemade breads

37
Q

Sugar consumption

A

High sugar consumption is associated with an increased risk of obesity and type 2 diabetes, as many sweet foods are high in kilocalories , leading to weight gain

Refined carbohydrates cause an increase in insulin production, which raises low-density lipoprotein (LDL) levels, which in turn increases the risk of heart disease.

Sugar has also been identified as a major cause of tooth decay

Consuming too much sugar may lead to a diet lacking in more nutritious foods such as vegetables, causing deficiencies of some nutrients, such as minerals and vitamins

38
Q

To reduce the intake of high sugar foods

A

Replace sugar-rich snack foods with fruit,
vegetables and nuts.

Be aware of other terms used on food labels that indicate sugar content, such as sucrose, glucose and maltose.

Drink water instead of soft drinks and be
aware of the sugar content of fruit juices.

Choose wholegrain, less refined breakfast cereals instead of more processed varieties which have sugar added (eg:) porridge over Frosties

Use artificial sweeteners instead of sugar

39
Q

Culinary applications of Carbohydrates
Sugar

A

Sweetens desserts, cakes and beverages

Adds colour, (e.g:) when brown sugar is
used

Acts as a preservative
in jams

Stabilises egg white foam

Main ingredient in icings and syrups

Necessary in yeast fermentation

40
Q

Culinary applications of Carbohydrates
Starch

A

Thickens soups and sauces
Main ingredient in bread and cakes
Absorbs water - used in baking powder to prevent chemicals reacting before use
Browning of foods caused by dextrins eg: toast

41
Q

Culinary applications of Carbohydrates

A

Adds texture Eg: whole grain breakfast cereals and bread

42
Q

Culinary applications of Carbohydrates
Pectin

A

Setting agent in jams and jellies

43
Q

The effects of heat on carbohydrates
Moist heat

A

Sugar dissolves easily in warm liquids (Eg:) it is used to sweeten custard sauces or in syrups
Moist heat causes starch grains to swell and burst and absorb liquids (Eg:) four is used to thicken gravy
Heating fruit in a small amount of water assists the extraction of pectin (Eg:) jam-making
Moist heat causes cellulose to soften (Eg:) cooked vegetables

44
Q

The effects of heat on carbohydrates
Dry heat

A

Dry heat results in carbohydrate food browning because if the presence of dextrins (Eg:) toast
Dry heat causes sugar to caramelise (Eg:) toffee-making
Dry heat results in the Maillard reaction due to a reaction between carbohydrates and amino acids
(Eg:) roast potatoes

45
Q

Biological functions of carbohydrates

A

Carbohydrates are used to produce head and energy in the body

Sufficient carbohydrate in the diet allows protein to be used for its primary function: growth and repair

Excess carbohydrate is converted into glycogen and stored in the liver and muscles as an energy reserve or converted into fat and stored as adipose tissue, which acts as an insulator

Cellulose helps food to move through the digestive system, preventing constipation and other bowel disorders

46
Q

Digestion of Carbohydrates

A

Mouth: food is chewed. Amylase changes some starch to maltose
Stomach: no carbohydrate digestion
Small intestine: amylase into dudodeum, changes starch to maltose
Intestinal juice contains three enzymes:
Maltase
Lactase
Sucrase

47
Q

Mouth/Salivary glands

A

Secretion: Saliva
Enzyme: Salivary amylase
Substrate: Starch
Product: Maltose

48
Q

Pancreas

A

Secretion: Pancreatic juice
Enzyme: Amylase
Substrate: Starch
Product: Maltose

49
Q

Small intestine

A

Secretion: Intestinal juice
Enzyme: maltase, lactase, sucrase
Substrate: maltose, lactose, sucrose
Product: glucose, glucose and galactose, glucose and fructose

50
Q

Absorption and utilisation of carbohydrates

A

Monosaccharides are absorbed through the villi of the small intestine into the bloodstream. The portal vein carries them to the liver.

In the liver:
Fructose and galactose are changed to glucose
The glucose goes into the bloodstream, where it is oxidised to produce heat and energy
Some glucose is converted into glycogen and is retained in the liver as an energy store
The excess glucose is converted to fat and stored as adipose tissue

51
Q

Equation for photosynthesis

A

6CO2 + 6H2O + sunlight —> C6H12O6 +
6O2

Carbon dioxide + water + energy —> glucose + oxygen

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