Topics
Making flour mixtures
• Flour and flour mixture
• Methods of raising flour mixture
• Mechanical – air
• Physical – steam
• Chemical – carbon dioxide
• Functions of different ingredients
Flour
Flour and flour mixture
What is flour?
• Flour is the fine powder derived from the
endosperm portion of cereal seeds or
other starchy foods
• The most common source of flour is
wheat, but any cereal grain can provide
flour, e.g. oat, rye, barley, rice, corn, etc.
• Non-cereal sources such as soybeans,
potatoes, sweet potatoes, taro, arrowroot,
etc. can also be made into flour
Endosperm
Germ
Bran
Flour mixture
Flour mixture
What is flour mixture?
• The simplest flour mixture is one made from flour and water
• Other ingredients that may be added include:
• The ingredients of a flour mixture may be divided into categories as:
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Sugar
Salt
Milk
Fat
Eggs
Leavening agents
Flavouring
Additives (in the case of commercial manufacturers)
• Dry: flour, sugar, salt, and leavening agents
• Liquid: water, milk, fat, and eggs
• The types and proportions of these ingredients determine the
structure, volume, taste, texture, appearance, and nutritive value of
the finished baked product
Products made from flour and flour mixture
• There is a huge variety of baked goods that are made from flour,
examples include:
• Yeast breads (e.g. loaf breads, rolls, pita bread, bagels, English muffin, pizzas
crust, pretzels, raised doughnuts, etc.)
• Quick breads (e.g. pancakes, crepes, waffles, popovers, muffins, unleavened
breads, scones, etc.)
• Cakes
• Cookies
• Pastries
Methods of raising flour
mixture
Raising flour mixture
Raising agent
• Raising agents, also known as leavening agents, cause baked goods to
rise
• Providing lightness and volume to baked goods
• Leavened baked goods are more porous and tender
• During baking, heat causes matter to change from one physical form
to another
• There are three main leavening gases in baked goods:
• Air
• Steam
• Carbon dioxide
• Solid to liquid (butter melts)
• Liquid to gas (water to vapour)
• Molecules move faster and spread farther apart
• This expansion is the basis for leavening
Raising agent - air
Raising agent - air
• A physical leavener added into batters or doughs
• Air is gas in the atmosphere that is composed of a mixture of gases,
primarily nitrogen
• Air is incorporated by mechanical means such as:
• Sponge cake and angel cake
contain eggs that are whipped,
and this adds volume of air to
the batter.
•
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•
Creaming
Whipping
Sifting
Folding
Kneading
Stirring
Air is incorporated into batter of sponge cake by whipping.
Raising agent - air
Raising agent - air
• When heated, air expands a little, not as much as water does, because it is
already a gas
• Air is added to batters and doughs as small air bubbles, and will be
distributed uniformly during mixing
• During baking , no new air bubbles will be formed, but steam and carbon
dioxide that is generated will move into the air bubbles, enlarging them
• Therefore, under-mixed batter with less air bubbles results in coarse
texture and low volume, the size of each bubble is larger
• Over-mixed batters and doughs will contain many air bubbles. Surface of
air bubbles becomes overstretched, thin, and weak. During baking, the thin
surface stretches further and collapses, and finally causing poor volume
Muffins made with same
ingredients but at different level
of mixing.
Raising agent - steam
Raising agent - steam
• A physical leavener present in batters or doughs
• Steam is water vapour, gaseous form of water
• Forms when water, milk, eggs, syrups, or any other moisturecontaining ingredient is heated
• e.g. choux pastry is leavened almost exclusively by steam
Hollow space inside choux pastry
Under-mixed batter (left)
produces muffins that are
coarse in texture. The surface is
pebbly.
In the control (middle), air
bubbles are distributed evenly.
Over-mixed batter (right) causes
some loss of carbon dioxide and
a strong gluten formation. During
baking, gas follows gluten strands
and forms tunnels and a peak.
Theory behind choux paste
• Choux paste contains a large amount of liquid
from water or milk, and eggs
• It is baked in a very hot oven, which allows
the liquid to evaporate to steam quickly
during the first 10 minutes of baking
• Egg protein and gelatinised starch granules
play very important roles
• As steam expands in oven, egg proteins uncoil
and stretch, paste puffs up, pressure breaks
the egg protein structure, creating a cavity in
the baked choux paste
• The outside shell of choux pastry is dried by
the high heat, gelatinised starch and
coagulated egg proteins hardened and set,
defining the shell’s final volume and shape
Raising agent - carbon dioxide
Raising agent - carbon dioxide
• Although it is present in air, in trace amounts only
• There are two sources:
Yeast fermentation
• Biological or organic production of carbon dioxide results primarily
from yeast fermentation
• Yeast fermentation, which is a biological leavener
• Chemical leavening agents
• Baking powder
• Baking soda
• Bacterial fermentation also exist in product like sourdough. Lactic acid
bacteria (LAB) such as lactobacillus spp. are naturally present in flour and the
surrounding, as water is added into flour, a stable culture of LAB is formed.
LAB produces lactic acid which contributes flavour
• Yeast produces gas for leavening, while bacteria produce mostly acids and
other flavour molecules
• When carbon dioxide is warmed by the heat of the oven, it moves
into existing air bubbles, causing them to expand.
• Breads and cookies are examples of baked products that rely on
carbon dioxide to raise
• Yeast is usually applied in baked goods with the presence of wheat
(gluten), so that porous and rigid structure can be formed
Raising agent - carbon dioxide
Raising agent - carbon dioxide
What is yeast?
• Yeast cells are very small single-celled microorganisms
• It can break down sugars for energy, this process is called
fermentation
• When energy is released, yeast can survive, grow, and reproduce
• Human beings have been using yeast in making breads for thousands
of years, but it was until mid-1800s when scientist, Louis Pasteur
proved that living yeast was necessary for fermentation
How does yeast produce carbon dioxide?
• Yeast can break down sugars into smaller simpler molecules
• Yeast lacks amylase and cannot break down starch into sugar
• Sometimes, amylase is added as an additive in bread, especially in
lean dough where the ingredients are just flour, water, salt, and yeast
• In the breakdown of sugars to carbon dioxide, many steps are
involved, the process is called glycolysis
Raising agent - carbon dioxide
Raising agent - carbon dioxide
Glycolysis
Adding water to yeast
sugar
yeast
Adding water to yeast and
sugar
CO2 + alcohol + energy + flavour molecules
5 minutes later
• Alcohol evaporates to a gas and expands during baking
• Therefore, alcohol also becomes an important leavening gas in yeastraised baked goods
5 minutes later
Click on the above video
to see what happens
when water is added.
Click on the above video
to see what happens
when water is added.
1 hour later
Raising agent - carbon dioxide
Raising agent - carbon dioxide
Types and sources of yeast
• Yeast dough is traditionally made by continual fermentation of “old
dough” – a piece of dough saved from one day’s production
• Pure yeast culture can also be obtained, the strain for bread baking is
Saccharomyces cerevisiae, usually ferment faster and more consistent
• The three forms of yeast available to bakers are:
Factors affecting yeast fermentation
• Temperature of dough
• Compressed yeast – moist, and packed in blocks
• Active dry yeast – dry granules
• Instant yeast – can be used instantaneously without hydrating
1 hour later
• Yeast is dormant at 0-1oC and begins to be quite active starting at about 10oC.
• At about 50oC, fermentation slows, because yeast cells begin to die. Optimum
fermentation is at 25-28oC
• Amount of salt
• Salt retards yeast and bacterial fermentation, therefore higher amount of salt,
slower fermentation rate
• Amount of sugar
• Sugar favours fermentation, but excess amount of sugar slows down
fermentation
Raising agent - carbon dioxide
Raising agent - carbon dioxide
Bread with three different salt
levels:
low salt (0%, 0g) (left),
medium salt (1%, 5g) (middle),
and high salt (2%, 10g) (right).
1% salt is the control.
Excessive salt will lower the
volume of baked product.
Dough of loaf bread with three
different sugar levels:
low sugar (0%) (left),
medium sugar (5%) (middle),
and high sugar (> 15%) (right).
5% sugar is the control.
Sugar will affect the volume of
bread dough.
Raising agent - carbon dioxide
Raising agent - carbon dioxide
Factors affecting yeast fermentation (cont’d)
• Type of sugar
Factors affecting yeast fermentation (cont’d)
• Presence of spices
• Sucrose, glucose, and fructose favour fermentation
• Yeast with maltose ferments slowly
• Yeast with lactose does not ferment at all
• The pH of dough
• The optimum pH for yeast fermentation is 4 to 6, rate of fermentation slows
down beyond this range
• Presence of antimicrobial agents
• Calcium propionate as a preservative to prevent mould growth, will slow
down or stop the growth of yeast at the same time
• Most spices, including cinnamon, have strong antimicrobial activity and can
slow down yeast fermentation
• Chlorine content in water
• Chlorine is an antimicrobial agent. High levels of chlorine in water can inhibit
yeast fermentation
• Addition of yeast foods
• Ammonium salts and calcium salts provide nitrogen and calcium respectively,
which aid yeast fermentation
Raising agent - carbon dioxide
Raising agent - carbon dioxide
Factors affecting yeast fermentation (cont’d)
• Amount of yeast
Chemical leavening agents
• Chemical leaveners break down in the presence of moisture or heat,
and give off gases
• Chemical leavener:
• The more yeast, the faster the fermentation. However, a large amount of
yeast can add an undesirable yeasty flavour, and yeast can also use up all the
sugar
• Type of yeast
• Different types of yeast ferment at different rates
• Baking soda
• Baking powder (baking soda combined with one or more acids)
• Baking ammonia, used in European and Chinese cuisine
Raising agent - carbon dioxide
Raising agent - carbon dioxide
Baking soda
• Also known as sodium bicarbonate or bicarbonate of soda
• Gives off gas in the presence of moisture and heat
• However, a great amount of baking soda is needed to produce
sufficient carbon dioxide for leavening
• High amount of baking soda produce yellow or green discolouration
and a strong salty, chemical bite from sodium carbonate residue
• When baking soda is used for leavening, it is used with acid
Acid-base reaction
baking soda + acid
moisture
CO2 + water + salt residue
• Acids react with baking soda in the presence of moisture, carbon
dioxide is released as leavening gas
• When a lot of baking soda is added to baked goods, both the
unreacted baking soda and the remaining salt residue contribute to
off-flavours , and in some circumstances, more browning due to more
Maillard reactions
Raising agent - carbon dioxide
Raising agent - carbon dioxide
From below clockwise: almond cookies, soda bread,
and muffin.
Acid-base reaction (cont’d)
• Acidic ingredients commonly used with baking soda:
Products made with baking powder (A) , baking soda
(B), yeast (C), and no raising agent (D) (from left to
right).
A
B
C
D
Baking soda in B causes more browning reaction.
A
B
C
D
Yogurt as an acidic ingredient is added to soda bread
to react with baking soda.
A
B
C
D
D did not rise because no raising agent is added.
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Buttermilk
Yoghurt
Sour cream
Fruits and fruit juices
Vinegar
Most syrups, including molasses and honey
Brown sugar
Unsweetened chocolate and natural cocoa
Raising agent - carbon dioxide
Raising agent - carbon dioxide
Disadvantages of using different acids in baked goods
• The acid content of ingredients can vary, hence the quality of baked
goods will be inconsistent
Baking Powders
• All baking powders contain:
• Buttermilk, sour cream, and yoghurt increase in acidity as they age
• These ingredients tend to react with
baking soda almost immediately,
especially in thin batters
• The batter has poor bench tolerance
and must be baked immediately upon
mixing
Bench tolerance is a measure of how well
batters and doughs withstand (tolerate)
being held before baking, without risking
a large loss in leavening gases.
Bench tolerance is affected by the thickness
of the batter or dough, and the leavening
agent used.
• Baking soda
• One or more acids (in the form of acid salts)
• Starch or filler, to absorb moisture
• Acid salts release acid once they dissolve in water
• E.g. cream of tartar, also called potassium acid tartrate, is an acid salt
• When cream of tartar dissolves in batter or dough, tartaric acid is released
• Tartaric acid reacts with baking soda to release carbon dioxide
Raising agent - carbon dioxide
Raising agent - carbon dioxide
• Adding water to baking
powder
• Reaction between
baking soda and acid
occurs when moisture
is present.
Types of baking powder
• Single-acting baking powder
• Adding water to baking
soda
• Baking soda do not
release carbon dioxide
in water without
heating.
When water is added
• Contains one acid that dissolves quickly in room temperature water
• Poor bench tolerance
When water is added
• Double-acting baking powder
• Contains two (or more) acids
• One dissolves and react with baking soda at room temperature
• Another acid requires heat to dissolve and react, allowing time for mixing
ingredients
Click on the above video
to see what happens
when water is added.
5 minutes later
Click on the above video
to see what happens
when water is added.
5 minutes later
• Nowadays, double-acting baking powder is being used
Raising agent - carbon dioxide
Raising agent - carbon dioxide
Types of baking powder (cont’d)
• Another way to classify baking powder is based on the amount of
carbon dioxide released at room temperature and with heat
Types of baking powder (cont’d)
• Fast-acting baking powder – more carbon dioxide is released in the first few
minutes of mixing and less of it in the oven
• Slow-acting baking powder – less carbon dioxide is released in the first few
minutes of mixing and more of it in the oven
• Different acids differ in reaction rates and flavours
Acid salt
Rate of reaction
Cream of tartar
Fast-acting
MCP (monocalcium phosphate)
Fast-acting
SAS (sodium aluminium sulfate)
Slow-acting
SALP (sodium aluminium phosphate)
Slow-acting
SAPP (sodium acid pyrophospate)
Slow-acting
Raising agent - carbon dioxide
Raising agent - carbon dioxide
Baking ammonia
• Also known as ammonium bicarbonate
• When it is exposed to heat (~38oC) in the presence of moisture, it
quickly decomposes into ammonia, carbon dioxide, and water, so it is
considered relatively fast-acting
• When properly used, baking ammonia leaves no chemical residue
• Baking ammonia is not very reactive at room temperature, therefore
batters and doughs containing baking ammonia have good bench
tolerance
Baking ammonia (cont’d)
• Baking ammonia has certain unique features that make it particularly
suited for use in small, dry baked goods and unsuitable for use in
large or moist products
•
•
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•
•
Reacts rapidly in the presence of water and heat
Increases uniformity and spread in cookies (cookies expand in size)
Increases browning
Produces a crisp, porous crumb
Adds an ammonia-like off-flavour to baked goods
Raising agent - carbon dioxide
Baking ammonia (cont’d)
• To be used in products that contain low moisture, as the ammonia gas
can fully bake out, otherwise, baked goods will have an ammonia offflavour
• Examples of products that use baking ammonia as leavener:
• Chinese fried dough
• Chinese walnut cookies
Chinese walnut cookies made
with baking ammonia
Functions of different
ingredients
Sugar
• Different types of sugars have different density, hence weight
• When making substitution, sweetness and amount of sugar must be
considered
• Sucrose is a kind of sugar that is commonly used in bakery
• Types of sucrose include:
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Raw sugar
White sugar (granulated sugar, and castor sugar)
Powdered sugar (confectioners’ sugar or icing sugar)
Brown sugar
Sugar
Sweetener
Nonnutritive
Sweetener
Natural Sweetener
Sugars
Syrups
Sugar alcohols
Other Sweeteners
Saccharin
Sucrose
Corn syrup
Sorbitol
Aspartame
Glucose
Honey
Mannitol
Acesulfame-K
Fructose
Molasses
Xylitol
Sucralose
Lactose
Maple syrup
Neotame
Maltose
Invert sugar
Cyclamates
E.g. Stevia
(steveoside)
Sugar
Sugar
Functions of sugar
Sugar does not only contribute to sweetness, it also influences the
volume, moistness, tenderness, colour, appearance, and caloric content
of baked products
• Increases the volume of cakes and cookies
Functions of sugar (cont’d)
• Increases the volume of the baked product and contributes to a finer
and more even texture
• Incorporation of air into the fat during creaming (especially with granulated
sugars)
• Contributes to the volume by providing food for the yeast
• More food for yeast, more fermentation, hence more carbon dioxide
produced
• Sugar raises the temperature at which gelatinization and coagulation occur,
starch granules have more time to swell before they gelatinize, and thus
giving the gluten more time to stretch
• Increases moistness and tenderness and also helps delay staling
• Sugar has water-retaining nature, this will improve the shelf life of baked
product
• Contributes to the tenderness
• Crust of baked product becomes softer as sugar attracts moisture
Sugar
Sugar
Sponge cake
with varied
levels of
sugar: 0g,
16g, 32g,
48g, and
64g (from
left to right).
Functions of sugar (cont’d)
• Helps to brown the outer crust of baked product
• Caramelisation and Maillard reaction take place with the presence of sugar
32g sugar is
the standard
amount for
making
sponge cake
in this
recipe.
Sugar
Too much sugar
• Baked product may fall
• A lower volume
• Coarse texture
• Gummy texture
• Excessively browned crust
• Too sweet
Salt
Too little sugar
• Dryness
• Reduced browning
• Lower volume
• Less tenderness
• Salt is a compound commonly used in food preservation. It provides
flavour to foods
• Types of salt include:
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•
•
•
Fortified table salt (iodine is usually added in salt fortification)
Unrefined sea salt
Light salt (potassium chloride) for reducing sodium levels
Gourmet salt (e.g. truffle salt)
Salt
Salt
Functions of salt
Small amount of salt is added to flour mixtures for flavouring, for
producing a firmer dough, for improving the volume, texture, and
evenness of bread crumb structure, and to prolong shelf life
• Adds flavour to baked product
Functions of salt (cont’d)
• In the production of yeast bread, salt helps control yeast growth
• Without salt, fermentation would be too rapid and result in a sticky dough
• Too much salt would inhibit yeast activity, reducing the amount of carbon
dioxide gas produced and decreasing the volume of the loaf
• Baked product made without salt tend to be bland
• Plays an important role in forming the dough
• Salt adjusts the solubility and swelling capacity of the gluten, making the
dough more pliable, and aiding gluten formation
Salt
Salt influences dough firmness.
Bread dough with varied levels of
salt: 0g, 5g, and 10g, (from left to
right).
5g salt is the standard amount for
making bread loaf in this recipe.
Salt
Too much salt
• A firm dough
• Low volume
• Dense texture
• Too salty taste
Too little salt
• A flowing, sticky dough
• Low volume
• Uneven texture
• Lack of colour
• Bland taste
Liquid
Liquid
• Liquid is required in flour mixtures to hydrate flour and to gelatinise
starch
• Liquid used in flour mixtures:
Functions of water
• Allows gluten to be formed
• Acts as a solvent for the dry ingredients
• Activates the yeast
• Provides steam for leavening
• Allows baking powder or soda to react and produce carbon dioxide
• Water
• Milk
Liquid
Liquid
Milk
• Although it is not necessary to include milk in a flour mixture, it is
usually recommended over water, because it improves the overall
quality of the baked product
• Important constituents of milk:
Milk (cont’d)
• Type of milk used depends on the desired end product
• Types of milk used in baked goods include:
•
•
•
•
•
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Protein
Milk fat
B vitamins
Calcium
Lecithin (a natural emulsifier)
Lactose
•
•
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•
•
Fluid milk
Butter-milk
Nonfat dried milk
Canned milk
Yogurt
Sour cream
Liquid
Liquid
Functions of milk
• Contributes water
• Adds flavour and nutrients (protein, B vitamins, and calcium)
• Contains compounds that help produce a velvety texture, a creamy
white crumb, and a browner crust
• Results in higher volume
Too much liquid
• A very moist baked item
• Low in volume
Too little liquid
• Dry baked product
• Low in volume
• Stales quickly
• Doughs are easier to shape, less sticky and heavier
• Doughs can retain gas better
• These are the result of the presence of milk fat and lecithin
• Results in a browner crust
• Lactose in milk participates in the Maillard reaction
Fat
Fat
• Fat in flour mixture interferes with the development of gluten,
creating a more tender crumb
• The higher the fat content, the shorter the gluten strands, and the
softer and more pliable the dough will be
• Types of fat used in baking include:
Functions of fat
Fat acts as a tenderiser and adds volume, structure, flakiness, flavour,
colour, and a resistance to staling; it also plays a role in heat transfer
• Improves volume
•
•
•
•
•
Shortenings
Butter
Margarine
Oil
Lard
• Fat surrounding air bubbles prevents rupturing of bubbles as bubbles expand
in baking
• Creaming of fat and sugar traps air which acts as a leavening agent during
heating
Fat
Fat
Functions of fat (cont’d)
• Affects strength, crumb and flakiness of dough
Fat influences the volume and texture of loaf bread
• With less fat, baked products may collapse during handling
• Low fat baked products have a fine, velvety crumb, whereas high in fat is
coarse
• Flakiness of pie crust and pastry is due to fat incorporated into dough
Bread loaf made with
3% fat
Bread loaf made with
20% fat
Expanded during
baking, softer and
greasier in texture
• Improves flavour and colour
• Flavour and colour are affected by the amount and type of fat used
• Delays staling
• Fat acts as emulsifier, prevents recrystallisation of starch, hence delays staling
Fat
Cross-section of low fat baked product with a fine,
velvety crumb (angel food cake) – 0% fat
Fat
Cross-section of high fat product with coarse crumb
(pound cake) – 25% fat
Layer of Fat
Steam
H2O
Steam
Layer of Dough
H2O
• Layers of dough are separated by the layers of
fat
• When heating in the oven, water in the dough
evaporates as steam and the layers of fat melt
• Melted fat can prevent the escape of steam
while the steam pressure can push apart the
dough layer from each other and create the
flakiness in pastries
Fat
Too much fat
• Batter becomes too fluid
• Weakens structure
• Decreases volume of finished
product
Eggs
Too little fat
• Batter is resistant to expansion
during leavening
• Results in a tougher crumb
• Eggs are added to flour mixtures to create different results
• Important constituents of eggs:
• Egg white – can be whipped into foam and trap air
• Supply protein and B vitamins
• Egg yolk – acts as emulsifiers, add flavour, nutrients, and colour
• Supply fat-soluble vitamins (A, D, E, and K), cholesterol, and fat
Whipping egg white
Eggs
Eggs
Functions of eggs
Eggs are added to enhance structural integrity, contribution to
leavening, colour, flavour, and nutritive value
• Enhance structural integrity
Functions of eggs (cont’d)
• Egg yolks add flavour, nutrients, and colour
• Coagulation of egg proteins during baking increases firmness
• Contributes to leavening
• Air is incorporated when beating eggs
• During baking, trapped air expands
• Liquid egg turns to steam when heated, product expands in volume
• Yellower crumb and browner crust can be formed
• Delays staling
• Emulsifier and fat in egg prevent recrystallisation of starch, hence delay
staling
• Improves appearance of baked product
• A shiny glaze is resulted with egg-wash
Eggs
Eggs
Buns that are egg-washed with egg white, whole egg, and egg yolk (from left to right); effects are pale, shinny,
and dark respectively.
Too much eggs
• Dense texture
• Tough, rubbery texture of baked
product
Eggs
Egg influences structure of pound cake.
Pound cake with varied levels of egg: 50g, 100g,
and 150g, (from left to right).
100g egg is the standard amount for making
pound cake in this recipe.
Too little eggs
• Insufficient volume
• Poor structural strength, colour,
flavour, and nutritive value
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