Tea Biscuits, Muffins, & Cakes

Question 1

What is the cross section of the wheat grain?

Answer 1

1. Endosperm
   - Starch granules
   - 70-75% protein
   - 20% B-vitamins
2. Aleurone cells
3. Bran
   - 20% of the protein
   - > 60% of B-vitamins
   - Fibre (hemicellulose, cellulose)
4. Scutellum
5. Germ
   - 8% of the protein
   - 30% of B-vitamins
   - Saturated fats

Question 2

What is mainly found in the aleurone layer?

Answer 2

• Protein

- B-vitamins

Question 3

What is milling of wheat?

Answer 3

• Conversion of wheat grain into white flours (all purpose, cake and pastry, bread)
• Involves 2 main processes:

1. Separating the bran and germ from the endosperm
2. Reducing size of the endosperm into flour size particles

Question 4

Discuss the types of flours.

Answer 4

1. White Flours
   - Made from endosperm only
   - Bran and germ are removed from wheat kernel
   - All purpose flour: 10.5% protein
   - Cake & pastry flour: 9.7% protein
   - Bread flour: 11.8% protein
   - The slight differences in protein have major effects on the baked product
2. Whole Wheat Flour
   - Composed of the bran, germ, and endosperm ground together into flour
   - 13% protein

Question 5

What is gluten and what properties does it give to baked goods?

Answer 5

• Complex protein created from proteins in wheat, rye, and oat flours
• Gluten itself is NOT actually present in these flours
• 2 proteins gliadin (plasticity) and glutenin (elasticity) are present in these flours and they form gluten
• Complex protein denatures and coagulates during baking and gives structure to baked products
• Excess gluten development makes baked products tough and therefore must be controlled

Gives visco-elastic properties to batters and dough:

• Allows them to hold small air cells
• Allows a dough to be kneaded and rolled
• Allows batters and dough to expand

Question 6

How does gluten develop?

Answer 6

Gluten forms when gliadin and glutenin in the flour are:

• Hydrated (water added, even eggs contain water) AND
• Manipulated (mixing muffins and kneading dough)

Question 7

What is responsible for the structure of baked products?

Answer 7

1. Starch in flour
   - Gelatinization during baking (heat, water, starch)
   - Retrogradation during cooling (“let cool before taking muffins out of pan”)
2. Gliadin and glutenin proteins in flour
   - Hydration + manipulation develops gluten (a protein)
   - Gluten denatures and coagulates during baking
   - No stirring during coagulation in the oven = GEL
   - Important to have enough gluten for structure but NO excess gluten which would result in a tough product
3. Liquid ingredients hydrating flour
4. Egg proteins coagulating and forming a gel

Question 8

How is tea biscuit flakes formed?

Answer 8

1. Cut solid fat (shortening, butter, or margarine) into flour mixture until fat is in discrete (you still should see them) pieces (size of small green peas)
2. Add milk to hydrate gliadin and glutenin proteins in flour to form dough
3. Knead dough to develop gluten
4. Roll dough to flatten pieces of fat and orient gluten strands in the same direction

BAKING:

5. Pieces of fat melt, leaving spaces between gluten strands and separates gluten strands
6. Leavening gases (carbon dioxide and steam) collect in the spaces and expand them so gluten strands are pushed apart
7. Gluten denatures and coagulates to create permanent layers with spaces in between = FLAKES

Question 9

What are the factors affecting gluten development?

Answer 9

1. Type of flour
   - All purpose: combination of hard and soft wheat, 10.5% protein (gliadin and glutenin), used for all baked products
   - Whole wheat: made from the entire wheat kernel (bran, germ, and endosperm), 13.3% protein, used for all baked products
2. Manipulation (mixing, kneading, rolling)
   - Increase in manipulation = increase in gluten development
   - Tea biscuits (dough): 150 mL milk to 500 mL flour
   - Muffins (batter): 250 mL milk to 500 mL flour
   - Muffins have a greater proportion of milk, therefore over-mixing can be a problem (13 is the magic number of mixing)
   - Causes excess gluten development which leads to a tough texture
   - Causes a peak to form on top of the muffin and tunnels to form inside the muffin due to air pockets not being able to go to gluten concentrated areas
3. Amount of liquid
   - Excess liquid = increase in gluten development
   In tea biscuits, adding extra liquid = sticky dough which cannot be kneaded or rolled out = more manipulation = more gluten development = tough texture
4. Tenderizers
   - Ingredients which control or limit gluten development so excess gluten is not produced
5. Sugar:
   - Competes with gliadin and glutenin proteins for water
   - Reduces hydration of gliadin and glutenin
   - Controls gluten development = tender product
6. Fat
   - Coats some flour particles
   - Water has more difficulty hydrating gliadin and gluten because fat and water are immiscible
   - Controls gluten development = tender product
7. Type of fat
   - Liquid (eg. vegetable oil in muffins) coats flour particles more extensively than solid fats (butter, shortening)
   - Decreases hydration of gliadin and glutenin
   - Decreases gluten development = more tender
8. Bran/cornmeal/oatmeal
   - Very dry + small particles
   - Bran can be an ingredient by itself or be a part of whole wheat flour
   - Dry particles compete with gliadin and glutenin (proteins in flour) for water (1)
   - Reduces hydration of gliadin and glutenin
   - Controls amount of gluten developed = tender
   - Small particles physically interfere with the development of long gluten strands into its elastic self with manipulation (2)
   - Shorter strands develop = more tender

Question 10

What fats can be substituted?

Answer 10

Tea biscuits

• Cannot use liquid fat instead of solid fat
• Will have adverse effects on flake formation

Muffins

• Can use solid fat instead of liquid fat
• Melt the fat into liquid = same ability to tenderize product

Question 11

Why do we need leavening gases?

Answer 11

Production or expansion of gases in a batter or dough which gives the final product an increased volume and light, porous texture

Question 12

How is air incorporated and what do they do?

Answer 12

Incorporated into batters and doughs by:

• Sifting flour and other dry ingredients (also ensures accurate measurements)
• Beating eggs with fork
• Mixing batters (for muffins and cake)
• During baking, air cells are expanded by carbon dioxide and steam = increase in volume (height)
• In tea biscuit doughs, melted fat produces air cells and CO2 expands pockets to push gluten strands apart = increase height of product; gluten coagulates during baking to give flakes = permanent GEL
• More air cells = greater volume

Question 13

How is steam incorporated?

Answer 13

• Produced from ingredients containing water
• Milk, yogurt, fruit, molasses, buttermilk, sour cream, fruit juices, egg white
• Not vegetable oil or dried fruit
• Produced during baking when water is heated

Question 14

How is carbon dioxide incorporated?

Answer 14

• Produced from baking powder and baking soda
• Many recipes have both baking powder and soda because as acid ingredient varies, CO2 produced also varies; so to increase leavening

Question 15

Discuss baking powder.

Answer 15

• Baking soda (sodium bicarbonate) + 2 dry acids
• In perfect balance (only react with each other) and give a guaranteed amount of CO2, can be used alone
• 5 to 10 mL baking powder for each 250 mL flour

Dry acid 1 (monocalcium phosphate monohydrate) + baking soda + moisture during mixing = CO2

Dry acid 2 (sodium aluminum sulfate) + remaining baking soda + heat of baking = more CO2

Question 16

Discuss baking soda.

Answer 16

• Sodium bicarbonate
• Alkaline ingredient which needs acid ingredients to react with to produce CO2 (fruit, fruit juice, molasses, buttermilk, yogurt, sour cream)
• Use if recipe contains acid ingredient already for flavour
• Acid ingredients vary in amount of acid they contain and amount of CO2 produced will vary (most recipes with baking soda also use baking powder)
• 2 mL baking soda for each 250 mL acid ingredient

Baking soda + acid = sodium salt + carbon dioxide + water
- No undesirable flavours or colours from sodium salts

Baking soda = sodium carbonate + carbon dioxide + water

• Results in undesirable flavour changes: sodium carbonate is bitter in flavour, sodium from sodium carbonate reacts with fat to produce soapy flavour
• pH of batter/dough increases to produce undesirable colour changes
• Flavonoid pigments in flour turn yellow = yellow interior
• Maillard reaction occurs faster = excess browning on outside surface if you bake for full time OR undercooked

Question 17

What are the types of fats?

Answer 17

1. Unsaturated
   - 1+ double bonds
   - From plant sources
   - Liquid at room temperature
   - Eg. Canola oil, olive oil, corn oil, safflower oil, peanut oil
2. Saturated
   - All single bonds
   - From animal source
   - Solid at room temperature
   - Eg. butter, lard (pork fat)

Question 18

What are the fats commonly used in baking?

Answer 18

• Butter: water-in-fat emulsion (80% fat, 20% water), saturated fats (animal source)
• Margarine: water-in-fat emulsion (80% fat and 20% water), hydrogenated vegetable oils
• Shortening: 100% fat, partially hydrogenated vegetable oil, mix of solid and liquid fat = easier to manipulate and incorporate air
• Vegetable oil: 100% fat, unsaturated liquid fat (canola, olive, corn, safflower, peanut)

Question 19

What is fat rancidity and the 2 types?

Answer 19

Unpleasant odours and flavours which develop in:

• Pure fats (butter, margarine, shortening, vegetable oils, etc.)
• Foods which contain fat (eg. meats, nuts, cake mixes, snack foods, cookies)

Two types:

1. Oxidative rancidity: occurs to vegetable oils
2. Hydrolytic rancidity: occurs in animal fats such as butter (cows) and lard (pigs)

Question 20

What is oxidative rancidity?

Answer 20

• Occurs in unsaturated fats which have double bonds (vegetable oils)
• Higher degree of unsaturation = more double bonds = increased susceptibility to oxidative rancidity
• Tastes waxy and stale
• Complex chain reaction involving oxygen coming into contact with double bonds
• Usually takes a while but can be catalyzed by heat, light, iron, or copper
• Results in the production of aldehydes and ketones = unpleasant odours and flavours

Question 21

How do you prevent oxidative rancidity?

Answer 21

• Opaque packaging minimizes exposure to light
• Store oils away from light
• Keep away from heat sources, including oven and refrigerator
• Use of vacuum packaging (eliminates oxygen)
• Add antioxidants: BHA, BHT, propyl galiate (stop chain reaction); citric acid, EDTA (tie up metal ions Fe/Cu)

Question 22

What is hydrolytic rancidity?

Answer 22

• Occurs in saturated fats (all single bonds) from animal sources
• More rare and noticeable than oxidative rancidity
• Fatty acids split away from the glycerol backbone
• Some fatty acids have unpleasant odours and flavours
• Eg. butter and lard contain butyric acid which smells and tastes like rotten eggs
• Catalyst: heat, lipase

Question 23

How do you prevent hydrolytic rancidity?

Answer 23

• Prevention: store fats at cool temperatures

- Butter is more susceptible to rancidity in summer when left at room temperature for extended periods of time

Question 24

What is the relative sweetness of sugars?

Answer 24

• Fructose
• Sucrose (table sugar)
• Glucose
• Galactose
• Maltose
• Lactose (least sweet)

Question 25

Discuss aspartame.

Answer 25

• Sold under brand names NutraSweet and Equal
• Dipeptide composed of 2 amino acids (aspartic acid and phenylalanine)
• 160-200x sweeter than sucrose
• Cannot be consumed by those with phenylketonuria (PKU)
• Approved by Health & Welfare Canada in 1981

Question 26

Discuss sucralose.

Answer 26

• Sold under brand name Splenda
• Synthesized from sucrose
• 3 Cl atoms substituted for 3 of the OH groups on sucrose
• 600x sweeter than sucrose
• Looks and tastes like sugar whereas aspartame is more powdery
• Behaves like sugar in baked products whereas aspartame you can’t
• Not broken down by heat
• Not broken down in the body = no calories
• Limit/ADI: 15 mg/kg body weight/day
• Approved by Health & Welfare Canada in September 1991

Question 27

Discuss stevia.

Answer 27

• Leaves of plants which are native to South and Central America and Mexico
• 30-45x sweeter than sucrose
• Extract of one component from the stevia leaves is sold under the brand names Truvia and PureVia
• Slower onset and longer duration of sweetness than sugar (not instant)
• May have bitter or licorice-like aftertaste
• No calories, no carbohydrates

Question 28

What are the functions of fats and oils in baked goods?

Answer 28

1. Tenderizer (applies to all baked products)
   - Fats coat flour particles
   - Inhibits hydration of gliadin and glutenin proteins
   - Controls gluten development
   - Liquid fats (vegetable oils) have a greater ability to coat flour particles than solid fats = increase in tenderness
2. Flake formation (tea biscuits only)
   - Requires solid fat
   - Fat pieces melt in the oven
   - Spaces left for steam and carbon dioxide to expand
   - Gluten strands are pushed apart
   - Gluten strands denature and coagulate during baking = creates permanent flakes
3. Air incorporation (cakes only)
   - Occurs during creaming of solid fat
   - Creaming = manipulating shortening, butter, or margarine with a wooden spoon or electric beat to incorporate air cells
   - Easier to cream shortening because it is a mixture of solid and liquid fat = plasticity (able to play with it more) = able to incorporate more air
   - During baking, fat melts releasing air cells
   - Steam and carbon dioxide collect and expand air cells = cake volume increases/cake rises
   - Creaming of fat is most important step in achieving high volume cake
4. Emulsification (cakes only)
   - Cake batters contain large amounts of fat and water (mainly milk and egg whites)
   - Cake batter is fat-in-water emulsion
   - Therefore emulsifier is needed to keep fat and incorporated air cells evenly distributed throughout cake batter
   - Cakes will have more eggs and more milk than muffins
   - 2 sources of emulsifiers: lecithin in egg yolks, mono and diglycerides in shortening
   - Emulsifiers have hydrophilic and hydrophobic ends
   - Emulsifiers increase number of air cells and decrease size of air cells
   - Cakes made with shortening are more uniform
   - Ensures fat and air cells stay evenly distributed throughout cake batter
   - If emulsifiers are not present: fat floats to top of butter = cake is light and airy on top, dense and heavy on bottom

Question 29

What are the functions of sugar in baked goods?

Answer 29

1. Tenderizer (muffins, tea biscuits, cakes)
   - Competes with flour proteins gliadin and glutenin for water
   - Less hydration of gliadin and glutenin
   - Controls gluten development
2. Creaming of the fat and sugar together (cakes)
   - Leavening agent
   - Air clings to sharp edges of sugar
   - Air is incorporated into fat
   - Air clings to white, granulated sugar or brown sugar NOT icing or powdered sugar
3. Decreases loss of carbon dioxide from batter (muffins and cakes)
   - Leavening agent
   - Sugar dissolves faster than baking soda and baking powder in water
   - Protects against carbon dioxide loss from batter during mixing
   - Sugar and flour will take necessary amount of water and has less water for reaction to occur
   - Carbon dioxide will be produced as it is going into the oven instead of right away
4. Allows batter/dough to reach maximum volume (muffins, tea biscuits, cakes)
   - Sugar forms hydrogen bonds with:
   - Starch granules in flour: increases gelatinization temperature therefore delaying gelatinization
   - Proteins (gluten, egg, whey): increases coagulation temperature therefore delaying coagulation
   - Therefore, more time for carbon dioxide and steam to expand air cells (in muffins and cakes) or air pockets (in tea biscuits)
   = maximum volume
5. Caramelization of sucrose (muffins, tea biscuits, cakes)
   - Colouring function
   - Nonenzymatic browning reaction
   - Occurs in dry heat conditions (top and sides of product)
   - Sucrose (white sugar) hydrolyzes into fructose and glucose which go through a series of reactions creating brown pigments

Question 30

What are the browning reactions that occur in baked goods?

Answer 30

1. Maillard browning
   - Between amino acids and reducing sugars
   - High heat, low moisture conditions (dry heat)
   - Occurs faster in alkaline conditions
2. Caramelization of sucrose (above)
3. Dextrinization of starch

Question 31

Discuss chocolate cakes.

Answer 31

• Colour is affected by pH
• Slightly alkaline (pH 7.5-8.0) = deep brown (mahogany brown)
• Acidic pH (pH < 7) = yellow brown
• Therefore, add small amount of baking soda to increase pH
• Any unpleasant flavours and colours are masked by chocolate

Question 32

What is the convention mixing method of cake?

Answer 32

Use electric beater to:

• Cream fat (butter, margarine or shortening)
• Cream fat and sugar together
• Beat in eggs, one at a time

Use wooden spoon to:

• Mix dry ingredients (flour, baking powder and/or baking soda) alternately with liquid ingredients until well blended
• Eg. butter cake, applesauce cake, chocolate cake (using chocolate squares)

Question 33

What is the quick mix method of cake? How is excess gluten prevented?

Answer 33

• All mixing is done with an electric beater in one bowl
• Mix together dry ingredients (flour, sugar, baking powder and/or baking soda) + fat + ¾ milk (2-3 minutes)
• Add eggs and remainder of milk and beat until batter is well blended (3 minutes)
• Receive more manipulation (electric beaters)
• Contain extra liquid to make beating with electric beater easier
• Therefore, excess gluten can develop
• However, quick mix cakes also contain:
• More fat and sugar (tenderizers)
• Limits hydration of gliadin and glutenin
• Controls gluten development
• Therefore, quick mix cakes are just as tender as conventionally mixed cakes

Question 34

What is meant by “texture”?

Answer 34

• Number, size, and distribution of air cells

- Characteristics of supporting matrix

Question 35

What are the ingredients contributing to texture/leavening?

Answer 35

• Soft, velvety crumb and even grain: many, small air cells evenly distributed throughout cake batter
• Air cells incorporated through creaming of fat
• Plastic fats like shortening can trap more air cells than butter or margarine (narrow plastic range)
• Hydrogenated fats contain emulsifiers mono and diglycerides which help in retaining air by decreasing size and increasing number of air cells in batter
• Emulsifiers from fat and lecithin aid is distributing ingredients evenly
• Granulated sugar added to cream fat causes air clinging to edges of sugar incorporated into batter
• Icing or fruit sugar in powder form do not incorporate air into mixture because lack sharp edges of granulatd sugar
• During baking, air cells fill with steam produced from liquid ingredients which contain water and caron dioxide produced from baking powder/soda
• Cause air cells to expand and become grain of baked cake

Question 36

What are the ingredients contributing to structure?

Answer 36

• Liquid to batter hydrates proteins (gliadin and glutenin, starch)
• Gluten is developed during mixing and coagulated during baking to give structure
• Soft wheat flour that has low protein content would produce more tender product than flour like all-purpose with more protein
• Over mixing after flour has been added will increase amount of gluten formed, producng tough product
• Starch of flour gelatinizes during baking and retrogrades during cooling of cake which provides structures
• Eggs contain protein which is coaglated by heat and form part of cake structure
• Egg white supplies additional water for hydration of proteins and starch

Question 37

What is the function of wet ingredients?

Answer 37

Liquid ingreidents with water
Dissolve salt, sugar, and baking powder
Disperse fat and flour
When baking powder is moistened, allows baking soda and dry acid to produce leavening gas caron dioxide
Baking, liquids produce steam for leavening

Question 38

What is the function of liquid ingredients containing water?

Answer 38

• Hydrate gliadin and glutenin proteins and starch in flour (structural)
• Dissolve baking powder and soda so carbon dioxide can be produced (leavening)
• Provide water to produce steam during baking (leavening)
• Lactose in milk is involved in Maillard browning reaction (colouring)

Question 39

What is the function of eggs?

Answer 39

1. Structural
   - Water in egg whites hydrates gliadin and glutenin proteins and starch in flour
   - Egg proteins denature during beating and coagulate during baking of cake
2. Leavening
   - Lecithin acts as an emulsifier
   - Water in egg whites produces steam during baking
3. Colour
   - Carotenoid pigments in egg yolk give colour to cake
   - Amino acids are involved in Maillard browning reaction

Question 40

What does baking powder and soda do?

Answer 40

• Produce CO2

Question 41

What does flour do?

Answer 41

• Gluten coagulates and contributes to structure

- Starch retrogrades and contributes to structure