Science Of Cooking Food Flashcards
What are 4 dry heat cooking methods
Toasting, grilling, roasting, baking
What are 9 moist heat methods
Poaching, boiling, simmering, braising, stewing, pressure cooking, steaming, blanching, sous vide
4 types of frying
Stir frying
Shallow frying
Deep frying
Dry frying
What is conduction
Transfer of heat by direct contact from a hot surface
Which out of convection and conduction involves direct contact with the hot surface
Conduction
Conduction is the transfer of heat…
By direct contact with a hot surface
In conduction what must the surface be that’s cooking the food and why
A good conductor of heat
Examples of surfaces used in conduction to cook food
Any good conductor of heat
E.g metal saucepans and frying pans (but with plastic handles to avoid burning your hand)
Examples of cooking methods that involve conduction
Grilling, bbq, dry frying and more
(Any where the food is in direct contact with the hot surface (pan))
What is convection
Transfer of heat by mass movement of heated particles into a cooler mass/ area (through a gas/ liquid)
2 types of convection and what’s the difference
Mechanical (fan assisted oven)
Natural (water as warm liquid/ gases rise and cooler ones sink so there’s a constant circulation of heat)
True or false, convection can be used for both moist heat and dry heat methods
True
It includes fan oven and warm water in a pan
Reasons why food is cooked
Kills bacteria (safe to eat)
Palatable (improves flavour)
Digestible (easier to digest)
Makes it more attractive and appealing
+ adds variety, keeps food warm when it’s cold, enables certain ingredients to work together, reduces ‘bulk’ of food
Why does cooking food make it safe to it
May food sources like meat contain harmful bacteria that can make us ill
When the food is cooked at a high enough temperature the bacteria are killed
Some foods like kidney beans contain harmful toxins that are destroyed when cooked
How can cooking food develop flavour
Chemical reactions e.g caramelisation makes food sweeter
Roasting meat/ veg creates more intense flavours and the food becomes browner and crispier
Allows flavours of different foods to combine e.g braising meat in a pot of liquid or veg
How can cooking food improve shelf life
At high temperatures bacteria and mould are destroyed which helps preserve the food during the manufacturing process
E.g milk is pasteurised (heated to high temperature then cooled) to stay fresh for longer
How can cooking food improve texture
Makes food easier to chew, swallow and digest
Some foods become softer when cooked e.g broccoli/ carrot become more flexible and rice/ pasta swell as their starch molecules soften
Meats become more tender (soft, more succulent and easier to chew)
Some foods like protein become more firm from coagulation
3 types of heat transfer
Conduction
Convection
Radiation
What is radiation
Transfer of heat through waves of radiation
In radiation is there direct contact between the heat and the food
No
Examples of ways food is cooked through radiation
Grills, toasters, microwaves
What heat transfer does boiling use
Convection (heat transferred through liquid)
What happens to proteins when they are cooked
They denature and then coagulate
What comes first when proteins are cooked, denaturation or coagulation
Denaturation
3 ways protein can be denatured
Acids e.g lemon juice and marinades
Change in temperature e.g heat
Physical agitation e.g whisking, beating and kneading
What happens to the chemical bonds holding the structure of protein together when it’s denatured
They break down so the protein unravels and changes shape (this is irreversible)
What happens to protein once it has been denatured
It coagulates
Protein molecules collide with other protein molecules and join together
What happens to water during the coagulation process (where denatured protein molecules collide with each other and join together)
Water becomes trapped between the protein molecules
However if the food is overcooked the protein tightens forcing water out of the molecules making it dry and chewy
What happens to the protein if it is overcooked and there is too much coagulation and why
The protein tightens forcing water out of the molecules making it dry and chewy
Molecules of gluten are… which means they are able to stretch and bend and gives dough its elasticity
Coiled
True or false, gluten is a protein found in wheat flours
True
Why can gluten molecules stretch and bend which gives the dough elasticity
The molecules are coiled
True or false, gluten molecules are coiled
True
It allows them to stretch and bend and gives the dough it’s elasticity
What must be done to a dough to ‘work the gluten’ for the dough to become longer, stronger and stretchier
Kneaded
3 things kneading does to the dough
Makes it stronger, stretchier and longer
What happens to gluten when it reaches a high temperature and why
It coagulates because it is a protein
Foams are formed when air is…
Trapped
True or false, gelatinisation helps to thicken foods containing starch
True
Examples of foods that are thickened by the process of gelatinisation
Sauces, custards, gravies (must contain starch)
What happens to starch granules when they absorb water
They swell in size and soften
E.g when cooking pasta
What happens to the bonds between starch molecules when they are heated with water
Start to break down
(Allows water to enter molecules and be absorbed so the starch granules swell in size and soften)
Between what temperatures do starch granules burst open and release their starch into the liquid
62 and 80 degrees
(Release of starch causes liquid to thicken)
When starch granules are heated in a liquid, what makes the liquid thicken
When between 62 and 80 degrees the starch granules burst open and release their starch into the liquid
When does dextrinisation occur
When starch is exposed to dry heat e.g toasting
What happens to starch molecules when they are exposed to dry heat (dextrinisation)
The starch molecules in the food break down into smaller molecules (dextrins)
True or false, for dextrinisation the longer the food is cooked then the more starch there is that’s converted into dextrins
True
This is why the longer you toast bread for the darker and crispier it becomes
2 ways dextrinisation affects the sensory properties of food
Becomes darker and crispier (e.g toast)
What is the process called when sugar molecules are broken down when they reach a high temperature causing it to turn brown and change flavour
Caramelisation
What traps air more easily oil or fats
Fats
When fat and sugar are beaten together why does the mixture become lighter (in colour) and fluffier
Air becomes trapped in the mixture
2 changes to the mixture once butter and sugar have been creamed together and air has been incorporated
Lighter in colour
Fluffier
What texture does aeration give cakes when cooked
Spongy and light
What is meant by shortening
The effect of adding fat to a floury mixture giving it a crumbly texture
What texture does shortening give foods (when a fat is rubbed into a floury mixture)
Crumbly
When a fat is rubbed into a floury mixture (shortening) the flour particles become covered in fat giving them a…
Waterproof coating
Why do flour particles have a waterproof coating when rubbed with a fat
The flour particles become coated with a fat
Rubbing fat into a flour/ floury mixture is called…
Shortening
Why does shortening make the dough not stretchy
Flour particles become covered in fat so have a waterproof coating
When water is added to the flour long gluten molecules can’t be formed
1 example of a food that use the ‘shortening’ method
Shortbread
Radiation is the transfer of heat through…
Waves of radiation
When starch granules burst open, what do they release into the liquid that thickens it
Starch
What is caramelisation
The browning of sugar and change in flavour when heated
How does yeast help bread rise (it acts as a raising agent)
When the bread is proved it ferments to release carbon dioxide. The carbon dioxide is trapped inside the bread. When cooked the yeast is killed, fermentation is stopped and any alcohol produced is evaporated
Mould gives cheese what 3 things
Sharp, tangy taste
Creamy texture
Bacteria are used in what 3 foods
Cheese
Yoghurt
Fermented meat
Moulds are added to what food (remember mould is different to bacteria as bacteria is added to both cheese, yoghurt and fermented meats)
Cheese
How can you make yoghurt from bacteria and milk
Pasteurise milk
Add bacteria
Bacteria ferments lactose producing lactic acid
Lactic acid acts on protein to thicken it and give a sour/ tangy taste
How is salami made
Raw meat mixed with flavourings
Bacteria added to mixture, fermenting the sugar to produce lactic acid which lowers the PH and denatures the protein in meat which coagulate and force water out
Low PH prevents bacteria from growing
Plain flour + baking powder makes what
Self raising flour
Bicarbonate of soda + what makes baking powder
Cream of tartar
Why does Choux pastry have a high liquid content
To produce enough steam during baking to make the mixture rise properly
Examples of raising agents
Yeast (produces CO2)
Baking powder
Bicarbonate of soda
Steam
Mechanical techniques that add air e.g whisking, creaming, beating
Why are fat and sugar beaten together during creaming
To aerate the mixture
Plasticity of fat meaning
The ability to be spread and manipulated
Role of egg yolks during emulsion
Contain lecithin (natural emulsifier)
Holds oily and watery parts of sauce together to prevent them from separating
Why could rolls have a rubbery texture
Cooked for too long so protein coagulates too much forcing water out of mixture
Basting meaning
Pour fat juices over meat during cooking to keep it moist
Blanching helps preserve what 3 aspects of a food
Colour, texture, nutrients
Between 62 and … degrees, starch granules burst open and release their starch into the liquid
80 degrees
