Section 2 - Food Science Flashcards
Reasons why food is cooked
To make it safe
Improve shelf life
Develop flavours
Improve texture
Bring variety to a diet
How does cooking make food safe
some foods have harmful bacteria or toxins that are killed when cooked
How does cooking improve shelf life
Bacteria get destroyed and dont lead to decay
How does cooking develop flavours
Chemical reactions and falvour mixing occurs
How does cooking improve texture
It makes it easier to eat and digest. Become softer or harder to desire.
How does cooking bring variety to a diet
By making different dishes from the same thing.
Conduction
the transfer of heat through the vibration of particles
How does conduction work in food
A particle vibrates and bumps into the others. In a pan, the particles vibrate and get hot. Then it transfers the heat to the food.
Convection
the transfer of heat through gases or liquids.
How does convection work in food
the warmed up liquid or gas rises, and the colder particles get pushed down. They the nget heated up and this causes circulation. This is called a convection current. It causes the whole fluid or air to be heated.
radiation
The transfer of heat energy through waves of radiation.
How does radiation work in food
There is no direct contact. For example, in a microwave, microwaves are released, which are absorbed by the water particles in the food and cause them to vibrate. This heats up the food.
Water-based cooking methods
Boiling
Steaming
Blanching
Braising
Simmering
Poaching
How does boiling work
Food is added to a pan of boiling water and cooked.
What foods can be boiled
Meat
Potatoes
Rice
Pasta
Veg
How does boiling affect food
Softens food.
Healthy because no fat is added
Not that tasty or attractive
How does steaming work
Cooking food with steam from boiling water.
What food can be steamed
Fish
Rice
Veg
How does steaming affect a food
Keep food taste texture and colour
Very healthy
Not much flavour
Good for delicate foods
How does blanching work
Part cooking food in boiling water before putting it in cold water.
Foods that can be blanched
Raw onions
Tomatoes
Almonds
Fruit
Veg
Blanching effect on food
Preserves colour, texture and vitamins
Removes harsh flavours
Makes skin easier to remove
How does simmering work
Cooking food in water slightly below boiling point
Foods that are simmered
Soups
Curries
Simmering effect on food
More gentle so preserves more nutrients than boiling
How does poaching work
Cooking food in a pan of liquid below boiling point, around 80*C.
Foods that are poached
Eggs, fruit, fish
Poaching effect on food
keeps food tender
Nutrients and flavoured are lost
Can be a sauce used rather than water to improve flavour
How does braising work
Slowly cooking food in an ovenproof pot with the lid. It contains liquid and ofte nherbs and veg.
Food that are braised
Big joints of meat
Braising effects on food
Tenderises meat
Helps meat absorb flavours from herbs and veg
fat-based cooking methods
Stir-frying
Shallow-frying
How does stir-frying work
In a wok, a small amount of oil is added and the food is fried whilst being stirred quickly
Foods that get stir-fried
Noodles, veg, tofu, pieces of meat and fish
Sir-frying effect on food
Doesnt burn
Healthy
Veg keep more nutrients
How does shallow frying work
Uses a frying pan with a medium amount of fat or oil.
Food that gets shallow fried
Meat, fish, eggs, pancakes
Shallow frying effects on food
Crispy texture
Less healthy due to fats
Dry methods of cooking
Baking
Grilling
Roasting
Dry frying
How does baking work
Cooks food using dry heat, often in an oven
Foods that are baked
Bread
Pastries
Cakes
Pies
Potatoes
Fish
Baking advantages
Wide variety of food
Caramelisation
Quite healthy
Baking disadvantages
can take a long time
Food can become dry
uses lots of energy
How does grilling work
Uses dry heat at a higher temperature and lets fat drip out to make the foods golden and crisp.
Food that is grilled
Smaller joints of meat
Veg
Cheese
Grilling advantages
Food cooks quickly
Fairly healthy
Caramelisation
Smoky flavour from BBQ
Grilling disadvantages
Hard to cook evenly
Easily burnt
Cross-contamination on BBQ
How does roasting work
Roasting uses dry heat from an ovenwith fat added to the food
Food that is roasted
Large cuts of meat
Potatoes
Veg
Chestnuts
Roasting advantages
Extra fat helps with caramelisation
Ftas can be used for other food
Moist
Rare meats
Roasting disadvantages
Isnt too healthy
Takes a long time
How does dry-frying work
Cooking food in pan without fat
Food that is dry fried
Minced meats
Bacon
Nuts
Seeds
spices
Dry-frying advantages
Healthier
Pleasant aroma
Dry-frying disadvantages
Takes longer than other frying methods
Only be used for small range of food
Protein denaturing
The chemical bonds in the proteins break down. the proteins unravel and their shape changes.
Ways protein is denatured
Physical agitation
Changes in temperature
Acids(such as marinades)
Protein coagulation
When denatured proteins collide together and join together.
Effects of coagulation
Water gets trapped between molecules.
Appearance changes
Overcooking leads to water being forced out and food becoming dry and chewy
Foam formation in food
When gas gets trapped inside liquid
Ways foam forms
When proteins are agitated and denature.
Protein coagulation
Gluten formation
A protein found in wheat flours that is formed when water is mixed with the flour to make dough
Effects of gluten on a food
Gives it elasticity
Coagulates when heated and the dough stays stretched.
Foods containing gluten
Bread
pasta
Cakes
Pastries
What is starch gelatinisation
When starch molecules absorb water and burst, releasing the starch into the liquid
Effects of gelatinisation
The liquid thickens, and cools into a solid gel which can be used in deserts.
What temperature does gelatinisation occur
Between 62 and 80 degrees
What is dextrinisation
When starchy foods are cooked with dry heat, the starch molecules break down into dextrins
Effects of dextrinisation
The food turns browner and get crispier, as well as having a different taste.
What is caramelisation
Sugar molecules break down at a high temperature and turn brown/orange as well as changing flavour.
Effects of caramelisation
Sugar turns into a sweet liquid, then into a smooth caramel. When it cools it becomes more like a candy.
Issues with caramelisation and how they are solved
Easily burnt which leads to it being black and tasting bitter. Water is added early to prevent this.
What is aeration
When fats are beaten with sugar, air bcomes trapped in the mixture tirning it fluffier and lighter in colour.
Effects of aeration
Baked goods become spongy with a light texture.
What is shortening
When a fat is rubbed into flour, and the flour particles get coated in the fat and become waterproof.
Effects of shortening
Long gluten molecules cant bond from lots of flour molecules when wwater is added. Baked good such as shortbread therefore become firm and crumbly rather than stretchy
What is plasticity of fats
Fats are able to be spread and manipulated due to having a mixture of triglycerides that melt at different temperatures. The more plasticity, the easier it is to spread.
What is the plasticity of unsaturated and saturated fats
Unsaturated fats are soft or liquid at room temperature so they have high plasticity. Saturated fats are ofte nsolid at room temp so have low plasticity.
What is high plasticity useful for
Decorating cakes with buttercream
Rubbing fat into flour for shortening
Spreading butter
Creame cheese
What is emulsification
When oily and watery liquids are shaken together and the droplets spread through eachother to make an emulsion
Why dont emulsions stay mixed and how can they be made to
Water and oil dont mix so they separate unless shaken again or an emulsifier is used
What is an emulsifier
A substance used to hold oil and water together in a stable emulsion.
How do emulsifiers work
It has a hydrophilic head and a hydrophobic tail. The head attracts water, and the tail repels water.
When added to an emulsion, the water molecules bond to the hydrophilic head and oil molecules bond to the hydrophobic tail, keeping them together.
Raising agents which produce co2
Chemical and biological
Chemical rasing agents eg
Baking powder, bicarbonate of soda, self-raising flours
How does bicarbonate of soda work
When heated with an acid it breaks down to produce co2 bubbles that expand. It has an unpleasant taste so needs to be masked
How does baking powder work
A mixture of bicarb of soda and cream ogf tartar(acid). This makes it rise and doesnt have a bad taste due the neutralisation reaction
Self-raising flours are
a mixture of baking powder and plain flour
Biological raising agent eg
yeast
How does yeast work
A microorganism that causes fermentation which releases alcohol and CO2. Needs warmth. When baking, CO2 expands, yeast dies, alcohol evaporated.
Mechanical ways of adding air to a mixture eg
Whisking, beating, creaming, sieving
Mechanical adds air by
Folding to trap air between layers.
Beating to drive air into it
When creaming, air gets trapped between flour particles.
How does team act as a raising agent
When a hot oven is used for a liquidy mixture, water evaporates as steam.
The mixture then hardens and rises
Enzymic browning is where
Oxygen in the air cause fruit and veg to turn brown
Oxidation is where
Fruit or veg lose water soluble vitamins B,C when exposed to the air
