Food science Flashcards
Why do we need to cook foods?
To kill bacteria to make them safe To soften the food so we can chew it To make the food digestible To improve and intensify the flavour To make it look more attractive and appealing To reduce the bulk of food To provide variety to our meals To enable certain foods to work together To keep warm
What are the three methods of heat transference used when cooking foods?
Conduction
Convection
Radiation
What is conduction?
Transfer of heat by direct contact with a hot surface
What is convection?
Transfer of heat by the movement of heated particles into a cooler mass/area
Give examples of cooking methods that use conduction
Fry frying
Griddling
Searing
Sauteing
Give examples of dry heat cooking methods that use convection
Baking
Roasting
Give examples of wet heat cooking methods that use convection
Boiling Braising Simmering Poaching Steaming Pressure cooking
What is radiation?
Transfer of heat using waves of light or heat
Give examples of cooking methods that use radiation
Toasting
Grilling
Barbecuing
How does microwave radiation cook foods?
Radiation penetrates 1cm of the food
The radiation agitates the water molecules in food
Causes friction which spread heat energy around the rest of the food
What is baking?
Food cooked in the dry, hot air of the oven
Give examples of baked foods
Cakes Pastries Bread Puddings Biscuits Fish
What are the advantages of baking foods?
Good colour and texture
Several items can be cooked at once
Outside of food goes brown and adds flavour
What are the disadvantages to baking foods?
Need specific cooking times
Need specific temperatures
What is roasting?
Cooking food using the dry, hot air of the oven but fat has been added to stop it drying out
What are the advantages to roasting foods?
Good flavour (added fat)
Crisp texture
Attractive appearance (golden brown)
More than one item can be cooked at a time
What are the disadvantages to roasting foods?
Can take a long time (joints of meat)
Have to add extra fat (unhealthy)
Meat can become tough and chewy if cooked on too high a heat
What is toasting?
Dry radiant heat applied to food. Can be directly onto foods.
Give examples of foods that can be toasted
Bread
Nuts
Seeds
Whole spices
What are the advantages to toasting foods?
Lower the glycaemic index (food takes longer to digest)
Flavours released
Flavours enhanced
What is a disadvantage to toasting foods?
Need to be careful not to burn
What is grilling?
Small pieces of food cooked by the radiant heat of a grill or barbeque
What are the advantages of grilling food?
Healthy method - fat drains out of the food during cooking
Quick
What are the disadvantages to grilling foods?
Need to be careful not to burn
Only tender cuts of meat should be grilled
What is shallow frying?
Cooking small pieces of food in a small amount of hot oil/fat
What are the advantages to shallow frying foods?
Quick method
Uses a minimal amount of fat
What are the disadvantages to shallow frying/
Should not be left unattended
Unhealthy due to added fat
Wet foods can spit and splash when fried
What is deep frying?
Foods are submerged in very hot fat/oil
What are the advantages to deep frying?
Golden colour
Crunchy surface
Very quick
What are the disadvantages to deep frying?
Can’t be left unattended
Very unhealthy
Over-heated fat/oil can combust and cause a fire
What is stir frying?
Very small pieces of food quickly cooked in a small amount of oil/fat whilst being move continuously.
What are the advantages to stir frying?
Very quick
Vegetables remain crunchy
Healthier frying method
Limited loss of water soluble vitamins
What are the disadvantages to stir frying?
Needs constant attention and stirring
Needs fat/oil with high smoke point
Food needs to be fully prepared before cooking
What cooking methods use dry heat?
Baking
Roasting
Toasting
Grilling
What cooking methods use frying?
Deep frying
Shallow frying
Stir frying
What cooking methods use moist heat?
Boiling Simmering Poaching Stewing Braising Pressure cooking Steaming Blanching Sous vide
What is boiling?
Usually starchy foods cooked in boiling water
What are the advantages to boiling foods?
Quick
Healthy as no fat is added
What are the disadvantages to boiling foods?
Water soluble vitamins easily lost
Food becomes soft
Unsuitable for meats as it toughens the protein
What is simmering?
Food submerged in water that is only gently bubbling
What are the advantages to simmering foods?
Good for tender pieces of food as it is a gentle way to cook
What are the disadvantages to simmering foods?
Tender food can fall apart if it becomes a boil
Loss of water soluble vitamins
What is poaching?
Food cooked in a small amount of simmering liquid
What are the advantages to poaching?
Tender foods cooked very gently
Healthy (no added fat)
Adds flavour if using something other than water
What are the disadvantages to poaching?
Loss of water soluble vitamins
Foods can break apart
Can taste bland if only poached in water
What is stewing?
Foods submerged in liquid, cooked slowly.
Whats the difference between a stew and a casserole?
Stew is cooked on the hob
Casserole is cooked in the oven
What are the advantages to stewing?
Tough meats are tenderised
Good flavour
Water soluble vitamins absorbed into the sauce
What are the disadvantages to stewing foods?
Takes a long time (2-3 hours) so need to plan ahead
What is braising?
Usually in the oven
Vegetables and liquid at the bottom of the cooking pan, meat is on top so is steamed
Needs a good fitting lid
What are the advantages to braising?
Tough meats are tenderised
Good flavour
Water soluble vitamins absorbed into the sauce
What are the disadvantages to braising?
Take a long time to cook (1-2 hours) so need to plan ahead
What is pressure cooking?
Cooked in a sealed pan where the temperature of boiling liquid can be increased to 105-120oC
What are the advantages to pressure cooking?
Really quick (3 x quicker than boiling)
Tough meat is made tender
Less fuel used
Water soluble vitamins not lost so easily
What are the disadvantages to pressure cooking?
Easy to over cook foods
Food can become soft
Liquids can quickly cook away so the food burns
What is steaming?
Cooking in the steam of boiling water
What are the advantages to steaming foods?
Water soluble vitamins not lost
Really healthy way of cooking
Food is easy to digest
What are the disadvantages to steaming foods?
Can take longer than boiling
Have to remember to fill the steamer up with water
Kitchen can fill with condensation
What is blanching?
Food is plunged briefly into boiling water or steamed, removed and then places into chilled water
What are the advantages to blanching foods?
Healthy
Keeps green and brightly coloured foods bright
Retains flavour, colour and texture as it stops enzyme action
What are the disadvantages to blanching foods?
Vitamins and minerals can be lost
Not suitable for all foods
What is sous vide?
Vacuum packed foods cooked at very precise temperatures
What are the advantages to cooking foods sous vide?
Little loss of moisture or weight
Flavour and aroma of foods preserved
Nutrients not lost into cooking water
Consistent results
What are the disadvantages to cooking foods sous vide?
Water bath is expensive
Foods do not brown
What are the disadvantages to microwave cooking?
Cold spots can form so foods must be stirred during cooking
Food needs to be left to stand once cooked
Can only use for foods that have a high water content
Foods do not go brown or crispy
Metal containers cannot be used
What are the advantages to microwave cooking?
Quick
Easy
What happens to proteins when they are cooked?
They denature (unravel) and coagulate (set)
Is the denaturation (unravelling) of proteins reversible?
No
Between what temperature do most proteins coagulate?
71-85oC
What term describes proteins and carbohydrates cooking and developing a brown colour and charred flavour?
Maillard reaction
What does the term plasticity mean in relation to fats?
How fats soften and liquify when heated
Can fats evaporate?
No
When cooked what does fat add to foods?
Colour and flavour
What does the term gelatinisation mean?
When starch granules and liquid are heated the granules soften and swell whilst absorbing liquid this causes the mixture to thicken e.g. roux sauce
At what temperature do starches start to gelatinise?
66oC
What does the term dextrinisation mean?
When starches and cooked by dry heat and turn brown
What does the term caramelisation mean?
When sugar is cooked and turns brown and changes flavour
What happens to water in foods during cooking?
Heats up, turns to steam and then evaporates
What is the pH value of neutral foods?
pH 7
What can acids do during cooking?
Soften connective tissue in meat Give meringues a marshmallowy texture Set proteins in milk to make cheese Preserve fruits and vegetables Denature proteins when used as a marinade
What can alkalis do during cooking?
Act as a raising agent
Destroy vitamin C
What term describes fruits and vegetables going brown when exposed to oxygen?
Enzymic browning
What gives red meat its bright red colour?
Myoglobin
What colour do red meats go during storage?
Brown/burgundy
What term describes fats that have been exposed to oxygen for too long?
Rancid
Why are meats hung after slaughtering but before butchering?
So that enzymes can soften muscle fibres and develop the flavour
Give examples of the use of microorganisms in food production
Yeasts in bread making
Lactic acid with milk to make cheese and yoghurt
Probiotics in yoghurt to aid digestion e.g. yakult
Lactic acid used to make salami, pepperoni and chorizo
Sauerkraut is fermeted cabbage
Soy sauce is fermented soya beans
Moulds to make blue cheeses
Mushrooms are edible fungus
What are five methods of adding air to foods so it can act as a mechanical raising agent?
Sieving Whisking Rubbing in Creaming Lamination
How does sieving add air to products?
Traps air as it is sieved and falls
What are unleaved products?
Products made without a raising agent
How does whisking eggs add air to products?
When eggs are whisked they trap air so create a foam
They trap air as the proteins unravel and stretch
How does creaming products together add air?
As you cream fat and sugar together tiny bubbles of air are trapped. Shown when the mixture becomes pale and fluffy
What is lamination in relation to pastry making?
Trapping air between the layers of pastry each time it is rolled and folded
Used in rough puff and flaky pastry
How does air act as a raising agent?
When heated it expands so the food swells and rises creating a light and airy texture
How does steam act as a raising agent?
During cooking water in mixtures becomes steam and forces its way upwards through the mixture creating hollow, risen foods
What gas creates a light, airy texture in cakes?
CO2
Carbon dioxide
Why is bicarbonate of soda used in products with a strong flavour?
Because it can have a strong soapy flavour
What is yeast?
Microorganism
What two forms can yeast be bought in?
Fresh
Dried
What gas does yeast produce?
CO2
Carbon dioxide
At what temperature does yeast produce gas the quickest?
Generally room temperature
Specifically 37oC
What does yeast feed on?
Natural sugars found in flour
What is the name of the process when yeast feeds on naturally occurring sugars?
Fermentation
What two proteins form gluten?
Gliadin and glutenin
What type of flour contains the most gluten?
Strong flour
What is an emulsion?
Mixture of fat and liquid (that normally don’t mix)
What emulsifier is used in mayonnaise?
Egg
What is a foam?
A food that has been aerated
What is added to foods to make a foam?
Gas
What happens to the proteins in eggs when they are whisked?
Denature
Why is flour commonly used in dishes?
Bulk (volume)
Thickening (gelatinisation)
Why is fat commonly used in dishes?
Flavour
Moisture
Colour
Traps air
Why are eggs commonly used in dishes?
Colour
Flavour
Set a liquid (coagulation)
Trap ait (aeration)
Why is sugar commonly used in dishes?
Flavour
Colour
Texture
At what temperature does water boil?
100oC
What does the term heat transfer mean?
The way heat moves from one area to another through conduction, convection or radiation
What does the term denaturation mean?
Altering a proteins molecular characteristics
What is the maillard reaction?
Chemical reaction between protein and starchy carbohydrates that turns foods brown e.g. charred steak
What does the term unleavened mean?
Breads and other baked goods made without a raising agent
What does the term plasticity mean?
The ability of fat to hold its shape (how soft it is)
