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Food Tech > Section 2- Food science > Flashcards

Section 2- Food science Flashcards

1
Q

Why is food cooked?

A
  • to make it safe to eat
  • to improve shelf life
  • to develop flavours
  • to improve texture (makes it easier to chew and swallow)
  • to give variety in the diet
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2
Q

What is conduction?

A
  • transfer of heat energy through vibrations of particles
  • in a solid the particles are held tightly together - when one particle vibrates it bumps into other particles and passes vibrations on
  • when a pan is placed on a hob, heat energy from the hob causes particles in the plan to vibrate more and more and gain heat energy
  • when these particles collide with nearby particles, they pass some of their extra heat energy onto them
  • this process continues throughout the pan, until heat is passed all the way through
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3
Q

What is convection?

A
  • transfer of heat energy through gases or liquids
  • heat up a liquid- the liquid near the heat source warms up faster
  • the warmer liquid rises, colder liquid takes its place
  • colder liquid is heated and when it starts to rise, colder liquid takes its place
  • this process continues and you end up with a circulation of fluid (convection current)
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4
Q

What is radiation?

A
  • transfer of heat energy through waves of radiation
  • unlike conduction and convection- no direct contact between the heat source and the food
  • cookers like grills and toasters use radiation to cook food
  • emit waves of radiation - when these waves reach the food, they are absorbed and heat the food up
  • microwaves use radiation to heat up the fat, sugar and water molecules in out food
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5
Q

What is boiling?

A
  • involves cooking food by heating it in a pan of boiling liquid, usually water
  • harsh method of cooking - cant be used on delicate foods
  • healthy way to cook as no fat is added (if veg is boiled for too long, colour, flavour and water soluble vitamins are lost)
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6
Q

What are some examples of food that uses boiling?

A
  • meat
  • potatoes
  • rice
  • pasta
  • veg
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7
Q

What is steaming?

A
  • cooking food with steam from boiling water or stock
  • no fat is added because their is no direct contact with water
  • gentle method
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8
Q

What are some examples of food that you can steam?

A
  • fish
  • rice
  • vegetables
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9
Q

What is blanching?

A
  • involves part cooking food is boiling water for a short time before putting it in cold/iced water
  • cold water stops cooking process (helps preserve colour, texture and vitamins)
  • removes harsh flavours in foods
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10
Q

What are some examples of food that needs blanching?

A
  • onions
  • prepare fruit and veg for freezing
  • tomatoes and almonds makes skins shrivel up, making the skins much easier to remove
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11
Q

What is simmering?

A
  • like boiling but more gentle as the temperature is slightly lower than boiling point
  • mainly for soups and curries
  • preserves more nutrients than boiling
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12
Q

What is poaching?

A
  • involves cooking food in a pan of liquid below boiling point (around 80 degrees)
  • gentle and keeps food tender
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13
Q

What type of food involves poaching?

A
  • eggs
  • fruit
  • fish
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14
Q

What is braising?

A
  • slowly cooking food in an ovenproof pot than has the lid on and contains liquid, and often herbs and vegetables
  • mixture of steaming and simmering
  • great for big or tough joints of meats, gentle cooking of meat helps tenderise it
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15
Q

What is stir- frying?

A
  • done in a wok coated in a small amount of oil, making it quite healthy
  • noodles, vegetables, tofu and small pieces of meat and fish
  • cooks very quickly and moved around the wok all the time
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16
Q

What is shallow frying?

A
  • uses a frying pan coated in a medium amount of fat or oil
  • meat (bacon and sausages), fish, eggs, pancakes
  • more fat is used so less healthy
  • gives a crispier texture
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17
Q

What is sweating?

A
  • releases moisture from food making it more tender and sweet tasting
  • vegetables like onions, small amount of oil on low heat
  • hot air rises (top of of oven is hotter than bottom)
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18
Q

What is baking?

A
  • uses dry heat, usually in an oven
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19
Q

What type of foods can be baked?

A
  • bread
  • pastries
  • potatoes
  • meats
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20
Q

Why are modern electric ovens more useful?

A
  • fan assisted
  • food bakes more evenly because all parts of the oven are at a similar temperature
  • oven heats up quicker and your food cooks quicker so they use less energy
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21
Q

What is grilling?

A
  • uses dry heat at a higher temperature than baking or roasting to cook food
  • as food is grilled fat drips out of the food and the outside of the food becomes golden and crisp
  • smaller bits of meat like steak and sausages, vegetables and cheeses like halloumi
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22
Q

What are the advantages of grilling?

A
  • foods quickly at a high temperature
  • fairly healthy as no fat is added and fat from the food drips off when cooked
  • grilling on a bbq gives food a smoky flavour
23
Q

What are the disadvantages of grilling?

A
  • high heat makes it hard to cook food evenly
  • easier to burn the food
  • handling raw and cooked meats on a bbq may lead to cross contamination
24
Q

What is roasting?

A
  • roasting uses dry heat from an oven
  • done at a higher temperature than baking
  • fat is added to the outside of the food
25
Q

What are examples of foods that have need roasting?

A
  • large cuts of meat
  • potatoes
  • vegetables
26
Q

What are the advantages if roasting?

A
  • extra fat and high temperature helps to brown and crisp the outside of the food
  • fat from roasted meat can be used to cook other food (potatoes)
  • can produce meat with an undercooked centre which people like
27
Q

What are the disadvantages of roasting?

A
  • isnt always healthy as extra fat is often added
  • takes a long time to roast food, uses a lot of energy
28
Q

What is dry frying?

A
  • cooking food in a pan without fat or oil
  • dry fry foods that contain natural fat (minced meat or bacon)
  • nuts, seeds, spices
  • uses a medium heat
29
Q

What are the advantages of dry frying?

A
  • no extra fats or oils added making it more healthy
  • gives a distinct aroma to nuts, seeds and spices
30
Q

What are the disadvantages of dry frying?

A
  • takes longer than other frying methods to cook meat thoroughly because lower temps needed at the start
  • only be used for a small range of foods
31
Q

What is aeration?

A
  • when fats such as butter and beaten with sugar (creaming) air becomes trapped in the mixture
  • air makes the mixture fluffier and lighter in colour
  • aeration gives cakes and spongey and light texture when cooked
32
Q

What are the different ways foods can be aerated?

A
  • whisking egg whites with a whisk
  • quickly beating ingredients with a spoon
33
Q

What is shortening?

A
  • rub fat into flour, cover flour particles with fat (gives flour particles a waterproof coating)
  • coating prevents long gluten molecules forming when water is added to the flour
  • dough cannot become stretchy and naked goods like shortbreads keep a short firm and crumbly texture
  • also used when making filled pies and tarts
34
Q

What is plasticity?

A
  • fats have plasticity as were able to spread and manipulate them
  • possible because fats contain a mixture of triglycerides (melt over different temperatures, so fats gradually soften over a range of temperatures rather than just melting at just one)
  • more plasticity=more easier to spread
35
Q

When is plasticity most useful?

A
  • decorating cakes with buttercream
  • rubbing fat into flour to make shortened dough
  • spreadable butter on sandwiches and toast
  • putting cream cheese on crackers
36
Q

What are emulsions?

A
  • formed when oily watery liquids are shaken together
  • milk, margarine and mayo are all examples of emulsions
37
Q

What are the two ends in an emulsifier?

A
  • hydrophilic (attracted to water)
  • hydrophobic (repulsed by water)
38
Q

What happens when you add an emulsifier?

A
  • water molecules bond to the hydrophilic side and the oil molecules bond to the hydrophobic side
  • this holds the oil and water together in a stable emulsion preventing them from separating
39
Q

What is an example of an emulsion?

A
  • mayonnaise is a stable emulsion of egg yolk, oil and vinegar
  • when making stable emulsions you need to ensure you add the oil or eater gradually and that you mix the ingredients for long enough
  • hollandaise sauce (made from butter, water, egg yolks)
40
Q

What are the steps to make a hollandaise sauce?

A
  • melt the butter in a pan
  • mix the egg yolks and lemon juice in a bowl
  • gently warm this mixture by placing the bowl over a pan of simmering water
  • slowly add the melted butter to the mixture, constantly whisking
  • keep whisking the sauce until its all mixed up together smoothly
41
Q

What is an example of a chemical raising agent used to produce carbon dioxide?

A
  • when its heated bicarbonate of soda breaks down to produce carbon dioxide bubbles that expand to make the mixture rise
  • unpleasant alkaline taste, used with a strong flavour (gingerbread)
  • baking power is a mixture of bicarbonate of soda and cream or tarter (neutralisation reaction takes place when baking powder is heated which gets rid of the soapy taste)
  • self raising flour = mixture of plain flour and baking powder
42
Q

What is an example of a biological raising agent to produce carbon dioxide?

A
  • yeast is used a biological raising agent used in bread dough
  • microorganism that causes fermentation (process of releasing alcohol and carbon dioxide)
  • doughs containing yeast and proved (when carbon dioxide is released and trapped in the dough, causing it to rise- fermentation stops during baking as yeast is killed by the heat)
  • dough is baked carbon dioxide expands causing the bread to rise even more
43
Q

How is steam used as a raising agent?

A
    • hot oven to cook a mixture that contains a lot of liquid - water leaves the mixture as steam - as steam rises it raises the mixture up
  • as the water leaves the food bakes and become more solid
44
Q

What is a mechanical raising agent?

A
  • add air to mixtures with elbow grease

air can be folded into mixtures and doughs by:
- to fold a cake mixture, you carefully use a spoon or spatula to repeatedly pour the liquid mixture over itself (trapping air each time)
- pastry doughs can be folded into layers trapping air in between the layers each time you fold

  • beating - spoon or fork to mix ingredients
  • whisking
45
Q

What happens to proteins as food is cooked?

A
  • denature
  • chemical bonds holding their structure together break down
46
Q

How can proteins be denatured?

A
  • physical agitation (whisking, beating)
  • changes in temperature
  • acids (lemon juice and marinades)
47
Q

What happens after proteins have been denatued?

A
  • protein molecules collide with other protein molecules and coagulate
  • water becomes trapped between the protein molecules
  • coagulation also changes the appearance and texture of the food
48
Q

How are foams formed when air is trapped?

A
  • foams (e.g chocolate mousse, whipped cream) form when gas becomes trapped (aeration) inside liquid
  • when liquids containing proteins are agitated the proteins inside the liquid denature - causing them to stretch and air becomes trapped in the liquid
  • when proteins coagulate air becomes trapped creating a foam
  • over whisking causes these new protein bonds to break as air escapes and the foam collapses
49
Q

How does gluten allow doughs to stretch and rise?

A
  • gluten is a protein found in wheat flour
  • formed when water is mixed with the flour to make a dough and can be found in foods like bread, pasta, cakes and pastries
  • molecules of gluten are coiled (stretch and bend giving doughs elasticity)
  • doughs need to be kneaded to work the gluten , causing the strands to get longer, stronger and stretchier
  • when it reaches a high temp, gluten coagulates and the dough stays stretched
50
Q

How does starch gelatinisation thicken liquids?

A
  • gelatinisation helps to thicken foods that contain starch (sauces, custards and gravies)
  • starch granules are mixed with the liquid- become suspended in it (if you don’t stir the liquid the granules sink to the bottom)
  • granules are heated with water, bonds between starch molecules start to break allowing water molecules to enter - water is absorbed and starch granules swell in size and soften
  • between 62 degrees and 80 degrees starch granules burst open and release their starch into the liquid
51
Q

How does dextrinization occur when starch is exposed to dry heat?

A
  • starchy foods like bread or biscuits are cooked with dry heat
  • starch molecules in the food break down smaller molecules called dextrin’s
  • breakdown is called dextrinization and it gives food a browner colour and crispier texture
  • longer the food is cooked the more starch is converted into dextrin
52
Q

How does sugar caramelise when its heated?

A
  • sugar molecules break down when they reach a high temperature - causing sugar to turn brown and change flavour (caramelisation)
  • can burn very quickly
53
Q

How can you avoid caramelised sugar burning?

A
  • water is added during the early stage of heating
54
Q

What are the three steps sugar goes through as it caramelises?

A
  • liquid is runny and has a sweet taste
  • time passes it become more like a smooth caramel
  • it turns harder and as it cools it becomes more like a candy

Food Tech (5 decks)

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