food commodities Flashcards
choux pastry, bread making, emulsions, milk, eggs, fats, cheese, yoghurt, fruit and veg
what is the ratio of choux pastry?
3:1flour to fat
why should you cool the choux paste before adding the eggs?
so they don’t denature and cook
what are some examples of choux?
chocolate eclairs, profiteroles, gougers, churros
what is the scientific process of browning in choux pastry?
the dry heat from the oven breaks down the carbohydrates into dextrins, dextrinisation occurs creating a brown surface, which is called the maillard reaction, the sugar caramelises and the pastry turns golden
how to cook choux pastry:
use a high temperature and DO NOT open the oven door, as this raises the liquid rapidly to boiling point, helps to produce steam and acts as raising agent, cold air will be introduced to the oven and the pastries will sink
what is the function of flour in choux
oo/ plain flour forms the bulk/ structure, acts as a thickening agent, gluten strands stretch to allow the gas bubbles to expand
what is the function of butter in choux
enriches the dough
what is the function of water in choux
binds the dry ingredients together to produce a dropping consistency, converts to steam during cooking and acts as a raising agent
what is the function of eggs in choux
the protein in egg dentures on heating and coagulates- which sets the mixture, adds colour, flavour and HBV protein
what is the purpose of a choux paste?
removes lumps, develops gluten strands when you beat it (which helps the pastry stretch when it rises), traps air (which acts as a raising agent)
what are the sensory qualities of choux
well risen- does not collapse, crisp texture, golden brown colour, hollow centre which is not soggy or doughy, light and airy
reasons for why the choux mixture is too thin to pipe:
too much water used, water not at boiling point or was allowed to cool when flour was added, too much egg, incorrect proportions/ ratio of ingredients, not enough flour
reasons for why the choux pastry has a dense and heavy texture when cooked:
too much flour used, not enough water, incorrect oven temperature, incorrect proportions, opened the door during cooking
what are the main ingredients used to make bread, and why are they used?
strong plain flour- high gluten content which gives a strong elastic dough
yeast- to make the bread rise
salt/sugar- to add flavour and control action of the yeast
fat- to extend shelf life
water- to activate gluten formation
define the term ‘leavened’ in bread making
a substance has been added to the dough to start fermentation and make it rise
what is yeast, and how is it used in bread making to make the dough rise?
microorganism that produces gas to make the dough rise (multiplies and turns starches and sugars into alcohol and produces carbon dioxide gas)
why is yeast mixed with warm water before adding it the flour? what would happen if it was mixed with hot or cold water?
so that it can multiply
cold water- wont multiply
hot water- kills the yeast
what is the name the proteins found in flour
gliadin and glutenin
why are gliadin and glutenin important in bread making?
because when water is added, the 2 proteins join together to form gluten. gluten gives the dough softness and elasticity (so it can expand when the gas bubbles produced by yeast form)
gluten also sets when the bread is baked (forms the structure of bread)
what are the main stages of bread making?
mixing, kneading, proving, knocking back, shaping, baking
define ‘kneading’ and why it is important in bread making
working/mixing the ingredients together
helps gluten formation which softens and strengthens the dough
define ‘proving’ and why it is important in bread making
leaving the dough to rise
this helps the yeast cells multiply and produce carbon dioxide gas
define ‘knocking back’ and why it is important in bread making
removing large gas bubbles
which ensures a more even texture and better rise
what is unleavened bread
bread made without yeast or other raising agents
extended question: describe the function of strong plain flour, yeast and water when making bread and explain how they work together to produce a quality product (8 marks)
strong plain flour
-provides gluten
-forms an elastic stretchy dough- when mixed with a liquid
-gluten stretches to hold the co2 bubbles produced by yeast
-provides structure- coagulates when cooked at high temp
-enables dextrinisation of starch- brown colour
yeast
-uses both respiration and fermentation to develop
-produces gas bubbles which is trapped by the dough and makes the bread rise
-uses available sugar for growth
water
-binds dry ingredients together
-if warm, provides suitable condition for yeast to activate
-provides moist conditions for the yeast
what is the yeast used by bakers called?
saccharymosa cereviserae
what is a colloidal structure?
more than one ingredient mixed together
fill in the blank:
colloidal structures give _______ to many products
texture
how are colloids formed
when one substance is dispersed (mixed) through another
give an example of a liquid colloid
vinegar, oil, water, milk
give an example of a gas colloid
air, carbon dioxide
give an example of a solid colloid
starch granules e.g. corn flour, arrowroot, wheat flour
what are the 5 colloidal structures
emulsions, foam, solid foam, gel, suspension
what 2 parts make up an emulsion
give an example
liquid + liquid
e.g. olive oil + vinegar
-mayonnaise
what 2 parts make up a foam
give an example
gas + liquid
e.g. air bubbles + egg white
-beaten egg white
what 2 parts make up a solid foam
give an example
gas + solid
e.g. air bubbles + baked egg white
-meringue, cakes, bread
what 2 parts make up a gel
give an example
liquid + solid
e.g. water, juice + fruit
-jams, jellies, cheesecake, pana cotta
what 2 parts make up a suspension
give an example
solid + liquid
e.g. starch grains + milk
-white sauce, blended sauce
define the term immiscible
give an example of 2 immiscible ingredients
substances that cant mix or dissolve in each other to form a homogenous mixture as they separate
e.g. water and oil
what emulsifier does egg yolk contain
lecithin
what is an emulsifier
give examples of some
‘match maker’- helps to bring 2 immiscible parts together
-lecithin in egg yolk (natural)
-lecithin in soya beans (synthetic and cheaper)
-glycerol monostearate/ GMS (made from glycerol and stearic acid, used in margarine)
what is a temporary emulsion? give an example
blending of ingredients that eventually separates
e.g. simple vinaigrette
what is a permanent emulsion? give an example
mixing of ingredients that come together and do not separate
e.g. mayonnaise
how is an emulsion made
when 2 equal parts of liquid are mixed together with a match maker (emulsifier)
define hydrophilic
water loving (e.g. water)
define hydrophobic
water hating (e.g. oil)
describe the steps you would take if mayonnaise curdles
pour out the curdled mixture into a measuring jug, put another egg yolk in the processor and gradually pour in the curdled mixture, then the remaining oil
what should you do if a cake mixture curdles?
add a tbsp of flour to the mixture
what is it meant by the plasticity of fats and explain why margarine has more plasticity than lard
plasticity= the ability of fat to soften over a range of temperatures and be shaped and spread with light pressure
margarine has more plasticity because it contains more unsaturated fats
name all the nutritional values of milk?
good source of HBV protein-3.5%
calcium
contains 55% water
3-5% fat
what does calcium need to be paired with to be absorbed?
vitamin D- complementary
how is milk treated??
via heat
what is the first step of the milk process and how does it work?
pasteurisation- heat raw milk to 75* for 25 seconds then rapidly cool to 5*- to kill any unwanted bacteria
what is the second step of the milk process and how does it work?
homogenisation- breaks up fat globules so they can be evenly distributed through the milk, creating a emulsion
what is the third step of the milk process and how does it work?
skimming- separate the cream (fat) from the milk, to produce semi and fully skimmed milk
what is the fourth step of the milk process and how does it work?
sterilising- place milk into sealed bottles and heat to 110-130* for 30 minutes
what is the last step of the milk process and how does it work?
Ultra-heat treating (UHT)- where milk is heated to 135* for 1 second, sealing it into storage packs that can be stored for up to 6 months
how should fresh milk be stored?
in a fridge (1-4C). must be sealed (lid) to prevent it from absorbing any strong smells such as garlic.
out of sunlight
when milk is heated it often forms a skin on the surface. why?
as the proteins denature
what are the main uses of milk in cooking?
sauces, batters, custards- gives nutrients and adds a creamy texture
what are the main substitutes for cows milk?
almond, oat, soy, rice and coconut milk
what are the main groups of people that won’t consume cows milk?
vegans, lacto-vegetarians, lactose intolerant
name all the classes of eggs?
battery, barn, free-range, organic
what information has to be printed on every egg?
the lion mark- food safety such as being vaccinated against salmonella, passport system (code), best before date, method of production, strict food safety controls
what are the 4 different sizes of eggs and name all their weights?
small- under 53g
medium- 53-63g
large- 64-73g
v large- 73g +
what are the nutritional values of eggs?
good source of HBV protein and omega 3
rich in vitamins A, D, E, riboflavin and B1
cheap source of protein
name all the functions of eggs in cooking?
aeration
binding
coating
glazing
emulsifying
thickening
enriching
garnish
where is aeration via eggs used?
in mousses and sponges
where is binding via eggs used?
fish cakes, burgers, falafel
where is coating via eggs used?
scotch eggs, fish cakes
where is glazing via eggs used?
bread, scones, pastry
where is emulsifying via eggs used?
mayonnaise, creaming cakes
where is thickening via eggs used?
custards, sauces (white sauce)
where is enriching via eggs used?
custards, sauces
how should eggs be stored?
left at room temperature or in a fridge for up to 3 weeks
stored point end down
not near strong smelling foods e.g garlic as the shell will absorb the smell
should always have a neutral smell
what does heat do to an egg when cooked?
it denatures the proteins, the egg albumen coagulates at 60C turning into a white solid, the yolk coagulates at 65/7-C.- used for setting quiche fillings
what does sugar do to the egg in cooking?
increase the coagulation temperature
when an egg is over heated in a mixture, what happens?
syneresis
why are eggs able to help form the texture of mousses?
as when whisked the egg can hold a large volume of air, forming a foam and creating an ‘airy’ texture
are fats commonly solid or liquid at room temperature?
solid
are oils commonly solid or liquid at room temperature?
liquid
is butter high or low in saturated fat?
high
why is butter used or added to many products?
as it adds a rich and smooth flavour
how should fats be stored?
in a fridge, tightly wrapped to avoid absorbing any strong smells
what is ghee?
its clarified butter that is used in many Indian dishes as it has a high cooking temperature
what are compound white fats?
fats blended from animal,vegetable and fish oils. they are aerated to give a smooth texture.
what are low fat spreads?
they are emulsions of blended vegetable oils and water. they contain half the amount of fat in butter and margarine- healthier.
what are hydrogenated vegetable fats?
liquid vegetable oils that have hydrogen added to change their state from a liquid to solid so it becomes saturated.
what are oils?
they are liquids extracted from seeds or fruits e.g olive oil. these are unsaturated fats and are suitable for vegetarians and vegans
what is margarine?
this is blended vegetable fats with vitamin A and D added by law.
what are soft margarines produced from?
polyunsaturated vegetable oils.
what are all the functions of fats in the body?
a macro-nutrient that is our main energy source- 1g provides 37kJ/9kcal
insulate our bodies and keep us warm
protect vital organs
contains soluble vitamins A,D,E,K
used for hormone production- needed to supply us with nutrients that our body can’t e.g omega 3
what is the RNI of fats for men and women?
women=70g
men=95g
what are the eight main uses of fats in cooking?
-aerate food- when creamed with sugar
-used as a preservative- increase shelf life of baked goods
-adds flavour
-adds a flaky texture to pastry- separate layers by creating steam
-oils form emulsions with liquids
-adds colour and shine- a golden colour on dough balls
-prevents lumps of flour within sauces- in a bechamel
-gives shortening ability to a mixture and changes the texture- in shortbread biscuits- gives the crumbly texture
what health problems could an excess amount of fat in the body cause?
obesity, type 2 diabetes, heart disease, strokes and cancers
why shouldn’t we eat lots of processed foods?
as they contain a high value of trans-fats and saturated fats
what could be caused by a deficiency of fats in the body?
as it will lead to a lack in vitamins A,D,E,K- could cause night blindness, dry and brittle nails and depression
what do saturated fats do to the body’s blood cholesterol?
it raises it
what is hydrogenation?
when hydrogen molecules are passed through an oil to change its state from a liquid to solid
what are the disadvantages of hydrogenation?
makes the fat less healthy, often causes clogged arteries and increases the risk of CHD when consumed, they reduce healthy cholesterol (HDL) and increase unhealthy cholesterol (LDL)
what are the advantages of hydrogenation?
cheap, increase shelf life of products, suitable for vegetarians
why are unsaturated fats more healthy?
they contain less hydrogen molecules and increase HDLs and reduce LDLs in the blood
what are monounsaturated fats?
fats where 2 carbon atoms are joined together to form one double bond- they reduces heart disease risk and increase blood HDL
where are monounsaturated fats found?
olives, avocados, hazelnuts, almonds
what are polyunsaturated fats?
when carbon atoms form more than one double bond in the fat- they increase blood HDL and lower blood LDL, they are a good source of omega 3 and 6 and reduce the risk of heart disease
where are polyunsaturated fats found?
oily fish, flax seeds, walnuts and sunflower oils
why do we need omega 3?
as it prevents blood from clotting and is good for the heart. also is good for the brain (memory) for infants
why do we need omega 6?
lowers blood cholesterol and reduces the risk of heart disease
what is cholesterol?
a fatty substance that is naturally in the blood
what does a raised cholesterol cause?
blocked arteries and increased chance of CHD and heart attacks.
are saturated fats solid or liquid at room temperature?
solid
are unsaturated fats solid or liquid at room temperature?
liquid
what are examples of visible fats?
fat on meat, butter and margarine and cooking oils
what are examples invisible fats?
cheese, burgers and sausages, ice cream and nuts
do saturated or unsaturated fats have more hydrogen molecules?
saturated
what is the first step of the cheese making process?
adding a starting culture to pasteurised milk to ferment the lactose into lactic acid- the lactic acid gives the flavour
what is the second step of the cheese making process?
add rennet to coagulate the milk to form curds and whey
what is the third step of the cheese making process?
drain the whey and cut the curds
what is the fourth step of the cheese making process?
the curds are put under high pressure, removing more whey, to form the cheese
what is the final step of the cheese making process?
leaving the cheese to mature for up to 24 months
give some examples of fresh cheese?
cottage cheese, ricotta, cream cheese
give some examples of soft cheese?
brie, feta, camembert
give some examples of semi-hard cheese?
edam, st paulin
give some examples of hard cheese?
cheddar, red leicester, parmesan
give an example of blue cheese?
stilton
give some examples of processed cheese?
slices, spreadable, cheese strings
how should cheese be stored?
always in a fridge and covered
what is added to blue cheese to give it the blue veins?
non-pathogenic mould spores
when cheese is heated, why does it change texture?
as the proteins denature and the bonds change. this causes it to become a liquid as the fat all melts
why is cheese added to products?
to add flavour, colour, texture and nutritional value
what are the nutrients found in cheese?
HBV protein, calcium, fat
how much of cheese is saturated fat?
1/3
what is the nutritional value in yoghurt?
HBV protein, calcium, vitamin A,D,B and fat
why do some yoghurts have higher values of fat than others?
as some yoghurts are made with semi or fully skimmed milk meaning less fat is present. and some yoghurts are made with cow’s milk alternatives.
what is the first step of the yoghurt making process?
milk is heat treated, homogenised and cooled
what is the second step of the yoghurt making process?
its incubated to 45C and the starter culture (lactobacillicus) is added
what is the third step of the yoghurt making process?
the yoghurt is fermented to allow the lactose to produce lactic acid
what is the fourth step of the yoghurt making process?
fermentation to allow the proteins to coagulate and set
what is the final step of the yoghurt making process?
sugar, sweeteners and fruit are added and then the yoghurt is cooled and packaged
what is a fruit
the part of the plant that holds the seeds, which will form new plants
what can vegetables be categorised as?
- root
- stems
- tubers
- fungi
- bulbs
- seeds and pods
- flower heads
- leaves
- sea vegetables
- vegetable fruits
give 2 examples of a vegetable
garlic (bulb)
pumpkin (vegetable fruit)
what can fruits be categorised as?
- hard
- soft
- citrus
- tropical
- dried
- stoned
- miscellaneous
give 2 examples of a fruit
orange (citrus)
apricot (stoned)
how many portions of fruit and vegetables should a balanced diet contain?
at least 5 (having more veg than fruit)
what nutrient is found in starchy, root vegetables and sweet fruits
carbohydrates
what nutrient is found in many yellow and orange vegetables and fruits
vitamin A
what nutrient is found in citrus fruits, berries, peppers, tomatoes and some green vegetables
vitamin C
what nutrient is found in all fruit and veg, but excellent sources are leeks, berries, figs and peas
dietary fibre/ NSP
true or false:
you can have fresh, canned or frozen fruit and veg
true!
when are fruit and veg best eaten
when they are in season
because they taste better and are richer in some nutrients, and they should be eaten when they are as fresh as possible
how can nutrients in fruit and veg be destroyed
through damage from cutting, heat and water from cooking, and oxygen in the air
what can cause spoilage and decay of fruit and veg
enzymes, oxygen and naturally occurring moulds and yeasts
how do yeasts and moulds cause spoilage on fruit and veg
they feed on the moisture and sugar, making them soft, mushy and discoloured- they will then look, smell and taste unpleasant
why do apples, pears, parsnips, potatoes, bananas and avocados go brown, grey or black once they are peeled, sliced or grated
due to enzymic browning
(reaction between the plant cell enzymes and oxygen)
how do you prevent enzymic browning?
- cover them with water/ water+lemon juice
- blanch
- or cook immediately
why do onions and bananas caramelise?
because they contain natural sugars that will caramelise when cooked (as the plant cells are heated, the natural sugars turn into caramel, browning the food)
how do starchy veg (like potatoes) thicken a liquid
through gelatinisation
(when the starch cells are heated, they will soften and absorb some of the surrounding liquid)
fill in the gaps:
- it is best to quickly _____ fruit and veg under a cold running tap to clean them
- do not ____ any fruit and veg
- peel ______ to preserve nutrients just under the skin
- do not prepare green leafy veg too far in advance to prevent loss of vital ________
- rinse
- soak
- thinly
- nutrients
fill in the gaps:
fruit and veg are often _________ and _________ to increase shelf life and give all-year-round availability
- processed
- preserved
how are bacteria, mould and yeast spoilage controlled
by removing the moisture or oxygen, using heat/ cold or altering the pH with sugar, salt or vinegar
what are some methods of preserving fruit and veg
- drying (fruit and herbs)
- canning and bottling (fruit and veg)
- MAP (bags of salad leaves and fruit)
- freezing (fruit and veg)
- UHT cartons (juices)
what should you look for when choosing fruit and veg
- choose the produce that are ‘fresh’ looking with good colour and are not blemished, bruised, wilted or damaged
- eat the produce ASAP and store in a cool, dark place or salad drawer in fridge
- will spoil quickly if in plastic packaging
why are fruit and veg cooked
- softens the textures making them easier to eat
- makes them more digestible
- improves the flavours
- reduces bulk
