chapter 13 - reactions in food during preparation and cooking Flashcards
what are the reactions in carbohydrate
gelatinisation
dextrinisation
caramelisation
what are the reactions in protein
maillard browning denaturation foaming coagulation gluten development
what are the reactions in fats
shortening
emulsion
what are the reactions in fruit
enzymatic browning
explain gelatinisation
when starch granules (amylose and amylopectin) are heated in the presence of water
it absorbs the water and swells
upon further heating, thick consistency is obtained
resulting in soft texture fr e.g. rice becomes fluffy after steaming
explain dextrinisation
when starch is exposed to dry heat at high temperatures
long-chain starch molecules break down into dextrins
result in a toasty and nutty flavour
explain caramelisation
where simple sugar turns brown when heated to a high temp
during this process, the sugar turns from thick, light brown syrup to a soft dark brown mass
it contributes to a caramel flavour (sweet, bitter and nutty)
explain maillard browning
is the reaction between sugars (glucose and fructose) and proteins at a high temp. forms = maillard browning
result in desirable brown colour and aromatic smell
explain denaturation
when proteins are subjected to
heat agitation or extreme pH changes
causes protein strands to uncoil (changes the physical appearance and texture of food) and lose their original structure
explain foaming
when air is trapped in liquid or solid
when an egg is beaten, protein strands denature + wrap and the air bubbles = volume increases
explain coagulation
is the solidifying or curdling of protein rich food
occurs when heat or acid is applied onto protein-rich food
protein strands uncoil, further heating results in a network being formed
this changes protein from liquid to semi-solid or solid-state
explain gluten development
when wheat flour - wheat proteins (gliadin and glutenin) and water are subsequently kneaded,
it rearranges the gluten to form a network of dough upon further mixing
explain shortening
when water is added to wheat flour,
it reduces contact between water and flour
= fewer gluten networks are formed
explain emulsion
by combining 2 liquids that mix
an emulsifier needed to stabilise fr e.g. water and oil mixture
explain enzymatic browning
when the flesh of the fruit is exposed to oxygen in the air
the brown discolouration is formed
vitamins are also destroyed through oxidation
explain how to prevent enzymatic browning
cut fruit and vegetable just before use or consumption
keep fruit in a chiller, in cling wrap
what is the function of raising agents
are used to increase the volume of cakes
name the chemical raising agent
baking powder or soda
name the physical raising agent
air and steam (from water)
why do we need to sift flour
to remove lumps from flour incorporate air
what are the common methods of cake making
rubbing in
creaming
whisking
what is the method of pastry making
shortcrust making
what are the methods of batter making
thin batter
thick batter
what are the methods of sauce making
roux sauce
blended sauce
what are the 6 common ingredients used in baking and food preparation
flour liquid (water/ mil etc) fat egg raising agent sugar
what is the function of flour in pastry making
form structure via gluten formation
what is the function of flour in batter making
form structure via gelatinisation
what is the function of flour in cake making
browning due to dextrinisation
what is the function of liquid in pastry making
physical raising agent (steam)
what is the function of liquid in batter making
binding agent for dry ingrediants
what is the function of liquid in cake making
solvent for dissolving soluble ingredients
what are the function of fat
contributes colour and flavour
provides tender texture
traps air during creaming
what are the functions of egg
emulsifier
binding agent - cake, biscuits & batter
foaming - sponge cake
what are the functions of sugar
it browns due to caramelisation and maillard browning maintains moistness provides sweetness provide tender texture trapping air during creaming and foaming
why do we sift four
to remove lumps from the flour
to incorporate air
in the rubbing in method, why do we cut cold fat into small pieces
to make rubbing in process faster and easier
In the rubbing in method, why do we rub fat into the mixture
to prevent fat from melting as the fingertip is the coolest part of the finger
in creaming method, why do mix the mixture using an electric whisk
to trap air bubbles in the mixture
in creaming and whisking method, why do we gently fold the sifted flour into the mixture with a spatula
to prevent knocking out the air bubbles
to allow even distribution of the ingredients
what will happen to the cake if you set the temperatures too high
the cake will crack
what is the cause of a sunken cake
adding too much baking powder or liquid
what is the cause of a cake with uneven air cells
incorporating too much air into the cake mixture
what are the cause of a dense and close texture cake
adding too much flour to the cake mixture
setting the oven temp too low
incorporating insufficient air into the cake mixture
what happens if you add too much liquid to the biscuit mixture
it will become a wet and sticky dough
undesirable spreading of biscuits
what happens if you bake the biscuits for too long
result in a hard and dry biscuits
what happens if you add too much flour to the biscuit mixture
result in a hard and dry biscuits
what happens if the butter melt in the biscuits dough before baking
undesirable spreading of biscuits
in shortcrust pastry, why do we wrap the dough in cling wrap and let it rest in the refrigerator
to prevent loss of moisture
why do you lightly floured the surface before rolling out the dough
to prevent the dough from sticking to the surface
in shortcrust pastry, why do we prick the base of the dough in the baking tin using a fork
to allow steam to escape so as to prevent uneven surface
what happens if you forgot to prick the dough before baking in shortcrust pastry
results in an unevenly risen pastry
what happens if you do not allow the dough to rest sufficiently in shortcrust pastry
result in
an unevenly risen pastry
a shrunken pastry
a tough and hard pastry
what happens if you over handle the dough in shortcrust pastry
result in
a shrunken pastry
a tough and hard pastry
what happens if you use too much flour when rolling out the dough
result in a tough and hard pastry
what happens if you add too much liquid into the mixture
result in a tough and hard pastry
in thin batter making, wy do we whisk the mixture while pouring in the remaining liquid
to allow the incorporation of air
to create a smooth and to prevent lump formation
what causes a runny coating batter
adding to much liquid into the batter
why does the fried battered food have a soggy texture
did not drain the oil from the food after cooking
not ensuring the oil is hot enough during frying
what causes a raw food within the cooked batter
not frying long enough
using oil at a high temp during frying
what causes a lumpy batter
not whisking the batter long enough
adding hot liquid into the flour
why do we add sauce to a dish
impart flavour to the dish
add colours to the dish
contributes to the variety of textures in some dishes
complement the richness of meat dishes
