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Cooking > Food > Flashcards

Food Flashcards

1
Q

Salt

A
  • draws out juices from foods through osmotic gradient
  • stops vegetables caramelising - need water to break down sucrose —> glucose + fructose in non enzymatic browning reaction (pyrolysis - high temp breakdown)
  • if you’re reducing sauce don’t add too much to start with (salt won’t evaporate in proportion with liquid)
  • Sodium chloride
  • natural preservative - kills bacteria through drawing out needed water through osmotic pressure on cell walls
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2
Q

Vinegar

A
  • add at the end
  • adjusting acidity levels
  • not for base of the sauce
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3
Q

Mono sodium glutamate

A
  • flavour enhancer
  • won’t make meaningful difference for strong flavours
  • naturally occurring in tomatoes and cheese
  • popular belief that it is neurotoxic but no experimental evidence
  • sodium salt of glutamic acid
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4
Q

Rice mix

A 
Onions (chopped once lengthways)
Ginger (chopped twice lengthways) 
Garlic 
MSG 
Red & green peppers 
Red & green chilli
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5
Q

Anchovies

A
  • strong flavour
  • cook in oil & garlic for 5-10 mins
  • let flavour dissipate through oil
  • chili flakes
  • garlic
  • pasta water & Parmesan
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6
Q

Tomato sauce

A 
Chopped tomatoes (Lidl) 
Passata 
Chilli pesto 
Onions & garlic 
Puy lentils 
Cook for 4 hours 
Add starch water to bulk into sauce
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7
Q

Milk general info

A
  • acidification causes milk protein to coagulate into curds
  • proteins in human milk coagulates less in acid and so is more easily digested
  • protein molecules in curds less easily broken down by digestion enzymes
  • bifidus factor, stimulates growth of lactobacillus bifidus protests infant against i festivals pathogens - salmonella, polio —> phased transition from protected environment of womb
  • lactase levels reach steady minimum between 1-3yrs old (black Americans 70% intolerant - only 10% white Americans)
  • cows only produce milk after giving birth —> milked for 10 mths, 2mth break, then calved again - requiring insemination 90 days have giving birth
  • milk provides infants all the macros and minerals it needs to grow: proteins, fats (both released by mammary gland cells), salts (sodium, potassium, magnesium, chloride, calcium, phosphate, sulfate & all recognised vitamins.
  • vitamin A (carotene) is what gives butter it’s yellow colour
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8
Q

Cream

A
  • fat phase of milk, from letting fat globules rise or through centrifuging - contains 10-40% fats compare for whole milk which is 4%
  • better for cooking, lower concentration of proteins so less skin or burning forming
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9
Q

Butter

A
  • 80% fat, 18% water, 2% protein
  • macro structures, free fat molecules, Crystaline fat, air and water-protein suspensions
  • more highly ordered crystals there are the more brittle and crumbly the butter
  • more free fat there is, can vary between 50-100% of total fat - more malleable and lower melting temp
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10
Q

Margarine

A
  • Napoleon III offered a prize for formulation of synthetic edible fat in 1860s
  • originally from animal fats that were also semi-solid at room temp
  • 1905 French & German chemists developed hydrogenation of liquid vegetable oils
  • until 1950 had federal taxes to predict dairy industry
  • now three times as much margarine is consumed than butter - cheaper & contains less cholesterol and saturated fats as butter
    —> proportion of saturated fats increases with melting temp of animal and vegetable oils
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11
Q

Yogurt

A
  • lactic acid producing bacteria —> caesin micelles aggregate
  • no rennet from cows stomach added, which is needed for cheese
  • misconception that normal yoghurt containing lactobacillus bulgaricus helps outcompete unhealthy bacteria in human stomachs - lactobacillus can not survive in humans
  • want bacteria that only breakdown lactose, rather than breaking down fats & protein which releases much more odourous smells
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12
Q

Cheese overall process

A
  • four stages 1) start acidification & aggregation 2) add rennet to further aggregation 3)concentration of curds & draining of whey protein 4) add ripening agents change bland crumbly intermediate into smooth texture and distinct flavour
  • different cheeses often distinguished by type of ripening bacteria used
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13
Q

Fermentation

A
  • yoghurt, fermentation only goes on long enough for lactose to broken down
  • in cheese fats & proteins are also broken down into highly odorous chemicals
  • similar microbial activity occurs on moist m, warm & sheltered areas of human skins
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14
Q

Cheese general info

A
  • acidification and aggregation (a form of fermentation) of casein and whey protein forced out of the curd
  • cheese drier and more acidic so less prone to spoilage, was a way of preserving nutritional value of milk through the year
  • milk used in production to end cheese produced is 10:1
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15
Q

Cheese process specifics

A
  • not much evidence that using pasteurised milk vs raw milk reduces the quality of the cheese, although you do loose the action of certain naturally occurring bacteria and enzymes - but these are compensated for in the commercial process with pasteurised milk
  • renin isolated from cow stomachs catalyses the curding aggregation - disabling the stabilising subunit in casein causing separate micelles to clump together
  • if enzymes digest more than they coagulate you get softer curd, the higher temperature you cook the curd at the more purified it becomes (whey proteins filtered out increasing conc of casein - denser structure of casein fibres)
    —> what happens for hard cheeses, soft cheeses cooked at lower temp
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16
Q

Milk chemical structure

A
  • milks would normally separate into a water phase and fat layer (fat less dense than water) - but now all milk is homogenised so you don’t get layering
  • curd: ceasin, forms micelles, when subunit removed (slightly denature) by calf enzyme renin/acidification/heat through boiling, binds to free calcium ions which bridge between ceasin molecules forming cures for cheese
  • whey: primarily antibody lactoglobulin
  • fresh milk: slightly sweet lactose, salts & light odour of short-chain fatty acids - off milk growth of bacteria excrete lactic acid
17
Q

Milk making process

A
  • pasteurisation: killing unwanted microbes, milk easily spoils due to richness of macros & micros
    —> despite pasteurisation 10s millions of bacteria in half a gallon of milk and will spoil quickly without refrigeration
  • homogenisation: forcing milk through very small nozzle at high pressure, larger fat globules breakdown into smaller ones, too small to rise individually
  • autooxidation - ordinary day light excites oxygen atoms which invade hydrocarbon chains in fats producing various volatile and odorous molecules
  • cooking with milk —> ceasin and calcium forms skin on surface, larger ceasin and whey coagulates sink to the bottom, stick and burn
  • milk naturally sours to yogurt due to useful mircrobes but pasteurised milk, no bacteria, level playing field, more unhelpful bacteria
18
Q

Ripening cheese

A
  • when cheese gets distinct characteristics
  • starter bacteria also used as the ripening agents for hard/semi hard cheeses such as Parmesan & cheddar
  • softer cheeses have more soluble products from casein matrix breakdown
  • how regional cheese got distinct characteristics was through different local bacterial strains
19
Q

Chicken

A
  • breast 67C
  • thighs 72C
  • five spice
20
Q

Milk eggs seeds

A
  • Designed to be foods to support early life
21
Q

Egg general info

A
  • fish eggs, protective membrane was simple, slightly salty solution of ocean comparable to that of its parents body
  • indeterminate egg layers, such as chickens lay eggs until they have accumulated enough (will replace eggs taken away from their nest) vs determinate egg layers who lay a set number regardless
  • chicks sexed (males discarded) typically live for a year producing 250-90 eggs, immediately
  • 1.1 trillion eggs produced annually
  • chick born with immature egg cells, mature sequentially, when you get a double yolk, eggs has matured simultaneously
  • the shell: 95% calcium carbonate, calcium derived from bones of the hen, porous letting oxygen in and CO2 out and a waxy cuticle to slow water loss
  • takes 25 hours after egg leaves ovum - expelled on the signal of prolactin, the same hormone that triggers milk secretion in mammals and uterine contractions
22
Q

Egg structure & storage

A
  • egg shrinks in shell, starts off with 1/8 air pocket, this grows as egg ages
    —> hence the egg float test
  • egg gets increasingly alkaline, causing proteins in the albumen (egg white) to repel and separate, reducing albumen thickness, also reduces strength of yolk membrane
  • 1 large egg contains 6.5g of protein (13% daily intake), 80 calories and iron, phosphorous, thiamine, vitamin A,D,E & K, but high cholesterol content
23
Q

Yolk

A
  • Yolk: 50% water, 34% lipids (including the emulsifier lecithin), 16% protein
    —> Yolk contributes 75% of calories
    —> ‘yolk’ yellow in old in English, due to pigment xanthophylls - precursor of vitamin A, but cannot in isolation be converted into vitamin A, so yellowness of egg not an indicator of nutritional value
  • continuous liquid phase is not fat, but a water solution with proteins called livetins which become the blood serum proteins in the Chick
  • yolk spheres and granules of lipid-protein are suspended in the livetin solution
24
Q

Albumen (the white)

A
  • contains a finer balance of amino acids than meat, for support of animal life
  • albumen contains 6 main proteins, one is ovomucoid which inhibits digestive enzyme trypsin
    —> will lower the nutritional value of egg proteins unless it is denatured in cooking
25
Q

Egg functionality

A
  • stabilise oil-water sauces with the emulsifiers in the yolk, thicken liquids into delicate solids
  • albumen proteins are globular net negative proteins, so repel one another
  • changes in acidity, salt and temperature can cause protein molecules to bond into a solid mass, to a coagulate
  • temperature: increase energy of all atoms & molecular structures disrupts the folding, exposing neighbouring amino acid chains, as temperature rises further, proteins bump into each other and bond to one another through ionic bonds and covalent bridges
    —> densely packed, and so reflect rather than pass through light rays - clear albumen becomes opaque
  • when egg is helping bond a liquid into a solid, if it is overcooked
  • water (and moisture) is retained through water molecules hydrogen bonding within and around the coiled proteins
    —> these break easily when heated, and proteins squeeze together more through covalent & ionic bonding, which survive the increased kinetic energy
  • e.g. scrambled egg has two phases, the excess water with fats & protein in solution, and the solid lumps of protein
26
Q

Cooking eggs

A
  • thin egg white begins to coagulate at 63C
  • thick egg white, section around the yolk, containing ovomucin which is most resistant to denaturation & coagulation, starts to coagulate at 66C
  • at 71C egg white is full set, any further cooking and egg becomes less tender
  • diluting eggs with liquids or sugar increases coagulation temp required, more molecules in between protein molecules, so they need to move faster to link up (need more kinetic energy)
  • adding acid (Tatar sauce, lemon juice, or juice of other fruit or vegetable) lowers the ph, therefore reducing the repelling net negative charges of proteins
  • adding salt, dissolving into sodium & chloride ions, disturbs electrical environment of proteins causing them to unfold and coagulate
  • overall, sweetening eggs delays coagulation, salting or acidifying accelerates coagulation
27
Q

Boiled eggs

A
  • should be cooked just below boiling point, avoid turbulent boiling water knocking eggs into each other and against pan, cracking shell and releasing albumen & hydrogen sulfide
  • pealability of boiled eggs, higher pH, inner membrane adheres less to the albumen, after few days of refrigeration, more easy to peal away shell
    —> putting them in cold water also helps pealability
28
Q

Poached eggs

A
  • main challenge is creating a compact shape without overcooking the white
  • grade AA eggs, with largest proportion of thick white are the best for this as they will spread the least
  • start: again water should be close to boiling point but not at boiling temp, boiling water will draw out the thin albumen
  • outer albumen will coagulate first, and then hold the rest of the albumen in shape
  • finish: raise to gentle boil, to enable to inside to heat through but avoiding overcooking the outside
  • vinegar & salt can be added to speed up coagulation of albumen surface
29
Q

Fried eggs

A
  • harder to apply even & precise heat when frying rather than boiling
  • want high enough heat to ensure egg sets in reasonably compact shape, but low enough to ensure albumen in direct contact with pan doesn’t overcook
  • 124-138C optimal temp, when butter sizzle but doesn’t brown
  • adding oil or steaming egg in its own moisture helps even out the heating - causes thin layer of white covering the yolk to coagulate
30
Q

Scrambled eggs

A
  • add a bit of milk/water, as coagulated proteins can hold a more liquid than they do in the raw egg
  • 2-5 teaspoons per egg recommended, if add liquid over the holding capacity of the proteins, even the slightest heating will cause water to be squeezed out forming a puddle

Cooking (2 decks)

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