Cooking Quiz — 50 Questions, Ending in Why It Works

Does adding salt to a pot of water make it boil at a higher temperature?

Answer Yes, but by so little that it changes nothing about how fast the food cooks

The rise at kitchen quantities is a fraction of a degree, far too small to matter. Salt goes in the water to season the food, not to speed anything up — and adding enough salt to change the boiling point meaningfully would make the food inedible.

Why do most recipes want the pan hot before anything goes in?

Answer A hot surface browns food and releases it; a cold one lets it stick and steam

Protein sticks to metal it touches while cool, and a hot surface makes it seize and release instead. That is why fish welded to the pan is nearly always a temperature problem rather than a nonstick problem.

What does putting a lid on a simmering pot mainly do?

Answer It keeps steam in, so heat escapes slowly and the liquid barely reduces

Trapped steam means very little evaporates, so a covered pot holds its liquid and comes back to temperature quickly. It follows that if a sauce is meant to thicken, the lid is working against you.

Food keeps cooking for a while after it leaves the heat. Why?

Answer The outer layer is hotter than the center, and that heat keeps traveling inward

The surface is much hotter than the middle and heat keeps moving inward after the pan is off. In a thick roast this can be several degrees, which is why it is pulled before it reaches the number you actually want.

How do you tell a simmer from a boil by eye?

Answer A simmer shows occasional small bubbles; a boil breaks across the whole surface

A simmer is quiet, with bubbles rising here and there; a boil is agitated all over. The difference is worth learning by eye because many things — eggs, dumplings, delicate fish — break apart at the second one and hold together at the first.

Why does a crowded pan steam instead of browning?

Answer The released moisture has nowhere to go and the pan temperature drops

Food gives up water as it heats, and a crowded pan cannot clear it fast enough. The moisture sits, the temperature drops below what browning needs, and the food ends up cooked but pale. Two batches take less time than one crowded one.

Water in an open pot cannot get much past its boiling point. So what does a higher flame do?

Answer It boils the water away faster without making it hotter

In an open pot, water sits at its boiling point no matter how big the flame; the extra energy goes into turning it into steam rather than into raising the temperature. So a violent boil cooks pasta no faster than a gentle one — it just empties the pot sooner.

Why do recipes insist on preheating the oven?

Answer A heating oven swings above and below the dial, so timings only hold once it settles

An oven overshoots and undershoots as the thermostat cycles, and only settles after a while. Worth knowing too: home ovens are often well off the dial, and an oven thermometer is the cheapest fix in any kitchen.

Two pieces of meat weigh the same but one is thick and one is flat. Which is done sooner?

Answer The flat one, because thickness decides how long heat takes to reach the middle

Heat has to travel from the outside to the middle, and the distance it must cover is the thickness. The relationship is steeper than it feels — doubling the thickness far more than doubles the time, which is why weight on the package is a poor guide.

Why is a roast brown outside and pale inside?

Answer Browning needs a dry surface hotter than boiling, and the inside stays wet

Browning needs a dry surface above the boiling point, and the inside of anything juicy stays at or below it while there is still water there. The two conditions cannot exist in the same place, so the crust and the interior are always cooked by different rules.

What does salting meat well before cooking do?

Answer Moisture is drawn out, then drawn back in carrying salt, so it is seasoned deeper than the surface

Salt first pulls moisture to the surface, and then that salty liquid is drawn back in. Done far enough ahead, the seasoning ends up through the meat rather than on it — which is why the instruction is about timing more than about quantity.

Why does a squeeze of lemon or a splash of vinegar rescue a heavy dish?

Answer Acidity cuts the sense of richness and makes the other flavors read as brighter

Fat and sugar both flatten a dish, and acid cuts against them so the other flavors register again. It is the most reliable fix for food that tastes like it needs something without tasting like it needs salt.

A tomato sauce tastes sharp. Why does a pinch of sugar help?

Answer It offsets the acidity, so the sauce reads as rounder rather than sweet

Sweet and sour work against each other on the palate, so a small amount takes the edge off without reading as sweetness. Italian cooks often use a grated carrot instead, which does the same job more slowly.

Beyond taste, what is fat doing in a pan?

Answer Carrying flavors that will not dissolve in water and spreading heat evenly across the surface

Many aroma compounds dissolve in fat and not in water, so fat is what gets them out of the ingredient and into the dish. It also fills the gaps between an uneven pan and uneven food, which is why a dry pan heats in patches.

Baking soda needs something to make bubbles. What?

Answer Moisture and an acid such as buttermilk, yoghurt or vinegar

On its own it does nothing; it needs moisture and something acidic to react with. Without the acid you get no lift and a faintly soapy taste, which is exactly what a recipe is preventing when it calls for buttermilk or yogurt.

How is baking powder different?

Answer It already contains its own acid, so it only needs moisture and usually heat

It is baking soda with a dry acid already mixed in, so the recipe does not have to supply one. Most types react twice — once when wetted and again in the oven — which is what gives a batter some tolerance for sitting a moment before baking.

What happens if you tip cornflour straight into a hot sauce?

Answer It seizes into lumps; it needs mixing with cold liquid first

The outside of each clump gelatinizes on contact and seals the dry powder inside, and no amount of stirring gets it out. Mixed with cold liquid first, every grain is separated before it ever meets heat.

Why does milk sometimes curdle in a tomato or wine sauce?

Answer Acid makes its proteins clump together instead of staying spread through the liquid

Milk protein stays dispersed only while the liquid is not too acidic; below that point it clumps. Warming the milk gradually and using something with more fat both help, because fat gets between the proteins and slows them finding each other.

What are the eggs doing in a custard?

Answer Their proteins set as they warm, turning a thin liquid thick

The proteins unfold with heat and link into a loose mesh that holds the liquid, which is what thickening is here. Go a little too far and that mesh tightens and squeezes the liquid out — the difference between custard and scrambled egg is a few degrees.

Why is butter often called for cold in pastry but soft in cake?

Answer Cold lumps make steam pockets and flaky layers; soft butter traps air for an even crumb

In pastry the aim is separate pieces of butter that turn to steam and push layers apart. In cake the aim is butter soft enough to hold air bubbles when beaten with sugar. Same ingredient, two entirely different jobs, decided by temperature.

A pan of oil catches fire. What must you not do?

Answer Throw water on it, which flings burning oil outward

Water hitting hot oil turns to steam instantly and expands hundreds of times over, throwing burning oil across the room. This is the single most dangerous thing that can be done in a domestic kitchen, and it is usually done by reflex.

What is the reasonable response to that same oil fire?

Answer Cut the heat and smother it with a lid or a large plate, then leave it to cool

Cut the heat and cover the pan to take away the air, then leave it alone until it is completely cool. Moving a burning pan is the other common mistake, because the danger travels with it.

Where should frozen meat thaw?

Answer In the fridge, or in cold water changed often, but not on the counter

On a counter the outside sits in the range where bacteria multiply for hours while the middle is still frozen. In the fridge it thaws slowly and stays cold throughout, and cold running or changed water is the fast alternative that keeps the surface safe.

You cut raw chicken, then need to slice a cucumber. What now?

Answer Wash board, knife and hands first, or reach for a different board

Wash, or use a second board. The reason this particular case is singled out is that the cucumber will not be cooked, so anything transferred to it goes straight to the table with nothing to kill it.

A large pot of soup is left to cool. What is the safer way?

Answer Split it into shallow containers so it passes through warm temperatures quickly

A deep pot of hot soup can stay warm in the middle for many hours, which is a long time in the range where bacteria grow. Split into shallow containers it passes through that range in minutes instead.

Why is raw cake batter a poor snack?

Answer Raw egg and raw flour have both been linked to food poisoning

Everyone thinks of the egg, and flour is the one that surprises people: it is a raw agricultural product that has caused outbreaks of its own. Neither ingredient is safe until it has been cooked, and that includes the spoon.

Which is the bigger risk with cooked rice?

Answer Leaving it at room temperature for hours before eating

A spore that survives cooking can germinate while the rice sits at room temperature and produce a toxin. Reheating kills the bacteria but does not destroy what they made, which is why cooling it quickly and refrigerating it matters more than how hot it is reheated.

Why is a blunt knife the more dangerous one?

Answer It needs more force and slides off the food instead of biting into it

It needs more pressure to do the same job, and when it skids off a curved surface all that pressure has to go somewhere. A sharp blade goes where it is pointed, which is why professional kitchens treat sharpening as a safety measure.

Where does raw meat belong in a fridge?

Answer On the lowest shelf, so nothing can drip onto food below

On the bottom, below everything else, so nothing can drip onto food that will be eaten uncooked. It is the one piece of fridge organization that is about safety rather than convenience.

Is the smell test enough to decide whether food is safe?

Answer No, several organisms that cause illness leave smell, taste and appearance unchanged

The organisms that make food smell bad and the organisms that make people ill are largely different sets. Food can be dangerous while looking and smelling completely normal, which is why time and temperature are the guide rather than the nose.

What is blanching?

Answer A short spell in boiling water, then cold water to stop the cooking

Seconds to a couple of minutes in boiling water, then straight into ice. It is used to loosen skins, set color, and switch off the enzymes that would otherwise keep degrading a vegetable in the freezer over months.

What is braising?

Answer Browning first, then cooking slowly in a little liquid with a lid on

Brown first for flavor, then cook slowly in a small amount of liquid with the lid on. It exists for the tough cuts: long, gentle heat turns the connective tissue that makes them chewy into gelatin, which is the same thing that makes the sauce rich.

What does saute mean in practice?

Answer Cooking quickly in a small amount of fat over lively heat, keeping the food moving

The word means to jump, and that is the instruction — the food is kept moving in a little fat over lively heat. It only works when the pieces are small and roughly the same size, since everything has to finish at once.

What is poaching?

Answer Cooking gently in liquid kept below a boil, so the food stays intact

The liquid is held below a boil, hot enough to cook and calm enough not to knock anything apart. It is the method for things that would disintegrate in agitation, and the visual cue is a surface that barely moves.

What are you doing when you deglaze a pan?

Answer Adding liquid to a hot pan to lift and dissolve the browned bits stuck to it

The browned residue stuck to the pan is water-soluble and packed with flavor, and a splash of liquid lifts it while the pan is still hot. Discarding that pan is throwing away the most concentrated thing produced by the cooking.

A recipe asks for julienne. What shape is that?

Answer Thin matchsticks

Thin sticks, roughly the size of a matchstick. Cut names are about cooking time as much as looks: pieces of the same shape and size finish together, which is most of what separates a neat dish from an uneven one.

Why does a recipe say fold rather than stir?

Answer Folding turns the mixture over gently so the air already beaten in survives

Stirring drives the air out of whatever was just beaten into the mixture. Folding cuts down through and turns the mass over, combining it with the fewest strokes — the instruction is really about how many times you touch it.

What is proving, or proofing, dough?

Answer Letting it rest so the yeast makes gas and the dough rises

It is the rest that lets the yeast work, producing gas that inflates the structure already built by kneading. Warmth speeds it and cold slows it, which is why a slow rise in the fridge is a technique rather than a delay.

A sauce is told to reduce. What is happening?

Answer Water evaporates, so what is left is thicker and stronger tasting

Water leaves as steam and everything dissolved in it stays behind, so the sauce gets thicker and more strongly flavored at the same time. It also concentrates the salt, which is why seasoning is judged at the end and not the beginning.

What does it mean to temper eggs?

Answer Warming them slowly by whisking in a little of the hot liquid before the rest

Adding a little of the hot liquid to the eggs first raises their temperature gradually so they thicken instead of scrambling. Pouring in the other direction is faster and is how most curdled custards happen.

Seared meat turns brown and smells completely different. What reaction is that?

Answer The Maillard reaction, between amino acids and sugars at high, dry heat

It is not one reaction but a cascade, and it produces hundreds of compounds that were in neither the meat nor the pan beforehand. It also runs slowly at low temperatures, which is part of what happens over weeks in aged and dried foods.

How does caramelization differ from that?

Answer Caramelization is sugar breaking down by itself; the other reaction needs protein too

Caramelization is sugar coming apart on its own with no protein involved, which is why it can happen in a pan of nothing but sugar. The other reaction needs amino acids as well, so it cannot happen without something protein-bearing present.

Why will food not brown while its surface is still wet?

Answer Evaporating water holds the surface near boiling, and browning needs it hotter than that

While there is water on the surface, evaporation holds it near the boiling point, and browning needs it hotter than that. So patting food dry is not fussiness — it is removing the thing that is actively preventing the reaction.

What does kneading actually change in bread dough?

Answer Proteins link into gluten, an elastic web that can hold the gas the yeast makes

Two proteins in flour link up when worked with water, forming an elastic network. That network is what holds the gas in, which is why an underworked dough leaks and collapses and a well-worked one keeps its shape as it rises.

Why is meat left to rest before slicing?

Answer Fibers relax and the juice spreads back through instead of running onto the board

Muscle fibers contract with heat and squeeze liquid toward the center under pressure. Resting lets them relax and the liquid redistribute, so it stays in the meat instead of running onto the board the moment the knife goes in.

Mayonnaise is oil and water, which do not mix. Why does it hold?

Answer Egg yolk carries emulsifiers that coat the oil droplets and keep them suspended

The trick is size: the oil is broken into droplets so small that they stay suspended, and something from the yolk coats each one so they cannot rejoin. It is less a mixture than a suspension held apart by a coating.

Why does that same sauce split if the oil goes in too fast?

Answer The droplets meet and merge faster than they can be broken up and coated

Droplets can only stay separate while there is enough coating to go around and enough agitation to keep breaking them up. Poured in too fast, they find each other before either can happen. A split sauce can be rescued by starting fresh with a yolk and adding the broken mixture drop by drop.

Yeast and baking soda both make dough rise. What is the difference in kind?

Answer Yeast is alive and gives off gas slowly as it feeds; baking soda is a reaction that fires once

One is a living organism that feeds over hours and gives off gas gradually, which also produces flavor as a byproduct. The other is a chemical reaction that fires when wetted and is finished — which is why one dough can wait and the other cannot.

Why do cooks save a cup of the cloudy pasta water?

Answer Starch has dissolved into it, and that starch helps a sauce cling instead of sliding off

The cloudiness is dissolved starch, and starch helps oil and water hold together so the sauce coats the pasta instead of pooling underneath. It is also already salted, so it seasons while it thickens.

Why does chopping an onion sting, and why does chilling it first help?

Answer Cutting releases a volatile irritant, and cold slows both the reaction and its escape into the air

Cutting ruptures cells and lets an enzyme meet a sulfur compound, producing a volatile irritant that reaches your eyes. Cold slows both the reaction and the evaporation, and a sharp knife helps for the same reason — it crushes fewer cells.