Rice, grains, beans and pasta

Cook a pot of rice on Sunday evening, leave it in the pan with the lid on while you eat, and turn it into fried rice on Monday. It's one of the most sensible things a cook can do with leftovers, and done this way it's also how a pot of rice can make someone ill. The rice is not dangerous because it was reheated. It's dangerous because of the hours it sat warm in the pan, and nothing you do on Monday can undo them.

Rice, grains, dried beans and pasta are the dry starches of the world's kitchens, and they share one mechanism: hot water gets into hard starch and softens it. How much water, how fast and with what else in the pot decide whether you end up with separate grains or glue, tender beans or pellets, pasta that holds a sauce or pasta that slides off it. Two of these foods also carry a hazard of their own, which lesson 4 left for here. Cooked rice can grow a germ whose toxin survives cooking, and raw red kidney beans contain a toxin that a slow cooker can't destroy. This lesson takes rice first, then beans, then pasta.

What hot water does to starch

A grain of raw white rice is a small, hard pack of starch. The starch sits in tightly organised granules that water cannot get into at room temperature. Heat them in water and the structure gives way. A 2025 review by Stefano Renzetti and colleagues describes the start of it: "Initially, water penetrates amorphous regions, causing granule swelling", and then, "In the initial stages, starch granules absorb water and expand until they reach a packed state". Heat them further and the granules begin to break open.⁵ That swelling is gelatinisation, and it is what turns a pebble into something you can eat.

It starts lower than you might expect. A study of starch from ten rice varieties found gelatinisation beginning between 57.9 and 64.4°C (about 136 to 148°F), depending on the variety.³ Water at a simmer is far above that, which is one reason rice doesn't need a hard boil to cook; what it needs is enough water, reaching the middle of the grain, for long enough. This course's reading, from lesson 2, is that the outside of each grain softens first and the centre last.

Much of the texture comes down to the kind of starch. Rice starch is a mix of two molecules, amylose and amylopectin, and the share of amylose differs a lot between varieties. A 2016 paper by rice breeders at the Chinese Academy of Agricultural Sciences and the International Rice Research Institute (IRRI) sums up what that does to a bowl: "Cooked rice kernels with high AAC (>25%) are dry, separate, less tender, and become hard upon cooling, whereas those with low (12–20%) are glossy, soft, and sticky". AAC is their abbreviation for apparent amylose content. They add that amylose "alone does not explain all of the variations", since varieties with the same amylose can still eat differently.⁴

The same swelling thickens a sauce when you stir flour or cornflour into hot liquid, which is where lesson 10 picks it up.

Rice by absorption

There are two ways to cook rice in water. In the absorption method you give it a measured amount of water and cook it covered until the rice has taken it all up. In the excess-water method you boil it in plenty of water, like pasta, and drain it. The question every cook asks about the first is how much water.

How much water rice needs

Recipes answer that with a ratio, and the ratios disagree: more water for long grains than short, more for brown than white. America's Test Kitchen (ATK) tested the idea behind them. Its cooks took 17 varieties, including white and brown short, medium and long grain, basmati, jasmine, and red and black rice, and sealed 1 cup of each with 1 cup of water in a vacuum bag (a US cup is about 240 ml; for a ratio, any cup-sized measure works if you use the same one for rice and water), so that nothing could evaporate. The bags cooked in a water bath until the grains were tender, rested 10 minutes, and were tasted. They repeated it three times.⁶

So the ratio on a packet is two things added together: about the rice's own volume of water, which it absorbs, and an allowance for what boils away. ATK's explanation for brown rice follows. It "doesn't require more water than a cup of long-grain white rice, but it does need to cook for a significantly longer period of time", and the longer cooking loses more steam.⁶ ATK's page on pressure cookers puts the extra plainly: in a covered pot, "we add an extra ½ cup water", which is where a stovetop 1 cup of rice to 1½ of water comes from.²⁶

That tells you when a ratio will fail. The allowance depends on things no recipe can know: "the size and shape of the cooking vessel, how tightly the pot is covered, and the source and intensity of the heat." And "the amount of evaporation doesn't necessarily double when we double the quantity of rice."⁶ ATK's own recipes show it. Two of them cook 2 cups of rice in 3 of water in a large saucepan. A third, written for 1 cup in 1½ cups in a tight-lidded pot, says that with 2 cups of rice you should use "two and one-half to two and three-quarters cups of water", not three, and warns against halving it at all.⁷ Each is right for the pot it was tested in. ATK's conclusion is that "set-in-stone ratios fail the home cook".⁶ The practical answer is to start from a tested recipe in the pot it names, and write down what your own pot and lid needed.

Resting, covered, off the heat

ATK's recipes end the same way. Turn off the heat, keep the lid on, and leave it 10 to 15 minutes; two of them put a tea towel under the lid, one while the rice cooks and one for the rest.⁷ The reason one of them gives is "so any extra moisture was absorbed", followed by fluffing with a fork "to break up any big masses".⁷ This course didn't find a test that compared rested and unrested rice, so treat the rest as the recipe's instruction with its stated reason, not a measured result. This course's reading is that it fits the mechanism: grains that were in the water at the bottom of the pan and grains that were in the steam at the top get time to even out.

A pilau, a risotto and a pot of sticky rice

The absorption method has as many forms as there are rice cuisines, and the UK's professional cookery qualification lists four methods of cooking rice with an example of each: "Boil/steam (eg basmati), braise (long grain eg pilau), stew (eg risotto), fry (eg egg fried)".¹⁰ They're the same starch doing different things.

The descriptions that follow are this course's, not the qualification's. A pilau starts by stirring the rice in hot fat before the liquid goes in, which ATK's fluffy rice recipe also does, "for 1 to 3 minutes, depending on desired amount of nutty flavor", and then cooks it covered in a measured liquid.⁷ A risotto goes the other way: liquid added a little at a time and the rice stirred, so starch from the surface of each grain comes off into the liquid and thickens it. A rice meant to be eaten in soft clumps wants the texture the IRRI paper gives low-amylose rice, "glossy, soft, and sticky".⁴ What you want from the grain decides the method, and every method is a way of controlling how much water gets in and how much surface starch stays on.

Rinsing, and cooking in excess water

Many recipes rinse white rice first, and the reason is the surface starch. In an interview published by ATK, Matt Slem, a culinary scientist at Lundberg Family Farms (a rice company), put it this way: "When you actually wash, rinse, or soak white rice, it becomes less sticky. And when you cook it up, the kernels of rice separate and get more fluffy." Brown rice still has its outer layer, so rinsing it does not change the texture in the same way.⁸ ATK's everyday recipe rinses for the same reason.⁷ So rinse when you want separate grains, as for a pilau, and don't when you want the surface starch, as for a risotto.

Some people also rinse rice to get rid of arsenic, and that's where a study by scientists at the US Food and Drug Administration comes in. Gray and colleagues cooked several kinds of rice rinsed and unrinsed, in different amounts of water, and measured what ended up in the cooked grain.⁹ Their finding on rinsing: it "has a minimal effect on the arsenic (As) content of the cooked grain, but washes enriched iron, folate, thiamin and niacin from polished and parboiled rice". Enriched rice has had those nutrients added back after milling, and rinsing takes some of them off again.

Cooking in excess water, then draining, did move the arsenic. It cut inorganic arsenic "by 40% from long grain polished, 60% from parboiled and 50% from brown rice". It also cut the added iron, folate, niacin and thiamin by 50 to 70% in enriched rice, and "significantly less so for brown rice, which is not enriched."⁹ So rinsing is a texture choice, and draining is a trade: less arsenic, and fewer of the added vitamins if your rice is enriched. The packet tells you whether it is. How much the arsenic in rice matters for health is a nutrition question that this course, which makes no health claims about what to eat, does not answer. What it can tell you is which step moves it and which doesn't.

To cook rice in excess water, bring a large pan of water to the boil, add the rice, keep it at a lively simmer, and start biting a grain once it looks swollen. When the centre has lost its chalky core, drain it well. There's no ratio to get wrong, which is its other advantage.

Long-grain rice two ways

Take the same long-grain white rice and cook it both ways on the same night. For the absorption pot: rinse 1 cup, bring it to the boil with 1½ cups of water and a pinch of salt, cover it tightly, cook it on the lowest heat until the water has gone, and rest it covered off the heat.⁷ For the excess-water pot: rinse another cup, boil it in a large pan of water until tender, and drain it well.

Put them side by side. This course expects the drained rice to be drier on the surface, with more separate grains, because the starch that came off went down the sink with the water; the absorption rice keeps everything it started with, so it should cling a little more. The practice at the end has you check. That is the same fact as Gray's study, from the other direction: whatever leaves the grain in the water, whether that is starch, arsenic or added vitamins, only leaves if you pour the water away.

Cooked rice and Bacillus cereus

Now the pot from the start of the lesson. Lesson 4's table gave the UK's rice rule and pointed here for the reason, which is a germ called Bacillus cereus. The FSA explains the problem in one line: "Uncooked rice can contain spores of a bacterium called Bacillus cereus." A spore is a dormant, tough form of the bacterium, and "The spores of Bacillus cereus can survive being cooked."¹

The FDA's reference on foodborne germs, the Bad Bug Book, fills in the rest. B. cereus grows best between 28 and 35°C (about 82 to 95°F), and it can grow anywhere from a minimum of 4°C to a maximum of 48°C (about 39 to 118°F).² A pot of cooked rice left to cool on the hob spends hours in that range, and the spores that survived cooking germinate and multiply. One of the two illnesses it causes, the vomiting kind, comes from a toxin the bacteria make in the food. The book says it "most often affects rice and other starchy foods", with symptoms from half an hour to 6 hours after eating, usually over within a day.² It lists "potato, pasta, and cheese products" among the other starchy foods implicated, so none of this is only about rice.²

The part that changes what you do is the toxin. The Bad Bug Book calls it cereulide, and says it "is stable after heating at 121°C for 30 minutes, cooling at 4°C for 60 days, and at a pH range of 2 to 11."² 121°C is about 250°F, and 30 minutes is a long time to hold it. This course's reading, from lesson 2's ceiling of 100°C for water in an open pot, is that no reheating in a pan or a microwave comes near it. Reheating kills the bacteria and leaves their toxin behind. That's why the FSA says "It’s not the reheating that causes the problem, but the way the rice has been stored before it’s reheated."¹ The course's question, from lesson 1, is what a rule protects. The rice rules protect the hours after cooking.

What the US and the UK say

The UK has a rule for rice, and it's strict. The FSA's fact checker says to chill leftover rice "as quickly as possible, ideally within one hour", to divide it into smaller portions to help, and "don’t leave rice in the rice cooker, steamer or pan to cool down." It says "Keep rice in the fridge for no more than one day until reheating", "you should never reheat rice more than once", and, whenever you do, check it is "steaming hot all the way through". If you're freezing it, it should go in the freezer "within an hour of cooking".¹ The NHS page on storing food for babies gives the same rule in almost the same words.¹¹

The US pages this course read give no rule for rice alone. Rice falls under the general rules from lesson 4: into the fridge within 2 hours, or 1 hour above 90°F (32°C); hot food may go straight into the fridge, in shallow containers; leftovers keep 3 to 4 days; reheat to 165°F (74°C).¹²¹³ The Bad Bug Book's advice to consumers about B. cereus is to "keep your food refrigerated at 40°F or lower", which is about 4°C.²

So the two countries agree about the direction, cool it fast and keep it cold, and differ on how fast and how long. The pages read don't say why the UK singles rice out, and this course won't guess.

Rice tonight for fried rice tomorrow

Say you're cooking a pot of long-grain rice on Sunday to fry on Monday evening. Here's the plan under each country's rules.

In the UK: take the rice out of the pan as soon as it's done, spread it thin in one or two shallow containers so it cools fast, and have it in the fridge within an hour. The FSA's "no more than one day" and "within 24 hours" put Monday evening at the edge, so cook it Sunday evening rather than Sunday lunchtime.¹ Fry it until it is steaming hot all the way through, and don't save what's left of the fried rice to reheat again, because that would be a second reheat.

In the US: the same shallow containers, into the fridge within 2 hours (or straight in while hot, which FSIS allows), and Monday is well inside 3 to 4 days.¹²¹³ Heat it to 165°F (74°C).

The step that fails in both countries is the one people do without thinking: leaving the rice in the pot, lid on, to cool on the stove. A covered pot of rice loses its heat slowly, and the time it spends cooling is time in B. cereus's range. The FSA names the rice cooker and the pan for exactly this reason.¹

Dried beans: soaking, salt and acid

Dried beans are starch too, inside a tough skin. They take far longer than rice, and Colorado State University's extension service puts a stovetop pot at "generally about 1-3 hours".¹⁹ Soaking helps. The same page calls it "optional, but it can help shorten cooking time and improve appearance by preventing beans from bursting when cooking".¹⁹ This course's reading of why, from lesson 2, is that a bean that has already taken up water has less to do in the pot, so its middle lags less behind its outside. Lentils are the exception: they "do not need to be soaked before cooking".¹⁹

Salt the soak

A familiar rule about beans is never to salt them until the end, or the skins stay tough. ATK tested the opposite and recommends it. Its formula: "For 1 pound of dried beans, dissolve 3 tablespoons of table salt in 4 quarts of cold water. Soak the beans at room temperature for 8 to 24 hours." Drain and rinse them before cooking.¹⁵ That's about 54 g of salt in 3.8 litres, roughly 1.4% by weight, taking the USDA's figure of 6 g for a level teaspoon of table salt.²⁵

ATK gives the mechanism: "the sodium ions replace some of the calcium and magnesium ions in the skins. Because sodium ions are more weakly charged than calcium and magnesium ions, they allow more water to penetrate into the skins, leading to a softer texture." The effect is mostly on the outside: "the sodium ions will only filter partway into the beans".¹⁵ The skins soften, and the beans are seasoned before they're cooked, which is lesson 3's point about salting early enough for it to get in. Colorado State's extension service agrees that salt in the soak "can shorten cooking time and helps to prevent beans from splitting".¹⁹

Where to soak is a small disagreement between sources. ATK soaks at room temperature for 8 to 24 hours.¹⁵ Colorado State says "If soaking for more than 12 hours, refrigeration is recommended."¹⁹ North Dakota State University's extension service is stricter: "When soaking beans for longer than four hours, place the container in the refrigerator for safety." Its reason is that beans "may contain bacteria that can grow to harmful levels or produce a toxin if they remain at room temperature too long".²⁰ None of the three says why its cut-off sits where it does. Soaking in the fridge costs nothing but shelf space, so if you have the room, it's the cautious choice.

Acid slows beans down

Salt, then, isn't what keeps beans hard. Acid is. ATK noticed that tomatoes in a pot of beans seemed to keep them firm, so it set up a test: three pots of black beans, one plain, one made alkaline with baking soda and one made acidic with citric acid, all simmered covered in the same oven.¹⁶ The chart uses the pH scale, on which 7 is neutral, lower numbers are more acidic and higher numbers more alkaline.

ATK, "Can Baking Soda Make Beans Cook Faster?", 2019: one cup of black beans in 5 cups of water per pot, simmered covered in a 350°F (about 177°C) oven, repeated three times.¹⁶ The acid pot was made with citric acid to pH 3, which is more acidic than the article says a tomato sauce is; the article doesn't give a tomato's pH.

The acidic beans were "still rock-hard after 45 minutes" and took an hour and 45 minutes in all, against an hour in plain water. ATK's explanation is that acid "causes the cell structure of legumes to remain firm. If there is too much acid in the pot, the beans may never soften enough to be ready to eat." Alkali does the reverse, which is why a pinch of baking soda speeds beans up; ATK warns that more than a pinch makes them taste soapy.¹⁶

The advice that follows is about timing. ATK adds citrus juice and vinegar "at the end of the cooking process" and tomatoes "partway through the cooking process, after the beans have softened considerably."¹⁶ Its note on chilli says the same, and adds one more thing that slows beans down, their age, which it says is "impossible to gauge".¹⁷ So if a pot of beans stays hard, ask what went in at the start before you blame the beans.

Red kidney beans

Raw red kidney beans contain a lectin, a kind of protein, called phytohaemagglutinin, and it is a genuine poison. The Bad Bug Book: "As few as four or five raw beans can trigger symptoms." The illness "Usually begins with extreme nausea and vomiting within 1 to 3 hours", and "Recovery usually is rapid, within 3 to 4 hours after onset", though some people have needed hospital.² It is measured in units of activity, and the numbers show how much cooking changes: "Raw kidney beans contain from 20,000 to 70,000 hau, while fully cooked beans contain from 200 to 400 hau." White kidney beans have about a third as much as red, and broad beans 5 to 10%.²

The outbreaks the Bad Bug Book describes are British. "Seven outbreaks occurred in the U.K. between 1976 and 1979", it says, while reports from the US are "anecdotal", and it says the illness "usually is caused by ingestion of raw, soaked kidney beans".² Soaked. Soaking hydrates a bean, and it doesn't cook it.

Why a slow cooker is the danger

Proper boiling destroys the toxin. A slow cooker is the problem. The Bad Bug Book says "Several outbreaks have been associated with beans cooked in slow cookers", and that casseroles cooked in them "often reached internal temperatures of only 75°C or less, which is inadequate for destruction of the toxin."² The FSA goes further: "You should not slow cook raw red kidney beans as it does not destroy the toxin and may increase its toxicity."¹ Neither page explains the "may increase", and this course won't try to.

Lesson 8 used a slow cooker for what it's good at, long and gentle cooking. Here the gentleness is the problem: hours at the temperatures reported in those casseroles, well short of a boil, never break the toxin down.

How long to boil, and where "10 minutes" came from

If you've learned to cook kidney beans in the UK, you may have been told to boil them hard for 10 minutes. That was NHS advice. The NHS page "Beans and pulses in your diet", in the version reviewed in 2015, gave three steps: soak "for at least 12 hours", then fresh water, then "boil them vigorously for at least 10 minutes, then simmer the beans for around 45-60 minutes to make them tender".¹⁸ By the version reviewed in July 2021, the numbers had gone. It said only that dried kidney beans must be "soaked overnight and then cooked properly", to "Follow the instructions on the packet", and not to slow cook them.¹⁸ The NHS has since removed the page altogether, and this course found no current NHS page that gives a boiling time.

The 10 minutes has a real source behind it. The Bad Bug Book reports that "Bender and Readi found that boiling the beans for 10 minutes (100°C) completely destroyed the toxin." And then it tells consumers something else: "Consumers should boil the beans for at least 30 minutes to ensure that the product reaches sufficient temperature, for a sufficient amount of time, to completely destroy the toxin."²

That gap is lesson 4's time plus temperature. Ten minutes of boiling at 100°C (212°F) destroyed the toxin in a study. In your kitchen, a pot of cold beans takes time to come back to a boil, a big bean's centre lags its outside, and a gentle simmer isn't a boil. The 30 minutes buys the margin that makes sure every bean spent long enough at the temperature. The FDA's consumer summary gives the whole procedure, and says where it comes from: "Studies done by British scientists suggest that beans should be soaked in water for at least 5 hours, the water poured away, and the beans boiled in fresh water for at least 30 minutes."²

Tinned beans skip all of this. The FSA says canned beans "are safe to consume as they have been pre-soaked and boiled to kill any toxins present".¹

A slow-cooker chilli with raw kidney beans

A recipe for slow-cooker chilli says to put in dried red kidney beans, soaked overnight, with the meat, tomatoes and spices, and cook it on low for eight hours. Here's what's wrong with it and how to fix it.

The beans are soaked, which the Bad Bug Book says is the usual way the illness happens, and a slow cooker on low may never bring them near a boil. Both countries' regulators say not to slow cook them raw.¹² The recipe also puts tomatoes in from the start, which ATK says may slow softening, so even if the toxin weren't a problem the beans could stay firm.¹⁷

Two fixes. The simplest is tinned kidney beans, drained and stirred in for the last part of the cooking, since they are already cooked.¹ Or cook the dried beans first: soak them, pour the water away, bring them to the boil in fresh water and keep them boiling for at least 30 minutes, then carry on until they are tender, and only then add them to the chilli.² Colorado State's extension service suggests a 10-minute boil before a slow cooker, which is a third of the FDA's figure; this course follows the FDA.¹⁹ A pot of rajma on the hob works the same way: boil the soaked beans hard first, and add the tomatoes once they've softened.

What about a pressure cooker? Lesson 8 explained that a sealed pot boils hotter than an open one, and it isn't a slow cooker. North Dakota State's extension service tested pressure-cooked beans in three brands and publishes times for kidney beans, but it says nothing about the toxin, and this course found no regulator who has.²⁰ So it gives no pressure-cooker instruction for kidney beans. If you use one, follow its maker's manual.

Cooked beans, once they're done, are leftovers like any other, and the Bad Bug Book lists beans among the foods linked to B. cereus outbreaks.² Lesson 4's rules apply: cool them quickly, and keep them 3 to 4 days in the US or 48 hours in the UK.¹²¹⁴

Pasta, and how much water it needs

Harold McGee, the food-science writer, gave the standard method, the one he found in Italian cookbooks and on pasta packets, in a 2009 New York Times column: "4 to 6 quarts of well-salted water per pound of pasta", about 3.8 to 5.7 litres for 450 g. He also gave the reasons usually offered: "abundant water quickly recovers the boil when the pasta is added, gives the noodles room so that they don’t stick to one another, and dilutes the starch they release, so they don’t end up with a “gluey” surface."²¹

Then he tested it. He put a pound of spaghetti in "just 2 quarts of cold water and 2 teaspoons salt" and turned the heat on. It took about 8 minutes to boil and another 10 to cook, stirring now and then at the start, and it came out with "the texture and saltiness I expected". He cut the water to 1½ quarts and "the spaghetti came out fine."²¹

His explanation is the mechanism from the start of this lesson: "the noodles absorb water only very slowly at temperatures much below the boil", so little happens in the minutes it takes the water to heat up. And on stickiness, "no matter how starchy the cooking water is, the solid noodle surfaces themselves are starchier".²¹ Diluting the water doesn't make the surface less starchy, so the big pot wasn't doing the job it was credited with.

ATK tested it again in 2023, with penne, linguine and elbows. "In our tests, 1 pound of dried pasta started in 1 quart of cold water cooked up just as nicely al dente as the same type of pasta started in 4 quarts of boiling water". It used 75% less water and cut total time by "as much as 45 percent"; ATK notes it didn't test fresh or filled pasta.²²

Take them seriously. McGee agreed with the cost Hazan named: "no matter what temperature you start with, this method requires more attention. That’s a disadvantage when you’re cooking several things at once." He found capellini cooks too fast for it.²¹ Bastianich's objection is about texture, and ATK's own report allows for it: with its shapes, "Only the most sensitive palates could discern any difference".²² So the evidence is that a small pot works, and costs attention; whether it costs texture depends on whose palate and which pasta. A middle route is McGee's other finding: 1½ or 2 quarts of water already boiling, which answers Bastianich's "butta la pasta" and still saves most of the water.²¹

Oil, and rinsing

Oil in the water is the other standard piece of advice. ATK's Scott Kathan: "don’t put oil in the pasta cooking water; it does not help prevent the pasta from sticking to itself. A good hard boil and proper stirring, especially at the start of cooking, are what prevent the pasta from sticking to itself as it cooks."²³ McGee, starting pasta in a small pot, had to push the strands around now and then until the water boiled, which is the same point.²¹

Rinsing cooked pasta washes off the starch the sauce needs. Kathan calls the starchy cooking water "a smart (free, flavor neutral) thickener for many pasta sauces", and McGee found that tossing pasta with oil and a couple of ladles of his thick, small-pot water made "an especially creamy" coating.²³²¹ This course's reading is that it's lesson 5's emulsion again, with the starchy water holding the oil in droplets. So for a hot pasta with a sauce, drain it, keep a cup of the water, and don't rinse it. Rinsing makes sense when you want the opposite, separate cold strands for a salad or some cold noodle dishes; this course did not find a test of that, so treat it as sound practice rather than a finding.

Salty as the sea?

The last rule is how much salt. Salt in the water is how pasta gets seasoned inside, since it absorbs the water it cooks in, and Kathan makes the case for salting generously: "Salting the pasta only at the end will make the seasoning taste superficial, because it is superficial." He also defends the famous comparison: "“Salty like the sea” may sound corny, but it’s accurate".²³

The arithmetic doesn't bear that out. NOAA says "about 3.5 percent of the weight of seawater comes from the dissolved salts."²⁴ McGee's 2 teaspoons in 2 quarts is about 12 g in 1.9 kg of water, roughly 0.6%, taking the USDA's 6 g for a teaspoon of salt.²¹²⁵

So the sea is roughly four to five and a half times saltier than these recipes, and this course expects pasta cooked in it to taste very salty indeed. Take "salty as the sea" as a way of saying "more than you'd think", which is the part of Kathan's case the arithmetic supports, and not as a quantity. This course's suggestion is to start near 1% of the water's weight, about 10 g per litre, and adjust by tasting the cooked pasta. McGee's own advice when you use less water is "to reduce the salt for smaller volumes of water", which keeps the proportion roughly steady.²¹

Cooked pasta left over is a starchy food like rice, and the same rules apply: cool it quickly, fridge it, and keep to your country's leftover limits.²¹²¹⁴

What people get wrong

"Reheating rice is what makes it dangerous." The FSA says the danger is how it was stored. Spores survive cooking and make a heat-stable toxin in rice left warm.¹²

"Rinsing rice gets rid of the arsenic." Rinsing barely changes it. Cooking in excess water and draining cuts it by 40 to 60%, and takes added vitamins with it.⁹

"Every type of rice needs a different amount of water." In ATK's sealed bags, every one of 17 needed about its own volume; the rest of a ratio replaces evaporation.⁶

"Never salt beans until the end." A salted soak gives softer skins.¹⁵

"Boil kidney beans for 10 minutes." That was on the NHS page reviewed in 2015 and gone by 2021, and a study found 10 minutes at 100°C enough. The FDA tells cooks to boil them at least 30 minutes, so that every bean gets there.²¹⁸

"Soaked kidney beans are safe to slow cook." Soaking doesn't destroy the toxin, and slow cookers often don't get hot enough.¹²

"Pasta needs a big pot of water." A pound cooks well in 1 to 2 quarts, with more stirring.²¹²²

"Oil stops pasta sticking." Stirring early and a good boil do.²³

"Salt the water like the sea." That's 3.5%; the recipes read here use about 0.6 to 1%.²¹²²²⁴

"Rinse pasta after cooking." Not for a hot sauced dish: the starch helps the sauce cling.²³

Practice

Connections

Lesson 2 gave you the centre that lags and water's ceiling of 100°C, and both did the work here: water at a simmer is far above the temperature where rice starch begins to swell, and the middle of a grain, a bean or a strand of pasta is always the last to cook. Lesson 3's salt came back in the bean soak and the pasta water, as salt that gets inside the food instead of sitting on it. Lesson 4's time plus temperature explained the gap between the 10 minutes that destroyed the bean toxin in a study and the 30 the FDA tells cooks, and its cooling rules became the rice rules, with the reason at last. Lesson 8's slow cooker, so good for a long, gentle braise, turned out to be the wrong tool for raw kidney beans for exactly that reason.

Lesson 10 uses this lesson's swelling starch to thicken a sauce, and comes back to cooling, this time for a big pot of stock or stew and a different germ. Lesson 12's week of meals is built on a pot of rice and a pot of beans, and the storage rules you wrote in step 3 go into its plan.

Go deeper

• America's Test Kitchen, "Nailing the Perfect Ratio of Water to Rice", 2019. Read in full for this course. A short, clever experiment that explains every rice ratio you'll ever see, and why none of them travels to your pot unchanged.
• Harold McGee, "How Much Water Does Pasta Really Need?", New York Times, 2009. Read in full (a hosted copy). Worth reading for the method as much as the answer, and for the way he gives the two cooks who disagreed with him their say.
• FDA, Bad Bug Book, 2nd edition, 2012, the chapters on Bacillus cereus and phytohaemagglutinin. Both read in full. Each chapter opens with a plain-language box for consumers before the science.
• Food Standards Agency, "Home food fact checker". Read in full. The UK's answers on rice, kidney beans and eggs, among others, in a question and answer form.

Sources

1. Food Standards Agency, "Home food fact checker", GOV.UK, updated 21 August 2026, https://www.gov.uk/government/publications/home-food-fact-checker/home-food-fact-checker . Read level: full, directly. Supports: spores in uncooked rice surviving cooking, storage rather than reheating, one hour, dividing into portions, not cooling in the rice cooker or pan, no more than one day, 24 hours, never reheating more than once, steaming hot, freezing within an hour, tinned beans, and not slow cooking raw red kidney beans.
2. US FDA, Bad Bug Book: Foodborne Pathogenic Microorganisms and Natural Toxins, 2nd edition, 2012, chapters "Bacillus cereus and other Bacillus species" and "Phytohaemagglutinin (kidney bean lectin)", https://www.fda.gov/media/83271/download . Read level: both chapters in full, directly. Supports: B. cereus growth temperatures, the vomiting illness and its onset, other starchy foods, cereulide's stability, beans among outbreak foods, refrigerating at 40°F; the kidney bean dose, onset, recovery, hau figures, white kidney and broad beans, UK outbreaks and anecdotal US reports, raw soaked beans, slow cookers and 75°C, Bender and Readi's 10 minutes, and the consumer advice of 5 hours and 30 minutes, attributed on the page to British scientists.
3. H. D. Woo and colleagues, "Physicochemical and Gelatinization Properties of Starches Separated from Various Rice Cultivars", Journal of Food Science 80(10), 2015, E2208 to E2216, PMID 26352343 . Read level: abstract. Supports: onset of gelatinisation at 57.9 to 64.4°C across ten cultivars, and amylose not tracking the thermal properties.
4. Y. Pang, J. Ali and colleagues, "Relationship of Rice Grain Amylose, Gelatinization Temperature and Pasting Properties for Breeding Better Eating and Cooking Quality of Rice Varieties", PLoS ONE 11(12), 2016, e0168483 . Read level: the introduction, directly. Supports: high and low amylose rice described, and amylose not explaining all the variation. The authors' affiliations (the Chinese Academy of Agricultural Sciences and the International Rice Research Institute) are from the paper's author list; the lesson's short name, "the IRRI paper", is this course's.
5. S. Renzetti and colleagues, "Hydrogen bond density and glass-transition temperature govern gelatinization and gel rheology in cereal and tuber starches", Current Research in Food Science 10, 2025, 101101 . Read level: the introduction, directly. Supports: the description of granules taking up water, swelling and rupturing.
6. America's Test Kitchen (Cook's Illustrated), "Nailing the Perfect Ratio of Water to Rice", 10 April 2019, https://www.americastestkitchen.com/articles/1692-nailing-the-perfect-ratio-of-water-to-rice . Read level: full, directly. Supports: the 17-variety sealed-bag test and its result, brown rice's longer time and greater evaporation, the factors in evaporation, doubling, and "set-in-stone ratios fail the home cook".
7. America's Test Kitchen, "Fluffy White Rice" (2007), "Everyday White Rice" (2018) and "Basic White Rice" (2013), recipes, https://www.americastestkitchen.com/recipes/1542-fluffy-white-rice , /11284-everyday-white-rice , /5035-basic-white-rice . Read level: all three in full, directly. Supports: 1 to 1½ and 2 to 3, the scaled-up water and the warning against halving, toasting in fat, resting covered 10 to 15 minutes, the towel under the lid (Fluffy White Rice while cooking, Basic White Rice for the rest), the stated reason for the rest, and rinsing to remove surface starch. That this course found no test of resting is the course's own statement.
8. Sawyer Hill, "Do You Really Need to Rinse Your Rice?", America's Test Kitchen, 26 October 2021, https://www.americastestkitchen.com/articles/3946-do-you-really-need-to-rinse-your-rice . Read level: full, directly. An interview; the quoted answers are Matt Slem's, of Lundberg Family Farms. Supports: rinsing and stickiness, and brown rice.
9. P. J. Gray, S. D. Conklin, T. I. Todorov and S. M. Kasko, "Cooking rice in excess water reduces both arsenic and enriched vitamins in the cooked grain", Food Additives & Contaminants: Part A 33(1), 2016, 78 to 85, PMID 26515534 . Read level: abstract. Supports: the design as the abstract describes it, rinsing's minimal effect on arsenic, enriched nutrients washed out, 40, 60 and 50%, and 50 to 70% of added nutrients.
10. City & Guilds, Level 2 Diploma in Professional Cookery (7100-12), qualification handbook v1.6, February 2023 . Read level: the handbook, directly, for the units cited. Supports: the four rice methods and their examples. The descriptions of pilau and risotto that follow are this course's, apart from ATK's toasting step.
11. NHS, "Storing and reheating food" (weaning), https://www.nhs.uk/best-start-in-life/baby/weaning/safe-weaning/storing-and-reheating-food/ . Read level: full. Supports: the same rice rule for babies' food.
12. USDA FSIS, "Leftovers and Food Safety", last updated 31 July 2020, read through the Internet Archive . Read level: full. Supports: hot food straight into the fridge, shallow containers, 3 to 4 days, 165°F.
13. USDA FSIS, "Danger Zone (40°F - 140°F)", last updated 28 June 2023, read through a 2026 Internet Archive capture . Read level: full. Supports: the 2-hour and 1-hour rules.
14. Food Standards Agency, "Cooking your food", GOV.UK, https://www.gov.uk/government/publications/cooking-your-food/cooking-your-food . Read level: full. Supports: leftovers within 48 hours.
15. America's Test Kitchen (Cook's Illustrated), "Salty Soak for Beans", no author or date, https://www.americastestkitchen.com/cooksillustrated/how_tos/5803-salty-soak-for-beans . Read level: full, directly. Supports: the formula, draining and rinsing, the sodium mechanism and its partway effect. The 1.4% is this course's arithmetic, with note 25.
16. America's Test Kitchen (Cook's Illustrated), "Can Baking Soda Make Beans Cook Faster?", 22 May 2019, https://www.americastestkitchen.com/articles/1745-can-baking-soda-make-beans-cook-faster . Read level: full, directly. Supports: every figure in the chart, the method, the explanation, the timing of acid and tomatoes, and the warning about too much baking soda.
17. Cook's Country (America's Test Kitchen), "Adjusting the Cooking Time of Dried Beans when Making Chili", no author or date, https://www.americastestkitchen.com/cookscountry/how_tos/6563-adjusting-the-cooking-time-of-dried-beans-when-making-chili . Read level: full, directly. Supports: acidic tomatoes in chilli slowing beans, and the age of beans.
18. NHS, "Beans and pulses in your diet", https://www.nhs.uk/live-well/eat-well/beans-and-pulses-nutrition/ , versions reviewed 15 May 2015 and 26 July 2021, read through Internet Archive captures of 28 May 2018 and 19 March 2022; the live URL now redirects to the NHS's "page removed" notice . Read level: both versions in full, directly. Supports: the 12 hours, 10 minutes and 45 to 60 minutes of the 2015 version, and the 2021 version's wording.
19. Colorado State University Extension, "Cooking Dry Beans", reviewed October 2025, https://extension.colostate.edu/resource/cooking-dry-beans/ . Read level: full, directly. Supports: 1 to 3 hours on the stove, soaking as optional and what it helps, lentils, refrigerating a soak beyond 12 hours, salt in the soak, and the 10-minute boil before a slow cooker.
20. Julie Garden-Robinson, "Field to Fork: Pressure Cook Dry Beans to Save Money and Time", NDSU Extension FN1939, reviewed July 2024, https://www.ndsu.edu/agriculture/extension/publications/field-fork-pressure-cook-dry-beans-save-money-and-time . Read level: full, directly. Supports: soaking in the fridge beyond four hours and its stated reason (Stage 4 note, lesson 9), and that it tested three brands and gives kidney bean times without mentioning the toxin.
21. Harold McGee, "How Much Water Does Pasta Really Need?", New York Times, 25 February 2009, read through a full-text copy hosted by Wekiva Culinary, https://www.wekivaculinary.org/wp-content/uploads/2020/04/NYTimes-22How-Much-Water-Does-Pasta-Really-Need22.pdf . Read level: full, directly. Supports: the standard advice, where he found it and its reasons, both tests, the mechanism, Bastianich's and Hazan's views, attention and capellini, the boiling-start alternative, the creamy coating, and reducing salt with water.
22. Lan Lam, "Want to Cook Pasta Faster? Don't Wait for the Water to Boil", America's Test Kitchen, 28 April 2023, https://www.americastestkitchen.com/cooksillustrated/articles/7181-start-pasta-in-cold-water . Read level: full, directly. Supports: the test, 75% less water, as much as 45 percent less time, fresh and filled pasta untested, and the salt in the method.
23. Scott Kathan, "Making Your Pasta Water Work for You", America's Test Kitchen, 4 April 2022, https://www.americastestkitchen.com/articles/5284-making-your-pasta-water-work-for-you . Read level: full, directly. Supports: salting generously, "Salty like the sea", oil, stirring, and cooking water as a thickener. The advice on rinsing for cold dishes is this course's, as the body says.
24. NOAA Ocean Service, "Why is the ocean salty?", last updated 23 September 2026, https://oceanservice.noaa.gov/facts/whysalty.html . Read level: full, directly. Supports: 3.5 percent by weight.
25. USDA Agricultural Research Service, Nutritive Value of Foods, Home and Garden Bulletin 72, revised October 2002, https://www.ars.usda.gov/arsuserfiles/80400525/data/hg72/hg72_2002.pdf . Read level: the salt row, directly. Supports: 6 g per teaspoon of salt. The percentages for McGee's water, ATK's cold start and ATK's brine, the 12 teaspoons and 0.25% in the quiz and checkpoint, and the checkpoint's 0.95%, are this course's arithmetic from it.
26. America's Test Kitchen, "How to Cook Rice in an Instant Pot (or Other Pressure Cooker)", no author or date, https://www.americastestkitchen.com/how_tos/11684-how-to-make-rice-in-a-pressure-cooker . Read level: full, directly. Supports: the extra half cup of water in a covered pot. That this is where the stovetop 1 to 1½ comes from is this course's arithmetic (1 cup plus ½).
27. Lisa Peterson, "Kidney Beans and Slow Cookers", University of Illinois Extension, Live Well. Eat Well. blog, 29 February 2024, https://extension.illinois.edu/blogs/live-well-eat-well/2024-02-29-kidney-beans-and-slow-cookers . Read level: the sentence quoted, directly. Supports: cannellini as white kidney beans with about a third of red kidney beans' toxin.