25Preserving: cure, smoke, pickle, can, dry, freeze

Fresh food is mostly water, and that is why it spoils. Microbes (bacteria, molds and yeasts) grow on it, the food's own enzymes keep working, oxygen reacts with it, and it dries out. Every method of preserving takes away one or more of the things harmful bacteria need, summed up as FATTOM: food, acid, temperature, time, oxygen and moisture.

• Take away moisture and you have drying and salting.
• Add acid and you have pickling.
• Shut out oxygen and you have canning or a seal of fat.
• Drop the temperature and you have freezing.

Each of those methods can fail, and some failures make people very ill. The most feared is botulism, a poisoning caused by Clostridium botulinum, a germ that grows without air, for example in food that was canned the wrong way and then eaten without further cooking. The rules below are worth following exactly. FATTOM, the danger zone and the temperatures for cooling and reheating are taught in full earlier. see chapter 2: What bacteria need: FATTOM

25.1 Curing, brining and smoking

An old craft

Meat and fish were very likely the first foods people learned to keep. Before they had fire, people probably dried meat; once they had fire, smoke could be added as well. Taking out moisture cut down the harmful bacteria, and that may have been the first step towards what is now called food safety.

Salt came next in importance. In the first century, the Greek geographer and historian Strabo wrote about houses in ancient Greece and Rome where fish was salted. Salt held back microbes and drew out water, so people had protein to eat in an age with no refrigerators. Today the goal is less about survival and more about the cured meats people enjoy, but the need to stop harmful bacteria is the same.

What a cure does to meat

A cure is made from salts, sugars and spices, and today also chemicals such as nitrates and nitrites. Four processes do the work:

• Osmosis. Water, salt and flavor move into the cells of the meat through their walls, while water, albumen and blood move out.
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• Dehydration. As the cure moves in, the meat loses moisture. Salt duck legs with quatre épices for duck confit, and water and blood soon drip into the pan beneath.
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• Denaturing. Acid changes the protein without heat. Fish or shrimp left in an acid dressing turns from see-through to opaque white. Ceviche is fish or shellfish marinated in lemon and lime juice this way. Raw marinated fish should still be cooked to make it safe.
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• Fermentation. Enzymes in the food break proteins down into gases and other compounds. Salt keeps this under control; without it the food would simply rot. As cured meat ages, the enzymes make it more tender, and the acid that builds up helps to preserve it. Kombucha, yogurt, sauerkraut and cured meats are all fermented.
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As the cure works, the meat loses water and grows firmer. With bacon and ham, that is the point at which smoking begins.

Keeping bacteria out with fat

Fat can preserve meat too, because it shuts out oxygen. For confit, duck is cooked in the fat that comes from the duck itself; as it cools, that fat sets around the meat and seals it. Rillettes are boned meat, stewed and then beaten to a paste with a mixer's paddle, mixed with melted fat and covered with more of it; they are eaten on toast. Tuna can be kept in oil in much the same way, and some chefs now keep tomatoes and red onion in fat or oil. Be careful with vegetables in oil: fresh garlic in oil is a potentially hazardous food.

Dry cures and wet cures

Salt pulls water out of meat, and bacteria need water to live. A cure also makes the meat a poor place for bacteria to grow. There are two kinds of cure:

• Dry cure: dry salt and sugar. Do not confuse it with a barbecue rub. A dry cure often buries the meat completely and may work for days, depending on how thick the piece is. In Europe, legs of wild boar are commonly buried in salt for close to two weeks.
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• Wet cure, also called a brine: salts, sugars and spices in water. The brine is often boiled first to draw more flavor from spices such as cloves, cinnamon sticks and allspice.
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Time depends on thickness. A thin slice cures in hours; a whole bone-in ham takes weeks. Check the meat often, so it is cured evenly all through and taken out before it has gone too far to eat.

Many older recipes use more salt than sugar, about 60 parts salt to 40 parts sugar. Many chefs now turn that round and use more sugar than salt, for example in brines for barbecued pork. Country ham is mostly cured with salt; city ham is mostly cured with sugar. Sugar for curing need not be white sugar: molasses, honey, maple syrup and corn syrup all work.

Curing agents

Besides plain salt and sugar, cooks use four curing agents:

• Unrefined salt.
• Saltpeter, which is potassium nitrate.
• Prague Powder I is also called tinted curing mix (TCM), pink powder or pink salt. It is 94% sodium chloride (salt) and 6% sodium nitrite. It is strong: 4 ounces cures 100 pounds of meat. It is dyed pink so that no one mistakes it for ordinary salt. Cooks favor it for bacon, deli meats, sausages and forcemeats; it keeps the meat's red color, and it protects against botulism. It is commonly used in hot smoking, at 185°F to 285°F.
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• Prague Powder II contains nitrate as well as nitrite: by weight it is 90% sodium chloride, with 6% sodium nitrite and 4% nitrate. It is needed for meat that will never be cooked, such as hard salami. It guards against botulism during the long weeks the meat hangs and dries at changing temperatures and humidity, and under controlled conditions it needs as long as six weeks to break down.

Sodium erythorbate and sodium ascorbate are sometimes added to cured meats, but they are not curing agents. Some products are now sold made with no curing agents at all, labeled, for example, as uncured pepperoni.

Getting ready to smoke

Smoke adds flavor, and it can also be part of what makes a food keep longer, as with country hams. A business that wants to make and sell smoked foods may need a variance (special permission) from its local food safety authority.

Read the recipe, because there may be steps between curing and smoking. A ham cured with blackstrap molasses, for example, is soaked in water in the cooler for 8 hours to draw out some of the salt. Next it is patted dry and goes back into the cooler, for some hours or up to a night, until it forms a pellicle: a thin, tacky skin on the surface. Smoke sticks to the pellicle and gets into the meat. Meat that goes into the smoker wet just collects a layer of soot that wipes off with a finger.

The smoke ring

Raw meat is red or pink because of a protein called myoglobin, which turns brown as the meat cooks. If enough nitric oxide from the wood smoke settles on the meat, it binds to the myoglobin that is still red and keeps it that color. That pink layer is the smoke ring. Moisture on the surface helps the gas settle, so cooks spray the meat or set a pan of water in the smoker. Guests like a smoke ring, but some barbecue competitions give it no extra points.

Cured sausages, and why every smoked sausage is cured, are covered with meat. see chapter 11: Fresh, cured and smoked

25.2 Charcuterie: forcemeats, terrines and pâtés

Charcuterie is the craft of making sausages, fresh and dried, as well as rillettes, terrines, pâtés and galantines; the word can also mean the people who make them. It comes from the French chair, flesh, and cuite, cooked.

Charcuterie makes good use of the cheaper, tougher cuts from low on the animal. The saying "eating high off the hog" refers to the costly, tender cuts higher up. Tough cuts are made pleasant to eat by braising them slowly or by grinding them. Sausage, its six basic parts, its casings and grinding are taught with meat. see chapter 11: What sausage is

Forcemeats

Decide first what texture you want. A rustic country pâté should be coarse and chewy, so grinding may be enough. A smooth one needs processing, puréeing and sieving. Two rules hold for every kind: keep the equipment cold, and taste before you cook the whole batch.

There are four kinds of forcemeat:

• Straight. Pork and pork fat, plus an equal amount of the main meat. The meat and fat are cubed, seasoned and cured, rested cold, then ground through a coarse die and again through a smaller one. This is called progressive grinding. Some cooks grind through a medium die and then finish the mixture in a mixer or food processor. Raw egg can help it bind, and heavy cream makes it smoother and richer. Keep the emulsion cold over ice baths as you work. Straight forcemeats fill pâté en croûte, terrines and galantines.
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• Country style. Coarse and boldly flavored, usually pork, pork fat and liver with other garnish ingredients; one country pâté was made mostly of mushrooms. Grind everything once through the coarse die. Keep some of it back, and grind the rest again through the medium die. Mix that twice-ground part with a panada (a binder of starch and liquid), then fold the two grinds together. The panada holds them together during and after cooking.
• Gratin. Close to a straight forcemeat, except that the meat, usually liver, is seared lightly first for color and deeper flavor. Work in small batches in a hot pan, and do not cook the meat through. Set each batch aside and leave the browned bits (the fond) in the pan. Some recipes then cook finely diced shallot or onion in the fond and flame it with brandy. Chill everything, then process it like a straight forcemeat.
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• Mousseline. Very light, made from lean white fish, chicken, veal or shellfish, with cream and egg to make it airy. Process the diced meat with the salt to a paste, then add the egg white, then the cream. Scrape the bowl down so the mixture is even, and stop as soon as it is smooth; it is quickly overworked. Scallops hold more water, so add the cream to them with care. A very fine mousseline can be pressed through a drum sieve called a tamis; with rabbit, the tamis also catches the sinew.
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A standard mousseline ratio, to be checked against your recipe:

Test before you fill. Cook a small amount and taste it, so you can fix the seasoning. Cook the test the same way as the finished dish. For a poached galantine, shape a spoonful into a small log inside plastic wrap, tie it off at both ends, and poach that. A test fried in a pan browns, and the browning changes the taste. Tasting is taught earlier. see chapter 6: Tasting like a cook: the senses

Terrines

A terrine is a pâté made in an earthenware mold. It may be baked in a water bath, or, as with a cold vegetable terrine, built up in layers of aspic. Any kind of forcemeat can become a terrine. Some are lined with plastic wrap so they come out of the mold easily; others are wrapped in bacon, ham or vegetables for flavor and looks. A terrine en croûte is baked inside a pastry crust. A terrine is sliced from the loaf, or, like rillettes, served as a single portion; it is usually its own course, alone or with a salad.

• Line the mold. Use thin slices of fatback, bacon, ham or prosciutto, blanched green leek leaves, caul fat, or plastic wrap. For plastic wrap, spray the inside of the mold lightly with water, lay the film in, and press it into the corners with a towel or brush. Leave no air between the lining and the mold.
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• Fill it. Pipe a fine mousseline in from a pastry bag. A country pâté can be thrown in by the handful, which packs it and drives out air; a spatula also works. Fold the lining over the top, tap the mold on the table to bring up trapped air, and put on the lid.
• Cook it in a bain-marie (a water bath), which shields the forcemeat from harsh heat. Lay a towel in a hotel pan, set the covered mold on it, and pour in simmering water most of the way up the mold's sides. Hold the water at 165°F, with the oven at about 300°F.
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• Cook to a safe internal temperature. Ground meat, including ground pork, beef and fish, must reach 70°C (158°F); poultry, and any food mixture containing poultry, eggs, meat or fish, must reach an internal 74°C (165°F) held for 15 seconds or longer. Cook the terrine until it reaches that internal temperature: 165°F for poultry.
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• Cool, press and chill. Cooked food must drop from 60°C (140°F) to 20°C (68°F) in two hours or less, then on down to 4°C (40°F) in no more than four further hours. Take the terrine out of the water bath and leave it on the table until it falls to 90°F, then set a wrapped plate on top with a 2-pound weight and refrigerate it.
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• Let it mature. Leave the terrine in the refrigerator for several days so the flavor develops, then coat it in aspic, or slice it and dip the slices. Food held in the cooler more than 24 hours is marked with the date it was made and a "serve by" date, and potentially hazardous foods still unused three days after they were made should generally be discarded.
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Terrines bound with aspic. Here the main ingredients are the stars, so season them well. Make the aspic from a well-flavored stock, keep it clear, and use only as much as you need between the layers. Set the mold in an ice bath and let each layer of aspic set firmly before you add the next, or the layers will slide apart. The aspic works like mortar between bricks.

Galantines

A galantine is nearly always chicken: the white meat is wrapped around a forcemeat of the dark meat (often with pork and fat), rolled into a log, and wrapped in the bird's own skin. A second wrap of cheesecloth or plastic goes round it; then it is poached, chilled, sliced, coated with aspic, and served on a platter coated with a decorative layer of aspic. Poaching is taught earlier. see chapter 9: What poaching is

• Get your mise en place ready.
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• Cut along the back and take off the skin in one piece. Square it off and lay it inside up.
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• Bone the bird: take out the tenderloins and the breast, and bone the legs. Keep the bones for stock, and pull the tendons from the tenderloins.
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• Pound the tenderloins to an even ¼ inch, and arrange the breast meat along the long side.
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• Mix the ground chicken with the spices and pork, and chill it. Process it with some ice into a smooth emulsion.
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• Spread forcemeat over the breast, lay the tenderloins on as a garnish, and cover with more forcemeat.
• Move the galantine onto plastic wrap and roll it up tightly, pressing out the air. Twist and tie the ends.
• Poach it. Poultry must reach an internal 74°C (165°F) for 15 seconds. Poach the galantine to that 165°F.

25.3 Aspic

Where aspic came from

Aspic is a savory jelly made by setting a well-flavored stock with gelatin. Meat aspics came before jellies flavored with fruit or vegetables. No later than the Middle Ages, cooks had found that a thickened meat broth could be turned into a jelly, and Le Viandier, written around 1375, gives a full recipe.

In the early 1800s, the French chef Marie-Antoine Carême created chaud-froid, French for "hot cold": a dish cooked hot but eaten cold. Aspic served as a chaud-froid sauce on cold fish and poultry, adding moisture and flavor, and Carême invented many kinds of aspic. In the United States, aspic became prominent in the early 1900s and was a dinner staple by the 1950s. During the Second World War, when rationing made meat scarce, tomato aspic filled the gap.

What aspic is used for

Aspic is also called aspic gelée or aspic jelly. It can be clear (white aspic) or any shade of amber. It does three jobs: it shields food from the air so it does not dry out, it adds flavor, and it decorates.

In the mouth, the cold jelly melts back into a sauce. Its uses:

• The early garde mangers in France used it to make a chemise (a "shirt"), a coat of aspic on a serving platter.
• It coats terrines, pâtés and galantines.
• It binds headcheese.
• Cut into shapes, it garnishes deli meats and pâtés.
• Food dipped in it gets a glossy, lacquered finish, which is why it is used to glaze dishes for cooking competitions.

There are three kinds:

• Delicate aspic is soft.
• Sliceable aspic is firmer and must be set in a terrine or an aspic mold.
• Inedible aspic is for decoration only, never for eating.

Aspic and chaud-froid

Aspic is gelatin added to a flavorful stock. Chaud-froid is gelatin added to a warm sauce such as béchamel, demi-glace or velouté.

• Clarify the stock the way you would for a consommé, so the aspic is not cloudy.
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• Soften (bloom) powdered gelatin in cool water, then warm it until the granules melt away.
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• Add the gelatin to the warm stock, in the amount the job calls for (see the table).
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• Cool it over an ice bath until it thickens. Aspic left to set can be cut up as a garnish, or warmed again later to coat a platter or a cold pâté.

How gelatin sets is explained in the chapter on heat. see chapter 7: Hydrocolloids

Building a cold platter

Cut the terrine or galantine into slices of equal size, and keep back one piece whole: the grosse pièce, the centerpiece of the platter. Coat the slices and the grosse pièce in aspic. Lay the slices in an overlapping line leading from the grosse pièce, so the eye travels to the center.

Decorate the platter first:

• Set it level and cold.
• Brush on a little aspic and stick the garnish to it.
• Pour over aspic that has cooled slightly.
• Let the jelly firm up before you set the grosse pièce and the slices on top.
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An aspic made from meat or fish stock is a food of animal origin, and so a potentially hazardous food. Keep it, and the dishes it coats, at 4°C (39°F) or colder.

25.4 Condiments, relishes and canning

Condiments

Strictly, a condiment is anything added to food for flavor, herbs, spices and vinegars included. Today the word usually means a prepared flavoring served alongside food: mustard, relish, bottled sauces, pickles. The guest uses as much or as little as they like. A condiment brings a bold note, tart, salty, spicy or sharp, to the food it is served with. Mustards, ketchups, chutneys, relishes, pickles and compotes are the garde manger's building blocks.

• Mustard is crushed mustard seed mixed with vinegar or wine and salt or spices. Its bite comes from an oil that forms only when crushed seed meets water. It may be smooth or grainy, depending on how fine the seed is ground and whether the hulls are strained out. Dijon mustard is smooth and complex, and French mustard sold as "Dijon" must come from that region. English and Chinese mustards, made from mustard flour and cool water, are very hot; American "ballpark" mustard is mild, sharp with vinegar, and bright yellow. Unless it has a lot of oil in it, mustard does not really spoil; it only loses flavor. In the kitchen it coats lamb under breadcrumbs before roasting, helps vinaigrette and mayonnaise hold together, and makes a dip or a sandwich spread.
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• Ketchup once meant any salty extract of fish, fruit or vegetables. Today's tomato ketchup is an American sauce, thick and sweet-sour. It can be kept in the refrigerator or at room temperature, and keeps well for up to four months once opened, though it darkens and loses flavor as it ages. Many chefs make their own. A good bought ketchup can also be the base of a cocktail sauce, with horseradish sauce and lemon juice added.
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• Chutney is a sharp relish of fruit, spices and herbs, much used in Indian cooking. Major Grey's is a well-known sweet-sour chutney of fruit, ginger and spices, served with meats such as duck and lamb. India also makes chutneys from vegetables.
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• Fish sauce is the liquid drained from salted, anchovy-like fish as they ferment, thin and golden to light brown, very pungent and salty. It is essential across Southeast Asia. Fermented black bean sauce is Chinese, made from black soybeans that are heavily salted, fermented, then left whole or puréed.
• Compotes are usually fruit cooked in syrup and served with sweet dishes, but a savory compote can be served with a pâté or terrine.

Relishes are usually served cold, on or beside something hot: a hot dog topped with pickle relish, or black-eyed peas topped with chow-chow, a relish made from cabbage, bell pepper, onion and tomato, in the American South. Cranberry relish, curried onion relish and red onion confit are other examples.

Pickles turn up all over the world, made from vegetables, eggs, fruit (as in Italian mostarda) and even pig's feet. Cucumber pickles can be sweet, hot or sour, and whole, sliced or chopped into relish: a sour relish is dill relish, a sweet one is sweet relish. Bread and butter pickles and pickled okra are Southern favorites.

Vinegar for pickling

Vinegar forms when bacteria turn the alcohol in wine or another alcoholic liquid into acetic acid; no alcohol is left at the end. Good vinegar is clear, never cloudy. Distilled vinegar, made from grain alcohol, is clear, with a stronger taste and more acid than other vinegars, and it is the one preferred for pickling and preserving. Commercial vinegar is pasteurized, so an unopened bottle lasts indefinitely somewhere cool and dark; opened and tightly capped, it lasts about three months. Strain out any sediment, but throw vinegar away if mold grows in it.

Why canning works, and how it fails

Canning began as a way to keep a big harvest beyond its season. Done properly, it removes oxygen, destroys the food's enzymes, stops bacteria, yeasts and molds, and leaves a strong vacuum in the jar. A good vacuum makes a tight seal that keeps liquid in and air and microbes out. The practices that achieve it:

• Choose fresh food carefully and wash it.
• Peel some foods.
• Hot-pack many foods.
• Add acid, such as lemon juice or vinegar, to some foods.
• Use proper jars and self-sealing lids.
• Process the jars in a boiling-water canner or a pressure canner for the right length of time.
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The danger is botulism, a deadly food poisoning. Clostridium botulinum lives as spores, a kind of seed, in soil and water and on most fresh food. Spores are harmless where there is air. Sealed in a jar, they grow into active cells when they have:

• moist food
• food that is low in acid
• a temperature between 40°F and 120°F
• less than 2 percent oxygen

Within 3 to 4 days those cells can produce a deadly toxin. Even a taste of food containing the toxin can kill.

Washing removes few microbes from food; peeling roots, tubers and tomatoes removes many, and blanching helps. What really controls them is the canning method, and following the research-tested process times published by the USDA (the United States Department of Agriculture) in its Complete Guide to Home Canning.

Acid decides the method

Acidity is measured as pH: the lower the number, the more acidic the food. The line that matters is pH 4.6.

• Acid can be natural, as in most fruit, or added, as in pickles. Lemon juice, citric acid or vinegar raise the acidity.
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• A mixture of low-acid and acid foods is usually low-acid too, unless its recipe adds enough lemon juice, citric acid or vinegar to make it an acid food.
• Some tomatoes, and figs, sit just above pH 4.6. To can them in a boiling-water canner, acidify them first, with lemon juice or citric acid, to pH 4.6 or lower.

Botulinum spores are very hard to kill at the temperature of boiling water; the hotter the canner, the easier they die. Low-acid foods are therefore sterilized at 240°F to 250°F, which a pressure canner reaches at 10 to 15 pounds per square inch on its gauge (PSI). A pressure canner is the only recommended way to can meat, poultry, seafood and vegetables. Canning them in boiling water carries a real risk of botulism. Pressure itself kills nothing; the high temperature, held long enough, does. At sea level, a canner at 10.5 pounds of gauge pressure is 240°F inside. Acid foods can go in a pressure canner, but a boiling-water canner is recommended for them because it is faster.

The exact time depends on the food, how it is packed, and the size of the jar, so take every time from a tested, up-to-date recipe for that food, jar and altitude.

What not to do

These are not recommended, because they do not remove every risk of spoilage:

• Open-kettle canning.
• Processing jars in an ordinary oven, a microwave or a dishwasher.
• Pressures above 15 PSI in new pressure canning equipment.
• "Canning powders". They preserve nothing and do not replace heat processing.
• Jars with wire bails and glass caps; one-piece zinc caps lined with porcelain; and zinc caps that seal with flat rubber rings.
• Small pressure saucepans.

Jars, lids and headspace

Use regular or wide-mouth Mason-type home-canning jars with self-sealing lids. Sizes run from ½ pint through pint, 1½ pints and quart up to ½ gallon; ½-gallon jars are only for very acid juices. With care a Mason jar can be used many times, with a new flat lid each time. Commercial mayonnaise jars can take acid foods in a boiling-water canner with new two-piece lids, but expect more seal failures and breakage, and never put them in a pressure canner.

The lid is a flat metal disc held on by a screw band. A ring of sealing compound under the disc softens in the canner, lets air out, and seals as the jar cools. Unused lids seal well for at least 5 years from when they were made. Buy only a year's supply, and never use old, dented or misshapen lids. The flat lid seals only once; the screw band can be used again until it rusts.

Cleaning and sterilizing jars.

• Wash jars in hot water and detergent and rinse them well, or run them through a dishwasher; leftover detergent can taint the food. Washing does not sterilize.
• To lift hard-water scale, soak jars for several hours in 1 cup of vinegar (5 percent acidity) to each gallon of water.
• Jams, jellies and pickles processed for less than 10 minutes must go into sterilized jars: stand the empty jars upright on the rack of a boiling-water canner, cover them with hot water to 1 inch over the tops, and boil 10 minutes below 1,000 feet of altitude, adding 1 minute for each further 1,000 feet.
• Jars for the pressure canner, and for foods processed 10 minutes or more in boiling water, need no sterilizing first.

Raw pack and hot pack

Fresh food holds a great deal of air, from 10 percent to over 30 percent, and the more air is driven out before sealing, the longer the canned food stays good.

• Raw pack: unheated food packed tightly into the jar. Fruit packed this way floats, and the trapped air can discolor it within 2 to 3 months. Raw packing suits vegetables for the pressure canner better.
• Hot pack: food brought to a boil, simmered 2 to 5 minutes, and packed loosely while hot. It drives out air, shrinks the food so more fits, stops floating, and gives a stronger vacuum. It is the preferred pack for the boiling-water canner.

With either pack, bring the juice, syrup or water to a boil before pouring it in.

To keep cut apples, apricots, nectarines, peaches and pears from darkening while you fill a canner load, hold them in cold water treated with ascorbic acid, 3 grams to the gallon. A level teaspoon of pure powdered ascorbic acid weighs about 3 grams; six crushed 500-milligram vitamin C tablets also make a gallon. Browning in cut fruit is explained with fruit. see chapter 18: Color: pigments, acid and browning

Filling and closing a jar

• Fill the jar with hot food and its liquid, leaving the right headspace.
• Free trapped air by sliding a flat plastic spatula, not a metal one, between food and glass and moving it up and down as you turn the jar. Jams, jellies and juices need no bubbling.
• Wipe the rim with a damp paper towel; a dirty rim can stop the seal.
• Put on the heated lid, compound side down, and screw the band on as the maker directs, fingertip-tight. Too loose, and liquid escapes and the seal may fail; too tight, and air cannot vent, the food discolors, and lids may buckle or jars break.
• Never tighten the bands again after processing.
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The boiling-water canner

The canner needs a rack and a lid, and must be deep enough for briskly boiling water to stand at least 1 inch over the jars. On an electric range it must have a flat bottom and be no more than 4 inches wider than the element.

• Fill the canner about halfway with clean water, enough for a load of pints.
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• Heat the water to 140°F for raw-packed food or 180°F for hot-packed food.
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• Lower the filled, lidded jars in on the rack, or one at a time with a jar lifter held below the band. Keep each jar upright.
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• Add boiling water to at least 1 inch above the jar tops, or at least 2 inches for processes longer than 30 minutes.
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• Cover, turn the heat to high, and start timing only when the water boils hard.
• Keep it boiling the whole time. If the boil stops, bring it back to a hard boil and start the timing again from zero. Top up with boiling water to keep the jars covered.
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• At the end, turn off the heat, take off the lid, and wait 5 minutes.
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• Lift the jars out onto a towel, at least 1 inch apart, and leave them undisturbed to cool for 12 to 24 hours.
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The pressure canner

A pressure canner has a rack, a gasket, a dial or weighted gauge, a vent port and a safety fuse. Two errors make it run cooler than it should, and both lead to under-processed food:

• Altitude. The higher you are, the lower the temperature inside, so the canner must run at the higher pressures the USDA guide sets for each altitude. A weighted gauge cannot be fine-tuned: above 1,000 feet, a process set at 5 PSI must run at 10, and one set at 10 must run at 15.
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• Trapped air. Air in the canner lowers the temperature at any pressure. Every pressure canner must be vented for 10 minutes before it is brought up to pressure.

Look after the canner itself:

• Have a dial gauge checked for accuracy every year. A gauge that reads high leads to under-processing and unsafe food.
• If it is up to 2 pounds out, the pressure can be adjusted; if it is more than 2 pounds out, replace it.
• Use only canners with Underwriters Laboratories (UL) approval.
• Do not pick at the safety fuse when cleaning.
• Pour hot water into the canner to a depth of 2 to 3 inches, or more if the food's process calls for it. Set the jars on the rack with a jar lifter, upright, and fasten the lid.
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• Leave the vent open and heat on high until steam flows freely.
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• Let the steam flow for 10 minutes, then close the vent with the weight or petcock. The canner comes up to pressure over the next 3 to 5 minutes.
• Start timing when the dial shows the right pressure, or the weight starts to jiggle or rock as the maker describes.
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• Keep the pressure steady, at or just above the target. If it drops below the target at any point, bring it back up and start the full process time again from zero.
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• When the time is up, turn off the heat and let the canner lose pressure by itself. Never cool it with cold water or open the vent early: that can make the food unsafe, pull liquid from the jars and break the seals.
• Once it has lost its pressure, take off the weight or open the petcock, wait 10 minutes, and unfasten the lid. Lift it away from you so the steam does not burn your face.
• Lift the jars out onto a towel, at least 1 inch apart, and leave them undisturbed to cool for 12 to 24 hours.
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Cooling and checking the seals

A hot jar must never go down on a cold surface. Keep the cooling jars out of drafts, but do not cover them to slow the cooling. If a jar lost liquid in the canner, do not open it to top it up; liquid loss is not a sign of spoilage.

After 12 to 24 hours, take off the bands and test each seal in one of three ways:

• Press the middle of the lid. If it springs back up, it has not sealed.
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• Tap the lid with the underside of a teaspoon's bowl. A clear, ringing note means a seal; a dull sound means no seal, or food touching the lid.
• Look across the lid at eye level. It should dip slightly in the middle. Flat or bulging may mean no seal.
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If a lid has not sealed, check the jar rim for tiny chips, use a new lid (and a new jar if needed), and process it again within 24 hours for the full time. Instead, the food can be frozen, with the headspace made up to 1½ inches, or refrigerated, and a single unsealed jar eaten within several days. A stricter limit for a refrigerated unsealed jar is one or two days. For a jar that has a bad seal, throw the food away unless the problem was found within a few hours.

Storing canned food

Before the jars go into storage:

• Take off the bands, wash the jars and lids without disturbing the seal, then rinse and dry them, because unseen residue can grow mold.
• Store them without bands: they stay dry, and a broken seal is easier to spot.
• Label and date every jar.
• Do not stack jars directly on one another more than two layers high, and put a firm support between layers.

A dry storeroom should be cool and dry, ideally between 10°C and 15°C (50°F and 59°F), so food does not spoil and cans do not swell. Store jars somewhere clean, cool, dark and dry, never above 95°F, near hot pipes, a range or a furnace, in an attic or in sunlight. Damp rusts lids and can break seals. Can no more than you will use in a year.

Spoiled jars and botulism

Never taste food from a jar with a lid that has not sealed, or food that shows any sign of spoilage. Check every jar before you use it:

• The lid should still be tight and dip in the middle. A swollen lid or broken seal means gas from spoilage.
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• Turn the jar at eye level and look for streaks of dried food running down from the top, rising bubbles, and odd color.
• As you open it, smell for anything off, and look for liquid that spurts out and for cotton-like mold (white, blue, black or green) on the food or under the lid.

• Still sealed: put the jar in a heavy garbage bag, close it, and put it in the regular trash or take it to a landfill.
• Unsealed, open or leaking: detoxify it first. Wearing disposable rubber or heavy plastic gloves, lay the jars and lids on their sides in a pot of at least 8 quarts. Add water gently, without splashing, to at least 1 inch above them. Cover, bring to a boil, and boil 30 minutes. Cool, then throw away jars, lids and food.
• Clean-up: mix a fresh solution of unscented household bleach (5 to 6% sodium hypochlorite), 1 part, with clean water, 5 parts. Wet every surface, tool and item of clothing that may have touched the food, and leave it 30 minutes. Wipe up with paper towels and bag them before binning. Apply the bleach again, leave it another 30 minutes, and rinse. Then wash everything thoroughly and throw away the gloves. Bleach irritates skin and lungs, so do not breathe it or let it touch you.

Home-canned low-acid food may be eaten without boiling it first only when you are sure of all of these:

• It was processed in a pressure canner used the USDA way.
• The gauge was accurate.
• The process time and pressure were current, tested ones for that jar size, pack and food, and right for your altitude.
• The lid is firmly sealed with a vacuum.
• Nothing has leaked.
• No liquid spurts out on opening.
• There is no off smell and no mold.

For low-acid and tomato foods that were not canned by the USDA's tested methods, even with no sign of spoilage, boil the food in a saucepan before eating it: 10 minutes below 1,000 feet, plus 1 minute for each further 1,000 feet. Boiling means large, foamy bubbles breaking all over the surface. Boil home-canned vegetables at least 10 minutes before anyone tastes them, and never taste them at all if anything seems wrong during cooking.

Making grape jelly

The processing times for this grape jelly are for 1,001 to 2,000 feet above sea level; at any other altitude, take the time from a recent USDA or state extension bulletin.

• Have six half-pint jars, lids and bands ready.
• Mix the pectin, lemon juice and grape juice well in a 6-quart saucepan and bring to a boil, stirring all the time, until bubbles form all round the edge.
• Tip in all the sugar at once and stir. Return it to a full rolling boil, then keep boiling hard and stirring until it reaches 104°C (219°F).
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• Take it off the heat and skim the foam with a metal spoon.
• Pour quickly into sterilized jars, leaving a ¼ inch headspace, and put on hot lids and bands.
• Process at once in a boiling-water bath for 11 minutes. It makes about 6 cups.

How fruit gels with sugar and pectin is taught with fruit. see chapter 18: Preserving: jams and jellies

25.5 Drying

Bacteria need moisture, and they grow fast in moist food, so dry and salted foods carry less risk. Beef jerky, uncooked rice, uncooked beans and flour are among the foods that are not potentially hazardous. Once it is cooked, though, food of plant origin counts as potentially hazardous.

Fruit and vegetables can be dried in a home dehydrator. Work in two sessions some weeks apart: one to treat, dry and pack the food, and one to bring it back to life and judge it.

Treat before drying

Enzymes keep working in cut fruit and vegetables and spoil them, so the food is treated first to hold them back.

• Carrots and onions are washed, trimmed and sliced, then steam blanched: spread thinly in a steamer and steamed until hot in the center, about 3 to 3½ minutes. Compare them with untreated slices.
• Apples are washed, peeled, cored and cut into rings, then dropped at once into one of three soaks for 10 to 15 minutes: nothing (left untreated), 1 teaspoon of salt in 1 pint of water, or 2 teaspoons of ascorbic acid in 1 pint of water.
• Peas get no treatment.

Blanching in general is covered with vegetables. see chapter 17: Blanch first, finish later

Drying and conditioning

• Drain the food and pat it dry. Lay cheesecloth on the dehydrator racks and spread the food on it in a single layer.
• Set the dehydrator at 140°F to 150°F.
• Dry vegetable slices until they are brittle, 3 to 6 hours, and fruit slices until they are leathery and bend without breaking, 6 to 8 hours.
• Put each sample in a labeled zip-top bag.
• Condition the food: keep it a week in a large container with a loose cover, stirring it every day, so the moisture evens out through the batch.
• Pack it into small airtight containers and keep it somewhere cool.

Bringing it back

• Dried carrots: cover with water and soak for at least 20 minutes, adding water to keep them covered. Then cook them like fresh carrots in a little of the soaking water.
• Dried apples: eat them as they are, or cover with water, soak for at least an hour, and simmer in the soaking water until tender.

Then compare each treatment for look, texture and flavor, and look closely at bought dried fruits: apples, apricots, currants, dates, figs, peaches, prunes and raisins. Buying and using dried fruit is covered with fruit. see chapter 18: Preserved fruit

25.6 Freezing

The cold-storage rules

The freezer must hold food at −18°C (0°F) or colder. Freezing does not kill most bacteria: between 0°C and −18°C, most bacteria survive but do not grow. If the freezer warms above −18°C, food can lose color and vitamins, and cooling it down again does not undo the harm.

• Wrap well. Anything not properly wrapped gets freezer burn: it loses moisture, and its texture and flavor suffer. Look for dry white or gray patches on the surface. Meat is especially prone to it.
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• Rotate. Use the oldest stock first (first in, first out). Chest freezers make this hard, because old stock must come out before new stock goes in.
• Count the cost. Frozen fruit and vegetables, well wrapped, keep for months, and so do well-wrapped meat and fish. Freezing fresh produce in the kitchen takes time and may cost too much, and fresh fruit that is not properly prepared will not freeze well.
• Cook with care. Partly frozen meat or poultry can have cold spots that do not cook through. Allow more time and check the inside temperature.

Frozen storage in general is covered in the food safety chapter. see chapter 2: Frozen storage

Freezing fast

To freeze food well:

• Freeze it as soon as it is ready.
• Keep packages apart, not stacked or touching, until they are frozen solid; only then stack them.
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• Label every package with the food, its treatment and the date.
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• Press the air out of bags and seal them tight.
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• Pack small bags together inside a larger freezer bag for protection.

Some of the methods below do not give a standard product; that is the point of trying them.

Fruit: apple slices

Freeze apple slices six ways and compare them:

• dry, with no treatment
• with dry sugar
• steamed 3 minutes
• in a 35% syrup
• in the syrup with a commercial anti-darkening product
• in the syrup, with the fruit sprinkled with lemon juice

For the 35% syrup, boil 2 cups of water with 1 cup of sugar at a rolling boil, then chill it before adding anything else. To judge them, thaw the sealed bags in lukewarm water for 20 minutes.

Vegetables: blanch first

Freeze cauliflower and carrots both blanched and unblanched, and compare them with fresh and canned.

• Wash the vegetables, peel the carrots, and slice or chop.
• Bring at least 1½ quarts of water to a boil for each cup of vegetable. Lower the vegetable in, cover, and keep the heat on high.
• Time from the moment the vegetable goes in: carrots 2 to 3 minutes, cauliflower 3 minutes, or until hot in the center.
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• Lift out with a slotted spoon and chill at once in at least 2 quarts of iced water. Drain well when cool.
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• Bag, press out the air, seal, and freeze at once.
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Prepared foods

Prepared dishes can be frozen too, to show what freezing does to them.

• Fruit pie. One pie is baked, cooled, wrapped in plastic wrap and foil, and frozen; one is frozen unbaked, with no vents cut. The unbaked pie is thawed overnight in the refrigerator, vented, baked at 450°F for 15 to 20 minutes, and finished at 375°F for about 20 to 30 minutes. The baked pie is thawed overnight in the refrigerator and warmed at 350°F for about 35 to 40 minutes, loosely covered with foil so the top does not brown too much.
• Gelatin and cornstarch pudding are frozen in covered plastic containers and compared with fresh. Do not use instant pudding mix.
• Casseroles. For Spanish rice, and for macaroni and cheese, the rice or pasta is cooked slightly short of done, and the dish is frozen unbaked. The frozen Spanish rice bakes covered at 350°F until it bubbles at the edges, about an hour; the macaroni and cheese bakes uncovered in a water bath at 350°F for about 50 to 60 minutes. Some baking dishes cannot go straight from freezer to hot oven; with those, do not preheat the oven.
• Spice cake. One pan of batter is frozen raw and one is baked and then frozen. The frozen batter is thawed overnight in the refrigerator and baked at 350°F for 20 to 25 minutes; the frozen cake is warmed in a heat-proof wrap at 300°F for about 15 to 25 minutes.
• Egg salad is frozen to show what happens to cooked egg white and mayonnaise.
• Ground beef patties are frozen raw and cooked. The recommended wrap is plastic wrap and then foil; wrapping in non-freezer plastic wrap or a bag is not recommended.
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Reheating safely. Food being reheated has to get to 74°C (165°F) or hotter and stay there 15 seconds or more, and on a stove or in an oven it must get there within two hours. Ground meat must be cooked to 70°C (158°F). Cook the beef patties fresh or from the freezer, and reheat the cooked frozen ones to 165°F. Reheat leftovers only once.