Canning Terms Glossary

Along the path to creating something unique, you may see a few terms you’re not familiar with. Let this area serve as your guide to help make things a little easier. Happy creating!

acetic acid

A pungent, colorless liquid acid that is the primary acid in vinegar (vinegar is 5% acetic acid). Acetic acid is what makes vinegar sour.


Any substance in a class of sour compounds.


An ingredient used in older pickling recipes to add crispness and firmness to pickles. Alum, if consumed in large doses, may cause nausea and/or gastrointestinal problems and is no longer recommended for use in pickling recipes. If used, it must be thoroughly rinsed away. The chemical name is potassium aluminum sulfate.


The vertical elevation (distance in feet or meters) of a location above sea level.


A substance, such as citric acid (lemon or lime juice), ascorbic acid (vitamin C) or a blend of citric and ascorbic acids, that inhibits oxidation and controls browning of light-colored fruits and vegetables. Antioxidants are believed to neutralize free radicals, harmful particles in your body that can cause long-term damage to cells and lead to disease.

artificial sweetener

Any one of many synthetically produced non-nutritive sweet substances. Artificial sweeteners vary in sweetness but are usually many times sweeter than granulated sugar.

ascorbic acid

The chemical name for vitamin C, a natural, water-soluble vitamin that is commercially available in a concentrated form as white, odorless crystals or powder. It is used as an antioxidant to inhibit oxidation and control browning of light-colored fruits and vegetables.


Microorganisms, some of which are harmful, found in the soil, water and air around us. Some bacteria thrive in conditions common in low-acid preserved food and produce toxins that must be destroyed by heating to 240°F (116°C) for a specified length of time. For this reason, low-acid foods must be processed in a pressure canner.


See screw band.


To submerge a food in boiling water or steam for a short period of time, done to loosen the skin or peel or to inactivate enzymes. Blanching is immediately followed by rapidly cooling the food in ice water.


To heat a liquid until bubbles break the surface. At sea level, this happens at 212°F (100°C). At elevations above 1,000 feet (305 m), the boiling point is reached at a lower temperature. A boil is achieved only when the liquid is continuously rolling or actively bubbling. See also boil gently or simmer or boil, full rolling.

boil gently or simmer

To cook food gently just below the boiling point (180°F to 200°F/82°C to 93°C). Bubbles rise from the pot bottom, only slightly disturbing the surface of the food.

boil, full rolling

A rapid boil, usually foaming or spurting, that cannot be stirred down, achieved at a temperature of 220°F (104°C). This stage is essential for attaining a gel when making cooked jams or jellies.

boiling point

The temperature at which liquid reaches a boil (212°F/100°C at sea level).

boiling water canner

A large, deep saucepan equipped with a lid and a rack to lift jars off direct heat. The pot must be deep enough to fully surround and immerse jars in water by 1 to 2 inches and allow for the water to boil rapidly with the lid on. If you don't have a rack designed for preserving, use a cake cooling rack or extra bands tied together to cover the bottom of the pot.

boiling water method

The fresh preserving method used to process high-acid foods. Heat is transferred to the food product by the boiling water, which completely surrounds the jar and two-piece closure. A temperature of 212°F (100°C) is reached and must be maintained for the time specified by the recipe. This method is adequate to destroy molds, yeasts and some bacteria, as well as to inactivate enzymes. The boiling water method must not be used to process low-acid foods.


Food poisoning caused by the ingestion of the toxin produced by spores of the bacterium Clostridium botulinum. Botulism can be fatal. The spores are usually present in the dust, wind and soil clinging to raw food. They belong to a species of bacteria that cannot grow in the presence of air, and they do not normally thrive in high-acid foods. The spores can survive and grow in any tightly sealed jar of low-acid food that has not been processed correctly. Using the correct processing temperature and time to preserve low-acid foods will destroy toxin-producing spores.

bouquet garni

A spice bag, or a square of cheesecloth tied into a bag, that is filled with whole herbs and spices and is used to flavor broth, soup, pickling liquid and other foods. This method allows for easy removal of the herbs and spices after cooking.


A salt-water solution used in pickling or when preserving foods. Although salt and water are the main ingredients, sugar and spices are sometimes added.

brined pickles

See fermented pickles.


The unfavorable color change caused when the cut surface of some fruits and vegetables is exposed to the oxygen in the air. The reaction is called oxidation.

bubble remover

A non-metallic utensil used in fresh preserving to remove or free air bubbles trapped inside the jar. To ensure appropriate headspace, air bubbles should be removed before the two-piece closure is applied.


See fruit butter.

calcium chloride

A naturally occurring salt found in some mineral deposits, used as a crisping agent. The food-safe ingredient is added to the jar before processing, or used in a solution with water as a presoak. Calcium chloride is used commercially to produce crisp, firm pickles. See also Pickle Crisp® granules.

candy or jelly thermometer

A kitchen thermometer that usually comes with adjustable hooks or clips to allow it to be attached to the pan. During the preparation of soft spreads without added pectin, it is used to determine when the gel stage is reached (this occurs at 220°F/104°C, or 8°F/4°C) above the boiling point of water). Always insert the thermometer vertically into the jelly and ensure that it does not contact the pot surface.


Either one of two pieces of equipment used in fresh preserving to process jars filled with a food product and covered with a two-piece closure. The two types of canners recommended for use in fresh preserving are a boiling water canner for high-acid foods and a pressure canner for low-acid foods.

canning/preserving liquid

Any one of many types of liquids, such as water, cooking liquid, pickling liquid, broth, juice or syrup, used to cover solid food products. Adding liquid prevents darkening of food exposed to the surface and allows for heat penetration.

canning/preserving salt

See salt, pickling or preserving.


See two-piece closure.


A lightweight, woven cloth that has many uses in the kitchen. For fresh preserving, it can be used in place of a jelly bag to strain juice from fruit pulp when making jelly or homemade juice, or it can be formed into a bag to hold whole herbs and spices during the cooking process, aiding in easy removal.


A combination of vegetables and/or fruits, spices and vinegar cooked for a long period of time to develop favorable flavor and texture. Chutneys are highly spiced and have a sweet-sour blending of flavors.

citric acid

A natural acid derived from citrus fruits, such as lemons and limes. It is available as white crystals or granules and is used as an ingredient in commercial produce protectors to prevent oxidation and in pectin products to aid in gel formation by increasing the acidity of the jam or jelly.


A commercially available modified food starch that is approved for use in fresh preserving. Unlike regular cornstarch, products thickened with ClearJel® do not break down when heated to high temperatures and/or cooled and reheated. ClearJel® can be ordered from online sources or by mail order.


See two-piece closure.


See raw-pack method.


A sweet or savory sauce used to enhance or garnish entrées.


A soft spread similar to jam, made with a combination of two or more fruits, along with nuts and/or raisins. If nuts are used, they are added during the last five minutes of cooking.

cool place

A term used to describe the best storage temperature for fresh preserved products. The ideal temperature is 50°F to 70°F (10°C to 21°C).

crisping agent

Any one of many substances that make pickles crisp and firm. Some older pickling recipes call for pickling lime, alum or grape leaves to crisp pickles, but these are no longer recommended. Using fresh, high-quality produce, the correct ingredient quantities and a current, tested fresh preserving recipe will produce firm pickles without the addition of crisping agents. The texture of some quick-process or fresh-pack pickles, however, can be enhanced with the use of a product called Pickle Crisp® Granules.

cucumber, pickling

A small variety of cucumber used to make pickles. Pickling cucumbers are usually no more than 6 inches (15 cm) in length. Cucumbers deteriorate rapidly at room temperature and should be stored in the refrigerator and used within 24 hours of harvest.


A naturally occurring form of glucose. Dextrose is available as a white crystal or powder and is less sweet than granulated sugar. It is also called corn sugar or grape sugar. Dextrose is widely used as an ingredient in commercial food products. It is found in commercial pectin and produce protectors and functions as a bulking agent or filler.

dial-gauge pressure canner

A pressure canner fitted with a one-piece pressure regulator and a gauge to visually indicate the correct pressure level.


A pungent, aromatic herb that can be used fresh or dried. Fresh dill has feathery green leaves. The most useful dried form is dill seeds. In fresh preserving, dill is primarily used for pickling. One head of fresh dill is equivalent to 1 to 2 tsp (5 to 10 mL) dill seeds or 2 tsp (10 mL) dried dillweed.

E. coli

A species of bacteria that is normally present in the human intestines. A common strain, Escherichia coli 0157:H7, produces high levels of toxins and, when consumed, can cause symptoms such as diarrhea, chills, headaches and high fever. In some cases, it can be deadly.


A protein that acts as a catalyst in organisms. In food, enzymes start the process of decomposition, changing the flavor, color and texture of fruits and vegetables. Enzyme action can be neutralized by following recommended food preservation methods.


See venting.

ethylene gas

An odorless, colorless gas that occurs naturally in nature. It is produced by and released from fruits during the ripening process. In turn, the ethylene gas acts as a ripening agent and, when exposed, speeds up the ripening of under-ripe fruits.


A reaction caused by yeasts that have not been destroyed during the processing of preserved food. Bubble formation and scum are signs that fermentation is taking place. With the exception of some pickles that use intentional fermentation in preparation, do not consume fermented fresh preserved foods.

fermented pickles

Vegetables, usually cucumbers, that are submerged in a salt-water brine to ferment or cure for up to 6 weeks. Dill, garlic and other herbs and spices are often added to the brine for flavoring. Fermented pickles are also called "brined pickles."

firming agent

See crisping agent.


The degree to which screw bands are properly applied to fresh preserving jars. Use your fingers to screw band down until resistance is met, then increase to fingertip-tight. Do not use a utensil or the full force of your hand to over-tighten bands.

food poisoning

Any illness caused by the consumption of harmful bacteria and their toxins. The symptoms are usually gastrointestinal.

fresh-pack pickles

Cucumbers that are preserved in a spicy vinegar solution without fermenting, although they are frequently brined for several hours or overnight. All fresh-pack pickles should stand for 4 to 6 weeks after processing to cure and develop optimal flavor.

fresh preserving

A modern term used to describe the process of preserving fresh produce and freshly prepared foods in glass preserving jars with lids and bands in the presence of heat to destroy microorganisms that cause spoilage. This term is synonymous with home canning.

fruit butter

A soft spread made by slowly cooking fruit pulp and sugar to a consistency thick enough to mound on a spoon and spread easily. Spices may be added.

fruit pickle

Fruit, usually whole, that is simmered in a spicy, sweet-sour syrup until it becomes tender or transparent.


A plastic utensil that is placed in the mouth of a fresh preserving jar to allow for easy pouring of a food product into the jar. Funnels help prevent spillage and waste.


A rubber ring that sits along the inside circumference of a pressure canner lid and comes in contact with the base when locked into place. The gasket provides a seal between the lid and the base so steam cannot escape.

gelling agent

Any substance that acts to form a gel-like structure by binding liquid.

gel stage

The point at which a soft spread becomes a full gel. The gelling point is 220°F (104°C), or 8°F (4°C) above the boiling point of water.


The unfilled space in a fresh preserving jar between the top of the food or liquid and the underside of the lid. The correct amount of headspace is essential to allow for food expansion as the jars are heated and for the formation of a strong vacuum seal as jars cool.

heat penetration/heat processing

See processing.

hermetic seal

A seal that secures a food product against the entry of microorganisms and maintains commercial sterility.

high-acid food

A food or food mixture that contains sufficient acid — naturally or added as an ingredient — to provide a pH value of 4.6 or lower. Fruits, fruit juices, tomatoes, jams, jellies and most soft spreads are naturally high-acid foods. Food mixtures such as pickles, relishes, salsas and chutneys contain added vinegar or citric acid, which lowers their pH, making them high-acid foods. High-acid foods can be safely processed in a boiling water canner.

high-methoxyl pectin

A type of pectin that requires a high sugar content and the presence of acid to produce a gel when making jams and jellies. Powdered and liquid commercial pectin products are usually high-methoxyl.

home canning

The process of preserving fresh or prepared foods in glass jars with two-piece closures, using heat processing to destroy microorganisms that cause spoilage. See also fresh preserving.

hot-pack method

Filling jars with preheated, hot food prior to heat processing. Preheating food expels excess air, permits a tighter pack in the jar and reduces floating. This method is preferred over the raw-pack method, especially for firm foods.


A fresh preserving method in which hot foods are ladled into jars, two-piece closures are applied and the jars are turned upside down (inverted) for a period of time. Since no heat processing takes place, this method is not recommended.


A soft spread made by combining crushed or chopped fruits with sugar and cooking to form a gel. Commercial pectin may or may not be added. Jams can be made with a single fruit or with a combination of fruits. They should be firm but spreadable. Jams do not hold the shape of the jar.


A glass container used in fresh preserving to preserve food and/or liquids. For safe fresh preserving, jars must be designed to seal with two-piece metal closures and to withstand the temperatures and reuse associated with fresh preserving. See also mason jar.


A soft spread made by combining fruit juice or acidified vegetable juice with sugar and cooking to form a gel. Commercial pectin may or may not be added.

jelly bag

A mesh cloth bag used to strain juice from fruit pulp when making jellies. A strainer lined with many layers of cheesecloth may be substituted. Both the jelly bag and cheesecloth need to be dampened before use.

jelly strainer

A stainless steel tripod stand fitted with a large ring. A jelly bag is placed over the ring. The stand has feet that hold it onto a bowl to allow juice to strain from the bag into the bowl.

kosher salt

See salt, kosher.

kPa (kilopascal)

A metric unit of atmospheric pressure (force).

L (liter)

A metric unit of volume. One liter is similar in volume to 1 U.S. quart.

lactic acid

The acid produced during fermentation. The fermentation process converts the natural sugars in food to lactic acid, which, in turn, controls the growth of undesirable microorganisms by lowering the pH (increasing the acidity) of the food product and its environment. Lactic acid also adds a distinctive tart flavor and transforms low-acid foods into high-acid foods that can be safely processed in a boiling water canner.

lemon juice

Juice extracted from lemons that is added to food products to increase the acidity. Lemon juice can also be purchased commercially. In fresh preserving, lemon juice is added to certain foods to increase acidity and ensure proper processing. In some soft spread recipes, especially those prepared with added pectin, the acid in the lemon juice also aids with gelling. The acidity of freshly squeezed lemon juice is variable, depending on the lemon variety and harvest conditions, whereas bottled lemon juice is produced to consistent acidity standards. In recipes that specify bottled lemon juice, it is crucial for the success of the final product not to use freshly squeezed lemon juice. Where bottled is not specified, either freshly squeezed or bottled lemon juice may be used.


A flat metal disc with a flanged edge lined with sealing compound used in combination with a metal screw band for vacuum-sealing fresh preserving jars.


See pickling lime.

long-boil soft spread

A sugar and fruit mixture boiled to concentrate fruit's natural pectin and evaporate moisture until a thick or gelled texture is achieved. Long boiling works best with fruits containing naturally high pectin levels. It yields smaller quantities per amount of fruit used and creates a caramelized fruit flavor. It may require a smaller measure of sugar as an ingredient, but the final cooked-down product isn't necessarily lower in sugar than other products.

low-acid food

A food that contains little natural acid and has a pH higher than 4.6. Vegetables, meat, poultry and seafood are all low-acid foods. Bacteria thrive in low-acid foods. The only recommended and practical means of destroying bacteria naturally found in low-acid foods is to heat the food to 240ºF (116ºC) (at sea level) for a specified time in a pressure canner.

low-methoxyl pectin

A type of pectin that does not require the presence of sugar to produce a gel when making jams and jellies. No sugar needed fruit pectins are usually low-methoxyl.


A soft spread that contains pieces of citrus fruit and peel evenly suspended in transparent jelly. Marmalade is cooked in small batches and brought rapidly to, or almost to, the gelling point. Marmalades are similar in structure to jam.

mason jar

A glass jar that is suitable for heat processing food and/or liquids using a boiling water canner or a pressure canner. Mason jars are designed to seal with two-piece metal closures and to withstand the temperatures and reuse associated with fresh preserving. True mason jars also conform to specific shapes and capacities compatible with established safe heat processing methods and times. The jars are available in regular mouth (70 mm) and wide mouth (86 mm) styles and in capacities ranging from 4 ounces (125 mL) to 1 quart (1 L). Most mason jars have rounded shoulders, but some have straight walls. Straight-walled mason jars can be used for freezing as well as fresh preserving. See also straight walls.

measures or measuring cups

Standard kitchen utensils used to accurately measure liquid or dry ingredients. Liquid measures are commonly glass or plastic and have a handle and a pour spout. Dry measures can be either stainless steel or plastic. Both types are available in imperial (cups) and metric (mL) sizes.

metal band

See screw band.


A living plant or animal of microscopic size, such as molds, yeasts or bacteria, that can cause spoilage in preserved or frozen foods.

mL (milliliter)

A metric unit of volume, 1/1000th of a liter. Measures for dry ingredients are available in 1, 2, 5 and 25 mL spoons and 50, 125 and 250 mL dry measures. Metric liquid measures, usually glass or plastic, show levels for quantities divisible by 10.


Microscopic fungi that grow as silken threads and appear as fuzz on food. Molds thrive on acids and can produce mycotoxins. Mold is easily destroyed at processing temperatures between 140ºF and 190ºF (60ºC and 88ºC).


Toxins (poisons) produced by some species of molds that grow on high-acid foods.

open-kettle canning/preserving

A fresh preserving method in which hot foods are ladled into jars and two-piece closures are applied. Since no heat processing takes place, this method is not recommended.

oven canning/preserving

A fresh preserving method in which jars are placed in the oven and heated. This method is not recommended.


A period of time from 8 to 12 hours.


The reaction that takes place when cut fruits and vegetables are exposed to the oxygen in the air. Oxidation causes the cut surface of the produce to brown and can also lead to texture changes.

paraffin wax

A pure, refined wax used in an older fresh preserving method. The wax was melted and poured over soft spreads in the jar. It is not a reliable method of preventing contamination by microorganisms, and in many instances mold growth will occur. Since no heat processing takes place, paraffin wax has not been recommended as a safe closure for soft spreads for many years.


A naturally occurring carbohydrate found in fruits and vegetables that is responsible for cell structure. The natural pectin content decreases as fruits and vegetables ripen. Thus, they become soft and lose their structure. Pectin is available commercially in powdered and liquid forms. Commercial pectin is used to make jams, jellies and other soft spreads.

pH (potential of hydrogen)

A measuring system in chemistry for determining the acidity or alkalinity of a solution. In preserving, foods are separated into high-acid and low-acid. A boiling water canner is used for processing high-acid foods; a pressure canner must be used for processing low-acid foods.

Pickle Crisp® Granules

A crisping agent that uses calcium chloride, a naturally occurring salt found in some mineral deposits, to enhance the texture of pickles. Pickle Crisp® Granules may be added to jars of quick-process or fresh-pack pickles before processing. Look for it where fresh preserving supplies are sold.


Preserving food, especially cucumbers and vegetables, in a high-acid (vinegar) solution, often with spices added for flavor. Pickled foods must be processed in a boiling water canner.

pickling lime (calcium hydroxide)

A white, almost insoluble powder, also known as slaked lime, used in some older pickling recipes to add crispness to pickles. Due to its caustic nature, pickling lime is no longer recommended for making homemade pickles. Failure to remove lime adequately may increase the risk of botulism. Lime can also cause gastrointestinal problems if too much is ingested.

pickling or preserving salt

See salt, pickling or preserving.


A soft spread in which the fruit is preserved with sugar so it retains its shape and is transparent, shiny, tender and plump. The syrup varies from the thickness of honey to that of soft jelly. A true preserve does not hold its shape when spooned from the jar.


To prepare foods to prevent spoilage or deterioration for long periods of time. Some methods of preservation are fresh preserving (home canning), freezing, dehydration, pickling, salting, smoking and refrigeration. The method used determines the length of time the food will be preserved.

pressure canner

A tall, usually heavy pot with a lid that is locked in place and a pressure-regulating device. The lid is fitted with a safety valve, a vent and a pressure gauge. Pressure canners are used to process low-acid foods, because steam at 10 lbs (68 kPa) of pressure (at sea level) will reach 240°F (116°C), the temperature needed to destroy harmful bacteria that thrive in low-acid foods.

pressure canning/preserving method

The fresh preserving method used to heat-processs low-acid foods. Low-acid foods must be processed in a pressure canner in order to destroy potentially harmful bacteria, their spores and the toxins they produce. In practical terms, this can be done at 240°F (116ºC). Because the steam inside the canner is pressurized, its temperature can exceed the boiling point of water (212°F/100°C). In a weighted-gauge canner at sea level, the temperature will reach 240°F (116ºC) at 10 lbs (68 kPa) of pressure.


Blanching or treating produce with an antioxidant to prevent browning, slow enzyme action or destroy bacteria.

processing or heat processing

Heating filled jars of food to a specified temperature for a specified time to inactivate enzymes and destroy harmful molds, yeasts and bacteria. Heat processing is essential for the food safety of all home-preserved foods. Processing destroys microorganisms that are naturally present in food and/or enter the jar upon filling. It also allows gases or air to be vented from the jar to create an airtight vacuum seal as the product cools, thus preventing recontamination of the food.

processing time

The time in which filled jars are heated in a boiling water canner or a pressure canner. The processing time must be sufficient to heat the coldest spot in the jar. The processing time is specified for every current, tested fresh preserving recipe and depends on several factors, such as acidity, type of food product and size of jar.

produce protector

A commercially available antioxidant that prevents cut fresh produce from browning when exposed to the oxygen in the air, a reaction known as oxidation.

raw-pack method

Filling jars with raw, unheated food prior to heat processing.


The process of decreasing the temperature for cold storage of produce. Refrigeration slows the growth of microorganisms and prolongs deterioration for a short period of time.


A pickled product prepared using chopped fruits and/or vegetables cooked in a seasoned vinegar solution. If a sweet relish is desired, sugar is added. Hot peppers or other spices may also be added for flavor.


Repeating the heat processing of filled, capped jars when a lid does not seal within 24 hours. The original lid must be removed and the food and/or liquid reheated as recommended by the recipe. The food and/or liquid must be packed into clean, hot jars and covered with a new, clean lid with the screw band adjusted. The filled jars must then be reprocessed using the preserving method and full length of processing time recommended by the recipe.

rubber gasket

See gasket.

salt, kosher

A coarse-grained, textured salt that is free of additives. Kosher salt may be used when making pickles. Because of the variance in density and form, contact kosher salt packers for information regarding equivalencies.

salt, pickling or preserving

A fine-grained salt used in pickling and fresh preserving. It is free of anti-caking agents, which can cause the pickling liquid to turn cloudy, and iodine, which can darken the pickles.

salt, table

A free-flowing, fine-grained salt. Table salt is the most common salt and is used as a table seasoning. It contains additives that may yield unfavorable results when pickling. Iodized table salt (sodium iodide) is not recommended for pickling because it contains an anti-caking ingredient that can make brines cloudy, as well as iodine, which may darken the pickles. Non-iodized table salt can be used for pickling. The pickling liquid may be cloudy, but the pickles will not be dark.

salt, sea

A type of salt produced by the evaporation of sea water. It comes in fine- and coarse-grained textures and is usually more costly than other types of salt. Sea salt should not be used for pickling because it may contain minerals that could darken the pickles.

saucepan, large

An 8- to 10-quart (8 to 10 L) heavy pot essential for cooking soft spreads. The pot must have a broad, flat bottom for good heat distribution and deep sides to prevent food from boiling over.

screw band

A threaded metal band used in combination with a flat metal lid to create vacuum seals for fresh preserved food. The band holds the lid in place during processing.

sealing compound

The red, shiny material, also called plastisol, found in the exterior channel on the underside of the flat metal lid. The sealing compound comes in contact with the lip of the jar and forms a seal when the jar cools after processing.


See boil gently or simmer.


A metal kitchen utensil that has a long handle attached to a wide, flat surface with perforated holes. Skimmers are used to skim foam from soft spreads after cooking or to drain hot liquid from hot vegetables.

smoke curing

A preservation method achieved by smoking food, usually meat or fish, at a certain temperature to partially or fully cook it and to impart a smoky flavor. Even if meat or fish is smoke-cured prior to fresh preserving, it must go through heat processing in a pressure canner to become shelf-stable.

spice bag

A small muslin bag used to hold whole herbs and spices during cooking. The bag allows the flavor of the herbs and spices to seep into the food or liquid, and makes removing the spices easy when cooking is complete. Spice bags come in various sizes. If a spice bag is not available, tie herbs and spices in a square of cheesecloth.


The evidence that a food product has not been completely rid of microorganisms. If microorganisms are present, the nutrients in the food product will allow them to grow and multiply. Spoilage occurs when food products have not been processed correctly. Signs of spoilage include broken seals, mold, gassiness, cloudiness, spurting liquid, seepage, yeast growth, fermentation, slime and disagreeable odors.

steam pressure canner

See pressure canner.

steam pressure canning/preserving method

See pressure canning method.


The process of killing all living microorganisms. In fresh preserving, this is achieved by heating food in capped jars to a high enough temperature for a length of time sufficient to destroy the most heat-resistant microorganism known to be associated with that food.


A cool, dry, dark place where fresh preserved goods can be kept until ready to be consumed.

straight walls

Some glass preserving jars possess straight sides that taper downward and allow for expansion during the freezing process. Jars with straight walls can be used when freezing.


The separation of liquid from a gel. In fresh preserving, this can happen to soft spreads, usually during storage. It is not a safety concern.

syrup or canning/preserving syrup

A mixture of water (or juice) and sugar used to add liquid to canned food, usually fruit.

thermal shock breakage

Stress exerted on preserving jars when glass is exposed to sudden temperature differentials. This stress weakens the glass and can lead to glass breakage, commonly evidenced by the bottom breaking out.

two-piece closure

A two-piece metal closure for vacuum-sealing fresh preserving jars. The set consists of a metal screw band and a flat metal lid with a flanged edge lined with sealing compound.

vacuum seal

The state of negative pressure in properly heat-processed jars of home-canned foods. When a jar is closed at room temperature, the atmospheric pressure is the same inside and outside the jar. When the jar is heated, the air and food inside expand, forcing air out and decreasing the internal pressure. As the jar cools and the contents shrink, a partial vacuum forms. The sealing compound found on the underside of fresh preserving lids prevents air from re-entering.


1.) Forcing air to escape from a closed jar by applying heat. As a food or liquid is heated, it expands upward and forces air from the jar through pressure buildup in the headspace. 2.) Permitting air to escape from a pressure canner, also called exhausting.

vinegar, distilled white

The standard form of vinegar. It is a clear, colorless acidic liquid derived from grain alcohol that possesses a sharp, pungent flavor. Unlike apple cider vinegar or malt vinegar, distilled white vinegar does not compete with the distinctive flavors of herbs and spices in brine. Because it is clear, it does not change the color of white or light-colored fruits and vegetables. In fresh preserving, use 5% acidity (50 grain).

vinegar, cider

A type of vinegar derived from apples that is light golden in color and has a tart fruit flavor. Cider vinegar has a milder flavor than distilled white vinegar. Because it has color, it may darken white or light-colored fruits and vegetables. In fresh preserving, use 5% acidity (50 grain).

vinegar, red or white wine

A type of vinegar derived from wine. The flavor reflects the source of the wine.

weighted-gauge pressure canner

A type of pressure canner that is fitted with either a three- or a one-piece weight unit, both with 5-, 10- and 15-lb (35, 69 and 103 kPa) pressure adjustments. (Only 10- and 15-lb/69 and 103 kPa pressure weights are used in fresh preserving. The 5-lb/35 kPa weight is used for cooking, but not preserving.) Steam, exhausted throughout the processing period, causes the weight(s) to rock, indicating that the pressure level has been achieved or is being maintained.


Microscopic fungi grown from spores that cause fermentation in foods. Yeasts are inactive in foods that are frozen and are easily destroyed by heat processing at a temperature of 212°F (100°C).