Canning & preserving glossary

The home-preserving words you will meet across this site, in plain language. A few of these terms — pH, headspace, low-acid food — carry real food-safety weight, so we have kept the definitions accurate and pointed you to the fuller guides. This page explains what the words mean; it is not a recipe. Always follow a tested recipe for actual processing times, pressures, and quantities.

Food-safety essentials

Botulism: A rare but potentially fatal illness caused by a toxin from Clostridium botulinum bacteria, which thrive in the low-oxygen, low-acid, moist environment inside a sealed jar. The toxin is odourless and tasteless, so you cannot detect it — preventing it through correct method and processing is the only defence.
See also: Botulism: what every Canadian canner needs to know
pH: A measure of acidity, and the single most important number in canning. Foods at or below pH 4.6 are "high-acid" and can be safely water-bath canned; foods above pH 4.6 are "low-acid" and must be pressure canned.
See also: Water-bath canning
High-acid food: A food with a pH of 4.6 or lower — most fruit, properly acidified tomatoes, pickles, jams, and jellies. The acidity prevents C. botulinum from producing toxin, so these foods can be processed in a boiling-water bath.
See also: Water-bath canning
Low-acid food: A food with a pH above 4.6 — vegetables, meat, poultry, fish, beans, and most soups. These can only be made shelf-stable safely in a pressure canner, which reaches temperatures a boiling-water bath cannot.
See also: Pressure canning
Acidification: Adding a measured amount of bottled lemon juice or citric acid to bring a borderline food — most often tomatoes — reliably below pH 4.6 so it can be safely water-bath canned. The amount comes from a tested recipe, never a guess.
See also: Water-bath canning

Methods

Water-bath canning: Processing filled, sealed jars fully submerged in boiling water (100 °C / 212 °F at sea level). Safe only for high-acid foods such as jam, pickles, and acidified tomatoes.
See also: Water-bath canning
Pressure canning: Processing jars in a sealed canner that traps steam to reach about 116 °C / 240 °F — hot enough to destroy C. botulinum spores. The only safe method for low-acid foods.
See also: Pressure canning
Open-kettle canning: An obsolete and unsafe practice of ladling hot food into jars and sealing them without any processing in a canner. It does not reliably destroy spoilage organisms or produce a dependable seal — Health Canada and Bernardin advise against it.
Hot pack: Packing jars with food that has been heated or briefly cooked first. Driving out air helps prevent floating, improves colour retention, and lets you fit more food per jar.
Raw pack (cold pack): Packing raw, uncooked food tightly into jars and covering it with hot liquid before processing. Simpler than hot packing but more prone to floating fruit and trapped air.
Blanching: Briefly boiling or steaming vegetables and then plunging them into ice water to halt the enzymes that degrade colour, texture, and flavour — a key step before freezing or dehydrating many vegetables.
See also: Freezing & blanching
Fermentation (lacto-fermentation): Preserving food by encouraging beneficial lactic-acid bacteria to convert sugars into acid in a salt brine, lowering the pH and producing sauerkraut, kimchi, and lacto-pickles.
See also: Fermenting & root cellaring
Dehydrating: Removing moisture with low, steady heat and airflow so that bacteria, yeast, and mould cannot grow — used for herbs, fruit, vegetables, fruit leather, and jerky.
See also: Dehydrating
Root cellaring: Storing hardy vegetables and fruit through winter in a cool, humid, dark space without any processing — the oldest Canadian preserving method.
See also: Fermenting & root cellaring

Equipment

Water-bath canner: A tall pot fitted with a rack that keeps jars off the bottom and lets boiling water cover them by at least 2.5 cm throughout processing.
Pressure canner: A heavy pot that locks shut and traps steam under pressure to reach about 116 °C / 240 °F. It is not the same as a pressure cooker — only a tested pressure canner is safe for canning low-acid foods.
See also: Pressure canning
Pressure cooker: A smaller sealed pot for fast cooking, including electric multicookers. It is not a substitute for a pressure canner when canning low-acid foods unless the specific model has been tested and approved for canning.
See also: Pressure canning
Dial gauge: A pressure-canner gauge with a needle that shows the exact pressure inside. It should be tested for accuracy once a year.
Weighted gauge: A pressure-canner regulator that rocks or jiggles at fixed pressures (typically 5, 10, or 15 lb). It needs no annual calibration but offers only those set pressures.
Jar lifter: Rubber-coated tongs shaped to grip hot jars securely when lifting them in and out of the canner.
Canning funnel: A wide funnel sized to the jar mouth that fills jars cleanly and keeps the rim free of food, which is essential for a good seal.
Bubble remover / headspace tool: A non-metallic tool for releasing trapped air bubbles and measuring headspace. A plain plastic spatula does the same job.
Food mill: A hand-cranked tool that purées cooked fruit or tomatoes while straining out skins and seeds — handy for sauce, apple sauce, and tomato passata.

Jars, lids & sealing

Mason jar: The generic name for a threaded glass home-canning jar designed for a two-piece lid. In Canada the standard brand is Bernardin.
Bernardin jar: Canada’s standard home-canning jar, sold in 125 mL, 250 mL, 500 mL, and 1 L sizes — the sizes Canadian tested recipes are written for. Use these rather than US pint/quart sizes.
Snap lid (flat): The flat metal disc with sealing compound around the rim that bonds to the jar during processing to form the airtight seal. For canning it is single-use.
See also: Can you reuse Bernardin snap lids?
Band (ring / screw band): The threaded metal ring that holds the snap lid in place during processing. It is reusable and is removed once jars have sealed and cooled.
Two-piece lid: The snap lid and band used together — the standard Canadian jar closure.
Headspace: The empty gap between the surface of the food and the rim of the jar. Too little prevents a seal; too much leaves air that can discolour food or cause seal failure. Always use the headspace your tested recipe specifies.
Vacuum seal: The airtight seal formed as a jar cools, its contents contract, and the snap lid is pulled down. A sealed lid stays concave in the centre and does not flex when pressed.
See also: My jar didn’t seal — is it safe?
Fingertip tight: Tightening the band only until you meet gentle resistance with your fingertips, so air can still escape during processing. Over-tightening can buckle lids or cause seals to fail.

Ingredients & chemistry

Pectin: A natural carbohydrate in fruit that, with the right balance of acid and sugar, sets jam and jelly into a gel. Low-pectin fruit needs added commercial pectin to set.
See also: Pectin guide for Canadian canners
Acid (bottled lemon juice, citric acid, vinegar): Added to lower a food’s pH for safety (acidifying tomatoes) or for flavour and texture (pickling). Use bottled lemon juice rather than fresh for canning, because its acidity is consistent. Pickling vinegar must be at least 5% acidity.
Pickling salt: Pure granulated salt with no anti-caking agents or iodine, both of which can cloud brine or darken pickles. Table salt is not a direct one-to-one substitute by volume.
Pickle Crisp (calcium chloride): A food-grade firming agent added to pickles for crunch — a modern, optional replacement for old-fashioned pickling lime or alum.
Brine: A solution of salt and water — often with vinegar — used to ferment or pickle vegetables.
Syrup (light / medium / heavy): A sugar-and-water solution used to pack canned fruit. It carries flavour and helps the fruit keep its colour and texture, but it is not what makes the fruit safe — that is the acidity and processing.

Process terms

Processing time: The minutes jars must stay at a full rolling boil (water bath) or at pressure (pressure canning) to be safe. It always comes from a tested recipe and is adjusted for altitude — never shortened or guessed.
See also: How we source our recipes
Altitude adjustment: Increasing the processing time (water bath) or the pressure (pressure canning) at higher elevations, because water boils at a lower temperature the higher you are. Essential across much of Canada — Calgary sits at about 1,045 m.
See also: Canning altitude adjustments for Canada
Venting (exhausting): Letting a pressure canner release a steady jet of steam (usually for 10 minutes) before adding the weight, to drive out air so the canner heats evenly to a safe temperature.
Come-up time: The time a canner takes to reach a full boil or full pressure before the timed processing actually begins. It does not count toward the processing time.
Gel point (set / sheeting / cold-plate test): The stage at which jam or jelly has set. Tell-tale signs: the mixture sheets off a spoon in a single curtain, or a drop on a chilled plate wrinkles when nudged.
See also: Why didn’t my jam set?
Siphoning (liquid loss): Liquid drawn out of jars during processing, usually from fluctuating heat, over-tight bands, or too little headspace. A small loss is cosmetic as long as the jars seal.
See also: Why did my canning jars lose liquid?

Problems & failures

False seal: A lid that looks sealed but is not — often the result of a dirty rim or the open-kettle method. The jar can unseal in storage, so always confirm the lid centre is firmly concave and does not flex.
Flat-sour: Spoilage that sours the food without bulging the lid, caused by heat-tolerant bacteria when jars cool too slowly or are underprocessed. The jar looks normal but the food is off.
Buckled lid: A snap lid left warped or wavy at the edge, usually from bands tightened too hard before processing.
See also: Why did my canning lids buckle?
Spoilage signs: Bulging or unsealed lids, spurting liquid, off smells, mould, or cloudiness can all signal unsafe food. When in doubt, throw it out — never taste a home-canned food to test it.
See also: How to tell if canned food is bad