| Term | Definition |
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| Headspace | 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.
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| Heat Penetration/Heat Processing | See processing.
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| Hermetic Seal | A seal that secures a food product against the entry of microorganisms and maintains commercial sterility.
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| 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.
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| 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.
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| 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.
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| 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.
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