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Potted Ham
Trim all the meat from the remains of a boiled ham, chop it very fine, being careful to remove all outside pieces and gristle, pound it to a paste, measure it, and to each pint, mix in one teaspoonful of mixed mustard and a small pinch of cayenne, and should the ham be very lean, one tablespoonful of butter. Pack this smoothly in small earthen jars, paste paper over and put on the covers. Stand the jars in a deep baking-dish, surround them nearly to the top with hot water and let them steam slowly for two hours. When done, remove the jars from the pan and let them cool with the covers on. When cold, remove the covers, pour into each jar a little melted butter, place fresh covers on and keep them in a cool, dry cupboard until wanted for use. Ham prepared in this way makes delicious sandwiches and will keep for months.
This is a classic hotel economy dish — a way of turning the last of a boiled ham into sandwich paste — but the preservation method at its heart is one that food science has since ruled out. The notes below explain the terms and then the hazard.
- The hazard: a sealed, low-acid meat kept at room temperatureCooked ham packed into a jar, sealed under a layer of butter and stored for months in a cupboard is the textbook anaerobic, low-acid, low-salt environment in which Clostridium botulinum spores germinate and produce toxin. The toxin is odourless and tasteless, and the paste is eaten without further cooking.
- Two hours in a water bath does not steriliseJars standing in hot water in a baking dish reach at most boiling point, around 212F. Botulinum spores survive that; only pressure processing above 240F destroys them in low-acid foods. The steaming here cooks and firms the paste, it does not make it shelf-stable.
- The butter seal makes it worse, not betterA cap of melted butter excludes air, which was the point in a pre-refrigeration kitchen. It also excludes oxygen from the surface of the meat, which is precisely the condition anaerobic bacteria require.
- "Will keep for months" was true of spoilage, not safetyThe seal genuinely delays the visible moulds and sour smells that told a nineteenth-century cook food had turned. It does nothing about the organisms that give no warning. A modern potted-meat or rillette recipe with measured refrigeration and a stated shelf life should be used instead.
- Mixed mustardPrepared mustard, mixed with water or vinegar to a paste — not dry mustard powder. English or Dijon are the closest current equivalents.
- Measuring by the pintThe pounded ham is measured by volume, not weight: a US pint is two cups, which for a dense meat paste comes to roughly a pound. The seasoning ratio therefore works out at somewhere around a teaspoon of mustard per pound.
- "Paste paper over"A disc of paper stuck down with flour-and-water paste under the jar lid, a standard nineteenth-century closure for preserves. It is a dust and moisture barrier, not a hermetic seal.
Potting is an English preservation technique of long standing — cooked meat pounded to a paste, packed tight to drive out air and sealed under a layer of clarified butter — and it travelled to American kitchens as the standard way of using up a ham, a tongue or the last of the game birds. By the time Oscar Tschirky, the Waldorf's celebrated maître d'hôtel, assembled this book in 1896, a hotel of that size would presumably have cooked ham in quantity, and a recipe that converted the trimmings into sandwich filling would have had obvious appeal to the household cooks who are generally assumed to have been his readership. The instruction to remove "all outside pieces and gristle" is the mark of a professional kitchen: potted paste lives or dies on texture, and a single tough scrap ruins a jar. What the recipe cannot account for is that the butter seal, which looked like protection, was understood only as a defence against air and mould; Clostridium botulinum was isolated and named by van Ermengem in 1895-97, contemporaneous with the book, though its implications for sealed preserves were worked out later.