Important: Safety Warning
This page describes home-canning methods from before the causes of botulism were understood. Canning low-acid foods without a pressure canner, as described here, can allow the growth of Clostridium botulinum, whose toxin is among the deadliest known. Follow current USDA home-canning guidelines instead.
This information has been left in for historical purposes but should not be acted upon.
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Milk, to Preserve
Pour the milk into a bottle, and place the vessel up to its neck in a saucepanful of water, which is then to be put on the fire, and allowed to boil for a quarter of an hour. The bottle is now to be removed from the water, and carefully closed with a good and tight-fitting cork, so as to render it as air-tight as possible. Milk which has been preserved by this process has been kept for more than a year without turning sour. Milk may also be preserved by putting a table-spoonful of horse-radish scraped in shreds into a panful. When milk thus treated is kept in a cool place, it will be found to remain good for several days, even in hot weather.
This is a shelf-stable canning procedure for a low-acid food, written before the bacteriology of anaerobic spoilage was understood. Neither method described here can be made safe by adjusting the details.
- Milk is a low-acid foodMilk sits around pH 6.5-6.7, well above the 4.6 threshold below which Clostridium botulinum cannot grow. A sealed, corked bottle of milk is precisely the oxygen-free, low-acid, moist environment in which the spores germinate and produce toxin.
- A quarter-hour in boiling water is not a sterilisationWater in an open saucepan cannot exceed about 212F, and botulinum spores can survive prolonged boiling at that temperature. Fifteen minutes at boiling kills the vegetative bacteria that would otherwise sour the milk and warn you something is wrong; the spores it leaves behind are the dangerous ones. That is why the milk "keeps" for a year without turning sour and why that keeping is not evidence of safety.
- The cork is the problem, not the solutionAn "as air-tight as possible" cork pushed into a hot bottle gives an imperfect, unverifiable seal, and there is no way to tell a good one from a bad one afterwards.
- Botulinum toxin gives no warningIt has no smell, no taste and no visible sign. The book's own test - that the milk has not gone sour - detects nothing relevant. Dairy products have been implicated in a small number of documented botulism outbreaks, and the fatality rate before modern antitoxin and ventilation was very high.
- Boiling in glass on direct heatSeparately from the microbiology, a bottle stood in a saucepan of water and then lifted out hot is a thermal-shock and scald hazard.
- The horse-radish methodGrated horse-radish releases allyl isothiocyanate, which does have real antimicrobial activity. It may slow souring bacteria; it does nothing against pathogens such as Salmonella, Listeria or Campylobacter, which raw milk of the period could well carry. Milk "kept good for several days" in a Victorian larder was raw milk held in the growth range for those organisms.
- If you want to keep milkUse commercially pasteurised or UHT milk, refrigeration, or freezing. Milk is not a candidate for home canning under any current guideline, pressure canner or not.
Home bottling of milk belongs to the long aftermath of Nicolas Appert, who showed around 1810 that food heated in sealed vessels would keep, and whose method spread through European household manuals for the rest of the century without any understanding of why it sometimes worked and sometimes killed people. The entry is a fair snapshot of what a well-informed household could be told in the later nineteenth century: heat and exclusion of air were known to help, but the heat-resistant spore was not yet part of the picture, and Clostridium botulinum was only isolated by Emile van Ermengem, from an 1895 Belgian outbreak traced to cured ham. The horse-radish tip is older and folkloric; pungent roots of this kind were credited with keeping milk sweet, and the belief is not baseless, since horse-radish oils are genuinely antibacterial. What the entry really records is a period problem rather than a solution: before reliable refrigeration and rail-delivered chilled milk, urban households were constantly fighting a highly perishable and often filthy commodity, and it was the arrival of commercial condensed milk and then compulsory pasteurisation, not domestic bottling, that settled the matter.