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Fermented milk from United States

Acidophilus milk (US therapeutic sour milk, 1920s)acidophilus milk

Acidophilus milk is skim milk sterilised until slightly caramelised and soured with a pure culture of Lactobacillus acidophilus at 35–37 °C. In the 1920s it was given by the litre to patients to change the gut flora. Today Codex defines it by its culture and acidity, and US rules cover it as a cultured milk.

Fully documentedFermented milk2.5 days – 3 days

Recipe

Amounts from a sourceLaboratory method from a 1926 treatise. Resting cultures were kept in 500 cc flasks holding about 250 cc of milk, and the working inoculum was grown in 100 cc of milk. The usual daily dose given to patients was 1000 cc.
Fresh skim milkSterilised before inoculation[kopeloff1926]
Pure L. acidophilus milk cultureAbout 2 cc per 100 cc of milkTransferred daily from the previous day's coagulated milk[kopeloff1926]
Starterdefined-culture: pure Lactobacillus acidophilus (then 'Bacillus acidophilus')

Total time across the recorded steps: 2.5 days – 3 days

Start
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What changes: Skim milk is autoclaved under pressure until it turns slightly caramel

Step 1 of 4
Sterilise the milk
Time
20 min
Reported
Temperature
Not documented
Salt
None given
Acidity
Not documented
Which microbes the steps name, step by step
L. acidophilus

Output: sterile milk.

Flavour
Not documented
Texture
Not documented
Colour
white to slightly caramel

Microbes at work in this step

all bacteria killed

Method

Measured measured in a studySet fixed by a specification or tested recipeReported one source reports itTypical a general value, not sourced for this fermentUnconfirmed not yet checked against a source

At a glance

Acidophilus milk is skim milk sterilised until slightly caramelised and soured with a pure culture of Lactobacillus acidophilus at 35–37 °C. In the 1920s it was given by the litre to patients to change the gut flora. Today Codex defines it by its culture and acidity, and US rules cover it as a cultured milk. Made in 4 steps over 2.5 days – 3 days. The longest step, grow the working inoculum, takes 36 h – 2 days (Kopeloff N. 1926) and runs at 35 °C (Kopeloff N. 1926). Lactobacillus acidophilus does most of the fermenting.

Key numbers
Main step36 h – 2 daysReported[kopeloff1926]Grow the working inoculum
Temperature35 °CReported[kopeloff1926]Grow the working inoculum

What makes this one different

Acidophilus milk uses one pure intestinal lactobacillus instead of the yogurt pair. In the 1926 method the milk is sterilised, not just heated, before it is soured.

Related ferments

Variants

  • Large-scale acidophilus milk (1920s)Skim milk held at 190–195 °F for one hour, cooled to 98 °F for 3–4 hours, heated again, then inoculated with 2 per cent culture and held at 98 °F.

Safety

The milk is sterilised before inoculation and the culture is checked for purity under the microscope. Codex requires at least 10^7 cfu/g of the starter in the product; US cultured milk must be made from pasteurised milk.

History and sources

Every number is labelled with how it is known. How this atlas is made

Rettger and Cheplin at Yale ran feeding experiments on people to implant Bacillus acidophilus in the gut (PNAS 1920) and Kulp and Rettger compared L. acidophilus with L. bulgaricus (1924). Kopeloff's 1926 book collected the method and clinical results. Codex now lists acidophilus milk by its culture.

  1. [kopeloff1926] Kopeloff N. 1926, Lactobacillus acidophilus, Williams & Wilkins, Baltimore (appendix, "Preparation of L. acidophilus milk" and temperature studies)book
  2. [codex243] Codex Alimentarius, Standard for Fermented Milks CXS 243-2003 (revised 2008, 2010), sections 2.1 and 3.3spec
  3. [cfr131112] US Code of Federal Regulations, 21 CFR 131.112 Cultured milk (2024 edition, govinfo)gov
  4. [cheplin1920] Cheplin H.A., Rettger L.F. 1920, Studies on the transformation of the intestinal flora, with special reference to the implantation of Bacillus acidophilus, II. Feeding experiments on man, PNAS 6(12):704 (title)paper
  5. [kulp1924] Kulp W.L., Rettger L.F. 1924, Comparative study of Lactobacillus acidophilus and Lactobacillus bulgaricus, Journal of Bacteriology 9(4):357–395 (title)paper