This peer reviewed article suggests that:

Fermentation has been used to preserve and store milk since the days of the Pharaohs

And also:

fermentation is considered a successful preserving method

However, the FDA gives us precious little advice in this regard, and seems to just apply a blanket 2-hour unrefrigerated rule to "perishables". Thus, the FDA considers homemade yogurt to be, not merely not a preservation method, but downright unsafe for consumption (homemade yogurt involves leaving milk unrefrigerated for more than 2 hours).

Do other cultures around the world still use fermentation as a means of preserving milk? If so, are different methods used in these traditions to prepare milk for short vs long term preservation?

1 Answer 1


I note your linked page specifically doesn't mention yogurts or other fermented milk products such as cheeses. This is because the risk from these types of foods is minimized by the fermentation itself.

Typically, what happens in these fermentations is that the bacteria in them consume the sugars and produce acids as a metabolic product. The common ones you are likely to have heard of are lactose (sugar), which is metabolized into lactic acid. The presence of this acid inhibits the growth of almost all species of bacteria to some extent.

For the production of these fermented products, you need to inoculate the milk with sufficient bacteria that they out-compete other contaminating species and acidify the product to an extent that inhibits growth. Yogurt typically has a pH (measure of acidity) of around 4.0 - 4.5, which is quite sour (most commercial yogurts in many parts of the world have lots of added sugars, so don't taste sour; trust me, they are still sour, just disguised - try a plain Greek yogurt to get some indication). This pH is enough to inhibit the growth of most of the serious pathogens that we worry about with milk products.

This is not to say that you should/could store your yogurt outside the fridge, as low temperature also inhibits growth of almost all bacterial species, but merely that production of yogurt is mostly safe, especially if you use pasterized milk for production (not raw milk - these are associated with a low incidence of some very serious infections such as tuberculosis (usually Mycobacterium bovis rather than M. tuberculosis though), salmonella and brucellosis and typhoid). These diseases, while rare, can result in death or serious complications in the elderly, very young, pregnant and foetus/baby in particular.

Hard cheeses (cheddar etc.), but not soft cheeses (cream cheese, sour cream), which are often basically just very thick yogurts, work slightly differently, in that they lower the water available to the bacteria. This, along with the metabolic compounds produced by the fermentation inoculuum result in inhibition of contaminating bacterial species.

Many cultures used and still use fermentation to preserve milk products, including the Western world. This applies to literally every culture that farms milk producing animals (as far as I know), including people like the Maasai. The exact methods used for preservation and the resulting products are widely varied. A list of the products can be found on Wikipedia. One thing to note is that most of these, despite the different names and methods rely on common groups of bacteria and/or fungi that are found in milk naturally (i.e. raw milk contains these too), but at lower levels that you might like for preservation of the milk by fermentation. This is very likely how soured/fermented milk products were first made/discovered - through observation that if you took milk and left it somewhere warm, sometimes you would get good tasting stuff that kept longer than milk alone and that if you took some of this and added it to milk you would get more of the good tasting/long keeping stuff. It also explains how such disparate cultures have discovered very similar products.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.