Lactic acid fermentation – the nitty gritty

Safety

Since fermenting foods is all about getting microorganisms, including bacteria, to grow, it is only natural to ask Is it safe? After all, many bacteria cause diseases. Looking at different blogs and articles around the internet, you will see a multitude of claims about how safe it is, how it can’t be dangerous etc. The issue with these claims is that they are often based on loose quotes and personal experience or reasoning. It is true that fermented foods are eaten across the globe to a huge extent on a daily basis and have been eaten for thousands of years.

To be on the extra-safe side, I decided to do some digging in the scientific literature and make up my own mind. What I can find seems to confirm these claims to a large extent but it appears you can mess up. If you manage to get your micro-organisms of choice to grow fast enough, they will create their own environment and protect themselves. But if the growth is slow, other fast-evolving organisms can adapt to the changes. For instance, E. Coli (a bacterium family found in your gut, responsible for some forms of food poisoning ​[1]​) can adapt to survive in up to 11% salt if the salinity is increased over generations ​[2]​. Similarly, Leyer et al. found that E. coli could evolve to survive for more than 80 h in a lactic acid solution with pH 3.85 ​[3]​ (in the range of most lactic acid ferments).

The good news is that most of the time, these harmful bacteria will cause unpleasant odours and make the food too disgusting to eat. This might sound like you put yourself at risk every time you eat a fermented food but bear in mind that people eat enormous amounts of fermented foods every single day and people all over the world make their own ferments at home regularly without many issues. The trick is to keep decent sanitation (wash hands and utensils, no need for boiling) and discard ferments that smell bad.

So how often does botulism really occur in fermented foods? According to the CDC reports the leading causes of botulism are (in order of significance):

1. Home-canned foods using improper canning technique (by far #1)
2. Commercially prepared/distributed foods (pasteurized and/or preserved)
3. Improperly stored/handled cooked food (at home and in restaurants)
4. Fermented meats and fish (almost all reports from Alaska)
5. Unkown (very low incidence of undetermined sources)

I did not find a single incident of fermented vegetables, sauerkraut, kimchi, lacto-fermented pickles, kombucha, lacto-sodas, kvass, kefir, yogurt, cheese, etc.

Tim Hall, The Wild Fermentation Forum ​[2]​

Getting into the nitty gritty

If you think you might be having issues, look into which “type” of chlorine is added to your water. If you’re lucky, your municipality uses chlorine and not chloramine. If you want to get rid of chlorine, you can just let your water sit on the counter overnight or boil it briefly and chlorine will leave the solution. Chloramine needs filtering or boiling to get rid of it. UV treatment or vitamin C can also be used to get rid of chlorine/chloramine ​[6], [7]​.

Iodine

You will also likely see many recipes calling for kosher salt or pickling salt. From what I can tell, this is all to avoid iodine (some recipes call for non-iodized salt instead). One reason I’ve seen stated is that iodine will inhibit the growth of lactic acid-bacteria and should thus be avoided but this has been called into doubt ​[8]​. Müller et al. put this to the test and made sauerkraut with salt with and without iodine (1%), using both wild fermentation and inoculation ​[9]​. They saw no difference in LAB growth between the different salts. They did see a non-significant indication that yeast and mold were decreased by using iodized salt. (This is a point in favor of iodine.)

Though I have read that iodine might cause darkening, discolorations, and softer pickles (though no effect on flavor) ​[10]​. In addition, ‘table salt’ often contains a bunch of other additives. (When we first moved to Canada we noticed that one brand of table salt even contained sugar. Why??) So, despite iodine not inhibiting LAB growth, it might be good to avoid the other additives often found in processed table salt.