Fermenting veggies and other foods is wonderfully simple. Chop up, for instance, some tomatoes, cucumbers, eggplant, toss in some garlic cloves and basil leaves. Combine them in brine (non-iodized salt, filtered non-chlorinated non-fluoridated water), keep veggies submerged below the air interface, and within 72 or more hours you will have a delicious mix of veggies and microbes that provide health benefits. You can rely on the microbial species that are normally resident on the external surface of vegetables such as Leuconostoc mesenteroides, Pediococcus pentosaceus, and Lactobacillus plantarum. Or you can add one or more microbes from a commercial starter culture (e.g., from Cutting Edge Cultures for whom I occasionally provide consultative advice) that allows you to pick and choose fermenting microbes and abbreviates the fermentation process, often accomplished in 48 hours. Given the current limited benefits of haphazardly created commercial probiotics, including plenty of fermented foods in your lifestyle is among the most important strategies you can adopt to rebuild a healthy gastrointestinal microbiome.
Many people, however, are intimidated by the process and fail to add this important aspect of diet and thereby fail to obtain the outsized benefits they provide. Or some people just desire the convenience of foods that are pre-fermented to purchase in a grocery or specialty store. You might be traveling, for instance, and didn’t bring your fermentation setup with you.
Here’s the problem: Whenever something is commercially produced, production time is important. Say you are a shoemaker. It takes you one week to make a pair of shoes. Your competition has mechanized the process and can make a pair of shoes in four hours—who is going to make more money? Obviously, the shorter the production time, the greater the productivity, the more there is potential to sell more product. The same principle applies to fermented foods. Fermenting foods requires days to weeks (several weeks is common, for instance, to ferment cabbage to make sauerkraut or to ferment cucumbers to make fermented pickles). You can be sure that most manufacturers do not wait weeks to ferment their products. It therefore means that the sauerkraut, kimchi, pickles, kefir and, most certainly, yogurts undergo an abbreviated fermentation process and thereby have limited numbers of fermenting microbes. As with our L. reuteri and other yogurt ferments, extended fermentation generates 100s of billions of bacterial counts, typically a thousand-fold greater than commercial yogurts. If the commercial kimchi or sauerkraut you bought was fermented for, say, 24 hours, the microbial counts are going to be low. They still provide benefit, but not the benefit of hundreds of billions, or even trillions, provided by extended fermentation.
When you purchase a pre-fermented product, it is therefore helpful to let it sit on your kitchen counter for at least 48 hours or longer to allow fermentation to proceed further and thereby increase bacterial counts. Unlike the microbes we use to ferment our yogurts, mostly Lactobacillus and Bifidobacteria species that reproduce best at human body temperature (around 98 degrees F, 37 degrees C), most microbes that ferment veggies do fine at room temperature and a heating device is not necessary. (Of course, if you use a starter culture with Lactobacillus or Bifidobacteria species, you can then use your heating device.) You can therefore just allow these products to ferment without heating. Should any discoloration or peculiar growth occur on the surface, skim off and discard, then refrigerate to halt any further fermentation. The discoloration is evidence for fungal contamination and you want to discourage any further growth.
After your additional period of fermentation, refrigerate to slow any further fermentation. Most fermented foods are then safe to consume for several months because fermentation generates acids, such as lactic acid, that are antimicrobial against contaminating bacterial species.