# Traditional fermentation

Spontaneous lactic fermentation: microbial succession in vegetable ferments, the pH 4.6 safety hurdle, why salt concentration is a selection tool, and the trade-off between shelf stability and live cultures.

Salt, exclusion of air and time select for the organisms you want — a microbial ecology managed without ever isolating a strain.

Source: https://en.bioecon.ru/docs/agri-food/food-alt-protein/traditional-fermentation/
Updated: 2026-08-24



Sauerkraut, kimchi, brine pickles and their relatives are made by *not* adding a culture. The organisms are already present on the vegetable; the process consists of creating conditions in which the desired ones outgrow everything else. It is applied microbial ecology, practised for millennia before anyone knew microbes existed.

## Selection by salt and by oxygen

Salt does two things. It draws water and solutes out of plant tissue by osmosis, creating the brine in which fermentation happens, and it suppresses many spoilage organisms while the salt-tolerant lactic acid bacteria continue. Concentration is therefore a control variable, not a seasoning: too little and spoilage organisms and moulds compete successfully, too much and the fermentation stalls because even the lactic acid bacteria are inhibited.

Submersion below the brine excludes oxygen, which suppresses moulds and aerobic spoilage and favours organisms that ferment rather than respire.

## Succession, not a single organism

A vegetable ferment is a sequence. Heterofermentative lactic acid bacteria, typically *Leuconostoc* species, dominate early: they tolerate the starting conditions, and produce lactic acid, acetic acid and carbon dioxide — the CO₂ further displacing oxygen. As acidity rises they are inhibited by the environment they created, and more acid-tolerant homofermentative *Lactiplantibacillus* and *Lactobacillus* species take over, driving the pH lower still.

The two stages contribute differently to flavour. The early heterofermentative phase generates the aromatic complexity; the later phase generates the sourness and most of the preservation.

## The safety hurdle is a number

The reason fermentation preserves is that the pH falls below the point at which *Clostridium botulinum* can grow — conventionally taken as 4.6. Reaching that value reliably and fast enough is what separates a safe ferment from an unsafe one, and it is why a ferment that stalls is a hazard rather than merely a disappointment. Undissociated lactic and acetic acid contribute more than pH alone, since the uncharged molecule crosses the cell membrane and acidifies the cytoplasm directly. Some lactic acid bacteria also produce bacteriocins, narrow-spectrum peptides that inhibit related bacteria.

This stack of overlapping barriers — salt, anaerobiosis, acid, competitive exclusion, sometimes low temperature — is what food science calls hurdle technology: no single barrier is sufficient, and their combination is.

## The unresolved part

Two things are genuinely uncertain. First, whether the live organisms in a traditional ferment deliver a measurable health benefit: the strains are undefined and vary batch to batch, most survive stomach acid poorly, and evidence established for specific characterised probiotic strains does not transfer to them automatically. Second, biogenic amines — histamine and tyramine, produced by decarboxylation of amino acids by some lactic acid bacteria — accumulate variably in long-fermented and high-protein products, and are a real reason to care which organisms dominated.

A practical consequence worth stating plainly: pasteurising a ferment for shelf stability kills the cultures. Shelf-stable and live are, for these products, alternatives.