Fermentation
A process of transforming food using micro-organisms (bacteria, yeasts) that break down sugars, changing flavour, texture, shelf life and nutritional value.
Fermentation is one of the oldest preservation techniques, predating writing. Micro-organisms convert carbohydrates into acids (lactic, acetic), alcohol or gas. Examples: yoghurt, kefir, sauerkraut, kimchi, miso, sourdough bread, cheese, wine, beer.
An original angle (a beneficial pre-digestion): fermentation is a form of external « pre-digestion ». Microbes do part of the digestive work before we do:
- They reduce antinutrients (phytic acid, lectins): sourdough bread is better tolerated than ordinary bread because the starter breaks down part of the gluten and FODMAPs
- They increase the bioavailability of certain nutrients (B vitamins, minerals)
- They synthesise new vitamins (K2, and B12 in some ferments)
- They provide live probiotics (if unpasteurised) and postbiotics
A striking example: fermenting cabbage into sauerkraut multiplies its bioavailable vitamin C content and creates anti-cancer compounds (isothiocyanates).
An important caveat: shop-bought fermented products are often pasteurised (heated), which kills the probiotics. For probiotic benefits, you need « live », unpasteurised products from the chilled aisle (raw sauerkraut, live kefir, fresh kimchi).
Fermented foods also feed the existing microbiota: a Stanford study (2021) showed that a diet rich in fermented foods increases microbial diversity and reduces inflammation, even more than a high-fibre diet alone.