The Food Forest

Fermentation of Food

The fermentation of food by a range of specific micro- organisms (yeasts and moulds, which are both fungi, and bacteria) has been used by humans for millenia to help preserve or transform foods. Cheese, wines, beers of , soy sauce, sauerkraut, yoghurt and other fermented milk products, tea, some sausages, fish pastes and sauces, bread and yeast products are just some of the things for which we can thank fermentation.

In general, fermentation stabilises food by making it so acid (low pH) or alcoholic that undesirable micro-organisms find it difficult to grow. Fermented products are often further protected from oxidation and infection by micro-organisms using air-tight containers, heat and possibly smoking. If wine is not protected from air an aerobic fermentation by Acetobacter will convert the alcohol into Acetic acid (vinegar).

Yeasts like a substrate which is neutral (pH 6-7), sweet, alcoholic, aerated or malty; they are not particularly worried by some salt. So to halt or inhibit a yeast fermentation antioxidants, food acids, anaerobic conditions and heat are used.

Bacteria like almost the opposite conditions to yeast and salt is often used in modest quantities (20% by weight) to control undesirable bacteria while the ever-useful Lactobacillus gets going and produces an acid (low pH) environment in which it thrives but other bacteria don’t.

However quite often yeasts and bacteria team-up together as in the ‘mixed organism’ known as ‘mother of vinegar’ which exists within a leathery layer of polysaccharides secreted by the bacteria.

Fermentation aids the preservation of Vitamin C and actually produces Vitamins B and K; it also produces more complex, high grade proteins than were present in the raw food. It makes food more digestible, particularly some hard-to-digest starches and it detoxifies food of such substances as hydrocyanic acid, oxalic acid, aflatoxins and nitrites.

Lactic acid ferments reduce pathogenic organisms and are a way to keep the body functioning more normally when taking antibiotics (many of which are themselves products of fermentations).

There are thousands of fermentations known to man so it is not within the scope of a fact sheet to describe them. Some good, practical references are:

  • 'The Permaculture book of Ferment and Human Nutrition' - Bill Mollison, Tagari Publications
  • 'The Complete Guide to Self Sufficiency' - John Seymour, Corgi (Transworld)
  • 'Wine from 100 Vines' - John Dixon, Agmedia

Here’s a recipe for that great standby... Sauerkraut!

  1. Shred the cabbage.
  2. For each 2.25kg of cabbage quarter of a cup of salt and 1 cup of shredded apple are added progressively with the cabbage as it is layered into a crock.
  3. Weight the cabbage down and leave for some three weeks.
  4. Refrigerate or bottle.

You can cheat and save time by simply adding vinegar to shredded cabbage but its not quite the same.

Fermentation is one of nature’s miracles - unpredictable and always slightly different because of the myriad of variables involved, from temperature to the exact nature of the substrate and the particular micro-organisms that do the work for you. Try it!

making vinegar


One way of making your own vinegar is to soak hardwood shavings in vinegar and put them in a barrel, with a container with small holes bored in it suspendedover the shavings. Wine is poured into the container and drips slowly down through the shavings, being well exposed to air and the vinegar - forming microorganisms. After a week you'll have vinegar. Turn the tap and do your pickling!