by Dr Ann Ashworth.

The benefits of fermentation have been recognised from the earliest times. There are records of fermented foods being used by the Sumerians, ancient Egyptians, Babylonians and Assyrians. Chinese descriptions of miso from soy sauce go back to 1000 BC. Other foods that are commonly fermented are milk (to make soured milks and yoghurt), cereals and cassava.

In Africa ogi, uji, ting, koko, kenkey, obusera, and nasha are common fermented porridges. Fermented dough can be made into bread, as in injera and kocho in Ethiopia. In Latin America, maize and cassava are fermented. Examples are pozol, chicha and farinha. In the Indian subcontinent, cereal and pulses are often fermented together to make idli, dosa and dhokla. In south-east and east Asia, most fermented foods are based on pulses and fish. Many of these are used as flavourings, such as miso, natto and fish sauce.

These products may be appreciated far from their country of origin. There are two kinds of fermentation: sour fermentation which produces acid, and alcohol fermentation. In each case, special harmless micro-organisms are introduced into the food and allowed to remain and multiply. The microorganisms bring about beneficial chemical changes in the food.

Benefits of fermentation

  • The acid produced in sour fermentation helps to preserve the food. In fermented porridges, the main acids are lactic and acetic acids.
  • In Tanzania, children given fermented porridge have less diarrhoea than children given unfermented porridge. Porridges are often contaminated with bacteria that cause diarrhoea because of impure water or poor hygiene. Fermentation helps to reduce contamination because these harmful bacteria cannot multiply as easily in fermented food.
  • Fermentation improves the absorption of important nutrients, particularly iron and zinc.
  • Fermentation improves the protein content and adds vitamins and minerals.
  • Many people prefer the flavour of fermented food. It has been suggested that the sour taste helps to restore appetite when people are ill.
  • Fermentation reduces the toxin (cyanide) that is naturally present in cassava, particularly in the bitter varieties. The traditional way of making gari and farinha by grating cassava and then letting it soak in water to ferment, cleverly allows the acid to release the toxin. The benefit of this practice was appreciated by our ancestors, although the ‘science’ of it has been known only recently.

Fermentation is a good example of traditional wisdom! Unfortunately its use is in danger of declining in favour of western products. In Kenya the decline in some areas has been attributed to missionaries discouraging the preparation of sour porridges in the mistaken belief that they contain alcohol. Also, health workers tend to stress the need to prepare fresh food and so discourage the use of fermented foods. Encourage people to value their traditional fermented foods.

Dr Ashworth works at the Centre for Human Nutrition, London School of Hygiene and Tropical Medicine, 2 Taunton Street, London, WC1H 2BT, UK.