Fermented foods
Practical Action
Shiokara
Small pieces of strongly flavoured meat in a viscous brown paste, made
from heavily salted, fermented seafood viscera (e.g. cuttlefish, squid,
tuna, oyster, shrimp, crab or sea cucumber).
Soy sauce
A condiment produced by fermenting salted soybeans with Aspergillus
oryzae and Aspergillus soyae. All types of soy sauce are salty, earthy,
brownish liquids with a distinctive umami flavour.
Tempeh (or tempe)
A fermented soybean cake that has a firm texture and strong flavour.
Tian mian jiang
A thick, brown or black Chinese sauce made from wheat flour, sugar, salt
and fermented soybean residue from soy sauce production.
Tibicos
A drink made by bacteria and yeasts in a matrix similar to kefir grains.
The fermentation produces lactic acid, alcohol and carbon dioxide, which
carbonates the drink.
Tương
Different types of Vietnamese salty dark brown pastes or liquids used as
condiments, made from roasted soybeans fermented with Aspergillus
oryzae.
Viili A type of Nordic yoghurt with a ropy, gelatinous consistency and a sour
taste produced by lactic acid bacteria. Traditional cultures also contain
yeasts.
Zha cai (Sichuan
A spicy, sour and salty Chinese pickle (similar to kimchi) made from
vegetable)
salted, pressed and dried mustard stems rubbed with red chilli paste and
fermented in earthenware jars. It is washed before use to remove the
chilli paste and excess salt.
Table 1. Examples of fermented foods
(Adapted from multiple sources based at http://en.wikipedia.org/wiki/Fermentation_%28food%29)
Fermentations can be grouped into those that take place using solid foods and those that use
liquid raw materials. Most solid food fermentations use micro-organisms that require air to
grow and produce the characteristic flavours (i.e. ‘aerobic’ micro-organisms), whereas most
submerged fermentations using liquid foods require anaerobic conditions in which air is
excluded. This difference is reflected in the different production methods and equipment
described below.
Solid fermentations
Most solid food fermentations involve the growth of moulds, yeasts and/or lactic acid bacteria
on moist materials such as tubers, cereals, soybeans or meats, and also food-processing
residues (e.g. wheat bran, or soya flakes remaining after oil extraction). Traditional products
produced by mould fermentations include Indonesian tempeh and Indian ragi. Yeasts and
moulds are used to produce tapé, and yeasts and/or lactic acid bacteria produce raised bread
dough as well as fermented cassava and rice products.
The first stage is to prepare the food by shredding, grinding or flaking the material, and
sometimes by heating it to remove any contaminating micro-organisms. It is then inoculated
with the required micro-organism(s), either from bought cultures or using previously fermented
material. It is incubated within a specific temperature range and moisture content to allow the
micro-organism to grow into the food. Fermentations that are traditional to an area are
successful at ambient temperatures, whereas fermentations that are introduced from other
areas may require temperature control. This can be done by continuously mixing the food or by
blowing cool air through the material. Depending on the product, the moisture content is
usually maintained between 30-75% to allow maximum cell growth. The final product may be
the fermented material itself, or liquid components that are drained or washed from the
fermented material.
The simplest technologies for solid food fermentations such as kenkey, bread dough and gari
are trays, bowls or other containers of food that are incubated in a room or a cabinet. Many
types of sausage are also fermented in their casings (see Technical Brief: fresh and cured
sausages). At a larger scale, equipment known as a ‘bioreactor’ is used. Different types of
batch bioreactors include rotating or rocking drums, and stationary or stirred aerated beds. For
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