For thousands of years human beings have used microorganisms to produce foods, condiments and beverages, with enhanced nutritional value, digestibility and flavour and also as a means of preserving perishable foodstuffs. Obvious examples are wine, beer and bread. There are many others, however. Often their origins are unknown and colourful folklore and remarkable health benefits are attributed to them. It is common for some part of the culture to be retained to inoculate the next batch of food or beverage. Some of these 'starter cultures' have remained in the hands of certain families for generations and are considered heirlooms and as such are jealously guarded.
Often cultures are made up of several different organisms, which appears to increase their hardiness and longevity as they are carried from place to place. They are easily cultured once a few basics have been grasped. Most of the cultures described in this article require a temperature of 25-30°C, which is quite easily met in a warm room, or an airing cupboard - the latter being one of my favourite locations for culturing. It is well worth determining the temperature fluctuation of your airing cupboard, using a max/min thermometer. As with the preparation of all food, sensible and prudent hygiene will prevent the growth of harmful spoiloage organisms. If the foods are cultured correctly, the beneficial organisms tend to suppress the undesirable ones. Here are some of the cultures I have tried.
East Asian Fermentations
Tempeh is a traditional Indonesian fermentation process by which dehulled and partially cooked soya beans are inoculated with the spores of the mould Rhizopus oligosporus and kept at a temperature of 30°C for 24 hours. The resultant 'cake' is tightly bound by the fungal mycelium and has a pleasant aroma. When deep fried, it is absolutely delicious and any fears about mouldy food are quickly allayed. It is certainly one of the best ways of eating soya beans, as the mould's enzymes help to predigest the beans, aiding the human digestive system and reducing flatulence. I have successfully made 'low food miles' tempeh from field beans, split peas and broad beans. Another product, also from Indonesia and used in similar ways, is onchom, made by inoculating peanut presscake or soya bean pulp with Neurospora intermedia. The cake produced is similar in texture and taste to tempeh, but has an amazing bright orange colour, looking rather like a fish finger. It is kept at 25°C for two days. To date I have only used soya beans to make onchom, but am intending to experiment with local legumes.
The third mouldy product is miso, made from rice and barley (or even potatoes), which are inoculated with Aspergillus oryzae. When the grains are covered in mould, they are mixed with mashed cooked beans and salt and undergo a second fermentation by yeasts such as Hansenula and Saccharomyces, and Lactobacillus and Pediococcus bacteria, among others. This can take a few weeks or several years, depending on variety. Miso is a paste somewhat like Marmite in appearance, with a delicious aroma and flavour, which can be used in stews, spread on bread or as a Bovril-like winter drink. A staple in the Japanese kitchen, it is highly valued for its tonic effects and is believed to have helped prevent radiation sickness in some survivors of the atomic blast at Nagasaki.
The airing cupboard is a familiar location for rising bread. Sourdoughs, with their long proving period and distinctive flavour and texture are worth trying. Made up of wild yeasts and Lactobacillus bacteria, the cultures are very resilient and hardy; those from different locations have different flavours and baking qualities. The long rise, often 12 hours or more, actually makes the bread more digestible and liberates minerals such as zinc, which are usually bound in the form of phytates. If you get bored of sourdough bread-making, the culture can be put in a jar in the fridge and left for several months before reviving and all will be well.
There are a number of milk-based foods which can be easily cultured and renewable. Kefir, beloved of Cherry Hills, is well known. It is made up of a number of Lactobacilli (notably L. caucasicus, lactic Steptococcus and yeasts. Originating in the Caucasus, it is made up of small irregular grains, a bit like cauliflower florets in appearance. The grains, transferred from batch to batch, gradually increase. It should be kept at a temperaure of around 20°C for a couple of days, stirring occasionally. The resultant yogurt is fairly thin and mild. I use it to make a soft cheese, straining it through a close weave cloth and then adding salt, garlic and herbs.
Another yogurt, or perhaps more strictly, a buttermilk, is viili, a Finnish delicacy with a creamy, custard-like texture and flavour. It is composed in the main of Streptococcus cremoris and a mould, Geotrichum candidum. A spoonful of the mature yogurt is added to milk and kept at a temperature of 20-2° C for a day. My culture came from America, where it was taken by Finnish immigrants 85 years ago and is still going strong. Normally it needs to be cultured at least once a week or it goes off, although I have kept it on UHT milk for several months in the fridge. It can also be cultured on soya milk, as long as it is reinvigorated every so often on cow's milk.
Apart from the obviously fermented beverages like wine, there are often others that can be produced in the airing cupboard. One of the most peculiar cultures is kombucha or tea fungus. The first name, which means 'kelp tea' in Japanese, is a complete misnomer, although this is the name most often used. Tea fungus is more accurate, although the organisms present are actually the bacterium Acetobacter aceti var xylinum and the yeast Schizosaccharomyces pombe. The culture consists of a tough slippery skin, a bit like a jellyfish, which is placed on sweetened black tea for a week or ten days at 20-25°C. The drink that results, when properly prepared, has a taste just like a sweet cider. If left too long, or kept too hot, the Acetobacter secretes large quantities of vinegar, making the drink unpalatable. It is the bacteria which produce the remarkably tough skin which has, apparently, been used to produce an imitation leather. All sorts of remarkable therapeutic benefits have been attributed to it and at the moment it is the subject of controversy in the USA, where it is being promoted for the health benefits it brings to AIDS sufferers.
On the subject if vinegar, it is very easy to make your own using a vinegar 'mother'. Similar in appearance to the kombucha culture pad, being produced by the same bacterium, it can be placed on any alcoholic drink and kept at 20-25°C for a month or two until the alcohol turns to vinegar. Unlike most commercial vinegars, which are produced by a different culture and are pasteurised, the vinegar mother, sitting on top of the alcohol, prevents the loss of aromatic compounds in the original drink. The result is a very distinctive and flavourful vinegar. Almost any wine, beer, cider or similar drink will do. The woman who supplied my culture makes hers with Guinness!
I hope this brief overview of culturing foods in your cupboard gives an idea of the range of possibilities. Other cultures to try include sauerkraut, kisiel (fermented porridge from Poland), nuka zuke (bran fermented pickles from Japan), kenkey (sour maize balls from Ghana) and many others I hope to experiment with over the years.