Starter cultures explained: a beginner's guide to kefir grains, ginger bugs and more

Many ferments can be started with basic ingredients you have lying around your house. Others - like kombucha, kefir and tempeh - need a bit of a helping hand. Read on for an introduction to some of the most common starters used in fermentation, and how to use them.

Great British Chefs is a team of passionate food lovers dedicated to bringing you the latest food stories, news and reviews.

Great British Chefs is a team of passionate food lovers dedicated to bringing you the latest food stories, news and reviews as well as access to some of Britain’s greatest chefs. Our posts cover everything we are excited about from the latest openings and hottest food trends to brilliant new producers and exclusive chef interviews.

Great British Chefs is a team of passionate food lovers dedicated to bringing you the latest food stories, news and reviews.

Great British Chefs is a team of passionate food lovers dedicated to bringing you the latest food stories, news and reviews as well as access to some of Britain’s greatest chefs. Our posts cover everything we are excited about from the latest openings and hottest food trends to brilliant new producers and exclusive chef interviews.

There is a huge range of different things which can be called starters in fermentation. From slimy wads of SCOBY to dehydrated microbial cultures and even shop-bought yogurt. This guide will help you understand how to use some of the most popular starters used in fermentation - as well as when you might not even need one in the first place.

Some starters are optional

Most fermented vegetables - like kimchi, sauerkraut and tepache - don’t need a starter culture at all. Although some recipes will recommend adding a bit of whey or pickle brine to a vegetable ferment as a fermentation starter, it’s not essential. Through the combination of salt, an anaerobic environment, and time, vegetables will ferment quite happily with no encouragement from a starter culture whatsoever.

Some starters are essential

Incorporating some of an old ferment into a new one is rather delightfully called ‘backslopping'. And, although backslopping is optional for lacto-fermented produce, it’s fundamental to making kombucha, vinegar, yogurt and many other ferments. When making these ferments, starter cultures - and backslopping - are essential.

Some starters are just part of the story

For some simpler ferments - like yogurt, kefir and sourdough - you pretty much just need a starter and whatever you're fermenting. For other ferments, things get a bit more complicated. Isolated microbes are needed to make many cheeses like feta or brie. These microbes are sold as ‘starter cultures’. But unlike microbial starter cultures for natto, koji and tempeh, cheese starters often need to be used in conjunction with other ingredients, like rennet and cheese salts.

Making starters from scratch

Sourdough starters, ginger bugs and turmeric bugs can all be made from scratch in a few days from basic ingredients like sugar, flour, ginger and water. This style of fermentation was dubbed ‘wild fermentation’ by fermentation expert Sandor Katz. Naturally occurring yeasts and bacteria in the air and flour multiply and form microbial communities, which can then be used to make fermented food and drink.

Wild fermentation is also how most lacto-fermented fruits and vegetables are made. The key strain of bacteria which makes lacto-fermented produce taste so great is lactic acid bacteria (or LAB). Unlike many microbes, LAB thrive in salty, low pH, anaerobic environments. So long as the ferment is made with plenty of salt and kept in anaerobic conditions, LAB can multiply quickly and produce lactic acid. Lactic acid lowers the pH of the ferment, and allows LAB to out-compete other potentially harmful microbes, which tend to prefer less salty and acidic aerobic environments. This results in a safe and tangy ferment without the need for microbial starter cultures.

A guide to starter cultures

Read on for a quick introduction to some of the most popular and beginner-friendly starter cultures, and how to use them to make delicious ferments at home.

Sourdough starters

Sourdough starters are one of the most famous types of starter around. Easy-ish to make at home with just flour and water, sourdough starters are the basis for yeasted breads, waffles and cakes across the world. With a bit of tinkering they can be used in the place of commercial yeast in almost any recipe. They come in a huge range of forms, including liquid, stiff and dehydrated. We have a range of sourdough starter recipes on the website, including both classic wheat and tangy rye starters. Discard sourdough is also delicious in pancakes, waffles and any recipe where you want a bit of funk.

Milk and water kefir grains

Kefir is a great ferment for beginners. It doesn’t require any special equipment - or even heating up - and once you’ve bought them, kefir grains can be reused again and again. Although they are both called kefir, milk kefir and water kefir (also known as tibicos) are very different products. Milk kefir grains make milk thicken and turn tangy, a bit like yoghurt but slightly runnier. Water kefir grains on the other hand make a sweet, slightly acidic bubbly drink. Water kefir can be made from all sorts of things like fruit juice, coconut water and tea, whereas milk kefir is usually just made from milk.

Kombucha SCOBY

If there was an award for the strangest looking type of fermentation starter, it might have to go to the SCOBY, or symbiotic culture of bacteria and yeast. These rubbery, slimy discs look a far cry from anything you’d expect to be food-safe. However, they are in fact the key to making kombucha, a vinegary tea-based drink. In order to make kombucha at home, all you need is a kombucha SCOBY (from a kombucha-brewing friend or bought online), some kombucha from a previous batch, sugar and tea. The kombucha SCOBY ferments the sugars into acid, producing a tangy, funky drink. Jun tea is a cousin of kombucha which is made with a SCOBY that likes to ferment honey rather than straight sugar.

How to make kombucha
How to make kombucha

Vinegar mother

Many people buying Bragg’s apple cider vinegar will have seen - and possibly been confused by - the proud claim emblazoned on the front of the bottle that it is sold 'with the ‘mother’'. A vinegar mother is the starter for making vinegar, and looks very similar to a kombucha SCOBY (that is, like an alien blob). The vinegar mother contains acetic acid bacteria (AAB). AAB like to eat alcohol and turn it into acetic acid, (the main acid in vinegar) as well as smaller amounts of other acids like gluconic acid and ascorbic acid. To make wine vinegar you need some vinegar from a previous batch, the wine you’re fermenting and a vinegar mother. You can also make vinegar completely from scratch through a two-step process, where you first make wine and then ferment it into vinegar. You can use homemade vinegar in other ferments like homemade shrubs for cocktails, or infuse with raspberries or elderflowers.

How to make a shrub
How to make a shrub

Ginger beer plants and turmeric bugs

Ginger beer plants (also sometimes called ginger bugs) are the starter culture for ginger beer, and like sourdough starters they are easy to make at home. You simply mix sugar, water and ginger or turmeric together, and then feed the mixture daily with more sugar and ginger until it starts to bubble. Homemade ginger beer will be slightly alcoholic - more so than kombucha - reaching about 1% ABV after 3 days of fermenting and around 2–3% after a week.

Tempeh starter culture

Like tofu, Indonesian tempeh is made from soybeans, but where tofu is made from coagulated soy milk, tempeh is made from fermented, whole soybeans. In order to make tempeh all you need are hulled soybeans, tempeh culture and vinegar. Tempeh culture contains mould spores - specifically, Rhizopus oligosporus - which grow on the soybeans, binding them together into a delicious block. Tempeh can be a bit finicky - it needs to be kept warm but not too warm, and can easily either over-ferment or overheat. However, homemade tempeh is really delicious and it is a lot of fun to learn to make from scratch.

Yogurt starter

For most home cooks, yogurt starter is simple - it’s just more yogurt. Add a small amount of shop-bought yogurt with live cultures to warm milk, and incubate it for 12 hours and you’ve got yogurt. However, you can also buy yogurt starters to make specific types of yogurt. Viili, a ropy, stretchy, slimy yogurt, filmjölk and piima are all Nordic yogurts with specific textures that call for specific starter cultures. Matsoni (also called ‘Caspian Sea yogurt’) starters produce a thin, less sour type of yogurt. Skyr looks and tastes a lot like a strained yogurt, but it is actually coagulated with rennet as well as some Skyr starter. This makes it more like a cheese. However, it’s not much harder to make than strained yogurt, and a small container of rennet lasts a long time.

Many Nordic yogurt starters - and all matsoni yogurt starters - are ‘mesophilic’, meaning that they will coagulate even at low temperatures. This makes them particularly easy to make at home since they don’t need to be incubated, unlike store-bought yogurt starters.

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