One of the awkward things about writing recipes for baked goods leavened with yeast is that there are three different types of yeast available commercially. Each has a slightly different quality, each is used in a slightly different way, and there are several different names to boot. It can make for some convoluted recipe ingredient lists.
I wrote more here about the specific species of yeast that we use for foods and our relationship with them, but here I want to look at the types of commercial yeast and how you use them.
Leaving aside sourdough / natural leavens / wild yeasts, the three yeast products in question are: fresh, active dry yeast and instant yeast.
Also known as cake yeast, compressed yeast and, in Italian, lievito di birra fresca (fresh beer yeast), fresh yeast is my preferred form. It is strangely both squidgy and crumbly.
In large scale bakeries, they may use 200g, 500g or 1kg blocks of the stuff, but for the home baker you may find it in 25g, 42g or 50g cubes or in the US I believe it comes in 2 ounce (57g) packs. Italian supermarkets stocked it, but most British ones don’t. I’ve heard that you can ask in in-store bakeries, but as these places are generally not actually bakeries – they mostly buy in pre-made dough and bake it off, rather than making it from scratch on-site – I doubt this. I get mine from a health food shop that sells it in 30g and 60g bags. You can buy it mail order easily enough (eg from Bakery Bits in the UK).
Using fresh yeast, typically you activate it in your liquid – water, or perhaps milk if you’re doing an enriched dough. If the liquid is tepid, the yeast will form a froth after a short while. I prefer to use mine like this as I feel it makes it easier to distribute it into the flour, but Breton-born, Britain-based baker Richard Bertinet, for example, simply rubs it in as you would to add fat to flour. I’ve done this, and it works fine.
Fresh yeast is best stored in the fridge and will only last a few weeks, max. Then it’ll darken and go sludgy and not do you any favours.
Active dry yeast
ADY was the baking yeast I grew up with – small granules that sat in the fridge door in a jar or orange tin. It doesn’t need to be stored in the fridge, but arguably that way it’ll last for months, possibly even years, as it’s pretty much inert, the live component encased within the shell of the granules.
You do need to activate ADY to use it – again by adding it the liquid component of your recipe, and letting it froth up. Adding some sugar or honey to the liquid encourages this, as it gives the yeast some immediately accessible carbohydrates to start feeding on before it gets access to the carbohydrates in the flour.
Also known as easy-blend, easy-bake yeast, fast action or quick, this is another type that can, confusingly, also be referred to simply as dry or dried yeast.
It’s similar to ADY but is finer, almost powdery. I don’t tend to use this, it’s just not something I learned to bake using, or have a particular affinity for, but it’s probably the most commonplace type of yeast available these days.
You can buy it in packs, such as these 125g ones from Dove’s Farm, but most typically you’ll find it in sachets of 7g (1/4 oz), which is about 1 1/2 teaspoons and is considered a convenient amount – you’ll often find recipes with 400g flour and 1 sachet, but recipes that rush the fermentation and proving times may do, for example, 500g and 2 sachets.
The big difference when using instant yeast is that you don’t need to activate it or mix it with the liquid first – you add it directly to the flour.
Compared to fresh yeast – which is essentially a product consisting of exactly the same commercially cultivated microorganisms – instant yeast will contain additives. Nothing too scary – just ascorbic acid and sorbitane monostearate (E491), an emulsifier. Though personally I would rather use a product that’s been industrially messed around with less, even if it’s just a little bit.*
Converting between types of yeast
As with all these things, if you look around online no one is quite in agreement about how to convert quantities of the different types of yeast, but a good rule of thumb is to use half the weight of fresh if converting to ADY, and a third of the weight of fresh if converting to instant.
So for example, a recipe that calls for 20g fresh yeast you could replace that with 10g ADy or 7g instant yeast. Or as percentages where fresh yeast is 100%, ADY is 50% and instant is 33%.
Of course, as you learn more about baking you’ll learn more about these variables – so for example, if you do a longer fermentation, you may be able to reduce the amount of yeast in a recipe and just leave the yeast to keep working. If you want a quick loaf (which I don’t recommend, because long fermentation = more digestible = less issues with wheat), a recipe may call for a much higher proportion of yeast.
My basic recipe made with commercial yeast works with these quantities:
1000g flour (100%)
350g water (70%)
20g fresh yeast (2%) or 10g ADY (1%)
20g fine salt (2%)
If you’re interested in food history – as I am – Dorothy Hartley’s round-up for yeast types from her 1954 book Food in England is an noteworthy comparison. She lists five types of yeast:
Brewer’s Yeast – made by “the brewer’s wife; and sold to the farmer’s wife at market, to which it was carried in earthenware jars.” This is what we’d call barm, and something I’ve experimented with thanks to a supply from my brewer friend Michele.
Dry yeast – for storage or use aboard ships, “made by spreading the yeast out on a wide board, and more on top, over and over, as it dired, till it was a couple of inches thick.” It was then cut into pieces and stored, then reactivated in warm water as we commonly do with fresh yeast.
Potato yeast – potato boiled “and pounded up with some treacle and their own boiled water” with a little yeast added. So not really a type of yeast in itself, more of a medium. Although if left, such a mixture will develop its own wild yeast culture – this is the technique used for Maori rewena bread.
German yeast – imported from Hamburg then later Holland. “It was introduced in about 1850, and by 1866 we imported 5,735 tons in a year.”
Modern yeast – “obtained from a grocer will have a fresh clean smell, and be cool and firm.” She describes breaking it up and activating it in sweetened water, so it actually sounds like fresh yeast.
Possibly creating confusion, in The Last Food of England (2007), Marwood Yeatman says “Compressed yeast, known to the Victorians as ‘German’ or ‘dried’, and which we call ‘fresh’, is descended from brewer’s yeast.”
* All these yeasts are industrially cultivated of course, fed sugars and pushed through a series of tanks, vats and fermenters, sealed to prevent any contamination from wild yeasts. But it’s a matter of degrees and where you prefer to draw your line as the number of additives in our foods increases, even in tiny incremenents. I strongly believe the ever-increasing industrial processing and additives in our food are responsible for so many health and dietary issues and disorders.
When I was a kid in the 1970s, maybe one person in school (say 1%) had a food allergy or intolerance, now every second person has one.
Take wheat – a lot of people have difficulties with it today, or believe they do, hence the proliferation of gluten-free products (many of them hideously industrially processed) and gluten-free baking blogs and books. I ardently believe, however, that for most people (not all) the problem is more likely to be with the industrial “food” product and the ingredients, not with the grain itself. Human civilisation was largely built on wheat, at least in the Middle East and Europe.
If you eat a sandwich made of white sliced “bread” you may well feel bloated and sick; if you eat a sandwich made with real bread – made from just wheat, water, salt and yeast (better yet, sourdough) and fermented for at least five hours, preferably more – you may not have the same reaction. I stopped eating sliced industrial “bread” because it made me feel ill. This is what got me more interested in making real – really digestible, really nutritious – bread.
Humanity developed the skill of converting wheat into a nutritous foodstuff by giving it a long fermentation: a form of processing. And not packing the bread with additives. Sliced industrial “bread” may only be fermented for 20 minutes and is packed with additives. Is it any wonder modern “food” is making people ill when we so readily reject knowledge garnered and honed over millennia in favour of hubristic chemistry experiments?