When you first saw my Butterkuchen post, did the yeast put you off?
I know several accomplished bakers who shy away from it and as it was also mentioned a few times in my survey, I thought I would write a post trying to demystify using yeast. I'm not an expert at bread making but I do like making enriched breads and, as you can see in my successive Hot Cross Bun posts, I've increased in confidence over the years.
There are several types of yeast you might come across: dried (often called active dry), instant, fresh (a.k.a. cake/compressed) and sourdough starters. For the sweet bread baking I do, I use instant or fresh.
Instant yeast is generally easy to find. You can get it in sachets (often 7g or around 2 teaspoons) or bigger packs. I prefer instant to active dried yeast as you can mix it straight into the ingredients (dried yeast needs activating, usually by mixing it with warm liquids and leaving it for a bit). Instant yeast is formed into lots of tiny rod shapes (as you can see in the photo above) to give a big surface area, which means the yeast starts working quickly once it comes into contact with liquid.
Sometimes the packets have other ingredients - emulsifiers are relatively common, as is the addition of ascorbic acid (a.k.a. vitamin C - some say it increases the rise and/or helps create consistent results, I imagine partly because the optimum pH for yeast fermentation is slightly acidic).
{The photo series below shows a batch of dough rising in my relatively cold kitchen a few days ago - the number in the corner refers to the number of minutes.}
In Switzerland you can buy fresh yeast in the chiller cabinet in supermarkets - even the small ones. It's harder to find in the UK. Bakeries will sometimes give or sell you a small amount but it can be a struggle to find somewhere that bakes on site (surprisingly, one of the best bets is the bakery in a big supermarket). You can also get it online from the Bertinet Kitchen Bakery (they also sell via amazon) - it's delivered in temperature-controlled packaging and I was really pleased with the batch I received last week. It's often sold in small blocks of 42g (you can see one on the right in the top photo). Generally I crumble it into the wet ingredients but it can also be added straight into the dough.
One of my favourite things about working with yeast is the way my hands smell after I've crumbled fresh yeast into the bowl.
To convert a recipe from instant yeast to fresh, triple the quantity (i.e. 7g instant = 21g fresh). Essentially, 10g fresh = 4g active dry = 3.3g instant.
Yeast is a single-celled fungus. There are many species of yeast - the one we use for brewing and baking is called Saccharomyces cerevisae.
Yeast metabolizes sugar in the dough to produce energy for itself. This anaerobic reaction creates carbon dioxide and alcohol:
The carbon dioxide gas is trapped by the dough and inflates it. When you put the dough in the oven the alcohol evaporates - becomes a gas - and therefore also expands, adding to the early rise called oven spring.
This occurs even in a dough where sugar is not added as an ingredient because enzymes in the dough (such as amylase, which we also have in our digestive system) work on the starch, breaking it down into glucose.
Generally, the idea is to use as little yeast as possible to get the rise - a slow rise gives better flavour, partly because of other flavour molecules that develop during fermentation. This is why many recipes call for the first rise to occur overnight in the fridge or use a pre-ferment. If the recipe doesn't tell you to rise the dough overnight and you decide to, you can reduce the amount of yeast (I'd go for half or a third).
Yeast will work fastest at around 38C/100F, but this won't necessarily give you the best result. If you want a quick rise then a temperature of around 26C/80F (a warm place/airing cupboard, perhaps) is convenient - otherwise go for room temperature (usually around 21C/70F) or the fridge.
I've also heard that you can freeze fresh yeast in small pieces to improve the length of time you can keep it. I froze some a few days ago but I haven't tried using it yet so I can't verify it personally. We've always kept fresh yeast in the fridge for 2-3 weeks and dried yeast in the cupboard.
As you can see in the photos, dough can take a bit of time to get going - be patient. It may take longer than the recipe states. The more enriched the dough, the slower the rise is likely to be. Spices (especially cinnamon) can also slow the fermentation - which is why cinnamon rolls usually have the spices in the buttery filling.
So, overall, the three things most likely to cause problems are:
TEMPERATURE
Yeast is a living organism and so, at temperature extremes, it will die (like you or I). The main time this is a danger with enriched breads is if you're scalding milk, melting butter or heating something similar just before you add it to the dough - you need to make sure it cools down (transferring it to a metal bowl and putting it in the fridge will speed it up). I go for body temperature.
SALT
Too much salt or salt that gets directly into contact with the yeast will also cause problems. The key with most recipes is to stir the salt into the dry ingredients before you add the yeast so that the salt is distributed through the flour (so you don't spoon the yeast directly on top of the salt you've just tipped into the bowl). You can also add them to different sides of the bowl.
ALREADY DEAD
If your yeast is out of date, hasn't been used in time or hasn't been stored correctly, it probably won't work. Check the packet date and the amount of time you can use it after opening (for instance, a packet of instant I have states that the sachet must be used within 48 hours of opening). Fresh yeast should be a pale creamy colour, ever-so-slightly damp and smell nice.
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This is the ninth post in my Foundations series, which explains techniques like making meringue (part one, part two) and brown butter.
Four recipes that use yeast:
Stollen
Butterkuchen
Cinnamon Cardamon Kringel Bread
Blueberry Braided Bread
