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Brewing Bread: All about yeast and how to get the best from it.

Updated: Oct 29, 2023


Understanding how yeast works and how to get the best from it can lift an ordinary loaf into the realms of excellence.


Here we consider what yeast is, how it behaves and how to get the best flavoured bread possible by using some simple management techniques.


This article only discusses yeasted baking which is where a dough is directly inoculated with commercial yeast.



History of yeast.

Yeast is not a thing. There are probably millions of different yeasts and some thousands which are specialised in fermenting grain. A natural leaven (a.k.a. Sourdough) has many hundreds of different varieties and they change depending on the flour you feed it with and where that flour came from. Commercial yeast is a blend of carefully selected varieties.

Yeast in a monocellular organism loosely related to the fungus kingdom. That is each ‘yeast’ is a single cell. Over the eons different yeasts have specialised to function in different environments living off different things they like to ‘eat’. This specialism is so precise that a vineyard does not inoculate a wine must with yeast, but uses the yeasts already on the grapes, as those yeasts have self-selected and evolved for that very particular variety of grape. The taste of Beaujolais, for example, comes not just from the Beaujolais grapes, but from the Beaujolais yeasts too.


Grain yeasts are the same. In your local field of barley, wheat, or rye there will be slightly different colonies of yeasts on the grain of each one. Each colony self-selected for that grain, area and climate just waiting for the right conditions to start fermenting the grain.


Many texts about the history of leavened bread posit that at some point someone got the idea of adding wine or beer to their dough and low and behold leavened bread was discovered. To a baker this is obvious nonsense. Mill some grain and leave it in a warm place and the yeast colony will grow and make a leavened dough. Leavened bread must have invented itself wherever there was a busy baker having to run off to do other things, or who thought, ‘I’ll mix the dough and bake it fresh in the morning.’ By which time it would have leavened a little.


Moving forward in time we know that Celts, Germanic peoples and Scandinavians (and probably more) used to add beer barm to their breads.

In the 19th Century using yeast left over from beer brewing was common practice. However, changes in the brewing industry led to increasing shortages. In 1846 the Viena Process was invented. This produced the first commercial baker’s yeast. It had the consistency of thick cream and it was called Cream Yeast. Later it was developed into Cake Yeast, with the same consistency as modern Fresh Yeast.


Then came the Biochemists who learned to select yeast strains to make 'cake' yeasts out of those strains which made the dough rise better and faster. We now call this fresh yeast.

Along came the second world war and the U.S. decision to enter the fray. Someone in the War Department asked a simple question. ‘What do our troops need in the field to make life better?’ Many products were improved, or invented. One being the portable petrol stove by Messrs Coleman. Another was dried yeast by Messrs Fleischman in answer to the War Dept.’s request for yeast that had good keeping properties to enable fresh bread to be made in the field.


Fleischmann’s active dried yeast gave way to instant yeast, a more modern process where near 100% of the yeast cells are live and viable. Fleischman’s yeast had 80% viable yeast cells and 20% dead yeast cells. I’ll come back to this as it’s important.

The biochemists kept up their work of selecting the best strains for fermenting bread dough. In the early 1950’s the Chorleywood baking process was invented. This was a high speed industrial baking process suitable for large industrial bakeries who could then produce a loaf from flour to bread in the bag in under three hours. The Chorleywood process needed speed and once again the hidden hand of the biochemists came into play and yeast strains were selected that produced more CO2 and they produced it faster.


These modern strains of yeasts are the same in Fresh Yeast, Active Yeast and instant yeast. Put another way, all of those products have the same yeast strains, varying a little from manufacturer to manufacturer and so whichever one you use you will get the same results. Though this also means that all of those yeast strains were selected for speed and not brewing in flavour.


Yeast has a memory.

It is well understood in the beer brewing trade that yeast has a memory. It remembers the flavours of the food it was fed in the culturing pool and it replicates that flavour in the medium in which it is fermenting.


There is a famous case of this with a Beer Brewer in Northern England. They had developed a new beer wanted a yeast with which to brew it. Yeast cultures were duly selected and in order to build sufficient stock they fed the yeast on apples and still do. Despite the beer having no apples in it the finished beer has gentle apple notes.


The yeasts we buy for baking bread are cultured on a chemical cocktail of nutrients. It’s cheap and it’s fast. However, if the home baker looks around there are some organic bread yeasts which are cultured only on wheat, or barley. I think they produce a better flavoured bread. Perhaps every home baker should try them out, just once and make their own mind up.


Dangerous Yeasts - The importance of dead yeast.

Some industrial bakeries add a little dead yeast to their dough mixes. When a yeast cell dies it ruptures and spills out a whole cocktail of enzymes and flavonoids. Flavonoids are a family of chemicals which impart flavour. Oranges have orange flavoured flavonoids and so forth. By doing this they can impart some flavour to their otherwise fairly flavour free breads. They also use industrially produced malt sugars and other complex sugars to the same end.


Those flavonoids impart some yeast flavours to the dough. However, at the same time the enzymes can destroy the gluten and starch structure and the finished bread can end up as a sticky mess. Only very small quantities should be used. Some people still prefer Active Yeast for that 20% dead yeast count which imparts a slight yeasty flavour to the bread.


Kill your own yeast? We don’t have to, there is a product called deactivated yeast it has no leavening value and is not interchangeable with other yeast types. Typically, it is used for pizza and tin, or pan bread doughs, it’s used at a rate of 0.1% of the flour weight. It also increases the extensibility of the dough as well. That is, it makes the dough less elastic and more prone to spreading. There are better ways of improving dough flavour such as through managing the fermentation.


Types of Commercial Yeast

In addition to the commonly available, Fresh Yeast (a.k.a. Cake Yeast), Active and Instant Yeast there are some specialist yeasts available for baking too.


Rapid Rise Yeast which produces even more CO2 faster than even the ordinary modern yeasts. I expect it is a case of adding to the dough wearing protective clothing and then standing well back. It produces the least flavour in a dough as there is little fermentation time. It really only has a role in commercial baking. Home bakers can always up the dosage rate of their yeast by 50% to get a fermented dough quickly when there is a need.


Osmotolerant Yeast There is something called osmotic pressure. Simply put if we have two bodies of water divided by a permeable membrane and dissolve salt, or sugar only on one side of it, then there is a pressure across a membrane to equalise the concentration of the salt or sugar with the water the other side of the membrane.


Yeast exchanges molecules in and out of its cell across a permeable membrane. If the water the outside of that membrane wall has too much sugar or salt the osmotic pressure is trying to draw the water out of the yeast cell and the yeast can no longer move sugars and other molecules into its cell and the fermentation process comes to a halt. If the pressure is too great the yeasts membrane ruptures and the cell dies.


Simply put, this sort of yeast is for sweet doughs with their high levels of sugar. It can tolerate higher osmotic pressure caused by the higher sugar levels. One source of this yeast is SAF Gold Label, other manufacturers have their own versions.


Deactivated Yeast. As above this is dead yeast sometimes used as a conditioner and flavour enhancer in commercial products.


Managing the Fermentation Process

Fermenting the dough is a brewing process, much the same as beer brewing. As the yeast ferments the sugars from the starches it also produces flavonoids and many other molecules which make a good loaf what it is. The chemistry which takes place within the yeast cell and across it’s membrane is so complex, with so many different processes, that it is not yet fully understood by the Biochemists despite countless millions of dollars having been spent on researching it. However, there are some basic things which are known and these can help us to manage our dough fermentation.


Fermentation Time We are used to judging the state of the dough by the amount it has risen. Essentially, we are gauging the progress of the fermentation by the amount of CO2 the yeast has produced. There are a myriad of other fermentation processes going on in addition to this and they are generally slower than the CO2 production and they need more time. The key one of these is the organic acid alcohol reaction. The Zymase enzyme in the yeast cells produces, CO2, alcohol and organic acids. The organic acids react with the alcohol to produce a range of aroma chemicals. These reactions are much slower than yeast fermentation. By fermenting the dough at a slower rate we give these processes the time they need to produce more flavour. This is one of the key reasons for using cold fermentation in home baking. In cold fermentation we arrest the yeast fermentation but the organic acid - alcohol reactions continue making more flavour.

There is a caveat here. Some flours are high in enzymes and for those doughs fermenting them too slowly, such as in extended cold ferments, can give the enzymes more time to damage the gluten and starch structures. I have discussed this in other articles.


Yeast inoculation rate The amount of yeast we add to the dough will directly affect the speed of the fermentation process. Modern yeasts are fast. Using standard inoculation rates can produce a bread quite easily in a couple of hours using machine kneading and fermenting the dough at 28C, 82F. a bread produced over 5, or 6 hours will taste a better and the crumb will have a better mouthfeel.


The standard manufacturers recommended inoculation rates as a percentage of the total weight of the flour used in the recipe. Divide the weight of the flour by 100 and multiply it by the percentage of the yeast.


Fresh Yeast 2%, or 10g per 500g, 1lb 2oz of four.

Active Yeast 0.93%, or 2.2 tsp per 500g, 1lb 2oz of flour

Instant Yeast 0.63%, 3.15g. or ½ a level teaspoon per 500g, 1lb 2oz, of flour.

Instant Yeast Maximum recommended dosage rate 1%, 5.0g, just under 1 teaspoons per 500g of flour. This will ferment the dough rapidly.

If we want a bread quickly we can double these amounts. Reducing them by 25% will give us a longer fermentation time and better flavour.


Temperature Generally speaking the warmer the dough the faster the yeast will ferment it.

The dough fermentation temperature window is generally about 24C – 28C, 75F – 82F.

2C, 36F the CO2 fermentation is imperceptible.

4C, 39F, The CO2 fermentation is extremely slow, about 1/40th of the peak fermentation of 28C, 82F.

22C, 72F Gives a slow fermentation.

24C, 75F is a generally preferred temperature for a steady slowish fermentation giving good flavour.

26C, 79F. This temperature gives a slightly brisker fermentation, but it is still slow enough to get reasonable flavour. This is a good temperature if the dough is going to be subjected to retarding, or cold fermentation, where there is ample time for flavours to develop in the fridge.

28C, 82F Is my preferred ‘bread wanted urgently’ temperature. The dough will ferment quickly. Flavour is not a prime consideration when there’s no bread for the table.


There are so many different varieties of yeasts all with different temperature profiles. Generally speaking yeasts' ability to ferment ferment slows down rapidly at temperatures above 30C-32C , 86F-90F.


These temperatures probably look fairly unusable to some of us. Using a proofing chamber to increase the dough temperature works exceptionally well. Otherwise, they can work as a guide as to what to expect from the dough. We can also use techniques to regulate the dough temperature. (See below).


Michel Suas in his book 'Advanced Bread and Pastry' notes that 24C / 75F is the ideal fermentation temperature. At this temperature the yeast is fermenting slow enough that the other enzymatic and brewing processes, which are slow, have time to do their work developing flavour. He says at higher temperatures the yeast produces gas faster, but the flavour has insufficient time to develop.


Retarding the Dough Some people refer to this as Cold Fermentation. I've posted another article on this site which goes into the subject in some detail. So I shan't repeat it all here. Retarding the dough is a good way to extend the fermentation time and develop more flavour in the dough. See above under 'Time'.

At 4C-5C, 39F-41F there is very little yeast activity in the dough. It's fermenting at approximately 1/40th of its rate at 28C, 82F. However the flavonoid developing chemistry continues and more flavours are developed.


For cold bulk fermenting I prefer to let my Bulk ferment progress in a warm place for a couple of hours. During this time it has a brief knead at the beginning and two spaced coil folds, the dough goes into the fridge, covered to stop it drying out, immediately after the second coil fold. I do not do any more coil folding to redistribute the temperature in the fridge. My 1kg, 2,2lb batches are small enough that they cool fairly evenly anyway. The dough will remain in the fridge for 12 - 18 hours after which it is removed and given 30min in a warm place before dividing and shaping.


For cold proofing I divide and shape and place the dough in a banneton or similar, covered to stop it drying. A shower cap is excellent for this. It's set to proof for 15min-30min in a warm place before being transferred to a fridge at 5C-C. 39F-41F. It's proofed in the fridge for 12hours - 18hours. From the fridge it can go straight into a pre-heated oven for baking.


Overnight cold proofing is a good technique to prep. buns, or rolls, for breakfast.


Tip: The fridge is a tremendous way to make a baking schedule fit into whatever other demands are going on. I have made a dough, done the initial kneed and then found I had to leave the house to do other things. I just pop the dough, covered, in the fridge, and continue when I am back. An evening bake can be started and continued the next day. It is a pretty handy technique for making bread baking fit into our busy schedules.


How to control Dough Temperature

There are three easy ways to control dough temperature if a proofer is not used.

Firstly, adjusting the water temperature when adding it to make the dough. Secondly using the fridge to cool the dough on hot days. Thirdly to warm the dough a little.

A cheap home proofer can be made by standing the dough container on a thermostatically controlled brewing mat. It is even more effective if large upturned bowl is used to cover it.


General Tricks In very hot weather I use some chilled water from the fridge to make a dough which is below the ideal temperature. Then I monitor the dough and when it reaches 28C 72F I place the dough in the fridge for 30 minutes and give it a coil fold when it comes out, to equalise the temperature throughout the dough mass. I call these fridge holidays.

Similarly, if there is no place warm enough on cold days a number of things can be done. Putting the dough container in a box and adding those microwavable hot packs. Just make sure they’re only warm. In an emergency 20 seconds in a microwave works. It does not harm the yeast, or dough. Some people put the bread in an oven with only the light on to keep it warm.


Controlling the water temperature when adding it to a dough

I do not make much use of this. The small amounts of dough we generally make at home will quickly come to room temperature anyway.


This technique was developed by commercial bakers who use high speed intense machine kneading. That method heats the dough up quite a bit. Even to the point of killing the yeast. Also, because they are working with large volumes of dough it can take hours for the dough to cool down after kneading.


We should not be machine kneading for anything more than a few minutes because the gluten develops of its own accord over time and we give our dough time so that it develops flavour.


When I use a mixer it gets 30 seconds with a beater on the slowest setting to incorporate the ingredients. Sixty seconds on the slowest setting, with a beater again to give the gluten a head start and nothing more. Such slight kneading does not increase the dough temperature by a measurable amount.


An aside on high speed kneading Extended high speed kneading was introduced to develop the gluten fully in order to reduce bulk fermentation times to fifteen minutes, or to skip that step all together. We do not need a dough that passes the window pane test before it goes into bulk fermentation. It also oxidises the dough which destroys the carotene colour and flavonoids. A more flavourless bread will result. Bakers developed two techniques to combat this and we need neither of them. First came the Autolysis method developed to reduce the high speed kneading time with white doughs only. 30minutes to let the flour hydrate without any fat and salt present is all we need. Fat and salt slow the hydration down. The other method that was developed was kneading in a vacuum. The gluten develops faster in a vacuum. I experimented with this and found that placing my dough in a container and making a vacuum with a home vacuum packer device worked really well, but why bother?


I have added a link at the end to Charlie Chain Baker’s superb video on Dough Temperature control using water temperature for those who want to use it.


Yeast Accelerants

This is not a formal term, but it describes these things well.


The millers task The starch in a grain, or berry, is in small packets, not freely distributed as starch. These are referred to as Starch Packets. Amylases breaks yeast down to produce sugars for the yeast, but with the starch being inside the packets it is very difficult for the amylase to access the yeast. Enter the miller’s world. Miller’s deliberately mill the grain to damage about 20% of the starch packets. This allows for good fermentation. If too many of the packets are damaged the amylases go on a binge and heavy gummy bread will result.

By some extraordinary coincidence the big old rotating stones in Water and Wind mills damage about 20% of the starch packets too. So too do the small home mills which use electrically driven stones, such as the Komo, Mockmill, and other similar brands.


Amylase Enzymes I have described enzyme activity in other articles. All we need to know here is to watch out for flours with added amylase. This is becoming more common in some countries, particularly with the weaker bread flours such as T65, T55 flours (French) and All Purpose flours. The amylase accelerates the production of sugars for the yeast enabling faster fermentation times. It also makes the dough more extensible and less elastic, so freeform breads won’t hold their shape so well.


Diastatic Malt is added because of its Amylase content. It also confers a slight malt flavour to the bread. It should be used at about 0.54% of the total flour weight. Much more than that and a gummy loaf will result from too much amylase.

I avoid flours with added amylase. Home baking does not need it and we want slower fermentation.


Non Diastatic Malt Extract Ordinary liquid malt or non-diastatic malts have no active amylase and they don’t cause an issue.

Use dried malt extract at 2.25g-4.5g, or 0.7tsp-1.4tsp to 500g flour, or 4.0%-9% of the total flour weight.

Use Liquid malt extract at 3.6%-7.2%, or 18g-36g per 500g flour, or 2.6%-7.2%

If too much non diastatic malt extract is used a cloying gummy bread will result.

Liquid malt extract is 20% water and so the dough water should be reduced by this amount.

Non-diastatic malt extract provides malt sugars for the yeast and the fermentation time is faster as malt sugars are so easily available to the yeast. They are alsoadded for the malt flavours they impart to the bread.


When to add the yeast

For direct baking, right at the beginning when the dough is mixed. It neither affects the flour hydration nor the autolysis for those who want to use that method.


Storing yeast

Instant yeast will keep in the fridge for a year. Active yeast probably will too, but I haven’t used it for so long I cannot give a time. I did keep once it in the fridge for three months with no problems.

Fresh yeast should be stored in the fridge and used within twenty days. If it has sat in the shop for a while that time is shorter.

Instant and Active yeast will freeze for a year of more. Yeast is not harmed by freezing. For those with a freezer compartment as part of their kitchen fridge, they can both be kept there and weighed out as needed on every bake.


Fresh yeast will freeze too, but it becomes gloopy and difficult to measure.



Here is Charlie Chain Baker's Video on using water temperature to control dough temperature.



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4 Comments


Unknown member
Aug 18, 2023

I put the bowl in a 2 gallon Ziploc bag on the seed mat, it rolls right up when you are done and space-saving.

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Unknown member
Aug 18, 2023
Replying to

Living where I do, with a warm kitchen, I don't need any more heat, but I also use the same bag to store my rising dough.

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Unknown member
Aug 17, 2023

Interesting. Well done. One thing, I do use a mixer, on the low speed for 5-8 minutes, and there is no noticeable change in dough temperature. Now, I do live in a cold house in a cold climate, and have to use a seed heating mat to get my dough to rise, so that may have something to do with it.

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Unknown member
Aug 17, 2023
Replying to

Thanks.

Yes, I'd forgotten about seed heating mats... great things!

I used to use a heated seed tray with a Perspex domed lid. It was thermostatically controlled. It worked really well and was inexpensive.


I a constantly surprised at creativity of home bakers when it comes to making things work for them.

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