Salt Kills Yeast

Lets talk baking myths

Hello everyone! Lets talk about baking myths.

Is there anything you’ve always believed to be true, but have found yourself questioning the logic of? Something you’ve been told is imperative to a recipe, which you’ve believed and followed without further interrogation? I’m thinking about things like avoiding dark bakeware because it affects how baking browns, avoiding stirring a caramel like your life depends on it, less the whole thing crystallise. These incredibly common theories seem to passed down through cookbooks, tv chefs and simply word of mouth, but are they actually true. Do we believe these things simply because a supposed ‘expert’ tells us? Or is it because they seem true? Or could it be simply that, the more you hear something, the more it is repeated, the more secure you feel in following the advice?

I started thinking about this topic because of a viral video. I posted a video, on tiktok and instagram, showing how to make my whipped caramel (from a recent newsletter) and it went viral on both platforms; as of writing the videos have a combined 3 million views. The amount of comments from people telling me ‘DONT STIR THE CARAMEL’ makes up a not unsignificant proportion of the comments. These comments don’t just come from home bakers but also plenty of professionals. These comments got me thinking about why we believe these rules and how they become embedded in our collective baking psyche? I also realised that every time I post a bread video there will inevitably be people telling me I know nothing, because I add my salt and yeast together. And that brings us to the topic at hand.

To delve further into this topic I want to start with the big one, the myth, or potential myth, that seems to have gained the most traction; the idea that salt kills yeast. Countless TV bakers, even more cookbooks, and just about every internet commenter out there, will have you believe that salt and yeast should never cross paths, that they need adding to opposite sides of the mixing bowl to segregate them, and that only when dispersed amongst flour are these two sworn enemies in a state of détente. The basic thought is that the mere presence of salt kills the yeast and prevents the bread from rising. The truth, unsurprisingly, is more complicated. Let’s dig into it.

To dispel, or to prove, this idea I devised a very simple experiment. I would take three identical jars and fill them with a small amount of bread dough adding the salt in a variety of different ways. This would allow me to measure how salt effects the yeast and to see if there is any truth to the myth. The jars would all include 75g bread flour, 1.5g yeast and 75ml water. The water level may seem high, but this is simply so the dough would be more of a batter so the dough could be mixed together very quickly, and without kneading, meaning the three jars would be ready within 2 minutes of each other, ensuring a fair test. The first two jars would also use the exact same amount of salt, just 2% so only 1.5g. The third jar would differ in that it would include a lot more salt, 10% in fact, to test a theory that it’s not the presence of salt but actually the amount of salt which would kill the yeast.

In bread baking, you’ll find many recipes are written using something called bakers percentage. This is simply a means of expressing the weight of the ingredients in relation to the flour. The flour is always 100% and the remaining ingredients are reflections of that amount. For example, if the flour used is 500g/100% the water amount being 350g would mean the dough is 70% hydration. Every ingredient can be expressed in this way and it enables you to scale up recipes with ease. When it comes to salt, most bread recipes use a relatively similar amount, around 2%. Some very rich breads like brioche use marginally more, but 2% is the most common amount of salt you’ll find used in bread recipes. This is therefore the amount of salt used in the first two jars, to make it a realistic real world test. The third jar uses a lot more salt, 5 times more at 10%. It is worth noting you would simply never use this amount of salt, the bread would be inedibly salty. I thought it was still worth testing, on the off chance we learn something.

In jar no.1 the salt and yeast were mixed together and left to sit for 5 minutes before being mixed into the flour. In jar no.2 the salt and yeast were added to the flour on separate sides of the jar and mixed together before the water was added. In jar no.3 the salt and yeast were also added separately, but a lot more salt was added. The water used for all three jars measured the same temperature, as did the flour, the jars and the room.

So What happened?

Jars 1 and 2 behaved identically, they rose at the exact same speed. In the hour it took jars 1 and 2 to double in size jar 3 seemingly did nothing, it looked basically the same as when it was mixed together. Proof that the rule is somewhat true, salt (in large amounts at least) appeared to kill the yeast, right? As it had no effect on the first two jars this would never be a problem though, because you’d never use 10% salt in bread baking. Rule semi proven, right? Not so fast. I decided to leave jar 3 for a while longer, 5 more hours in fact. After that window of time had passed, the dough had in fact doubled in size. What this seems to suggest is that salt doesn’t kill yeast but that it can simply slow it down, it affects the rate of fermentation rather than stopping it in its tracks. But what this test also shows is that bakers still shouldn’t worry about this rule, at the most common levels used to make bread, salt does not kill yeast. And further than that, it doesn’t matter one bit how you mix the two together. To further prove this point I did a second experiment.

For my first experiment I used fast action (instant) yeast as it is what I typically have on hand. Did the fact that the yeast had been dried out insulate it from the effects of the salt? To test this I repeated the test for jars 1 and 2 simply swapping out the dried yeast for compressed bakers yeast, also known as fresh yeast or cake yeast (because it is pressed into ‘cakes’). For jar 1 the yeast and salt were mixed together and left for a few minutes. In this time, the salt reacted with yeast breaking it down into a liquid, definitely interesting, but did it have any further effect? In jar 2 the salt was mixed into the flour and the yeast was dissolved in the water before being combined. Once again the behaviour of the two doughs was identical. This further confirms that salt doesn’t kill the yeast and when following an existing bread recipe you do not have to worry about how the salt and yeast are combined, using 2% salt will not kill your yeast. It is worth pointing out that there may be a percentage of salt which might actually cause the yeast to slow down so much as to seemingly kill it but in a real world, where 2% salt is the commonly used amount, and even accounting for some variation, salt isnt going to kill your yeast and the method of mixing doesnt matter.

Is there anything else to learn. Well, yes, salt is actually incredibly important to bread doughs. Firstly as you can tell from the above tests, salt controls the rate of fermentation. Bread made without salt rises quicker and the more salt you add the slower it rises. But it does more than that, it strengthens the gluten, it improves browning and of course it adds flavour. Dough made without salt will rise quickly but the resulting dough will be weak, and can collapse more easily that a dough made with salt, will be stickier and harder to handle. If you’ve ever made a bread recipe that includes an autolyse, where the salt is added after the flour and water have been mixed and allowed to rest for a period, you will know that when salt is added, the dough tightens and becomes instantly less sticky. The salt strengthens the gluten enabling the dough to more effectively hold onto the carbon dioxide the yeast produces as the dough ferments. Yeast works by eating the natural sugars in the dough and then burping out carbon dioxide; its this gas that allows the dough to expand. Salt slows the rate at which yeast can consume the sugars meaning that when the dough is baked, there are more sugars left in the dough meaning it can also brown to a deeper shade.

Final thought? Salt is incredibly important to the bread making process but the effect it has on yeast is massively overblown. When making bread with the most commonly used amounts of salt, you do not have to worry how its added, mixing it with the yeast wont cause any harm to the dough.