What is Kahm Yeast and Why is it in My Cultured Vegetables
What is that white stuff floating on my fermented vegetables? It is most probably kahm yeast.
The appearance of kahm yeast in one of your vegetable ferments can be alarming to say the least. Its appearance is far from attractive, and if one does not know what it is, a natural reaction would be to throw the whole batch of fermented vegetables out and start afresh.
Surprisingly, this is not necessary!
Kahm yeast can easily look like mold to the untrained eye. However once one knows what kahm yeast is, what it looks like and what causes it, you will easily be able to identify it. While kahm yeast is not harmful, it is still not what you want to see on the top of your beautiful culturing veggies – so let’s find out what it is, what it looks like – and what to do to make sure you never see it again. Or at least very rarely. : )
What is Kahm Yeast?
Kahm yeast, despite the misleading colloquial term, is actually a small colony of different species of yeasts, such as Pichia, Hansenula, Debaryo-myce, Mycoderma and Candida. These species of yeasts which occur in kahm yeast are not classed as harmful, and in fact most of them are considered probiotic!
But hold on, isn’t Candida really bad? Yes, Candida albicans, the yeast species responsible for what we refer to generally as ‘candida infections’ is not present in kahm yeast or fermented foods. The other members of the Candida family do not have an encouraging effect on Candida albicans and do not possess health threats. They too are largely considered probiotic, and actually compete with Candida albicans in the gut.
Appearance: Mold Versus Kahm Yeast
Kahm yeast manifests itself as a white layer which can completely cover the top of ferments. It looks terrible! Sometimes it can take on the look of fine crepe paper in texture. IF you examine the image above, you will see that the structure old mold (left) and kahm yeast (right) are distinctly different.
How to tell that it is not mold:
If you have got mold growing on your ferment, you definitely want to know about it, and not mistake it for kahm yeast. Thankfully mold has a definite feature in that if you look closely you will see that mold always has a dry, furry appearance, caused by a multitude of fine ‘hairs’ sticking up. Mold will also not grow onto the surface of water, whereas kahm yeast does so with ease. The trick is to take a super close look – you will probably be able to spot the difference with ease.
What Causes Kahm yeast
Kahm yeast often develops in ferments which have exposure to excess oxygen. Another main culprit when it comes to kahm yeast is using old vegetables which are no longer fresh. Very warm temperatures can also encourage the growth of kahm yeast, especially if either of the above factors are present.
Is Kahm Yeast Poisonous?
Fortunately, seeing as kahm yeast tends to pop up every now and again, it is in no way harmful to humans when accidentally consumed. As mentioned earlier, some of the yeast strains contained within it are considered probiotics!
Why You Don’t Want Kahm Yeast in Your Fermenting Vegetables
Although kahm yeast is not harmful when ingested, it is not the ideal thing to have in one’s fermentations, for the following reasons:
Kahm yeast usually does not have a pleasant smell, in fact it is quite unappetizing and can put you right off your batch of cultured vegetables.
If kahm yeast is allowed to go unchecked in your ferment, it will most probably result not only unpleasant smells, but can also add an unpleasant flavor in your ferment.
What to do About Kahm Yeast
While kahm yeast can easily develop if given a chance, and is a fairly common fermenting occurrence, it is also relatively easy to keep away. Below are six things you can implement to lower any chances of kahm yeast developing.
# 1 Keep Your Ferment Airtight by Using an Airlock
One of the best ways to keep out kahm yeast is to make your ferment completely airtight, and this can be achieved by using an airlock. Airlocks release pressure build ups, while not allowing any new oxygen into the ferment.
# 2 Use Fresh Vegetables
Make sure that you always use fresh vegetable for your ferments. Don’t wait around for them to get old in the fridge. If you have an excess, or have bought specifically for making a ferment, get right down and do it before they have any time to lose freshness.
# 3 Use a Vegetable Starter Culture
To secure your ferments against kahm yeast, you can ramp up the probiotic content and fermentation power by adding in a purchased cultured vegetable starter. This will inject a few of the most desirable probiotic strains which are harnessed in vegetable ferments, and make the fermentation process so strong that it will be difficult for foreign yeasts or bacteria to enter.
# 4 Add in Some Brine From a Previous Ferment
Another way to incorporate extra fermentation microbes from the start is to add in a little brine from a previous ferment. The brine will contain some free floating bacteria which can kick start the new ferment into action and help to keep out kahm yeast, mold and any other undesirables.
# 5 Try to Give Your Ferments a Cool Temperature Range
Kahm yeast often develops in warm temperatures. To protect your ferments from it, try to place them in a cool well ventilated spot. Take note that the cooler the temperatures, the slower the fermentation process will be. This however is not a bad thing, as long slow ferments can be higher in probiotics and develop complex flavor profiles.
# 6 Make Sure You Are Using Enough Salt
Salt is what provides the lactic acid bacteria (the main drivers behind vegetable fermentation) with an environment where they do not have competition, and can multiply and ferment. The reason for this is that they are resistant to salt, while many other microbes are not. If you have reduced the salt in the your fermentation recipes, you might want to increase it a little bit once more, to ensure that your fermenting veggies are still protected from kahm yeast, mold, and any other agents of decay.
Keep the Vegetables Submerged
One last trick to keeping kahm yeast from knocking at the door is to try and make sure that all of your veggies are properly submerged. This can be tricky, but keep in mind that any vegetables which are completely submerged in brine are safe from outside microbes.
While kahm yeast is not the terrible thing you probably suspected it to be on first encounter, it is also not an occurrence which you want to have in all of your vegetable ferments. The smell and taste of kahm yeast is unpleasant off putting. If you are endeavoring to get your family or friends to eat a little cultured veg, the last thing you want is to scoop some out for them from under a skin of kahm yeast!
Fortunately there a quite a few things one can do to keep kahm yeast out of your ferments. Implementing these things has the added benefit of not only deterring kahm yeast, but also protecting your ferments from mold and other pathogens, as well as injecting it with probiotic power!