Fermented Vegetables Troubleshooting Guide

It can be very unnerving for someone new to fermenting to see a layer of fuzzy white stuff floating on the top of the brine. More than one batch of fermented vegetables has been tossed in the garbage for fear of poisoning someone with a seemingly wayward culture, but fermented vegetables are some of the safest foods available. Once you understand the basic characteristics of a culture you will have more confidence in knowing when a ferment has actually spoiled and when you're seeing a harmless variation of normal. Below are some common issues that you may encounter with your cultured vegetables, along with simple remedies.


White Layer on the Surface

Usually a whitish layer floating on the surface of the ferment is not mold at all, but rather a layer of yeast called kahm yeast. It can develop as the lactic acid bacteria consume all the sugar and the pH of the ferment drops. This layer of yeast may have a textured or wavy surface. The easiest thing to do is simply remove the white layer and discard it as soon as you notice it forming. The vegetables below the surface are still fine. The most common reasons for the development of kahm yeast are that the vegetables are not submerged in brine, or the container is not sealed.

To prevent the development of kahm yeast, try to maintain an air-free environment for the vegetables as they ferment. An airlock is a good way to accomplish this. You could also cover the surface with vegetable leaves like the outer layers of cabbage leaves to keep the fermenting vegetables submerged in brine. A zippered plastic bag filled with water also works as a weight to keep vegetables submerged. Vegetables are more likely to develop mold in warmer temperatures, so try to keep your ferments in a location that does not get over 70°F.

Colorful Layer of Mold on the Surface

A colorful layer of lumpy or fuzzy material is most certainly mold. If your vegetable ferment grows mold, use this guide to figure out why mold may have grown and what to do about it.

Usually, a layer of mold or yeast on the surface may be scraped off and discarded, along with any discolored vegetables that may be above the brine level. Once mold is removed, always test the aroma first. If the batch smells fine, taste a small amount. If the vegetables taste fine and have a good texture, not mushy, they should be fine to consume.

If someone in your household has a mold sensitivity, always use your best judgment before consuming any vegetables that had mold growth on the surface. When in doubt, discard the entire batch. 

Brine is Foamy 

Some vegetables foam more than others. It is not uncommon to see some foaming on vegetables that have higher sugar contents, such as beets or carrots. The foaming is completely harmless and generally disappears after a few days. You may also notice some bubbling in the jar as gases are formed by the fermentation process. Again, this is normal. 

Ferment Has a Pungent Odor 

There is a difference between a putrid odor and just a strong fermenting odor. Let your nose be your guide here. If the ferment smells just downright rotten and has a layer of mold on top, try removing the top layer and see if the entire batch has the same odor. Some ferments won’t appeal to all noses, so if you can’t stand the smell, you may not want to eat it even if it isn’t something that would harm you. Truly putrid ferments could be a result of unclean equipment, or not enough salt, or vegetables that were too old to culture successfully. If the ferment is just plain nasty-smelling, it is safest to discard it.


Brine is Slimy 

Slimy brine or vegetables is an indication that slime-producing microorganisms are present. This can be from a too-weak brine, which allows the growth of such microorganisms, or it can be from too warm a culturing environment. Other possibilities include not enough brine (not covering the vegetables), an uneven distribution of salt in the ferment, or air bubbles left in the jar when you  pack the vegetables. (Make sure you push them down tightly!) You can also get slimy vegetables if you don’t remove scum from the surface of the brine regularly. If you are fermenting pickles, and don’t remove the blossom stem, enzymes from the blossom can cause softening of the pickles. If the brine or vegetables are not slimy, they are still safe to eat, but slimy vegetables should be discarded. 


Finished Product is Too Salty 

You can rinse off excess salt, but in doing so you lose the healthful probiotics as well. Overly salty sauerkraut is a great addition to a bland soup, though. If you taste the ferment before fermentation is complete and discover it is too salty, you can dilute the brine with additional water as long as you leave adequate space in the fermentation vessel. If necessary, pour off some of the salty brine before diluting. Overly salty ferments are entirely safe to eat, if unappetizing.


Finished Product is Soft and Mushy 

It’s heartbreaking to ferment a large crock of cucumbers only to have them turn out mushy and unappetizing. Surface molds that have not been removed can contribute to mushy vegetables, but most often, the reason for mushiness is too much heat. The temperature of the room where you are fermenting should stay around 70°F or below. In the summertime, when cucumbers are at their peak, temperatures can climb into the triple digits, so this can be a challenge. If you don’t cut off the blossom or blossom stem from cucumbers, enzymes may cause softening of the pickles. Another reason for mushiness, especially in cucumbers, is not enough tannin in the brine. An easy fix is to place an organic black tea bag in each jar of ferment. Some people use an oak leaf or grape leaf, but a tea bag will work just as well, and is often more convenient. Mushy sauerkraut can be used in soups or other dishes where texture isn’t important. 


Culture Has Crawly Things in It

The ultimate YUK factor, but not as dangerous as you might think. This comes from leaving the fermenting vessel open so flies can get in. They lay their eggs on the surface, and the flies then hatch into maggots. You can remove the surface layer (the maggots will usually be close to the surface) until you reach clean vegetables or you can compost the entire batch. It’s up to you. To prevent this from happening in the future always cover the fermenting vessel with some kind of lid. A clean cotton cloth or coffee filter secured with a rubber band is enough to keep flies out. A covered crock or an airlock completely eliminates this problem. 


Non-pink Vegetables Turn Pink

Red cabbage mixed with white turnips will yield lovely pink sauerkraut, but if your green cabbage turns pink there is a problem, and indicates that microorganisms are growing improperly. The most likely reasons are: too much salt was used, the salt was unevenly distributed in the ferment, or the ferment was improperly covered or weighted during fermentation. Pink ferments of non-pink vegetables should be discarded.


Ferment Bubbles Out of the Jar 

This is messy, but not harmful. If there is not adequate space left in the fermentation vessel to accommodate expansion due to the gases produced, the liquid will have no place to go but out the top of the jar, even if it has a lid on it. A plastic lid has enough space for the liquid to seep out, but a metal lid and band combination will keep building up pressure until the lid bends or the jar explodes. If you are using a metal lid and cannot depress it, gently loosen the ring around it very slightly. You will hear gases escaping as bubbles rise to the surface. If you open the lid too quickly you are likely to get drenched or at the very least have a mess to clean off your work surface. Never fill your fermentation vessel more than 80% full. If you are fermenting fruit or a high-sugar vegetable, try not to fill it more than half full. Check the lid on your ferment daily and release pressure if necessary. 


There is White Sediment in the Jars

A small amount of sediment in fermenting jars is normal, and a result of yeasts settling to the bottom of the ferment. You can also get this if you use table salt with anti-caking ingredients instead of pickling salt or sea salt. Ordinarily, the ferment is safe to eat, but if the vegetables have become slippery or slimy, it indicates an improper growth of microorganisms and you should discard the ferment.

Brine Becomes Cloudy

Some amount of cloudy brine is normal as the lactic acid is created in the ferment. If you are fermenting for more than a couple of weeks, it will usually settle. Sometimes brine will become cloudy when white sediment is disturbed. This is safe to eat.

Vegetables Become Dull or Faded

Vegetables that are originally somewhat pale, or vegetables that are overly ripe when fermented, can become dull. They can also fade if exposed to excessive sunlight. They are perfectly safe to eat, however.

Vegetables Turn Dark While Fermenting

If you are using hard water, minerals in the water can react with pigments in the vegetables to turn them dark. Iron is the worst offender for darkening, but is harmless to eat. If the water or your utensils contain copper, brass, or lead, there could be some leaching of these minerals into the vegetables, which is not good. If you suspect mineral overload in your water, you can consult with your water district or have your water tested.

Other reasons for darkening include: ground spices used in the ferment, vegetables unevenly salted, too warm a culturing temperature, brown sugar added to the ferment, or oxidization due to exposure to the air.

Garlic Turns Blue or Green While Fermenting

This reaction may be due to iron, tin, or aluminum in your utensils, water, or water pipes reacting with the pigments in the garlic. Or, the garlic may naturally have more bluish pigment, and it is more evident after pickling. Immature bulbs should be cured two to four weeks at 70°F. The ferment is safe to eat.


Vegetables Don’t Seem to Be Doing Anything 

Fermentation needs a moderately warm temperature (around 70°F). If it is much cooler than this, fermentation will be greatly slowed, but not necessarily stopped. If the temperatures in your house are on the cool side, consider moving the vegetables to a warm location like a cupboard above the refrigerator. Also, using whey or a vegetable starter culture will speed up fermentation by ensuring there are plenty of the right kinds of bacteria necessary for culturing.



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Fermentation Troubleshooting Guide

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