Spoilage is a concern of many people, especially when they are just getting the hang of pickling and fermenting foods. It DOES occur. It is detectible when it happens (see our article on how to tell if food is spoiled). But what causes it?
Spoilage CAN occur from a range of sources. But the most common causes are actually NOT the things people think they would be.
Foods are most likely to spoil during two specific phases:
1. During the beginning phase, when the ferment is just getting started. This will be noticeable right away – the ferment never really develops the characteristic pickled or sour smell. Instead, it gets a funky smell (ok, so there just isn’t another word for it… if you smell it, you KNOW). It is NOTHING like the sharp smell of properly fermented foods. It is musty or odd, or something that just makes you wonder exactly what happened.
There are a number of potential causes for this, but only FOUR primary causes. (We used to have only two, but two new ones have cropped up.) Surprisingly, it is NOT because you forgot to wash your hands, or because you did not sterilize your containers, or even the strength of the salt in the brine. The first two have minimal affects – people used to brine foods under appallingly unsanitary conditions and it worked very well. The salt brine strength can help to compensate for questionable conditions to a certain extent, but not completely, and foods can be successfully fermented without adding salt (though we do not recommend it because the rate of failure is pretty high).
The primary causes for failure of the ferment to properly establish in the first place, include ONE that is a method issue, and three that are quality issues:
Failure to submerge the food. All of the food must be held under the brine. With kraut, a heavy weight must be placed on it to press the juice out of the cabbage and keep the cabbage pieces under the liquid. Failure to do this is the number one User Error issue.
So Rule #1 is: Keep the food under the brine!
Spoiled Food. If your food is starting to mold, do NOT use it for fermenting. You need good fresh food for fermenting. Even if you trim off the moldy parts, and wash it well, there is a very high chance that the foods you are handling have already been contaminated with a high degree of mold spores. It actually takes a lot to spoil a batch, and usually in combination with other factors. Sometimes a stronger salt brine CAN compensate for food that is on the edge, sometimes not, depending on the food, the water quality, the temperature, and the cussedness of the molds involved.
So Rule #2 is: Good fresh food that is not starting to spoil already.
Water. NOT well water – untreated water is NOT the cause of the majority of water caused spoilage. Chlorinated water is the culprit. Chlorine and other chemical contaminants in water are designed to KILL bacteria and fungus. That is why they are there. They aren’t picky about WHERE they kill those microbes (in the water, in your gut, in your foods, etc). In a ferment, that often means that they will kill the good bacteria, and let only the really resistant nasties thrive – and after so many years of government requirements for chlorine in municipal water, there are some really mean resistant beasties thriving in chlorinated water, and living in your kitchen. You get a yucky ferment instead of a good one if your water happens to be over-chemicalized, or inhabited with resistant microbes.
This is not a simple thing – some water has so little chlorine, and few enough resistant strains that the good beasties grow anyway and you get a good ferment in spite of it. Sometimes a stronger salt brine will help compensate, sometimes not. Sometimes a Brita or Pur type filter will be sufficient, sometimes not. On occasion, municipal water is so contaminated with chlorine and other chemicals that no amount of filtering (other than reverse osmosis) will clean it enough to get a good ferment. In general, winter ferments are more likely to succeed with municipal water than summer ferments – because pathogens are more rampant in warmer temperatures, water levels tend to drop in the summer, concentrating the contaminants, and some municipalities will compensate at times in the summer with extra chlorination.
Boiling the water only partially helps – chlorine tends to evaporate slowly out, but many places are adding chloramines, which do NOT evaporate.
So Rule #3 is to use clean water – good fresh well water, or cleanly filtered water.
Preservative contaminated food. That’s right, there are preservatives sprayed on your produce, and no labeling requirement to indicate that they are there! If you purchase non-organic pickling cukes with the spines removed, or cabbage from the grocery store, or other vegetables from the produce aisle in the grocery store, chances are, it has been treated with some kind of preservative. EVEN SOME ORGANICS ARE TREATED WITH CHLORINE, but organics still usually have a better chance of not spoiling in a ferment. Preservatives on your produce will cause foods to spoil, even when you do everything else right.
Detergents used to “clean” foods will also cause this problem. DO NOT USE VEGGIE WASH on your foods if you are fermenting! Plain clear UN-CHLORINATED water is the best choice, NO detergents.
So Rule #4 is to purchase FRESH food, LOCALLY if possible, ORGANIC if not possible.
2. At the end of the storage phase. A ferment will progress through many phases of bacterial and yeast life. As one form of food is consumed, the microbes that consume that food will multiply, thrive, and then die off. As they do, they are replaced by the next cycle that consumes either what the first batch did not consume, or the byproducts from the first batch. The food may progress through many phases of this kind. Eventually the food sources for healthy microbes wears out, and there is nothing left but fodder for the unhealthy ones, which will take over, resulting in a fairly marked and rapid spoilage of the food – mold, slime, squishy feeling, gray color, and unpleasant smells, all of which tell you this is no longer food.
All ferments eventually spoil!
The problem is when they spoil too soon. After only a few weeks, or a few months. Good ferments, properly stored, should last 4-6 months if stored in a root cellar, and FAR longer if stored in a fridge.
There are THREE main factors that affect this. Again, it has less to do with the finer points of handling, and more with the biggies.
Temperature: This is the most influential factor. Cool temperatures, down to about 40 degrees, keep ferments fresh longer, as a general rule. There are some that don’t thrive at low temperatures, but they usually STORE best at lower temps. Your typical kraut, pickle, or condiment ferment stores best between 40 and 50 degrees.
Freezing will kill some of the bacteria, and leave it ripe for infestation by nasties when it warms back up. Higher temperatures mean that the fermentation progression just happens faster – sometimes WAY faster.
Keeping the Food Under the Brine: Again, this is a prime factor. Keep the food dunked, and it will be preserved much better. Small bits usually are not the issue. Big bits are. If they stick out of the brine very much, they’ll mold before they cure, or degrade faster after they cure.
Brine Strength: More salt generally means it stores longer. Successful ferments can be achieved using a wide range of salt concentrations, but as a rule, the heavier salt concentrations lead to a longer storage life. Salt can also help to offset other factors that may be less easy to control, but usually only to a certain extent – it can’t compensate for everything, and it can’t do it indefinitely. Eventually even the saltiest of foods will be overtaken by opportunistic microbes that do not have your best interests at heart.
Fermenting is NOT as complicated as it may seem at first. There really are only a few things that you absolutely HAVE to get right. The rest is artistry – improving on a good thing, simplifying or increasing the predictability in your results. The factors listed above are the key elements in controlling spoilage. Everything else is just a nudge factor.
SPECIAL NOTE: Airlock lids and anaerobic environments are NOT discussed in this article, because they are NOT critical factors regarding spoilage. SOME individuals MAY be sensitive to specific bacteria or yeast types that proliferate less readily in an airlock environment, but as a rule, an airlock is NOT required to prevent spoilage.
From a CONVENIENCE standpoint, an airlock DOES make the process SIMPLER, because you do not have to vent the jar, and you MAY be able to be less picky about keeping things completely submerged (we are still testing this, and this statement is only based on preliminary observation, not side-by-side testing). Generally an airlock is not required to eliminate or SIGNIFICANTLY reduce spoilage in fermented foods.