Many folks turn to canning, freezing, or dehydration to preserve the harvest. These methods are effective, safe, and relatively easy, but fermentation is another possibility for some vegetables, fruits, and even dairy products. Many well-known fermentation methods produce alcohol, but many more use microorganisms to help preserve the food through the production of tasty organic flavor compounds, such as lactic and acetic acids. If you’ve enjoyed sauerkraut or yogurt, you know the tart delight of lactic acid. If you are a vinegar lover, then you know the flavor of acetic acid. Not only do fermentation microbes preserve through the production of organic acids, but their action — the consumption of some of the nutrients in the plants or dairy — can also make certain nutrients readily available, and make it easier for your microbiome to fully digest food.
Sauerkraut is perhaps the most well-known example of lacto-fermentation. The process of making it may bring visions of huge crocks, large wooden packing mallets, and stone weights. Sauerkraut gives us a good example to dissect and further understand the process. First and foremost, cleanliness is important, but not sterility. The crock should be washed and rinsed, and care should be been taken to remove any antimicrobial residue. The wooden or ceramic inner lid should be treated similarly. The cabbage should be rinsed carefully, any blemished leaves removed, and the remainder shredded and then systematically packed into the crock in salted layers. Pack the shredded cabbage roughly; bruising helps the liquid in the cabbage seep out to form a brine. The salty brine is crucial to the success of this process. Now, where do the microbes come from that will partially digest the cabbage and create lactic acid? They exist naturally on the cabbage, along with other beneficial and potentially pathogenic bacteria and fungi, which could spoil the batch if allowed to grow. So, the salty environment inhibits undesireable microbes and allows the lactic acid bacteria to flourish. However, there’s a caveat. The lactic acid bacteria only produce lactic acid as an end product of metabolism in very reduced oxygen conditions, much like your muscles when you work them harder and faster than your lungs can supply them with oxygen. This is another reason for packing the shredded cabbage and covering it with a weighted disc. As the juice is drawn and the brine forms, the shredded leaves remain immersed. The oxygen in the brine is quickly used up, and the lactic acid bacteria enter anaerobic metabolism and produce the acid. Acid production continues until it’s in a high enough concentration that the lactic acid bacteria become dormant.
Lactic acid in the brine does a couple of things. First, it inhibits the growth of virtually all microorganisms that can’t survive in a low-pH (acidic) environment, which gives the lactic acid bacteria a further competitive advantage. This is also part of the reason you generally don’t need to worry about botulism poisoning with lacto-fermented foods. The botulism-producing bacterium needs anaerobic conditions to make its toxin, but it can’t do so in a highly acidic environment. So, the salt draws the liquid to create a brine that slows or stops the growth of all but a few types of microbes, and then the acidification of the environment does the rest. The lactic acid also works to make plant cell walls softer and more easily digestible, releasing nutrients into the juice in the process.
Now, let’s say you don’t want to make a 20-gallon batch of sauerkraut, pickles, or kimchi. No problem! It’s easy to make meal-sized batches of these ferments using small vessels, such as canning jars — especially if you employ any of the numerous kits available that come with a weight to keep fruits and vegetables immersed in brine, and a lid with a one-way valve on it called an “airlock.” As the bacteria are busy making acid, they’re also releasing carbon dioxide. In an open crock, this carbon dioxide is released into the air. In a sealed container, the carbon dioxide would build until it blew up the container, and the brine would be fizzy, like a carbonated beverage. The airlock allows carbon dioxide to escape without permitting oxygenated air back in. Some small fermentation kits use a water-filled airlock, while others use polymer seals that allow pressurized gas to escape in one direction only — a check valve of sorts. Both systems work well, but the polymer type doesn’t require you to monitor the water level in the airlock. Some small-scale kits have weights, while others have spring-loaded plates that keep the vegetable matter immersed. Both systems work well.
If you’re curious about lacto-fermentation or want to experiment with different seasonings, small fermentation vessels are great. Of course, if you’re feeding a family of four, you might want to invest in a small crock system. Either way, if you add fermentation to your preserving possibilities, you’ll access flavor and nourishment no other technique can match!
Hank has been brewing beer and fermenting sauerkraut off and on for more than 40 years. He currently raises sheep, cattle, and bees with his wife in rural Osage County, Kansas.