https://www.wildfermentation.com/aerobic-vs-anaerobic-fermentation-controversy/
Written by Sandor Katz
Posted on May 8, 2012
I hear that much controversy is brewing on the internet over vessels for fermenting vegetables, and the implications of whether or not they are totally anaerobic. I have made hundreds of batches of kraut in all sorts of vessels (most of them open crocks), and I have witnessed, consistently, that it doesn’t matter. Each vessel has advantages and disadvantages. No particular type of vessel is critical. People have been fermenting vegetables for millennia in crocks open and closed, in pits and trenches, in sealed and open vessels. It can be done many different ways. The only critical factor is that the vegetables be submerged under brine.
Whenever vegetables are submerged under brine, lactic acid bacteria (which are anaerobic) develop. Whether or not the vessel protects the surface of the ferment from atmospheric oxygen, the microbial development under the brine is anaerobic lactic acid bacteria. In the vocabulary of microbiology, lactic acid bacteria are “facultative” in that they that do not require oxygen, but are not inhibited by its presence; in contrast, certain other bacteria (for example Clostridium botulinum) are “obligate” anaerobes that require a perfectly anaerobic environment.
The only difference air exposure or lack thereof makes is whether aerobic organisms like yeasts and molds can develop on the surface. The barrel of kraut I have had fermenting in the cellar for six months now is good and sour, and I have been eating from it and sharing it widely for months. Each time I remove the cloth tied down over it, and the jugs of water weighing it down, and the two semi-circular oak boards that rest upon the surface, I skim off a moldy layer around the edges and down the middle, wherever the surface was exposed to air. I toss the moldy layer into the compost, and the kraut beneath it looks, smells, and tastes wonderful. Many people have reported how good it made them feel and not a single person has complained of any problems from it, ever. The brine protects the vegetables from the aerobic organisms that grow on the exposed surfaces. The ferment is a lactic acid ferment, even though the surface is aerobic. Surface growth should be scraped away because if it is allowed to grow it can diminish the acidity of the kraut and affect flavor and texture, but if you keep periodically scraping mold away, the ferment beneath is fine.
I have also fermented in Harsch crocks, Pickl-Its, Mason Jars, and many other types of vessels. Mason jars become highly pressurized if you fail to loosen them to release pressure. Even if they are not perfectly airtight, they permit little airflow. Many times I have witnessed carbon dioxide force its way through the airtight seal by contorting the tops to provide an escape for the pressure. The various air-locked designs that allow pressure to release while preventing air from entering the system are generally effective at preventing aerobic surface growth. Yet still I generally do not use them because I love to look at and smell and taste my krauts as they develop, and each time you open an air-locked vessel you defeat its purpose, allowing air in. The vessels are effective, but are not well-suited to my desire to taste at frequent intervals. Different vessels suit different needs and desires. No one type of vessel is essential for fermenting vegetables. I have had success using every type of vessel I could think of. As long as you can keep vegetables submerged, lactic acid bacteria will develop. The process is extremely versatile.
For more in-depth information on fermenting vegetables, fermentation vessels, and all realms of fermentation, check out my new book, hot off the presses, The Art of Fermentation. Keep fermenting….
Written by Sandor Katz
Posted on May 8, 2012
I hear that much controversy is brewing on the internet over vessels for fermenting vegetables, and the implications of whether or not they are totally anaerobic. I have made hundreds of batches of kraut in all sorts of vessels (most of them open crocks), and I have witnessed, consistently, that it doesn’t matter. Each vessel has advantages and disadvantages. No particular type of vessel is critical. People have been fermenting vegetables for millennia in crocks open and closed, in pits and trenches, in sealed and open vessels. It can be done many different ways. The only critical factor is that the vegetables be submerged under brine.
Whenever vegetables are submerged under brine, lactic acid bacteria (which are anaerobic) develop. Whether or not the vessel protects the surface of the ferment from atmospheric oxygen, the microbial development under the brine is anaerobic lactic acid bacteria. In the vocabulary of microbiology, lactic acid bacteria are “facultative” in that they that do not require oxygen, but are not inhibited by its presence; in contrast, certain other bacteria (for example Clostridium botulinum) are “obligate” anaerobes that require a perfectly anaerobic environment.
The only difference air exposure or lack thereof makes is whether aerobic organisms like yeasts and molds can develop on the surface. The barrel of kraut I have had fermenting in the cellar for six months now is good and sour, and I have been eating from it and sharing it widely for months. Each time I remove the cloth tied down over it, and the jugs of water weighing it down, and the two semi-circular oak boards that rest upon the surface, I skim off a moldy layer around the edges and down the middle, wherever the surface was exposed to air. I toss the moldy layer into the compost, and the kraut beneath it looks, smells, and tastes wonderful. Many people have reported how good it made them feel and not a single person has complained of any problems from it, ever. The brine protects the vegetables from the aerobic organisms that grow on the exposed surfaces. The ferment is a lactic acid ferment, even though the surface is aerobic. Surface growth should be scraped away because if it is allowed to grow it can diminish the acidity of the kraut and affect flavor and texture, but if you keep periodically scraping mold away, the ferment beneath is fine.
I have also fermented in Harsch crocks, Pickl-Its, Mason Jars, and many other types of vessels. Mason jars become highly pressurized if you fail to loosen them to release pressure. Even if they are not perfectly airtight, they permit little airflow. Many times I have witnessed carbon dioxide force its way through the airtight seal by contorting the tops to provide an escape for the pressure. The various air-locked designs that allow pressure to release while preventing air from entering the system are generally effective at preventing aerobic surface growth. Yet still I generally do not use them because I love to look at and smell and taste my krauts as they develop, and each time you open an air-locked vessel you defeat its purpose, allowing air in. The vessels are effective, but are not well-suited to my desire to taste at frequent intervals. Different vessels suit different needs and desires. No one type of vessel is essential for fermenting vegetables. I have had success using every type of vessel I could think of. As long as you can keep vegetables submerged, lactic acid bacteria will develop. The process is extremely versatile.
For more in-depth information on fermenting vegetables, fermentation vessels, and all realms of fermentation, check out my new book, hot off the presses, The Art of Fermentation. Keep fermenting….
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