The most frequently asked question: What is the difference between fermentation and canning? Da, da, da, aaaa…
Microbes, of course! Canning relies on eliminating microbes and deactivating enzymes with heat; fermentation encourages the growth of specific microbes while discouraging others. These preservation methods also differ in how acidity (drop in pH) is reached. Canning uses vinegar to acidify vegetables, thereby, prevent harmful microbes from growing. Lacto-fermented foods acidify through lactic acid produced by lactic acid-producing bacteria and to a lesser extent, acetic acid. Fermentation relies of microbes and the resulting by-products to preserve vegetables. Therefore, never confuse fermented pickles with canned pickles – the taste is much different.
Vegetable Fermentation Basics1. Does lacto-fermentation involve lactose or milk products?
2. Fermented vegetables are high in sodium. Can these still be part of a healthy diet, even for people with hypertension?
For health-conscious eaters who make fermented vegetables a regular part of their diet, sodium intake can accumulate easily. Still, sodium aside, the nutritional and probiotic benefit of fermented foods is astounding. Avoiding fermented vegetables due to its high sodium content is unnecessary even for people with hypertension. A better approach is to limit your portion size. I’d advise one ounce of beet kvass and a 1/4 cup of sauerkraut everyday for gut health and disease prevention. The only scenario for complete restriction of fermented vegetables is when a therapeutic low-sodium diet is ordered by a doctor to manage ascites or fluid overload.
3. I am new to fermenting in airlock jars. What jars should I start with?
Consider the following points when making your decision on jars sizes:
Storage. After packing jars with vegetables, jars are left on the counter for 7-10 days, then transferred to a cool place (<10 degrees, ideally) for 3 weeks (most whole vegetables) to 3 months (sauerkraut). Do you have a root cellar or cold storage area? If not, these jars should be transferred to a fridge to slow down bacterial activity. Do you have extra fridge space to spare? If it is minimal but you don’t have a root cellar, use a 3L jar for sauerkraut. Five-litres are usually too big for a fridge.
Yield vs. Fermenting time Think about how quickly you or your family can eat what you ferment compared to the time it takes to ferment. For example, sauerkraut requires 3 months to properly ferment. A family of six could work through a 3L jar of sauerkraut in around one month, if everyone likes it!
Type of Ferment Sauerkraut is best done in large vessels (i.e. 3L or 5L) to develop adequate brine. Beet kvass, which is finished after 10 days at room temperature, is best done in a 5L airlock jar. Whole or coarsely chopped vegetables such as cukes and pickled cauliflower, carrots, asparagus, etc. are done in 1 month. For these, I like to use a 1.5 or 3L jar. Shredded carrots are done in a few days, so I usually use a 1L or 1.5L. I use 1L for relishes, which is a slightly more advanced type of vegetable fermentation.
4. Many people have used open-systems for fermenting and dealt with surface mould and yeast by simply scrapping it away. If that was sufficient for them, why should I bother investing into airlock jars?
5. Vegetable fermentation has been around since the early centuries and refrigeration since the 1800's. Why is refrigeration recommended for the second period of fermentation?
For our modernized society, refrigeration in the second phase is best for crispy, flavourful, superior ferments. For those who are fortunate enough to have or have access to a root cellar kept below 10°C I encourage you to use it. Fewer new houses are built with vegetable preservation in mind. For people of previous generations, preservation was a way of life.
6. For whatever reason, can we open the airlock jar after starting fermentation or should we keep it clamped shut?
Do not make opening the lid a habit. At lower temperatures, bacteria are less active and produce less carbon dioxide. It would take longer to re-establish an aerobic environment, thus potentially leading to mould growth.
7. What temperature and what environment is best for fermenting and fermenting vegetables?
Keep your fermentation jar away from direct sunlight, and in an area where you can keep an eye on the activity. UV rays kills lactic acid bacteria, the key players in fermentation and many of which are known probiotics. Wrapping a dark, thickly woven towel around each jar will reduce UV’s penetrating the glass. However, avoid covering the airlock, which will prevent oxygen and excess carbon dioxide from escaping. It’s not recommend to put your jar in a closet for chances of forgetting about it. The airlock system takes the babysitting out of fermentation; however, it still requires attention, especially in the first week.
After this initial phase, ferments should be transferred to a cooler temperature to reduce fermentation rate. Ideally this is <10°C in a root cellar or fridge (keep the airlock inserted through the lid). Safe products are still possible between 10-18°C, yet the product may have inferior texture and taste.
8. Some fermentation resources recommend starters. Do I need to use one?
Commercial yogurts use pasteurized milk, which is heated to destroy native microbes. Specific microbial cultures are reintroduced for milk to ferment into yogurt. Some yogurt companies have patents on yogurt cultures to brand a specific flavour or health appeal. For example, Activia has a patent on Bifidobacterium lactic CNCM 1-2494 (on the label it reads B.L. RegularisTM).
9. Do I need to sterilize fermentation jars before packing?
Instead, prepare the jars and equipment by washing with non-antibacterial dish soap and hot water, then rinsing. Lightly rinsing with distilled water or filtered water rather than tap water is a good habit, but not essential. Finish by drying the jars and equipment with a clean cloth.
Alternately, if you are a successive fermenter, you may transfer the finished ferments to alternative containers, preferably airtight with or without an airlock, and start a fresh batch of vegetables in the previous fermenting vessel without washing it. Lactic acid bacteria that remain on the walls of the jar will kick-start the next batch of vegetables. Some people use a tablespoon of brine from the previous batch to start the next batch. This is slightly different than using a commercial starter.
Salt1. Salt comes in a variety of shapes, sizes, densities, flavours, and prices. What do I look for when buying fermentation salt?
Ideally, salt used in fermentation should have a wide range of minerals and trace minerals. This type of salt often comes in dry or wet forms, indicating its origin from land or from sea, respectively. Redmond Real Salt and Himalayan Crystal Salt are dry salts; whereas, Celtic Sea Salt and French Grey Salt are wet salts. Both give the end product different tastes. Wet salts can harbour more potential for mould growth, so my preference is dry salts especially in aerobic open systems. All ByDesign fermentation workshops use Redmond Real Salt.
At all costs, avoid using commercial pickling salt because it is usually iodized, coarse ground, and has a different ratio of sodium chloride to minerals.
2. What is the purpose of salt in fermentation?
Traditional salted vegetable ferments, on the other hand, use salt to narrow the range of bacteria that can grow. Salt discourages salt-intolerant spoilage microbes and promotes salt-tolerant lactic acid bacteria. Besides giving lactic acid bacteria a competitive edge, salt:
- draws water out of vegetables through osmosis, creating a brine in shredded vegetables;
- slows pectin-digesting enzymes to prevent mushiness; and
- controls the rate of fermentation by reducing the rate of fermentation and enzyme activity, thereby prolonging preservation.
3. What happens when insufficient salt is used? What happens when excess salt it used?
Excess salt will undoubtedly make the ferment difficult to stomach! Some people rinse ferments, including sauerkraut, before eating, yet rinsing excess salt also sends probiotics down the drain. In addition to saltiness, excess salt lends to more sourness (i.e. more acidic). Ferments made in the summer usually require more salt to temper the high fermentation rate due to higher temperatures.
Specific Vegetable Ferments: sauerkraut, kvass, and lacto-fermented pickles1. I don't have a scale. Will my sauerkraut turn out if I estimate my cabbage weight and follow volume measurements for salt instead of weighing?
If you do not have a weigh scale at home, the best you can do is weigh your cabbage at the grocery store. Buy 1 kilogram of cabbage for every 1 litre jar you are using. For example, if you are making a 5L jar of sauerkraut, buy 5 kg of cabbage from the grocery store. Keep in mind that the core, outer leaves, and any spoilage spots will be discarded. This reduces the weight of cabbage you will shred versus what you measured at the store. Usually this guideline leaves extra cabbage to use in salads without the chance of running out as you’re packing. I’ll admit, that has happened a couple times to me.
Recipes that recommend “x” number of cabbage heads for a certain size of fermenting vessel with “x” tablespoons of salt may result in varying brine concentrations – often excessive. Cabbage heads vary in size and density depending on the variety and harvest season, which will impact the resulting brine concentration. To prevent this, weighing your primary ingredients, salt and cabbage, is best.
If you do have a kitchen scale, measure your cabbage after it is shredded. This weight minus your holding container is used for calculating the amount of salt required for a specific brine concentration, 1.5-2%, depending on storage time and type of cabbage. *See “Fermenting Shredded Vegetables” handout given at ByDesign Fermentation Classes and Workshops or with jar sales for an easy bring-calculating formula.
If you need to estimate salt using volume measurements, one teaspoon is generally equal to 4 grams. This changes with the type of salt used – coarse vs. fine, wet vs. dry, and refined vs. unrefined – because volume measurements don’t account for air pockets or density. Weighing salt is more accurate than measuring. That said, some famous fermenters (e.g. Sandor Katz) judge the amount of salt needed by taste and by brine formed at the bottom of the bowl. Get into the habit of sampling your salted shredded vegetables before packing to associate brine concentration with taste, texture, and brine.
2. What is the best cabbage for making sauerkraut?
Sauerkraut will still work if green spring or summer cabbage is used, though its results will be inferior to white winter cabbage. The light weight and hollow spaces are distinctive of summer cabbage. If you are comparing two white cabbage heads of similar size, always go with the head that is heavier. Expect winter cabbage to be at least 2X heavier than the same size of spring/summer cabbage.
3. Should I add water to my fermentation jar if brine production is low?
4. Yikes, where did all my brine go after transferring my jar from room temperature to a cooler temperature after the initial fermentation phase?
The issue around freezing sauerkraut has to do with microbial viability. Does freezing reduce bacterial count in sauerkraut? Studies analyzing bacterial cell count in sauerkraut before and after freezing have not been done – or I could not find any with much searching. I did find one study that added lactobacillus planetarium (this probiotic species is in sauerkraut) to ice cream as a probiotic and accessed viable cell counts after four weeks. There was a decrease of 0.8-1.61 log cfu/g after four weeks. This is not particularly significant considering the high cell count most fermented products start with. This cell reduction emphasizes the need for good fermentation practices that optimize bacteria growth before freeze storing your sauerkraut. That means avoiding exposure to UV light by wrapping your fermentation jar with a towel and placing it out of direct sunlight; avoiding a salinity higher than 2%; and ensuring an anaerobic environment.
For you microbial science enthusiastic…Cell count of some microbes reduces with freezing because any water that freezes inside bacteria before it outflows forms water crystals. These pierce or essentially cut bacterial cells, causing cell death
Safety of Fermentation1. Do I need to test the pH of my ferments at different time points during fermentation? If so what pH levels protect against harmful microbes?
Testing the acidity of your ferments may give you peace of mind, but it is not 100% necessary. The time guideline included with my recipes are sufficient to produce this acidity drop. Initially, testing pH with test strips may help you understand how changing variable in fermentation like the vegetable, temperature, or brine concentration affects acid development. So pH testing may be a helpful learning tool.
2. Are fermented vegetable really safe to eat? I mean raw vegetables wouldn't keep for more than 2 weeks in my fridge without signs of age or spoilage.
Airlocks1. Why is brine drawn up into the airlock?
- Insufficient packing, especially of shredded vegetables, leaves air pockets, thus dead space.
- Juicier vegetables, such as winter cabbage versus spring/summer cabbage may release more brine at room temperature.
- Some vegetables contain more sugar depending on when these are harvested; other vegetables contain more sugar than other vegetables in general. More available starch, such as in carrots, beets, and other root vegetables will make for active ferments. Active ferments usually expand more, potentially driving more brine into the headspace
With experience comes better awareness of how full to fill jars, depending on the vegetable used and the time of the year, thus temperature.
2. If brine gets drawn up into the airlock, should I clean it and refill it with fresh water?
3.What does it matter if I loose brine from my jar through the airlock?
Troubleshooting1. Inadequate brine formation in sauerkraut.
- Heads of cabbage used for shredding are old. Long storage periods make for drier vegetables to begin with. Also, never use cabbage that has been previously cut and stored for later use. Exposure to air dries it out quickly.
- Instead: Best practice is to use local, fresh cabbage in season. If that’s not available, try to use cabbage from an autumn harvest before January of the next year.
- Shredded “threads” of cabbage were too thick, which minimizes surface area through which juice is extracted from cabbage via osmosis.
- Instead: A mandolin with angled blades gives the most consistent “thread” cuts. Adjust the distance between blades so that threads are fine and almost translucent.
- There has been insufficient time for brine to develop.
- Instead: Cover your bowl with a plate and set it aside for 30 minutes or more. Some time apart will hopefully be a good thing.