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While many people appreciate the tasty benefits that a pile of sauerkraut, or a sour pickle, not everyone fully appreciates the health benefits. According to the internet, your belly loves a good fermented food and all the healthy benefits that are a side-effect of the fermentation process. Does science back it up?

Hype: All pickled foods are fermented foods.

Fact: Some “pickles” are fermented and some are not. Recipes labelled “quick pickled slaw” contain vinegar, which may have some modest health benefits, but these are not fermented foods. “Quick” does not allow the fermentation process to happen, which involves allowing the right kind of bacteria to multiply, consuming the natural carbohydrates in the vegetables and forming lactic acid, carbon dioxide, and alcohol.

Hype: All fermented foods are good for you because they are “probiotics”- legitimate sources of “good” bacteria (e.g., Lactobacillus, Bifidobacterium, Saccharomyces).

Fact: The reason most fermented pickled foods are good for you isn’t because they directly supply your body with good bacteria that then spread all over you and work their magic. Nor are they probiotics, defined by The International Scientific Association for Probiotics and Prebiotics as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.” There’s not enough evidence that foods contain enough live bacteria to have a specific effect.

According to Dr. Rob Knight, Founding Director of the Center for Microbiome Innovation, Professor of Pediatrics, Bioengineering and Computer Science & Engineering at UC San Diego and expert on the microbiome, the current thinking is that fermented foods act as the “mulch” to support good microbes in the gut. Most of the bacteria in fermented foods don’t survive the acid in your stomach, but even those dead microbes are still beneficial. After all, seeds won’t grow on a parking lot – you need soil and mulch.

One small clinical trial showed that eating fermented foods helped increase the diversity of gut bacteria, not by simply adding new players, but possibly through this “support” mechanism. Having a healthy mix of the right types of microbes is linked to lower rates of chronic disease. Fermented foods may also reduce inflammation, a driver of many diseases, including several types of cancer. Additional research is currently underway to figure out how this translates into dietary recommendations.

That’s the science of why pickles are good for you. But there’s also a really precise science to how pickled foods are made. The reason precision is important is partly because of food safety. Without the right combination of ingredients, the “bad” bacteria will overpower the “good guys.” What would happen if you left a pile of vegetables out on the counter in a warm kitchen for several days without a pickling bath? As you can imagine, the bacteria in that science experiment are exactly what you DON’T want to creep into your homemade pickled veggies.

So what are the key elements of the pickling process that ensure that the right bacteria can do the fermenting, while keeping the bad guys out? These are the 4 things to pay close attention to.

1. Salt – Salt is important to the pickling process. This is not the place to go low sodium. (If your doctor has recommended a low-sodium diet, this may not be the recipe for you; on the other hand, you could consult your doctor about whether pickled foods as an occasional condiment would be acceptable.) For safe fermentation, the brine must contain a minimum percentage of salt by weight, which ranges depending on the type of food. If you don’t have a cooking scale, look for a recipe that gives volume instead of weight. Now, there’s a further complication that different types of salt have slightly different properties. One difference is in the size of the granules, so, by volume, 1 tablespoon of each will impart different saltiness. With that in mind, you might need to tweak the recipe a bit as you get good at this (or buy a scale if you become a pickling fan!). Avoid table (iodized) salt, as iodine can inhibit fermentation.
2. Rinse, but don’t scrub, your vegetables. Wait, what? You may be accustomed to giving your veggies a thorough wash and scrub (maybe with a vegetable brush). In this case, don’t. The outside has Lactobacillus and other bacteria needed for the fermentation process. Just trim off any spots that appear spoiled.
3. Get the amount of air in your pickling container down to zero. Fermentation happens in anaerobic conditions (no oxygen allowed!). If the veggies are exposed to air, mold may form. You’ll need a weight on the top of the veggies to keep them submerged as well as well-fitting lid on the container (but not too tight, to allow the carbon dioxide produced during fermentation to escape).
4. Proper storage after fermentation is complete. Refrigerate in tightly-closed containers, or, if you have a cool storage area, leave your pickles in the fermenting container, making sure that the surface is covered with brine.

This may seem too hard or dangerous. We usually, as food scientists, tell you all the ways you can modify a recipe to suit your needs and preferences. This time, as food scientists, we’re telling you: DON’T. On this one, you must follow a recipe, especially if you’re new to pickling.

Ready to try it? This month, sauerkraut is on the list of 30 healthy foods. Here’s a recipe.

One last note: Some PCF recipes are quick (e.g., 15-minute frittata). Pickling, on the other hand, is a slow process and should be approached when you are ready for the commitment.