That said, it’s important to understand what makes a recipe safe, so you can avoid inadvertently doing something that makes it unsafe. Sweet preserves deal mostly with high-acid fruits—in the preserving world that is anything with a pH lower than 4.6. This means they can be processed safely in a water-bath canner. There are exceptions—including figs and tomatoes, for example, in the recipes that follow—that must be acidified using bottled lemon juice, which has a more standard acidity than fresh lemons, to be safely processed in a water-bath canner. It is important to follow recipe directions from a trusted source, use bottled lemon juice when indicated, not add or subtract ingredients, and process for the indicated amount of time, adjusting for altitude as needed. Basically, follow a recipe from a trusted source and follow it to the letter, unless it indicates otherwise.
In doing so, you’ll ensure a high-acid environment where the botulinum bacterium—which secretes the botulinum toxin, responsible for the rare but potentially deadly food-borne illness botulism—cannot grow. I think that’s worth repeating: botulinum cannot grow in a high-acid environment. If you’ve followed a trusted recipe and something goes wrong in a sweet-preserve recipe, it will be very apparent. You’ll notice carbonation, mold, a popped lid, an alcoholic smell, or evidence that the jar has leaked after storage. These sorts of things are incredibly rare but are worth noting so that you know to discard any jars that exhibit these characteristics.
Vinegar-based preserves that are processed in a water-bath canner also rely on acidity to make them work and keep them safe. Although many pickles start with low-acid vegetables like cauliflower, they are made safe for water-bath canning with a high-acid vinegar brine. Unless otherwise noted, you must use a vinegar that has been diluted to 5 percent acidity, which will be indicated on the label.
With vinegar-based preserves, as with sweet preserves that are processed in a water bath, it is important to follow recipe directions from a trusted source; do not reduce or replace the vinegar nor add or subtract ingredients, and process for the indicated amount of time, adjusting for altitude as needed. In addition, acetic acid, the main acid in vinegar, evaporates quicker than water, so cooking a vinegar-based preserve for far longer than indicated can throw off your pH and should be avoided. Again, follow a recipe from a trusted source. If you have done so and something goes wrong, it will be immediately noticeable in the form of carbonation, mold, a popped lid, an alcoholic smell, or evidence that the jar has leaked after storage. Toss anything that looks or smells off.
Fermentation is quite a different beast, but ultimately similar in that it, too, relies on acid to preserve. Unlike the pickling process, for example, acid isn’t added at the onset; the lactic acid produced by bacterial fermentation preserves the food and inhibits the growth of spoilers. In order to create a safe and successful final product when you’re fermenting, it is important to observe standards regarding the amount of added salt. For dry-salted recipes (more on that later, but basically kimchis, krauts, and everything in between), calculate 1.5 to 2 percent of the total weight of the produce you’re using after it is prepped, and add that much salt by weight. To create a brine to safely ferment vegetables, calculate 5 percent of the weight of the water you’ll use and add that much salt by weight. Introducing the proper amount of salt into a ferment encourages lactic acid bacteria (that’s good) and creates an inhospitable environment for bacteria that cause spoilage (also good).
Another important safety element in lacto-fermentation is creating an anaerobic environment—no oxygen—to keep the anaerobic lactic acid bacteria working their best to preserve the food. This is why it’s important to keep vegetables submerged below the brine. When bits of veggies poke above the brine and are exposed to oxygen, spoilage happens. Using an airlock to allow carbon dioxide to escape during the fermentation process, without letting oxygen in, as I do in the small-batch recipes that follow, in effect expands the anaerobic area to include everything below the airlock. This means you can be a bit less meticulous when it comes to keeping things submerged below the brine at all times. That said, it is important to understand how the process works in general, particularly if you go on to use a crock for larger batches or decide that airlocks aren’t for you.
Within those parameters, in the realm of lacto-fermentation, we’re less tied to recipes than we are with water-bath canning. It is safe to experiment with a variety of vegetables using these standard salt ratios. More on how to do that successfully, that is, how to end up with something delicious, later.