“That’s disgusting.”

“But how can you be sure it’s safe”

“I guess I won’t be eating that from now on.”

I’ve received all of these reactions and more from friends when they’ve heard me explain that my wife and I make our own sourdough bread, yogurt and buttermilk. The products aren’t so distressing, but the processes, which are fundamentally the same, go against some deeply ingrained habits of thought: if germs are so bad, who in their right mind would deliberately cultivate germs and then eat the culturing medium?

It’s not so surprising that people feel this way. We are trained from early childhood to avoid microbes, instilled with the fear that they will make us sick-not entirely unreasonable, because some of them will. What our collective consciousness has lost, perhaps because so few of us are involved in food production these days, is that bacteria are responsible for the tastes and textures of many foods we love, while making many of them more easily digestible. Without careful application of bacterial cultures, we could never enjoy a salad with vinaigrette (we would have no vinegar), buttermilk pancakes (no buttermilk), numerous dairy-based South Asian curries and raitas (no yogurt), ripened cheeses, or pickled vegetables ranging from cucumber pickles to sauerkraut to jalape’os en escabeche.

Some time after toddlerhood we learn the word “fungus”, usually in association with mold that covers something lost in the refrigerator, or perhaps an infection such as athlete’s foot. We do our best to ignore the inclusion of edible mushrooms in this category. Those of us who bake bread may use packaged yeast, but tend not to know that it, too, is a fungus, and prefer not to think about it if we do know. We eat soy sauce and miso soup without considering the koji mold that gives the otherwise bland soybean such complex flavors, and those of us who drink alcoholic beverages rarely give a thought to the yeasts that make them possible. (Brewing sake involves two different fungi: koji to convert the rice starch to sugar and yeast to convert the sugar to alcohol.)

Our visceral reactions often betray a failure to recognize the complexity of an ecology too small to see with the naked eye. By producing acids, many of the bacteria used in food production actually inhibit the growth of pathogenic (illness-causing) bacteria and other harmful organisms. In sourdough, yeasts and bacteria form a stable and mutually beneficial culture that excludes other microbes from taking hold.

In a sense, fear of all microorganisms is a perfect form of paranoia: the very things that you can’t see are the ones that are out to get you! Why do we subject ourselves to this, rather than appreciate the wonderful effects these helpful creatures have on our health and our enjoyment of life? For that matter, why do we outsource to big companies a project that can be done at home with a minimal investment of time, effort and equipment? Making your own fermented foods offers a number of benefits over buying them: it is usually cheaper, it gives you complete control over the ingredients, and it knocks an item or two off your shopping list. It also provides an educational activity for children, who can learn from experience that the microbial world is a lot more complicated than they’ve been led to believe. Besides, doesn’t everything taste better when you make it yourself?

Yogurt

This method is a combination of two different approaches, one described by Poopa Dweck in Aromas of Aleppo, and the other by Neelam Batra in 1,000 Indian Recipes. It produces tart, fresh-tasting yogurt that matches or beats the stuff you’ll find in stores. Yogurt and buttermilk cultures both consist primarily of lactobacilli, which are bacteria that eat lactose and excrete lactic acid. The finished products have very little lactose, making them attractive choices for people who are lactose intolerant.

You will need:

• 1 quart milk, fat content of your choice.
• 1 cup dry milk solids, which may be sold under the names “dry skim milk” or “powdered milk.” (Optional. Use if you want yogurt with a texture similar to that of commercially produced yogurt. Yogurt without a thickening agent is much more watery, with a texture closer to that of buttermilk.)
• 1 cup yogurt with active cultures. (Begin with store-bought, then reserve some of the yogurt you make for the next batch.)
• A glass or ceramic crock with a loose-fitting lid and at least a six cup capacity.
• A probe thermometer.
• Toweling or something else to serve as an insulating blanket around the crock.

Instructions:

1. Combine the milk and the milk solids (if using) in a saucepan and heat to at least 180 F. This serves two purposes: it denatures the milk proteins so that they turn into smooth yogurt rather than curds when acidulated, and it eliminates competing bacteria to ensure that the yogurt culture dominates. (NB: I have tried several times to do this in the microwave, heating the mixture and stirring occasionally until the whole thing registers at 180 degrees. It never works right: the milk solids do not thicken the yogurt as they’re supposed to. Any readers out there want to tell me why?)
2. If the crock is non-pyrex glass, warm it first with hot water from the sink to ensure that it doesn’t crack due to a sudden temperature change. Transfer the hot liquid to the crock and let it sit uncovered until the temperature drops to 120 F.
3. Add the yogurt to the warm milk and whisk briefly to combine. Cover the crock and wrap it with a towel, leaving no surface exposed. (Alternately, if you have a warm place to put it that will hold it at just over 110 F, do that and don’t bother with the insulation.) Let it sit undisturbed for four to six hours, though a few hours more than that won’t hurt it.
4. Check the yogurt for consistency; if it is done, refrigerate for several hours. There may be a watery layer floating on top; you may carefully pour this off, if you like, after the yogurt is chilled.

Buttermilk

This method comes from Dr. David B. Frankhauser, a professor of biology and chemistry at University of Cincinnati Clermont College. In the American South, buttermilk is a traditional beverage. I’m a born and raised New York City boy who doesn’t really understand this, but I do cook with buttermilk quite a lot. It is absurdly easy to make. Some commercial buttermilks are thickened with concentrated milk or other products, so this may seem as if it’s on the thin side, but it is still good for any application.

You will need:

• 1 quart milk, fat content of your choice.
• 1 cup buttermilk with active cultures. (Begin with store-bought, then reserve some of the buttermilk you make for the next batch.)
• 1�jar or crock with a tightly fitting lid and a capacity of at least six cups. (A mason jar works well, but unlike the container used for the yogurt, this one need not be heat tolerant.)

Instructions:

1. Combine the milk and buttermilk in the jar.
2. Cover tightly and shake to mix thoroughly.
3. Leave the jar at room temperature for about 24 hours, but start checking it after about half that time, as higher ambient temperature or an unusually active culture can speed the process. The buttermilk is done when it is thick and aromatic. If after 36 hours it doesn’t seem to be finished yet, your culture may have died off. Start again with fresh buttermilk from the store.