Yogurt, Kefir, and Cultured Butter

Making yogurt

Yogurt is milk soured and set by two bacteria, Lactobacillus bulgaricus and Streptococcus thermophilus, which turn lactose into lactic acid; the acid makes the milk proteins gel ¹. Illinois Extension’s basic method ²:

1. Heat 1 quart of milk slowly to 180-185 °F, stirring so it doesn’t scorch. Heating changes the milk proteins so the yogurt sets thicker.
2. Cool to 108-115 °F. Hotter milk would kill the starter.
3. Inoculate: stir 2 tablespoons of plain yogurt into a cup of the warm milk, then stir that back in. Use store yogurt before its date, or homemade within 5 to 7 days.
4. Incubate covered at 108-115 °F for 6 to 10 hours, undisturbed.
5. Refrigerate at 40 °F or below as soon as it’s gelled, which stops the souring. Eat within 14 days.

Kentucky’s IP-36 is a quicker variant: heat to 160 °F for 1 minute, cool to 102 °F, add 3 tablespoons of starter per half gallon, hold in a 105 °F water bath for 3 to 4 hours until tiny flakes show when it’s dripped down a glass, then refrigerate at once ¹.

Incubators you already have ²: an oven preheated to 200 °F, turned off, and bumped on briefly to hold about 100 °F; a cooler or slow cooker half full of 120 °F water around the jars; or a yogurt maker or electric pressure cooker following its own directions.

Thicker yogurt: add nonfat dry milk. Kentucky recommends about 5% (1-1/2 cups per half gallon) to keep whey from separating ¹. For Greek yogurt, drain it in doubled cheesecloth in the refrigerator; drain longer for spreadable yogurt cheese ².

When it goes wrong

Illinois’s troubleshooting table ²:

• Not firm: starter without live cultures, incubation too hot or too cold, or milk not heated enough.
• Separated: incubated too long, or not refrigerated soon enough.
• Off flavors: milk or starter not fresh, or equipment not clean.
• Thin: dry milk not added to cold milk at the start, yogurt too cold before incubating, or not covered while incubating.

Kefir

Kefir is a tart, drinkable milk cultured by a mix of bacteria and yeasts, at room temperature rather than yogurt’s 110 °F. Utah State’s method ³:

• Start with a packet of kefir starter culture (or dehydrated kefir grains) in 1 quart of whole milk.
• Re-culture by stirring 1/4 cup of finished kefir into 1 quart of milk and holding it at about 80 °F (26.6 °C) until it’s thick and tangy, pH 4.6 or below; a counter in summer works.
• Re-culture from the last batch up to 7 times within a week, then start fresh.

Use it as a drink, in smoothies and dressings, or in place of buttermilk in baking ³.

Cultured butter

Cultured butter is made from cream that’s been soured with a culture first, which gives it more flavor than sweet-cream butter. The FAO’s small-scale dairy manual ⁴:

1. Ripen the cream: heat it (the FAO uses 80-90 °C, which pasteurizes raw cream), cool to about 18 °C (64 °F), stir in a little cultured buttermilk (about 50 ml, 3 dessert spoons) or a mesophilic starter, and leave 24 hours at that temperature.
2. Churn: a churn, stand mixer, or a jar shaken by hand. It goes from whipped cream to stiff to suddenly breaking; churn until the butter grains are the size of peas and the buttermilk looks watery. This takes 15 to 60 minutes, depending on temperature and cream.
3. Drain off the buttermilk (keep it for baking).
4. Wash with clean cold water, again and again; the more buttermilk you remove, the better the butter keeps.
5. Work it with damp wooden paddles until no water droplets show.
6. Salt if you like, about 10 g per kg (1%), and work it again the next day.

A liter of cream makes about 300 to 400 g of butter ⁴.

Try it

Make yogurt and butter the same weekend. Make a quart of yogurt by the Illinois method in a cooler; at the same time, culture a pint of heavy cream with 2 tablespoons of cultured buttermilk at room temperature. Churn the cream the next day in a jar or mixer, wash it until the water runs clear, and weigh the butter.

What to take from this

Yogurt: heat milk to 180-185 °F, cool to 108-115 °F, stir in 2 tablespoons of live yogurt per quart, hold 6-10 hours, and refrigerate at once; add about 5% dry milk for body and drain for Greek style. Most failures are a dead starter, wrong incubation temperature, or skipped heating. Kefir re-cultures at about 80 °F with 1/4 cup per quart. Cultured butter: ripen cream with buttermilk for a day, churn to pea-size grains, wash until clear, work out the water, and salt about 1%.