Sunday, January 09, 2011

The Yogurt Routine




Of all the things I tried in my kitchen in 2010, learning to make yogurt was by far the most valuable. I had tried once or twice in previous years, with rather poor results, but then in early 2010 I figured it out.  Euclidarms* wrote a long piece about his yogurt technique at La Vida Locavore that really opened my eyes, and soon thereafter Cherie Picked helped me a bit more.  By the middle of 2010 I had developed a system that worked for me and settled into a loose routine of home yogurt making.

I'm probably saving a good deal of money (perhaps $1 per quart), but what's more important to me is that I'm avoiding a good deal of plastic (like the tubs in the manipulated photo above). Instead of bringing home a new plastic container of yogurt every week, I buy milk in a reusable glass bottle or a compostable paper carton, thus making a big dent in plastic use (and of the piles of plastic in my container cupboard). In addition, it's one more thing I'm doing myself, which is often a good feeling.

Heat, Cool, Mix, Wait
Making yogurt at home is surprisingly easy: heat, cool, mix and wait. In more detail:
  • Heat: heat milk in a saucepan over gentle heat to about 190 °F (88 °C), stirring frequently. Heating the milk modifies the whey proteins, which will give you a finer, more compact curd. (For more on yogurt science, see a column by Harold McGee in the New York Times.)
  • Cool: let the milk cool to 120 °F (49 °C)
  • Mix: mix in some yogurt and pour the mixture into a clean pre-warmed container. Wrap the container with towels.
  • Wait: Let the container sit in a warm place for a few hours until it sets. 

That's the basic outline, and here are many more of the details woven into the system that I settled on. Note that what works for me might not work for you and that there are many ways of making yogurt at home, so another approach might be ideal for you.
  1. A few hours before heating the milk, I put a few tablespoons of yogurt from the previous batch into a room-temperature glass bowl and let it sit so that the cultures can reactivate and be ready for their big cultural event 
  2. When it is time to start the heating process.  I save about a half-cup of milk for the week's tea, and pour the rest into a saucepan that is set on top of a heat diffuser (something like this).  I turn the heat to medium.
  3. Stirring frequently, I let the milk get to about 190 °F (88 °C), then turn off the heat.
  4. After turning off the heat, I put some hot water into a very clean one-quart canning jar so the jar will be warm when it receives the milk-yogurt mixture (I only use jars that have gone through an automatic dishwasher cycle, but if I didn't have one available, I'd rinse the jar with boiling water to thoroughly disinfect the jar).
  5. I let the milk cool to about 120 °F (49 °C).
  6. I add a small amount of warm milk to the yogurt to temper it (thus avoiding thermal shock), then add the rest of the warm milk and whisk everything together.  Next, I pour the warm water out of the jar, pour the milk-yogurt mixture into the warm jar, give it one last stir, and screw on a lid. 
  7. Working quickly, I wrap the jar in two or three layers of kitchen towel, using rubber bands to hold each layer in place.
  8. I put the wrapped jar in a warm place — my oven (which has a pilot light) and prop the door partially open to avoid overheating (thanks to an absurdly large pilot light, the temperature of the oven with the door closed is far too hot to yogurt making, perhaps 140-150 °F).
  9. Four hours later (more or less), I remove the wrapped jar, unwrap it, and put the jar into the refrigerator.
Fitting it into the Rat Race
The process I just listed works great on weekends when I have a 4 1/2 hour block, but on weekdays it can be hard to get everything done between the time I get home and go to sleep.  So I've devised a slightly different process for reactivating the culture. I bring the last batch of yogurt and a glass bowl to work, putting the yogurt in the refrigerator and leaving the bowl at room temperature.  In the mid-afternoon, I put a few tablespoons of yogurt into the bowl and leave it at room temperature. This way, the culture has a chance to get reactivated during the end of the workday and is ready when I start the process at 6:30 or 7 PM at home. 

Additional Notes and a Question
Many months after getting into a routine, I noticed that Paula Wolfert's "The Cooking of the Eastern Mediterranean" has an appendix about yogurt and a recipe for making it at home. Wolfert writes that the most prized yogurt in the Eastern Mediterranean is made from buffalo's or sheep's milk because of the high butterfat content. With regard to home culturing, she relates an old saying about the culturing process: "the quicker the sweeter." In other words, the faster you can make the yogurt set, the sweeter it will taste, so some yogurt makers pour the warm milk-yogurt mixture into small jars for culturing.  At 100 F, a batch of yogurt will jell in about 6 hours. At a lower temperature, it could take as long as 24 hours and give you a much tarter result.


Writer and editor Jennifer Jeffrey wrote about a clever way of managing yogurt culturing temperature with a hacked slow-cooker. By installing a dimmer switch in the power cord, she could control the amount of energy reaching the cooker's heating elements, thus controlling the temperature of the water bath. (If you are going to hack commercial appliances, be sure you know what you are doing and follow good safety practices!)


Finally, a question for those who make yogurt at home:  wouldn't it make a lot of sense to use the microwave to heat the milk?  Microwave heating is even and gentle, therefore seeming less likely to scorch the milk than a pot on the stove. 


*euclidarms is the La Vida Locavore username of Ed Bruske, a.k.a. "the slow cook."  Bruske is a writer who has written some amazing pieces on school lunch in Washington, D.C., Berkeley, and Boulder. To research his articles, he doesn't just look around and talk to people, he actually works in the kitchen. You can find his multi-part articles at the Slow Cook (look to the right column).


Random link from the archive: Tempura at Ten-Ichi in Tokyo

Cross posted at La Vida Locavore

7 comments:

dogear6 said...

I use the microwave to heat my milk. It takes about 14 minutes to get to 185 degrees. I stir at the 5 and 10 mimute marks and take it out just as it starts to boil. Don't stir right away though or it will boil over.

Ed Bruske said...

Marc, great job teasing the specifics out of this yogurt process. As you said, my technique is very similar. However, the milk I use is whole "creamtop" from the local dairy that delivers to our home, plus some of their excellent heavy cream. The milk and the cream are the kind that develop a clot at the top that you have to eat with a spoon. I mix 3 cups milk plus 3/4 cup cream, which seems to be the exact amount that will fit into the typical 1-quart mason jar. I know your readers probably despise Styrofoam, but since we happen to own a small Sytrofoam cooler, I place the yogurt mixture in there with a couple of jars of hot water. And because I want to reduce as much as possible the lactose in the yogurt, I let the bacteria continue their feeding for up to 48 hours before I remove the yogurt from the cooler. As Harold McGee has explained, however, its the length of time the milk remains at high heat--not the fermentation process--that determines the thickness of the yogurt. Except maybe in the case of Greek-style yogurt, which is drained.

Bharati said...

Yes, a lot of people I know do use the microwave to heat milk - but remember what Euclidafarms says about heating and protein clumping/thicker yogurt. I think our Senor McGee says something similar.

To make the process even more low maintenance (and allow me to be even more distracted), I plonk a pot watcher into the milk boiling pan (set on medium heat). Then I don't need to pay attention to the pot till I hear some serious and steady clanking.

Also I don't really understand the devotion to jars at all - hard to get to the bottom of the jar etc. You can use just about any container to make yogurt. Those wide round storage containers, Anchor and Frigovere wide round storage containers. Spill proof lids are a plus but in South Asia, people make routinely make yogurt in regular handle-less wide mouth stainless steel pots and just plonk any old lid on top.

You don't discuss another problem which plagues some yogurt cultures and makes beginners thrown in the yogurt towel - "ropy" yogurt. For explanation of ropy polysaccharides see p. 165-167 of http://books.google.com/books?id=Sabnh9l76W0C&pg=PA165&dq=ropy+polysaccharide+yogurt#v=onepage&q=ropy%20polysaccharide%20yogurt&f=false.. [Google for more on S.thermophilus and ropy strains.]

Marc said...

One-quart Mason jars are not perfect, but they work for me. I like them because 1) they fit efficiently into my dishwasher (the tallness that makes emptying them difficult is an advantage in the dishwasher -- their aspect ratio is efficient), 2) I have lots of them, so there is always a perfectly clean one in my cupboard, 3) I have plenty of lids for the glass jars, so one is always at hand, 4) they fit nicely into my crowded refrigerator. To get the yogurt from the bottom of the jar I acquired some long-handled teaspoons.

Bharati said...

Do you use quart mason jars to store all your other prepared/cooked foods too? I wonder about cultural preferences** because I've often seen people use other (albeit glass) containers for soup or braised dishes say, but feel that yogurt must be made jars.

**: Though the mason jar has made a serious comeback in the Bay Area more recently. For example, several of my fellow hikers brought their non-liquid lunches in mason jars today.

Marc said...

Glass 1-quart Mason jars make up the backbone of my dry goods storage -- I must have 30 in my pantry holding flours, grains, dried fruit, etc. I use them far less frequently for wet goods in the refrigerator, mostly because of their narrow necks (even wide mouth are too narrow). Off the top of my head, the current quart Mason jars in my refrigerator hold soup, sourdough starter, and yogurt (and two days ago I used two jars to infuse water with kombu and shiitake for the next day's Japanese stock).

Stuart Anderson said...

If you're in a hurry, an ice bath will considerably reduce the cooling phase.

If you are interested in economy, powdered milk works for yoghurt just fine.