Homemade Yogurt Revisited

About a year ago I wrote a post chronicling the early stages of my foray into yogurt making.  Although there have been a few bumps along the way, I am happy to report that I am still making yogurt and that the yogurt I am making now is better than ever.  I can't imagine going back to store bought.  Since my original post was about the things I was just beginning to learn about the process, now seemed like a good time to share some of the things I have learned over the past year.  If you have never made your own yogurt...or if you missed my previous post...you might want to go back and give it a quick read to familiarize yourself with the basics before reading today's post.

After I had been making yogurt successfully for a couple of months, I had a sudden dip in the quality of my yogurt.  It started with a batch that took way too long to set.  Successive batches were thinner and had an odd rope-y kind of texture.  I began to ask around to see if I could discover what was going on.  What I found was that it seemed to be common knowledge among my yogurt-making friends that yogurt culture at some point just begins to diminish in strength.  The generally accepted way of dealing with this is to simply start over with a fresh culture. 

Well, this seemed like a very unsatisfactory solution to me.  Yogurt is an ancient food.  Cultures have been kept alive for centuries (how would we have them today if this were not the case?)  Surely there was something I was missing.  And as it turns out, there was.  While looking around on line, I ran across a company that sells heirloom yogurt cultures.  Their cultures are touted as being indefinitely reusable (some of the comments praising their products were from people who had been making yogurt from the same culture for over a year).  In reading over their site, as well as an NPR discussion of "eternal starters" (that linked me to their site), I discovered that keeping these heirloom cultures viable involved using them to make yogurt every five to seven days.  This sounded promising.  I thought about ordering one of the heirloom cultures so I could give it a try, but it was the middle of the summer and the risk of the culture dying from the heat in transit made me hesitate.  Furthermore, I had just restarted my yogurt making with some Dannon plain, so I thought I would first give the every five to seven days thing a shot with the culture I already had.  This was in August, and I am still using the same culture...with no indication of failure thus far.

The main reason I wanted to write this post was to share this little bit of information about having to make yogurt every five to seven days.  I read many blog posts and on-line magazine articles about making yogurt when I first started and found no mention of it.  I occasionally found an honest soul who admitted they had had a failure and then had to start over with a fresh culture, but by and large the issue seems to be unaddressed (perhaps I have just been looking in the wrong places...).  I'm guessing that this is because many people who make yogurt have naturally fallen into a yogurt making schedule that is more frequent than once a week.  For these people, they will have automatically avoided the problem I ran into.  In my house we consume about a quart of yogurt a week.  I had been making a half gallon of yogurt every two weeks or so.  Since reading about all of this, I have simply adjusted my schedule to making a quart every seven days.  It is an easy thing to adjust your schedule—along with the quantity that you make—so that you can maintain the viability of your culture.  

You might wonder why it was so important to me to be able to find a way to perpetuate my own yogurt culture. Why, one might ask, not just accept the fact that you will have to occasionally start over?  Well, the answer is that the yogurt I make seems to get better and better with each successive batch (this is probably one of the great advantages of an heirloom culture).  The first few generations of yogurt when I start from a commercial yogurt are always a bit milder than I would like.  I really like tangy yogurt and having to always start over would give me a continuous supply of mild yogurt, which is not what I want.  The yogurt I make also seems to get thicker with each successive generation.  Right about the time that the yogurt I was making had become thick, creamy and tangy was when I had my first failure.  I had no desire to go back to the mild, thinner yogurt of those first few batches. 

One final note:  I have no idea how rigid one has to be about consistently following an every five to seven day schedule.  It is probable that the yogurt you purchase to start your first batch will be more than five to seven days old.  And, I know from experience that the culture will remain viable for a few generations even if it is being made as infrequently as every two weeks.  To be honest, in August when I happened across the "every five to seven days" bit of wisdom, I was making yogurt from a store bought culture I had purchased in July and with which I had been following my haphazard—about every two weeks—schedule.  (If I were to guess, I would say that I was probably at about my third generation with that particular culture).  Instead of starting over yet again, I simply began making my yogurt every five days to see if I could reinvigorate my culture.  It was about two months ago when I transitioned into making it consistently every seven days.  I assume if I have to deviate from this schedule a bit in the future that my culture has become strong enough to be somewhat forgiving (I'm sure I'll find out).  In any case, I am extremely happy with the yogurt I am making now.  And you can be sure that as I learn and experience new things in my yogurt-making journey, I'll keep you posted (here, or on my Facebook page).

Here is the way I make yogurt now:
(I haven't changed my method too much over the past year—you can look at my first post for pictures)

Before you begin, gather the following:

a quart of whole milk (I use local, organic)

a tablespoon (15 grams) of yogurt (a commercial brand with live and active cultures or your own from a previous batch—no older than five to seven days)

a 3-quart saucepan

a candy thermometer and/or an instant read thermometer

a heat-proof rubber spatula

a ladle

a clean 1-quart jar (or 2 pint jars)

a clean insulated cooler.

Fill the cooler with warm water (115° to 120°), cover and set aside.  Place the glass jar in a 215° oven (after 10 minutes, I shut the oven off and open the door slightly so that the jar will cool down before I fill it—it's nice if it's still warm, but if it's too hot, it can kill the yogurt culture).  Place the tablespoon of yogurt in a small bowl and set aside.

Pour the milk into the saucepan, clamp the candy thermometer on the side of the pan and set the pan over medium-high to high heat.  Heat, stirring occasionally, until the temperature reaches 180° F.  Turn off the heat and let cool to 110° F (stirring occasionally).  I should mention that I have an electric stove.  Consequently, when I turn the heat off, the temperature of the milk continues to rise as the burner cools—often reaching a temperature of 200°F.  I actually think this is a good thing.  I remember reading somewhere (I don't happen to remember where) that holding the milk at (or slightly over) 180° F for a few moments will help firm up the milk proteins, which will in turn help produce a thicker yogurt.  I have no idea if this is true or not, but allowing the milk to heat to 200°F (over the cooling burner) and then cool down more slowly than it would if I actually removed it from the burner has worked well for me—my yogurt is nice and thick.

When the milk has cooled down to 110° F, ladle a small amount into the bowl with the tablespoon of yogurt and stir with the rubber spatula until completely smooth.  Add more milk until the yogurt is of a pourable consistency.  Pour this mixture back into the warm milk (scraping with the spatula to get all of it) and stir well.  (I have learned since my last post that this is called inoculating the milk.) Pour the inoculated milk into the prepared jar and seal the jar (screw on the lid or put on the rubber ring and clamp the jar shut).  Place the jar in the cooler filled with warm water, adding or removing water so that the level of the water is even with the level of the inoculated milk in the jar.  (I actually always pour the water out that has been keeping the cooler warm and start with fresh warm water...simply because my cooler doesn't do a great job of keeping the water warm enough and I want to start the yogurt culturing process no lower than 115° to 120°--I use my instant read thermometer to check the temperature.)

Close the cooler and let the yogurt sit undisturbed for at least five hours.  At the five hour point you should have yogurt. It will be obviously set (tilt the jar slightly to check—but don't jostle it too much). The longer you allow it to stay in the warm water, the sharper the yogurt will taste. I prefer mine at about six hours, but you can let it go even longer. 

Remove the jar from the cooler.  Dry the outside of the jar with a towel, open the jars and wipe the condensation off the inside of the lid.  Place the yogurt in the refrigerator and let it cool with the lid off.  When thoroughly chilled, close/cover the jar.

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Update, Summer 2018:

In mid-June, out of the blue, my almost five year old culture died.  I was very sad about this.  There was something very satisfying about having learned how to sustain a culture...and having done it for so long.  Furthermore, the yogurt I was making had just gotten better over the years.  It was tangy (store bought yogurt--even Dannon, the source of my original culture-- tasted bland by comparison), thick and creamy...every time.  It was a source of a daily "I can't believe I get to eat something so delicious for breakfast!" thought.

I wish I knew why it died.  I can only assume that I got the water in my cooler too hot.  There was a final batch that was able to reproduce one generation of yogurt...but no matter how many times I went back to this batch to make a jar, the jar I produced wouldn't set another batch of milk.  Someone with more knowledge of these things could probably tell me what happened.  I admit that my schedule had been a bit wobbly due to lots of travel for family graduations...but I was never more than a day outside of my 7 day window.  The only other thing that happened, is that I left the the last viable batch (that was able to reproduce), uncovered in the fridge for almost 24 hours by accident (I have always been very good about closing it after just a few hours once it was cool).  Perhaps this had an effect.

Oh well.  Since there was nothing to do but start over, I did.  I decided to try a few other starter cultures to see if I liked the result better than Dannon.  I tried Strauss Family Whole Milk Plain.  This was very good--thick and tangy.  It had a slightly different flavor profile (almost like buttermilk) than the Dannon.  I like the Dannon better.  I also tried the Bulgarian Heirloom culture from Cultures for Health (mentioned above).  I was not a fan.  Their products are very popular...and they have a good reputation...so I'm assuming my issue was that I have just cultivated a taste for whatever cultures Dannon is using.  So...I went back to Dannon....and am once again making thick, tangy and delicious homemade yogurt.

Over the five years I have been making yogurt I have made a few changes to my process.  I'm going to go ahead and alter them in the text above...but I'll mention what they are here.  I used to let my yogurt sit for about 5 1/2 hours in the warm water.  It is usually done in 5, but more time produces a more pronounced tangy taste.  I typically let it go for about 6 hours.  Occasionally I'll make yogurt over night--in which case it often goes for seven hours.

I also no longer bother to check the temperature of the water in the cooler at the mid-way point.  If I start it with a water temperature of 120°, it always stays warm enough to set the yogurt.  In the winter time the water temperature might dip below 100° by the end of the culturing period, but this doesn't appear to affect the taste or the set in any way.