Yogurt 101

As with so many kitchen adventures, I file Yogurt Making under "Why didn't I try this years ago?"

Well, of course, the reason is that I'd heard about the process and I was just stuck on the concept of leaving milk out all night. Won't it go bad? Isn't that just asking for food poisoning?!

But I picked up a book at the library about growing your own food a few months ago, which happened to have a chapter about making your own yogurt, Fresh Food from Small Spaces: The Square-Inch Gardener's Guide to Year-Round Growing, Fermenting, and Sprouting. Ruppenthal's chapter on yogurt-making and fermenting foods made me less sqeamish about the idea and I finally tried it.

But why do it, you ask?

I'm a sucker for a hands-on kitchen project that might be cheaper than purchasing a similar product at a grocery store. When I make my own, I know what is in it: Organic milk with just a little high quality commercial yogurt. I can sweeten it with just enough honey and top it with perfectly ripe fruit, which I think results in a far superior product than the high-fructose corn syrup- and gelatin-laden single serve products available in your grocer's refrigerated case.

I eat yogurt for breakfast with homemade granola. (We'll get to that Kitchen Adventure in due time, I promise.)

Making yogurt is a simple process and there are instructions all over the internet for it. Here are the basics:

• heat fresh milk
• cool it
• add yogurt culture (and optional powdered milk for a thicker product)
• keep warm for a few hours or overnight so the cultures can grow

Recipe: Basic Yogurt

Serve with granola and fruit for a wholesome, filling breakfast or use as the base for a fabulous frozen yogurt. Makes approximately 1 quart.

1/2 to 1 gallon milk, whole, 2% or 1%

1/2 cup good-quality, plain commercial yogurt -I like Mountain High brand.  You want a brand that contains no sweeteners, flavorings, gelatin or other additives, and that specifies "Live and Active Cultures."   Always taste the yogurt that you will be using as your starter before using it, as the cultures in the starter will be imparting their flavor to the milk you are using.  You also want to use the yogurt when it is as fresh as possible.

1/4 cup nonfat dry milk, optional

Special Equipment: large storage vessel with lid, such as a 2 qt plastic yogurt container or a mason jar.

Optional: candy thermometer, strainer, cheesecloth

1. Heat milk over medium to medium-high heat, stirring occasionally until approximately 180º. If you lose track of it and it boils, don't worry. Some recipes say that this will produce a thicker end product. Let cool. I usually pour it into a storage vessel at this point to speed up the process. If milk has burned onto the bottom of the pan, don't scrap the burned portion into the storage vessel. The finished product would still be edible, just not the pure white product that it should be.

2. When milk has cooled to just above room temperature (about 80º to 90º) on a thermometer, stir in yogurt and powdered milk. Stir thoroughly. Cover.  Yogurt cultures are living organisms.  They will die if they are heated to above about 118º, so always make sure your milk has cooled before adding them.

3. Leave jar unattended in warm place for approximately 8 hours. On hot summer nights, the back porch seems to be a perfect spot. I've also cultured yogurt successfully in the pantry of a warm kitchen. Some recipes suggest wrapping your storage vessel or using a crock pot to keep it at a constant temperature. I have not found this to be necessary. It is necessary, however, to leave it undisturbed. Turning the vessel before the milk has cultured properly may disrupt the process and leave you with a very thin, drinkable yogurt. Still edible, but not what I want when I think of yogurt.

4. After about 8 hours--if your storage vessel is kept warmer, it will take less time about 6 hours at 100º, but never let it get above 118º to avoid killing the culture and ruining the product--check for thickness simply by turning the storage vessel slightly. If the yogurt looks thick and pulls away from the edge of the vessel, it's ready.

At this point I transfer the storage vessel to the fridge and chill it thoroughly. You could eat it now. It's yogurt.  I really prefer the thickness and creaminess of a strained (aka Greek-style) yogurt.

5. To strain the yogurt:

 Line a strainer with a few layers of cheesecloth (or a large coffee filter or a double thickness of paper towels or a clean fine-weave dish towel). Pour yogurt into strainer. Set strainer over a bowl and return to the fridge. Strain 4-8 hours, until yogurt reaches the desired thickness. Return yogurt to a clean storage vessel. Store in refrigerator. 

The whey (liquid)  that is strained out can be used as a beverage (it's a little too sour for my taste, but my one-year-old loves it) or as the liquid in bread-making, but I have yet to try this. One Kitchen Adventure at a time.

Yogurt Making FAQs:

• Why the large range in quantity for the milk in this recipe?  Because the cultures in the starter culture expand and will use up whatever amount of milk you provide.  Whether you want a "small" 2 quart batch, or have most of a gallon of milk leftover after making another recipe, just heat the milk, add the culture and let them do the work.
• What if my yogurt storage vessel gets jostled during the wait time?  Depending on where the yogurt is in the process of coagulation, jostling the container may stop the process.  If this happens, the thin yogurt can be used as you would buttermilk.
• How can I make a thicker yogurt?   I've found many suggestions online:  Boil the milk before culturing.  Add powdered milk. Culture at a warmer temperature or for a longer period of time.  (Not above 118º).  Use whole milk.  Once yogurt has finished culturing, strain out some of the whey. 
• Can I use skim milk to make a nonfat yogurt?  I have not tried this.  I've made yogurt with 1% milk and I like the texture.  It is not as creamy as a fuller-fat would be, but to me it's the right texture after straining to mix into granola or fruit. If you try skim milk, let me know how it goes.
•  How long does homemade yogurt keep?  I don't know.  I usually make a batch to last about a week.
• Can I use the yogurt I make as a starter culture for my next batch?  Yes, but understand that with starter culture, fresher is better, so if your culture sat in the fridge more than 2 weeks, you may not be happy with the finished product.  Also, culture looses strength over time, so if you make yogurt weekly with your own culture, you'll want to plan to refresh it by using a commercial yogurt once a month.
• Can I use soy milk or another dairy alternative?  I've read that it is possible, as long as you add a couple tablespoons of sugar to give the cultures something to feed on, but I have not tried it.

A word about fat content:
The fat content of your homemade yogurt will be similar to that of the milk you used to make it:
1%       2.5 grams per cup
2%       5 grams per cup
Whole: 8 grams per cup

When yogurt is strained, most of the fat stays with the yogurt.  Whey has very little fat content.  If you start with 1/2 gallon (8 cups) of yogurt and strain out 1 quart (4 cups) of whey, the fat content of the strained yogurt is approximately double, so that 1 cup of whole milk strained yogurt would contain approximately 16 grams of fat. 

I find the richer yogurts more satiating, so while I might top 2/3 of a cup of granola with 2/3 of a cup of either 1% stained yogurt (3.5 grams of fat) or un-strained whole milk yogurt (5.5 grams of fat), if I were using a strained whole milk yogurt, I'd use about 1/4 of a cup ( 4 grams of fat).