​Yes, you can make yogurt without a thermometer.

​Yes, you can make yogurt without a thermometer. How do I know? Because I've been doing it for over 40 years. And I'll tell you here, in a little while, how I've been doing it. It's true that yogurt "recipes" call for heating the milk to 180 degrees F, cooling it down to 110 degrees F, adding the starter culture and then maintaining a steady temperature while it incubates. And it's true that if the milk is too hot when you add the starter culture then you will be killing all those lovely bacteria that you had hoped would start reproducing. But have you ever wondered what the yogurt-making folks of times past did prior to the invention of cooking thermometers or even electricity? If you get to pondering the history of yogurt you may end up not feeling intimidated at all about NOT following a yogurt "recipe" to the T.

HISTORY

On their website, The Dairy Farmers of Canada state the following:

• Most historical accounts attribute yogurt to the Neolithic peoples of Asia around 6000 BC. Herdsmen   began the practice of milking the animals, and the natural enzymes in the carrying containers (animal stomachs) curdled the milk, essentially making yogurt...
• Recorded history states that Genghis Khan, the founder of the Mongol Empire, and his armies lived on yogurt.
• Turkish immigrants brought yogurt to North America in the 1700s but it didn't really catch on until the 1940s when Daniel Carasso, the son of Danone founder, Isaac, and Juan Metzger took over a small yogurt factory in the Bronx, New York - the company is now called Dannon in the United States.

Yogurt is the most popular fermented milk in the world (1).The word yogurt or yoghurt or yoghourt is Turkish in origin. It is a tart, custard-like food made from milk that has first been heated and then inoculated with a bacterial culture; the bacterial action then curdles the milk (2).

BENEFITS

There are benefits to fermenting milk. During the fermentation process the milk protein casein is broken down, which allows many people with milk intolerance to freely enjoy milk in the form of yogurt. Additionally, the active bacterial cultures, while turning the milk into yogurt, are producing lactase, the enzyme which allows us to digest the lactose (milk sugar) in milk (3,4). And did you know that during the fermentation process both the vitamin B and the vitamin C content of milk increase (3)? How cool is that? Yogurt is simply good food. The beneficial bacteria in yogurt, as well as the by-products they produce, such as lactic acid (from the breakdown of the milk sugar lactose), aid our bodies in the fullest possible digestion of the foods we eat plus protect us from infection-causing bacteria, including those that cause "traveler's diarrhea" (3). So you can see that our gastrointestinal (GI) system really benefits when we eat yogurt, which is great since our GI system contains nearly 70% of our entire immune system (5)!

HOW-TO

So, on to the business of making yogurt. I won't be explaining the why, just the how. The KISS principle.

Types of milk easily obtainable in southern Indiana:

• Certified raw milk - which comes from animals routinely tested for T.B. and brucellosis; some farmers operate "cow shares", which are legal in Indiana. Look for sources of raw milk here: www.realmilk.com
• Goat milk
• Cow's milk from the grocery; I recommend choosing whole milk and always consuming it fermented.
• 1/2 and 1/2; this makes a thicker and creamier yogurt. The higher the fat content the thicker the yogurt. This is my personal current choice as I love rich and creamy; I use goat milk when I have my own goats.

Here are the general directions of how I make my yogurt (yes, without a thermometer):

1. I first "scald the milk", as my grandmother ("Granzie") called it. I gently heat the milk in a saucepan over medium-low heat until I see teeny tiny bubbles form a ring around the perimeter of the pan. And, just to keep myself honest when writing this article, I did check with a thermometer (!) and yes, the milk registered almost exactly 180 degrees F. 
2. When I see the tiny bubble ring I immediately remove the pan from the heat. I then cover the pan and let the milk cool. 
3. I keep checking the milk every little bit. And this is how I check- with clean hands, (scrubbed fingernails, too) I plunge my pinky finger well down into the middle of the milk. When I can comfortably hold my finger there for 5 seconds (1001, 1002, 1003...) then I figure the bacteria will be comfortable in there, too. Yep, I checked again with the thermometer and it registered very close to 110 degrees F. I have no recall of who first showed me this trick. Maybe the neighbor in Wittmann, Arizona who taught me in 1974 to milk my first goat? 
4. Next, I put about 1/4 cup of the warm milk into a tea cup and add 1 or 2 tablespoons (per quart of milk) of yogurt from a previous batch (only 1 tablespoon as it contains significantly more live bacteria) or a commercially made plain yogurt with live cultures* (2 tablespoons since they have considerably less live bacteria present - Stonyfield Farms Organic, Dannon, etc. - but NOT Dannon's Activia, which does not contain L. acidophilus). Sometimes I use a packet of commercial freeze-dried yogurt starter per quart. (note- if my yogurt ends up way too tart, then I sometimes use a bit less starter in the next batch; this usually happens when I am a bit too generous in adding starter from a previous batch). I mix the starter and milk well. 
5. I keep adding more milk until the mixture is runny. I pour this yogurt-milk mixture into my culturing container and, while stirring, add the rest of the warm milk, then I pop on the lid and place the container into the yogurt maker's pre-warmed water bath. 
6. I literally forget about it for 24 hours. When that time is up then I either spoon some out and eat it fresh and warm (yum), which incidentally disturbs the delicate curds and whey so that they separate, OR immediately pop the container into the fridge where the yogurt will firm up into a rich and creamy delight.

You can ferment your yogurt anywhere from 4-24 hours. It will usually coagulate within 3-4 hours, resembling the texture of custard. The shorter the fermentation time, the milder the yogurt and the fewer beneficial bacteria it contains. You might be interested to know that commercial yogurt is fermented for relatively short periods of time. 
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Why do I ferment my yogurt for 24 hours? Well, it gives the bacteria time to consume 100% of the lactose while they are reproducing. And reproduce they do -  into incredibly high numbers. Yogurt made this way contains 3 billion cfu/ml so that in just 1 cup (236 ml) you'll get over 708 Billion beneficial bacteria; this is about 50 times as much as the typical 15 Billion in one capsule of a commercial probiotic (6). As you can see, 24 hour yogurt is a low-cost source of probiotic.  Plus it is easy to digest, lactose-free, nutritious AND it tastes sooooo good!

Want a great yogurt maker?
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​If you'd like to make the 24 hour yogurt then you might like a yogurt maker like mine. I have been using a Yogourmet Electric Yogurt Maker for several years now (I purchased mine while I was in Canada for school). I love it and highly recommend it, especially if you are making the 24 hour SCD yogurt. Though the Yogourmet came with a thermometer, old habits die hard and the thermometer had been sitting unused in the drawer until I felt the need to verify temperatures for this article. 
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​MAKING YOGURT WITHOUT AN ELECTRIC YOGURT MAKER OR A THERMOMETER

Since you may want or need to make yogurt without an electric yogurt maker, I'll explain what I have done over the past 40 years and sometimes still do. I've only owned my Yogourmet since about 2008 so when I say these are tried and true methods, I mean it ;>).  Read on -

2 more ways to keep your yogurt cozy during the fermentation process:
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1) In a gas oven with only the pilot light on; this is pretty straight forward. Just place your prepared milk with the starter culture into containers (wide-mouth quart canning jars work well as containers; don't fill them too full) and then into the oven with only the pilot light on. Just don't forget you are making yogurt and accidentally preheat the oven for a pot roast - oh my!

2) In a Styrofoam cooler (I use the thick-walled ones); I bring water to a boil and fill 1 or more quart canning jars (depending on the time of year), screw on the lids and place the jars inside the cooler along with the glass canning jar(s) of future yogurt. Again, don't fill your milk jars too full; you are fermenting, remember. Then I tuck wool sweaters or old towels around the jars in the cooler and replace the lid. If fermenting for a few hours or overnight, this should be sufficient, but if you are making 24 hour yogurt then you will have to renew the hot water in the jar(s) in the morning.  I have my own system pretty much down pat since I heat with an indoor woodstove and the room temperature fluctuates quite a bit throughout the day and night. You will need to experiment with how many jars of hot water work best for your particular situation; with practice you'll get the hang of this method.

There is more of an art to using a Styrofoam cooler (or even a well-insulated cardboard box) versus a gas oven's pilot light. Too much heat will speed up the fermentation process and you may open your cooler to find a jar of separated curds and whey (don't ask me how I know this). No worries - it's still edible. Open the jars very carefully since it is likely that fermentation gases and some pressure has built up if the yogurt is "overdone" (again, personal experience). Pour off the whey and either drink it (rich in minerals), use it in cooking or use it as starter to make your own lactic acid fermented vegetables. Sprinkle a little Celtic Sea Salt on the curds and enjoy. With too little heat your yogurt won't "make"; i.e. it will look like the regular runny milk you started with instead of custard. Give it to the cat or your neighborhood possum and try again with a new batch of milk OR turn it into acid curdled cheese (ricotta) and other goodies. Check out this article (7).

Enjoy your yogurt!
                                                                                                                                                                                                                                                                            Dr. Gail
                                                                                                                           updated 7/17/2023
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Resources:
1) Sandor Ellix Katz. "Yogurt, an excerpt from 'The Art of Fermentation'".          http://www.splendidtable.org/story/yogurt-an-excerpt-from-the-art-of-fermentation. 5 April 2016.
2) Random House Webster's College Dictionary. Random House, Inc. 1991.
3) Sally Fallon with Mary G. Enig, PhD. Nourishing Traditions. New Trends Publishing- second revised edition, 2001.
4)  Dairy Farmers of Canada. "Yogurt". https://www.dairygoodness.ca/yogurt/ n.d. 3 April 2016.
5) G Vighi, F Marcucci, L Sensi, G Di Cara and F Frati. Allergy and the gastrointestinal system. Clin Exp Immunol. 2008, Sept;153 (Suppl 1):3-6.
6) "Yogurt - Why SCD Yogurt is so important". 
http://www.breakingtheviciouscycle.info/knowledge_base/detail/yoghurt-why-scd-yogurt-is-so-important/ n.d. 4 April 2016.
7) Pappas, Stephanie Loomis. Bon Appetit. Cooking. "Your 'Expired Milk' Still Has So Much More to Give: Make the most of your funky friend".   https://www.bonappetit.com/story/sour-milk-tips. 17 September 2020. Accessed 17 July 2023.