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To Heat or Not To Heat: A Yogurt Question PDF Print E-mail
Written by Linda Joyce Forristal, CTA, MTA   
Wednesday, 20 July 2005 16:39

In the Kitchen with Mother Linda

One of the most frequent questions we receive at the Foundation is the following: should you, or can you, make yogurt from raw milk? The controversy arises from the fact that the naturally occurring enzymes and bacteria in raw milk are destroyed by too much heat. Destruction of enzymes begins at 118°F and is complete at 180°F. So, if that’s true, why doesn’t everybody want to make yogurt with raw milk? It’s because raw milk yogurts oftentimes have a different texture from yogurts made with heated or pasteurized milk.

Left to its own devices, fresh milk sours naturally. This is not due to the enzymes in the mix, but to naturally-occurring lacto-fermenting bacteria found in raw milk. Those bacteria produce lactic acid that sours the milk by reducing its pH., i.e., making it more acid. While the uninitiated might think this is milk to be thrown out, the wise know this acid condition actually preserves the milk against spoilage. In days gone by, the Irish housewife typically soured fresh milk overnight by the dying fireplace in preparation for making soda bread the next morning.


Frank Kosikowski, a food scientist at Cornell University, classifies fermented milk in four different groups. The first group is "acid/alcohol" milk products such as kefir and koumiss. Kefir (which, by the way, does not rhyme with "reefer" but is stressed on the second syllable and pronounced "keh-FEER") is made with kefir grains, called "gift of the gods" but of unknown origin, which initiate a dual lactic acid/alcohol fermentation process. Traditional koumiss is made with mare’s milk and named for the horse-herding Kumanes tribe that lived on the central Asian steppes until 1235. It is fermented by a combination of acid producing L. bulgaricus and the alcohol-producing Torula yeast. (With mare’s milk in short supply most koumiss today is made with cow’s milk, but since the two milks are not the same composition, making koumiss can be a complicated endeavor.)

Kosikowski identifies the second class of fermented milk as "high acid" Bulgarian sour milk cultured exclusively with Lactobacilllus bulgaricus. The third category is "medium acid" acidophilus milk and yogurt, the main type of yogurt produced in the United States. It is primarily cultured with Lactobacillus acidophilus, a slow- and low-acid producer. The fourth category is "low acid" cultured buttermilk and cultured cream.

Today, most yogurt starters, even the "Bulgarian" one I recommend, combine at least two different bacteria. The presence of two bacterial strains, one high acid and one low, moderates the acidity of the finished product. For example, Streptococcus thermophilus ferments at 110°F to 112°F and produces .9-1.1 percent acid, Lactobacillus acidophilus ferments at 100° to 112°F and produces 1.2-2 percent acid, and Lactobacillus bulgaricus grows at 110° to 116°F and produces 2-4 percent acid. My favorite yogurt starter is 50:50 L. bulgaricus/S. thermophilus.


Now let’s get back to the "to heat or not to heat" raw milk controversy. What happens when you don’t heat the milk is that while the enzymes are preserved, the milk also retains its own natural complement of bacteria that will naturally sour the milk. These undisturbed bacteria will also compete with any added culture resulting in a different fermented product. Controlling the conditions of fermentation, most importantly temperature, the yogurt maker can achieve varied results by adding small amounts of microorganisms from tested and tried established cultures.

Most yogurt makers heat milk sufficiently to create a tabula rasa into which the new bacteria are dumped to do their handiwork, but the temperature needed for this will be many degrees higher than 110°F. Whatever temperature the milk will be heated to, in my opinion it is best to begin with raw milk. It is not homogenized so you get a wonderful cream on top. It has not had milk solids added to it, so it won’t stick to the bottom of the pan. Most important, raw milk has not been pasteurized, which is a violent, rapid-heating process that has a very detrimental effect on the proteins in the milk. A slow, gentle heating on your stovetop will more effectively preserve the integrity of fragile milk proteins, especially if you remove the milk from the stove as soon as the desired temperature has been reached.

When you start with raw milk, you can decide yourself how high a temperature you want to take the milk to--a modest 110°F, that will preserve enzymes and some of the competing naturally occurring bacteria, or to the more traditional 180°F, which is hot enough to kill competing bacteria. The texture, taste and thickness of the finished yogurt will be determined by the choices you make at every stage.


My own preference is for heated yogurt, which results in a smooth, thick product. I begin with raw milk which I slowly and gently heat to 180°F and then let it cool until I can stick in my finger for 10 seconds, which is around 110°F. When it has cooled, I add a rounded teaspoon of "Bulgarian" culture, which is really only 50 percent true Bulgarian, as explained previously. The finished yogurt comes out sharp, smooth and wonderful.


I want to pass on something I learned while researching the article. I have always made a gallon of yogurt at a time in four quart jars, and kept them up to two months. It does not spoil easily, so my family and I would happily scoop away at it until it was gone--adding our own preserves, maple sugar or honey. My favorite yogurt concoction is a couple scoops of yogurt, sprinkled with a tablespoon of freshly ground flax seed and topped with a quarter or half of a grated apple--applesauce is good, too.

But if master yogurt maker Max Alth is correct, milk begins to exhibit "antibiotic" powers as soon as the lactic acid bacteria start to curdle the milk--either naturally or in the process of making yogurt--and a peak is reached about seven days later. And according to Alth, the antibiotic effect disappears about a week later. At its most effective, the antibiotic strength of yogurt is equal to about .06 penicillin units per cubic centimeter, or about nine units of penicillin in every 8 ounces of yogurt. I have not confirmed this information, but if that’s true, in the future I plan to make smaller batches of yogurt more often.

Anna’s Bulgarian Yogurt

I have had the great fortune of living close enough to a Bulgarian friend, Anna Pavlova, to get a container of yogurt every so often from her as a starter. If you don’t have a Bulgarian friend, a company in California sells a Bulgarian-style Yogurt Starter®. (See and look in their specialty items.) This wonderful product is a combination of 50 percent Streptococcus thermophilus and 50 percent Lactobacillus bulgaricus. Each bottle is decorated with the picture of a Bulgarian woman.

8 cups milk (I prefer whole raw milk)
1/4 cup yogurt from a previous batch 
or 4 teaspoons of Natren yogurt starter
as directed on the bottle
2 glass quart jars with lids, sterilized

Over low heat, slowly bring the milk to at least 180°F, or until a ring of bubbles forms around the edge of the pan, but don’t boil. Let cool until you can keep your finger in the milk while you count to 10. Divide yogurt starter or reserved yogurt between two wide-mouth quart-size sterilized glass jars. Pour in about 1/4 cup milk and stir to incorporate the starter. Fill the jars with the rest of the milk and screw on the lids.Wrap the jars in a warm blanket and let sit overnight in a warm place or for at least eight hours. Unwrap and place in the refrigerator. I know you will enjoy this creamy, healthy yogurt.


Max Alth, Making Your Own Cheese & Yogurt, Funk & Wagnalls, New York, 1977
Frank Kosikowski, Cheese and Fermented Milk Foods, 1966.


In the Middle East, yogurt is a thick drink, not something you eat with a spoon. To make raw milk drinkable yogurt, place 1 quart raw milk in a glass container and add 1/4 cup yogurt. Place in a warm place (such as a warm oven) overnight. The milk will sour and become slightly thick and perhaps lumpy.

You can drink this as is, or whisk it to make it smoother. In Iran, the traditional yogurt drink is quite salty, so you may wish to add some unrefined salt. The addition of salt makes drinkable yogurt the perfect beverage for a hot climate. Of course, you may also use your drinkable yogurt to make smoothies by blending with fruit and a natural sweetener.

Another method, suggested by raw-foodist Aajonus Vonderplanitz, is to warm milk to about 80 degrees and add a small amount of good quality commercial yogurt or yogurt from a previous batch and put in a yogurt maker. Leave in the yogurt maker much longer than called for in the instructions, that is about 8 hours or overnight. Results may not be consistent and the product tends to be thinner than heated yogurt.


We are grateful to Maria Garcia for coming up with this wonderful raw milk yogurt, and to Kristina Boudrezux for working out the details. This recipe makes a smooth, thick yogurt loaded with beneficial stuff for your body. It requires no electricity, and ensures a high quality product using glass, versus plastic, for yogurt culture growth. It is easiest to start at night, after dinner, and let it set overnight. You will wake up to yummy yogurt for breakfast.

1 quart raw, organic whole milk
1-8 ounce container Brown Cow whole milk yogurt, plain flavor (for the first batch)
or 3-4 tablespoons reserved yogurt from the previous batch

Keep all of your utensils very clean, making sure there is no soap residue. This is especially true of the "mother" container, described below. Keep the metal lids out of the dishwasher, as this will cause rusting.

  • Nissan Thermal Lunch Tote thermos JLN 1400X), all plastic containers inside removed.
    (Available from 300 N. Martingale Road, Schaumburg, IL USA and in local stores)
  • 1 quart class container with metal, 1-piece lid, sterilized (boiled), then dried and cooled to just warm.
    (The 32-ounce Paragon Jar from California Glass Co. fits the Nissan Thermos)
    (510.635.7700 or
  • The "mother" container, a glass container with air-tight seal,
    4 tablespoon size to hold the starter for the next batch, sterilized
  • Small whisk
  • Measuring spoon for 1 tablespoon
  • Milk or candy thermometer


  1. Take the yogurt starter (Brown Cow, or container from a prior batch--the "mother") out of the refrigerator for 1 -2 hours, to bring to room temperature.
  2. Warm the 1 qt glass jar, if not already warm. Rinsing in hot water will do.
  3. Heat the milk in a pan to 110°F, then remove from heat immediately.
  4. Take a small amount of the warm milk into a separate bowl, then whisk in 3-4 tablespoons of the yogurt starter. Stir the mixture back into the main bowl of milk.
  5. Pour the milk-yogurt mixture from the pan into the warm, 1 qt glass jar and seal loosely with the lid. Make sure to leave about 3/4 inch of air at the top of the jar so the culture has some space to grow. Place the jar into the thermos and close. Put it on the countertop, and let it set overnight (8 hours).
  6. In the morning, remove the glass jar from the thermos and put it into the refrigerator.
  7. When you first open the yogurt jar, have your smaller container ready for the mother. There will be some delicious cream on the top. Before you do anything else, scoop out 3-4 tablespoons of yogurt (the "mother"), place it in the mother container, and put the mother in the refrigerator for later use to start your next batch--instead of using the Brown Cow.
  8. The yogurt and mother both last about one week. Enjoy your yogurt! Try adding a bit of honey for fun.

This article appeared in Wise Traditions in Food, Farming and the Healing Arts, the quarterly magazine of the Weston A. Price Foundation, Spring 2005.

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Comments (18)Add Comment
To Maryanne
written by Melissa, Mar 06 2014
I used to think about this, but I have since read that heating raw milk in your home does not denature the proteins in the same way pasteurization does. Pasteurization is heating, but the difference is this, it takes 15 seconds in a pasteurization coil to achieve what takes 45 minutes in your home. That is only the heat the milk is exposed to, and says nothing of the pressure of the machine moving the milk through. The proteins are not effected in the same way. Hope that is helpful.
low temp vs high temp, i see now
written by Simon M, Feb 13 2014
hi i came to the board to see whether i could stick to low-temp heating for yogurt, more out of the fact i was rushing out the door but wanted to get yogurt started and didn't have time to heat up to 180F and then back down to 110F. well, i did my batch at 110F and after 24 hours, not firm at all. i followed up with a 180F to 110F batch, and that thickened up nicely. same culture for both (thermophilus, bulgaricus, acidopilus, lactis, bifido blend). no dry milk in both. i can see how the heating up to 180F changes the proteins in some way. thanks for the help here, i'll keep my low-temp yogurt for drinking as mentioned in the posts and my high-temp for eating. ah, options!
Heating is pasteurizing, is it not?
written by Maryanne, Sep 07 2013
To keep the full nutritional value of raw milk it would make sense not to heat it? I'm confused, why seek out raw milk if you are simply going to pasteurize it?
written by Joel L, May 29 2013
Why do you prefer 180° to 110°? You cite no reason but tradition (the tradition of modern yogurt makers in the US), you don't like homogenization which is as you say violent but prefer the same temperature reached slowly. Why not leave the natural enzymes be?
Yoghurt didn't thicken well
written by Mary Burgess, Apr 04 2013
Is there anything I can do with yogurt that didn't thicken well? (it's kind of globby)
written by MOLLIE Aezen, Feb 05 2013
I USED RAW GOATS MILK PUT IT IN 2CUPS BALL MASON JARS (THE SQUATTED JARS THAT COME 4 IN A PKG) in my cousine yogurt maker that had the 7 little jars ugh. the cold milk and cold yogurt that i made with half and half (it has no sugar) mixed it up and put 2 2 cup jars for the cousine maker for 12 hours, then caped them and put in frige and it was thick. I will strain for greek yogurt.
written by Amy , Dec 08 2012
Hi, I am about to make yogurt from raw milk. My daughter is unable to eat much protein, but I currently buy her Australian style yogurt since it is lower in protein. If I were to strain my yogurt to produce Greek style yogurt for myself and add some of this back to the whey, would this produce a lower protein Australian style yogurt?
Love this recipe
written by Terri, Apr 23 2012
This worked well for me using raw goat milk. The texture and flavor were the best ever! Not thick like store-bought but not all that thin either.
HELP!! What happens if I boiled the milk? Can I still use it?
written by PAULA, Feb 28 2012
I am making yogurt for the first time using 'Yogourmet freeze-dried yogurt starter'(the only thing i could find at my grocery store). My questions is I put the 1% milk in the microwave for 9 mins. (1 Qt). It did not watch it adn I know it BOILED!! Everything I read says 'DO NOT BOIL'. What happens if the milk is spoiled? Will it still work? wil I get sick? What should I do? can I still use it?
What Happened?
written by Ashleigh, Feb 24 2012

I made the yogurt with my soured raw milk, which as far as I have looked up is good to use for yogurt. I followed all the directions of heating to 180 then cooling to 110 and using a storebought organic yogurt starter (I also cracked open a pill of good quality probiotics into each quart jar).
I wrapped in a warm blanket, left for 8 hours and the result is not at all yogurt. It is all separated, you can clearly see the whey separation and it is just as liquidy as in the beginner.
Can anybody explain what's happened and any way to fix/avoid this??

written by Mikki, Dec 24 2011
Linda, on straining yogurt. No you are not decreasing the nutritional quality I don't think. Greek yogurt is what you will get and my naturopath, ND, says that it's much higher in protein and recommends it for people who need more protein in their diets. Save the whey for lacto-fermenting, or drink a tablespoon mixed in a little warm water before meals as a digestive aid.
raw yoghurt
written by Mandy, Jul 10 2011
the thickest yogurt from raw goat milk for me seems to be when heated to 180, cooled to 110, and a thick yogurt used as s starter, then left 8 hours in a yogurt maker. Also made delicious vanilla fro-gurt / ice cream sweetened with stevia and using real vanilla seeds. Even more amazing with stewed rhubarb swirled through.......
written by Don Radina, Nov 10 2010
Put one or two gallons of raw milk in a roaster oven set at 100 degrees. Add some yogurt culture and leave overnight. Mix with a hand blender. Pour into quart canning jars with plastic lids.
Will store in frig for weeks getting more tart. Smooth and creamy.

I started my first batch with both yoghurt and kiefer. Have been keeping it going for months.
written by Jessica Powell-Thomas, Jul 21 2010
thank you so much for sharing your recipe with us all!

Just about to try. We are using raw milk over a slow heating process to 180. crossing fingers. Again thanks for sharing
written by D. M. Mitchell, Jul 09 2010
Regarding making yogurt. If pastuerization harms the milk protein, and destroys the beneficial enzymes, then wouldn't heating raw milk to 180 degrees F do the same? I can't see how a rapid temperature rise, versus several minutes on a stove top, would make much difference, especially since the pastuerization temperature is 19 or 20 degrees cooler. I have tried making yogurt with raw milk and "Yogurmet", a freeze-dried yougurt starter containing L. bulgaricus, S. thermophilus, and L. acidophilus. I tried the 110 degree and the 180 degree method, to less than satisfactory results. However, when I have used commercial milk and a couuple of tablespoons of a good commercial yogurt, I get good, smooth, thick yogurt. I like raw milk and drink it whenever I can afford it ($6.00/half gallon), but I am on a very limited income and can seldom afford it. And I can't find a full fat yogurt anywhere.
written by Tania, May 23 2010
Could I make ice cream with my raw goat milk yogurt?
Thank you,
written by Bill, May 16 2010
Thank you. I learned much from your website about yogurt. Like it will last up to 2 months in the fridge. I have a website dedicated to providing folks who are interested in integrating yogurt making into their lives:

Thank you again,

straining yogurt
written by Linda, Apr 29 2010
Sometimes I like to strain my home-made yogurt to make it really thick. When I do that -- strain out about a cup of whey -- am I also decreasing the nutritional quality of the yogurt?

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Last Updated on Tuesday, 09 June 2009 16:56