by Cat, July 2007; updated 2013 (with my learnings), and 2017 (for raw milk yogurt test); 2018 (with more learnings) (Photo, right, from Cheesemaking .com)

The yogurt culture likely originated in Bulgaria, in eastern Europe – at least, the main bacteria in yogurt culture bears ‘bulgaricus’ in the name. In the US, in order to be called ‘yogurt,’ the culture must include 2 specific bacteria:  Streptococcus thermophilus and Lactobacillus bulgaricus. S. thermophilus is what requires culturing at 110 – 116F (above room temperature); L. bulgaricus gives yogurt its sweet-tart flavor. Additional bacteria such as L. acidophilus or Bifidus may also be added, as these are more familiar probiotic cultures that people will recognize if they are looking for a probiotic yogurt.

In addition to providing valuable probiotics and probiotics for your gut, recent studies also indicate it can lower your risk of osteoporosis (11) and type-2 Diabetes (12). But it has to be plain, full-fat, unsweetened yogurt from clean, pastured dairy livestock.

• Includes: 1. Regular plain yogurt (using raw or pasteurized milk); 2. Greek Style yogurt; 3. Sweetened yogurt; 4. Homemade yogurt videos
• See also: 1. Culturing, Fermentation Menu; 2. Milk & Culturing of Milk (About); 3. Yogurt Cream Cheese & Liquid Whey (for Lacto-Fermentation); 4. Coconut Milk Yogurt; Other Sites: 1. 24-hour Goats Milk Yogurt

Serial Culturing with Yogurt

Serial culturing, or using from one batch to culture the next batch, works great for several batches of yogurt; however, eventually the concentration of required bacteria for it to be “yogurt”* decreases.  Starting over with a fresh culture is recommended

You don’t need to maintain a mother culture; if for any reason you need to start over, you can always buy a container of a good Organic plain, unsweetened yogurt such as Nancy’s or Brown Cow as a starter. Here in the Flathead valley, we have a local dairy that makes great Greek Yogurt that I like to use as starter: Kalispell Kreamery.

I do not recommend using a sweetened yogurt, or one with fruit added as a starter.

*In the US, required bacteria species for your cultured product to be called yogurt: Lactobacillus bulgaricus and Streptococcus thermophilus. Other commonly-used bacteria in yogurt starters include Lactobacillus acidophilus and/or Bifidobacterium lactis.

What Kind of Milk Can I Use?

Any dairy milk will work (except homogenized, ultra-pasteurized or UHT milk); I use raw milk (goat or cow). In my experience, you will get the best results if you pre-heat the milk to 185°F, then cool it to culturing temperature before adding the culture this is especially important for pasteurized milk. NOTE: In early 2017, I tried making raw goat yogurt again, with better luck, culturing it at 116F for about 6 – 10 hours; have to watch it closely for when it starts to thicken, or it will separate. It also produces a different tart flavor than regular yogurt.

Cow’s milk yogurt is my favorite because it makes a nice thick pudding; it also makes a better starter than any of the powdered cultures I’ve tried; and it gives a satisfying sweet-tart flavor.

Goat milk also makes a good yogurt that is more easily digested than cow’s milk yogurt. But it is thinner than cows-milk yogurt, and may have a stringy texture that many do not like (what I attribute to a strong surface tension – if you put a bit on your spoon, the yogurt tries to go back into the original container). This happened with the first local, raw goat milk I tried; even when I whisked in some powdered goat milk, the yogurt still had that stringy problem. However, when I switched to a different local source, that yogurt did not get stringy.

Some recommend adding a bit of gelatin to the milk for a thicker yogurt, but I have a food sensitivity to commercial gelatin, so I’ve not tried that. Another option is to add animal rennet (see instructions in the introduction to my recipe, below, or the Luci Lock video, below), but I’ve not tried that.

When using goat milk, I’ve found that using cow’s yogurt as a starter works better than the packaged powder.  Goat yogurt can be quite thin and slightly ‘stringy,’  but just as tasty as cow yogurt, and more easily digested.

Some nut milks can also be used. I’ve tried making almond-milk yogurt but was unhappy with the result. Coconut milk yogurt is much better. Soy milk will also work but I don’t recommend soy unless it has been fermented (as miso or soya sauce).

Culturing Temperature

There is some controversy about the ideal temperature. Most sources indicate 110° – 116° F. Other sources suggest 100° – 110° F.  The 24-hour yogurt method for raw goat’s milk (and other milks) (13) is strict about not exceeding 110° F.

My Yogurt Learnings

The following has been updated as of Oct 2013.

After much experimentation, I’ve come to the following conclusions on the fine points of making yogurt:

• For goat’s milk it works better to use a cow’s milk yogurt to inoculate the goat’s milk, than to use a freeze-dried starter.
• The best starter for your very first batch is a good quality Organic commercial yogurt like Nancy’s or Brown Cow. It should be plain and not sweetened (not even with honey).
• Yogourmet powdered starter doesn’t work very well for serial culturing; Natren brand is better.
• Many sources say to add a bit of powdered milk to your milk when heating it, to produce a firmer yogurt.  This is true; however, powdered milk is of questionable nutritional quality (it is heated and dried at high temperatures, which denatures the proteins and does other harm to the milk).  If you can find spray-dried powdered milk, that would be much better. I’ve tried pectin and gelatin, but don’t like the texture.  I’ve learned to enjoy the softer texture of homemade yogurt without thickeners.
• Once you inoculate and stir the milk, do not disturb the mixture by whipping, shaking, etc., as this will cause the yogurt to separate into curds and whey.  Simply let it rest while it is culturing.  Test for readiness by carefully inserting a knife, and then taste it for desired sourness.  When it’s ready, leave it in the culturing container and place in the refrigerator.  Once it has cooled, you may stir it.
• Simply heating raw milk to culturing temperature of 110 – 116⁰ F (to avoid denaturation of the proteins, which begins at 118⁰ F), and then culturing, has not worked well for me.  The warmth of the heated milk, along with the natural competing bacteria in raw milk, causes the milk to separate before the yogurt bacteria have a chance to work. I’ve concluded that you must kill the natural probiotics in the milk by heating to 185⁰ F and then cooling to culturing temperature. HOWEVER, I’ve been encouraged by blogs Nourished Kitchen (9) and Living the Nourished Life (10) to try this again, once my source of raw goats milk is available again (after kidding). So I tried again in early 2017 at it does work if I watch it closely after the first 4 hours, for when it starts to thicken and then refrigerate it. If I catch it too late, it will separate.
• Heating raw milk to culturing temperature does not appear to be a problem for kefir, which cultures at a lower temperature).

My learnings agree with the recommendation of Mother Linda (2), who is considered a yogurt expert:  she recommends a Bulgarian culture from the Natren website (5), heating milk to 185⁰ F to kill competing bacteria, then cooling to culturing temperature before adding the culture.

Heating raw milk to 110 – 1160 F culturing temperature (rather than to 185, then cooling to culturing temperature) articles: Nourished Kitchen (9) and Living the Nourished Life (10).

Troubleshooting

If you have trouble with your yogurt, refer to my Troubleshooting links in the Reference section at the bottom of this post.

Cat’s Yogurt Recipe

Using raw dairy milk: Simply heat the milk to culturing temperature (110° – 116°F) in a heavy-bottomed saucepan or in culturing chamber. I use my pilot-lit oven which maintains about 114°F at all times. I can take 6 to 24 hours to thicken. I recommend always culturing for 24 hours, because the longer you culture it, the more lactose and casein are broken down, and the more probiotics are produced. (9, 10).

When I first tried using raw milk, it would separate before culturing, so I gave it up and  scalded it as for pasteurized milk. But in 2017 I decided to try it again and am very happy with the result. See my Raw milk experiment, below.

Mar 2018 update: I started having trouble with my raw goat milk yogurt: it separates early in the process and will not thicken. I tried using different starters but none of them worked. It could be a problem with the milk. I decided to take a break from making my own and am using Kalispell Kreamery’s Greek Yogurt (Plain). When I return to making my own, I will get a Luvele 24-hour yogurt maker that heats only to 110° F.

Using pasteurized milk, or scalded raw milk (or raw milk if yours won’t culture if only heated to culturing temp): None of the milk or cream should be homogenized or ultra pasteurized.  For the starter, you can use good quality, plain and unsweetened and unflavored commercial yogurt (such as Nancy’s, Brown Cow, or our local brand, Kalispell Creamery), or yogurt from a previous batch.  Alternately a packet of freeze dried yogurt starter (such as Natren (5) or cheesemaking.com).

Use cow’s or goat’s milk for dairy yogurt. You may notice that goat-milk yogurt is softer, more liquid-y than cow-milk yogurt. (It can be thickened with rennet after culturing). My raw goat milk sometimes produced liquid-y yogurt when heated to 185F, but I’ve learned to hold it at that temperature for at least 5 minutes to produce thicker yogurt; it also depends on the goat.

Here’s the method for pasteurized milk from a cheese making book (sorry, I lost the link).

Adding Rennet (after culturing): To 4 tablespoons of water, add 1 drop rennet and stir well, then add 1 tablespoon of this diluted rennet to your cultured goat milk to help thicken.

Culturing temperature: 110⁰ – 116⁰ F

Ingredients & Equipment:

• 4 cups whole pasteurized or raw milk (from cow or goat)
• 1 – 2  Tbsp plain, unsweetened yogurt or recommended amount of freeze dried yogurt starter
• 1 – 3 tsp raw honey or raw maple syrup to taste (optional)
• 2 quart stainless steel pot

Method:

1. Pre-Heat:  If using pasteurized milk, you need to scald the milk first: heat to 180⁰ F and then cool to culturing temperature before proceeding.  If using raw milk, you can try heating to culturing temperature (110⁰ F) and proceed (see below), but in my early experience using raw cow’s milk, it needs to be scalded first; Mother Linda (2) agrees. In my later experience using raw goats milk, scalding is not necessary.
2. Starter:
   • Yogurt as starter:  Put about 2 Tablespoons of yogurt in a glass measuring cup, add about 2 Tablespoons of the warm milk and stir ’til combined.  Add back to warm milk in the pot and stir.  Don’t use too much starter or you won’t get a good result; I actually get a better result with about 1 Tbsp yogurt.
   • Freeze dried yogurt starter: pour about a cup of warm milk into a small bowl or cup.  Add the powdered starter and stir to dissolve.  Add this back to the rest of the warm milk and stir.
3. Culturing: the method depends on the equipment used to maintain culturing temperature:
   • Yogurt maker: pour into the container, cover and culture.
   • Luvele 24-hour yogurt maker (14): follow instructions that come with the equipment. You need 2 quarts of milk for each batch.
   • Oven or dehydrator (see ‘Equipment’ section of Cultured Milk article): Cover the pot  tightly (or pour into a quart jar and screw on the cap) and place in oven or dehydrator.
   • Allow to culture about 6 – 8 hours or overnight.  The longer it cultures, the greater the chance the whey will separate.  For the thickest yogurt, check carefully after about 2 or 3 hours; carefully remove any whey that separates with a paper towel (or leave it and blend it in later).  Resist temptation to jostle or stir it while it is coagulating, or the whey will separate early. (2) 
     
   • If the whey has separated, you can either blend it back together with a whisk (or in your blender), or you can strain off the whey through a very fine sieve.  I recommend blending the whey back in, as it is a very health-giving protein, but you may have to whisk it well each time you serve from the container. If you strain off the whey, the remaining yogurt has a cream-cheese like quality, and the whey can be used to make other lacto-fermented beverages, pickles, chutneys, or vegetables.

4. Greek-style Yogurt (optional): Line a fine strainer with cheesecloth and set over a bowl or measuring cup. Pour yogurt into lined strainer (reserving a portion to use as starter for next batch), place in fridge and let the whey drip off into the bowl, until the yogurt reaches desired thickness. Save the whey for presoaking flour or jumpstarting a fermentation project. NOTE: if you let the yogurt strain at room temperature, it will taste more like cream cheese than Greek yogurt.

If you want to sweeten with honey, add to the yogurt while still warm, before pouring into strainer (see Sweeten, below).

5. Sweeten (optional):  If you want to sweeten the yogurt, add honey or maple syrup to taste before chilling the yogurt (it’s easier to blend in the sweetener while the yogurt is still warm).  But I think the yogurt’s natural sweetness is enough.

6. Chill:  Transfer to refrigerator, and keep chilled.

7. Reusing Starter: Reserve a few tablespoons (2 – 4) of yogurt from each batch, to make the next batch of yogurt.  However, it’s best to reserve it BEFORE sweetening.

Raw Milk Yogurt: an experiment

Several sites say it should culture in 6 hours but  recommend culturing for 12 – 24 hours, because the longer you culture it, the more lactose and casein are broken down, and the more probiotics are produced. (9, 10,13)

3/1/17: For my trial batch, I used just 1 cup of raw goats milk and scant ½ tsp cultured yogurt (local brand: Kalispell Kreamery’s Plain Greek Yogurt). Placed milk in half-pint jar and set in a man of hot tap water, and placed in my pilot-lit oven to warm the milk to between 110° and 116° F. When it reached 114°F I stirred in starter. Place culturing jar in pot of  warmed water and set in culturing chamber at 10:30 AM. Checked at 4:30 (6 hours, normal culturing time), but it had not started to thicken nor sour. checked again at 5:45: still not thickening so added ¼ tsp Natren Yogurt Starter. Checked again at 7 PM; no change; very slightly thickened at 9 PM, so added another ½ tsp yogurt. Left to culture overnight; checked at 10:30 AM. Result: It has thickened, whey has not separated, and it tastes nicely tart. Total culturing time, 24 hours. Total starter added: 1 tsp Greek yogurt and ¼ tsp Natren Yogurt Starter. Not sure if the latter is needed. Next time I won’t add it.

Videos: Other Homemade Yogurt Methods

With Luci Lock, using raw milk:

This video is from Mercola (Ref. 7). Note that she doesn’t heat the raw milk so that it stays ‘raw.’ In my experience, it doesn’t always thicken and often separates, so you have to watch it carefully. When it does work, it’s the best yogurt and well worth the try.

Note: Luci is using a brand of culture which is no longer available on the Mercola site. Instead he now has his own brand.

https://www.youtube.com/watch?v=r1DosR6Pbd0

1-gallon yogurt, from HowTo and Style:

This next one makes a gallon (4 quarts) of yogurt at a time (reference 8). Like my recipe, this one heats the milk to 185°F; but then it holds it at that temperature for 15 – 30 minutes. I’ve tried this but find it hard to keep the temperature steady and the milk eventually boils or cools down. However, it is true that the longer you hold it at temperature, the more firm the yogurt. So even if you only hold it for 5 minutes, it helps.

Don’t forget to cool it down to culturing temp (110° – 120°F) before adding the starter.

This cultures the yogurt in a cooler with two gallon jugs of water at the culturing temp placed in the cooler. However, you could use your off-oven with the light on; or if your oven has a setting for setting bread dough to rise, you could use that.

References:

1. Nourishing Traditions, by Sally Fallon with Mary G. Enig, Ph.D.
2. ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=525
3. westonaprice.org/motherlinda/yogurt.html
4. motherlindas.com/yogurt_bulgarian.htm
5. Natren: store.natren.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=N&Category_Code=005
6. bean-sprouts.blogspot.com/2007/11/how-to-make-greek-yogurt.html
7. Mercola, with Luci Lock: Making Organic Yogurt with Luci Lock
8. HowTo & Style: Adeldor DIY on Making a gallon of yogurt (YouTube)
9. Raw milk yogurt on Nourished Kitchen (nourishedkitchen.com/raw-milk-yogurt)
10. Raw milk yogurt on Living the Nourished Life (livingthenourishedlife.com/my-version-of-easy-homemade-raw-milk)
11. Mercola: articles.mercola.com/sites/articles/archive/2017/05/29/yogurt-lowers-osteoporosis-risk.aspx
12. About the study: hsph.harvard.edu/news/hsph-in-the-news/yogurt-may-reduce-type-2-diabetes-risk/; study abstract:  bmcmedicine.biomedcentral.com/articles/10.1186/s12916-014-0215-1
13. 24-Hour Yogurt Method (SCD Lifestyle): scdlifestyle.com/2011/08/easy-scd-yogurt-–-directions-for-scd-legal-goat-milk-yogurt/
14. Luvele 24-hour yogurt maker: luvele.com/?rfsn=973376.f64a86

Troubleshooting:

1. westonaprice.org/motherlinda/yogurt.html
2. motherlindas.com/yogurt_bulgarian.htm
3. Univ. Nebraska: ianrpubs.unl.edu/epublic/pages/publicationD.jsp?publicationId=525
4. Mother Earth News: motherearthnews.com/Whole-Foods-and-Cooking/1980-03-01/Make-Your-Own-Yogurt.aspx
5. bean-sprouts.blogspot.com/2007/11/how-to-make-greek-yogurt.html ( scroll to bottom for troubleshooting)
6. Jim Hodge’s website: home.att.net/~jdhodge/Yogurt.htm  (scroll to bottom for troubleshooting)