Homemade Yogurt

​A few years ago, my husband and I began making our own yogurt as a means of cutting costs.  What we didn't expect was that it would ruin the appeal of nearly all other store-bought yogurt.  Not only is our yogurt less expensive, but we are amazed at how much better it tastes than what we can buy in a store.  It took me awhile before I tried making my own yogurt because I thought it would be complicated, difficult or time-consuming.  None of this has been accurate, as the process is really very simple, and actual hands-on time is minimal.  I am able to start the process when I wake in the morning and have Greek-style yogurt by the following morning.  There are various factors that can alter the taste of homemade yogurt, and we had (and occasionally still have) some batches that are not as tasty.  However, after playing around with yogurt starters, methods of heating, culture time and more, we've come up with a process that usually results in a yogurt flavor, consistency and degree of tartness that we like.  We prefer a Greek-style yogurt, but this process also works for regular, more fluid yogurt - we simply strain regular yogurt to get to the thicker Greek-style.

The basic idea of making yogurt is very simple:  1)  Heat milk to a high enough temperature to kill off any "bad" bacteria (165° - 180°F); 2) Cool the milk down to a temperature that won't kill off "good" bacteria from the starter culture (110° - 120°F); 3) Stir in the starter, which is 2-3 tablespoons of plain yogurt with live active cultures per gallon of milk used; 4) Let the milk/starter mixture sit in a warm area (90° - 110°F) for several hours (4-10 hours generally) until thickened to a yogurt consistency; 5) Optional - if desiring Greek-style yogurt, strain the yogurt for several hours to extract some of the whey.

That is the process in a nutshell.  But if you want more detail and tips on the yogurt-making process, specifically the process that we use, keep reading. 

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​How to Make Greek-Style Yogurt​

​Only 2 ingredients are necessary:  

• Milk (for this process, we use cow's milk; the process will be similar for using milk from other animals, but differ somewhat for alternative plant-based milks)
• Plain yogurt with live active cultures (the label on a carton of plain yogurt should indicate if it has live active cultures)

        Some people also use gelatin or pectin as a thickener, but we do not.

Step 1:  Heat milk to 165° - 180°F
             This step destroys the "bad" bacteria in the milk.

• The amount of milk to heat depends on how much yogurt is desired.  More milk is required to make the same volume of Greek-style yogurt as regular yogurt since a large volume of whey is strained off when making Greek-style yogurt.  We use a 6.5 quart slow cooker to heat our milk, so we purchase 2 gallons of milk to make a full batch, with some milk left over for other uses.
• Yogurt can be made from a variety of animal milks, but so far we have only used pasteurized and homogenized cow's milk.  Ultra-high temperature (UHT) pasteurized milk should be avoided, as the proteins needed to form yogurt may have been broken down.  Either whole, 2%, 1%, or skim milk may be used, though milk with a higher fat percentage will produce thicker and creamier yogurt.  (I personally don't notice a significant difference, and we usually use 2% or 1% milk.)
• Our method for heating the milk is to pour it into our 6.5 quart slow cooker and heat on the high setting for 4 hours.  Our slow cooker has consistently heated the milk to the required temperature range with this method, so I no longer even check the temperature.  Once the slow cooker has finished heating, it can warm until we are available to move on to the next step, but I have noticed that a longer cook/warm time results in a more yellow-tinted yogurt with a taste variation that I don't care for as well.
• We initially heated our milk in a stock pot on the stove top, but this required occasional stirring and monitoring to ensure the milk didn't scald or burn on the bottom (the latter lent a burnt taste to the yogurt that was not pleasant).  The slow cooker method is more consistent, and we can just turn it on and leave it.

Step 2:  Cool milk to 110° - 120°F
             This step brings the milk to a temperature where the live cultures that are to be introduced can survive and thrive.

• ​We use an ice bath to quickly bring the milk down to the desired temperature, with this entire step taking less than 10 minutes.  We pour the milk into a stock pot (carefully, because it is very hot); dump ice into our sink and add cold water; then place the stock pot in the ice bath, insert a thermometer and spin/stir the milk until we get to 110°F.
• ​The milk can be allowed to cool on its own, but this usually takes several hours, which might be fine if one is not able to move on to the next step as soon as the milk is finished heating, but might not be ideal if one wants to have yogurt available within a shorter time frame.   I find that the slow-cool method can result in a more yellowish yogurt and a different flavor - at least I can detect a flavor difference. 

Step 3:  Add the yogurt starter culture (plain yogurt with live active cultures) to the cooled milk
            This step inoculates the milk with the "good" bacteria that will culture the milk and thicken it into yogurt.

• Add 2-3 tablespoons of plain yogurt with live active cultures (the yogurt starter) per gallon of milk used.
• To add the yogurt starter, remove about 1-2 cups of the warm milk, gently whisk the starter into it, then add the milk/starter mix back to the rest of the milk and stir it in.
• Plain yogurt saved from a previous batch of homemade yogurt can be used as the starter culture.  Based on our yogurt-making trials, we hypothesize that continued use of this results in a yogurt that is more tart than what we prefer, so we usually buy a new container of yogurt at the store to use as our starter.  However, now that we have found a process that controls enough variables to rather consistently produce a nice, mild yogurt for us, I plan to try this again to see if I still find tartness to be a factor.  
• Though our hypotheses are not entirely scientific, we think that the brand of starter yogurt culture we use makes a difference in the final flavor of our yogurt.  The plain yogurt brand we prefer is Fage Greek-style yogurt.  Among the store bought yogurt we have tried, this one comes the closest in taste  to our homemade yogurt (though I think ours is still better).  
• Optional:  Some people will add in a thickening agent at this point, such as gelatin or pectin.  However, if you plan to make Greek-style yogurt by straining, as we do, this is not necessary.

Step 4:  Allow the milk and starter culture mixture to rest in a warm area at 90° - 110°F for several hours until thickened
            This step provides the right environment for the live culture bacteria to culture the milk and thicken it into yogurt.

• The longer the yogurt cultures, the more tart and thick it will be, so the amount of time to culture is somewhat based on personal preference.  Some people have a consistency and flavor they like after 4 hours, but I have found that I prefer the yogurt to culture for about 8-10 hours.
• We have discovered that the most convenient way for us to keep the yogurt at a warm enough temperature for several hours is to pour our milk/starter mixture back into our slow cooker crock, cover it with the lid and a hand towel, and put it in our over-the-stove microwave with the stove light on the bottom of the microwave turned on.  It is a bit of a pain to remove the crock whenever we need to use the microwave, but it does a good job of creating a warm, insulated environment.
• For those who are concerned about milk/yogurt being at warmer-than-room-temperature for hours and possibly leading to foodborne illness, it may be reassuring to know that we have never had an issue.  The heating of the milk in step 1 killed off all "bad" bacteria, and as long as bacteria aren't re-introduced by contaminated utensils, equipment, et cetera in other steps, this shouldn't be a problem.
• The timeframe on this is somewhat forgiving, as we have occasionally forgotten about the yogurt, leaving it to warm all day and through the night.  There have been no negative consequences other than flavor differences that might not be our preference but yet still result in good yogurt.

Following this step, if regular yogurt is the desired result, the process is complete.  The yogurt can be placed in other containers and refrigerated.  However, for Greek-style yogurt, there is one more step....

Step 5:  For Greek-style yogurt, strain the cultured yogurt until the desired consistency is achieved
            This step removes liquid acid whey (distinguished from sweet whey used in protein powders) from the yogurt.

• Our process for straining out some of the acid whey is to line a large colander with coffee filters, place it over our stock pot, pour the yogurt from step 4 into the colander, cover with a lid, and place in our backup refrigerator in our garage for several hours (typically overnight).   To prevent the coffee filters from moving as we pour the yogurt into the colander, we first use a spray bottle to spritz water on them so that they will adhere to the walls of the colander.  Some people prefer to use cheesecloth for straining, but we find our colander and coffee filter method to be less expensive than buying cheesecloth.
• We usually strain for 8-12 hours, and often the yogurt left in the colander is thicker and more dry than we would like.  However, the timeframe on this step is also forgiving - we can easily remedy too thick/too dry yogurt by putting the yogurt into whatever container we plan to store it in, pouring some whey back onto the yogurt and then mixing it in well with a whisk or our electric hand mixer.  The mixing also results in a more smooth, even consistency throughout the yogurt.
• The acid whey can be saved for other uses (see below) or discarded (please consider the high acid content of acid whey when choosing where to discard - it is harmful to waterways in large quantities).  

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​Finally, enjoy!

​Now the yogurt is ready to be enjoyed.  I typically prefer to eat my homemade yogurt plain.  I cannot say the same about most store bought yogurt I've tried, but I find my homemade yogurt to be so tasty that plain is fine for me.  When I or my kids do want flavoring (and the kids generally do), some of my favorite ways to add flavor or dress it up are:

• Honey
• Mashed banana (this does oxidize and turn the yogurt a brownish color if not eaten right away)
• Nuts (sliced or slivered almonds, chopped walnuts or pecans, toasted nuts...they are all good in my book)
• Fresh or frozen fruit (blueberries, strawberries, peaches, et cetera)
• Lemon curd - a nice dollop of homemade lemon curd stirred into our yogurt is as good as a bowl of ice cream, in my opinion.
• Cranberry relish - we started doing this around Thanksgiving, when we had leftover cranberry relish, and it quickly became a favorite; the creamy yogurt softens the tartness of the relish and the combination is really wonderful!
• Rhubarb sauce - mentioned in a previous post discussing farmer's market favorites
• Mashed sweet potato - stirring in the sweet potato creates more of a savory yogurt, especially if you add a few spices, but it is really yummy; it is reminiscent of sour cream on a sweet potato.  I first tried this when I made the combination as a first food for Hopper 3, an infant at the time. I took a bite, and decided to make some for myself.
• A combination of the above.

Other uses for plain yogurt:

• Can be used in place of sour cream in many recipes, such as toppings for tacos (I personally still prefer sour cream over yogurt on my tacos...yogurt doesn't have quite the same taste) or in baked goods that call for sour cream (e.g. some cake or muffin recipes use sour cream to make a more moist product).
• Add to soups for creaminess.  I like to put a dollop in my tomato soup and stir it in to create an instant creamy tomato soup.
• As a base for homemade salad dressings or vegetable dips - just add some salt and spices and some milk to thin, if needed.

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​Using Leftover Acid Whey

​Making Greek-style yogurt produces quite a bit of leftover acid whey.  This whey is a waste product which is harmful to waterways, making the disposal of it problematic for companies that produce large quantities of Greek style yogurt.  Many companies are becoming innovative with ways to reuse acid whey, and there are several ways in which the whey can be reused at home too.  An internet search for how to use whey from homemade yogurt will likely return several results.  Frankly, we have not tried many uses ourselves, so I'm passing along information more than speaking from experience.  As a side note, I've heard that acid whey can keep in the refrigerator for months, but I have not found that to be the case for us - black growth has appeared around the rim of our container after several weeks.

A few possible alternatives to discarding acid whey:

• Replace the water or milk in most baked goods with an equal amount of whey – just add 1/2 teaspoon of baking soda per 1 cup of whey to help with leavening.   We have tried this with some of our baked goods, such as waffles or muffins, and they have turned out well.
• Add to smoothies
• Use to make ricotta cheese
• Use a diluted mixture to water plants
• Feed to pets
• Add to a compost pile

For more reading on issues with mass disposal of acid whey and on useful solutions for this food production byproduct, here are a few resources:

• Dairy Reporter article
• Vice News article
• Bon Appetit article on uses for whey

If you decide to try making your own homemade yogurt, it may take some trial and error until you get to the flavor and consistency that you like.  Hopefully you'll stick with and will enjoy your yogurt as much as our family enjoys ours!