Recipe for Homemade Yoghurt
Ingredients
1 gallon (16 cups) milk
4 oz (1/2 cup) unflavored yoghurt as starter (containing live cultures) at room temperature.
A good cooking thermometer
Cheesecloth - not the basic from grocery store, which the weave is too loose -- a tighter weave is needed (look for one labeled ‘ultra fine’ or called ‘butter muslin’)
Yield = About 10 cups yoghurt
A note on the Milk: Any milk will work in making yoghurt (pasteurized, unpasteurized, homogenized, unhomogenized, low-fat, 2%, whole, raw, etc.). Some people use low-fat or non-fat milk. We try always to use organic, raw milk. Making things like yoghurt at home is partly about knowing what‘s in your food and with raw milk, pretty much what you are getting is only milk: uncooked, unprocessed, unadulterated. We have also used goat milk, which makes a nice yoghurt as well.
Step One: Pasteurize:
Heat the milk in a heavy sauce pan or pot to just below boiling about 180-185º F, to kill off the other bacteria in the milk. (Some recipes call for you to actually boil the milk, but that will change the flavor. Still other recipes say that a temperature of 170ºF is enough. I split the difference. It seems to work fine.) Then cool it back down to 110º to 120ºF. If you want to cool the milk down faster, you can put the pot in a bath of water. If you use a water bath to cool down the milk, I recommend keeping the bath water at about 100ºF; if the water is cool, I found that the milk cools down almost too quickly.
Step Two: Inoculate:
Inoculate your milk with the starter yoghurt. To do this, put the room-temperature starter yoghurt into a small bowl and mix in about 2 cups of the still-warm milk. Do not mix in the milk until it has cooled to below 120ºF as you can kill the live cultures in the starter yoghurt. After the milk and yoghurt have been mixed, stir that yoghurt/milk mixture back into the pot of milk.
A comment on starter yoghurt: you will want to choose as your starter a yoghurt you like, as your finished yoghurt will taste quite a bit like your starter yoghurt. The starter yoghurt contains the bacteria that trigger the fermentation process which turns the milk into yoghurt. There are several types of bacteria - Stoneyfield Farm yogurt claims six "active cultures" (including L. Acidophilus, Bifidus, L. Casei and L. Reuteri), while Fage's package only claims two: Streptococcus Thermophillus and Lactobacillus Bulgaricus. In my experience batches started with Stoneyfield yoghurt fermented faster, from four to five hours. The Fage yogurt will take significantly longer to ferment to a firm consistency - six to eight hours. The taste of your finished yoghurt will vary depending on the starter yoghurt (as well as other factors, see below). The two starters we have tried, Fage and Stoneyfield Farm yielded noticeably different yoghurts (the Fage was much tarter and thicker; the Stoneyfield Farm rather mild).
Step Three: Incubate:
Gently poor the warm mixture of starter yoghurt and milk into your chosen container and then set it aside. The live yoghurt bacteria are a bit sensitive and do not like to be bumped about. So set the milk in an area that will not be jiggled or shaken while it is incubating. You will want to keep the milk at between 100ºF and 120ºF while it is incubating to keep the bacteria alive and growing. The time needed for the yoghurt to set will depend largely on the temperature at which you keep it while incubating. If it is kept at a constant 110ºF, the time will be about 4-6 hours. If you are keeping it at closer to 100ºF, it will take closer to 10-12 hours (also, as noted above, the different bacteria in the starter yoghurt can change the incubation time).
Let the yoghurt stand incubating until it is the consistency of a delicate custard (not heavy pudding).
A few comments on incubation:
- Since the maintaining the proper heat is all important, you will have to find a technique for this that works for you. Some people suggest putting the yoghurt into the oven with just the pilot light on (I tried that, but our oven only stays at about 88ºF -- too cool). If you have a newer oven with a very low setting, that could work as well. Others suggest letting the yoghurt set in a thermos, or wrap the pot in a towel or heating pad to keep it warm (if you have a yoghurt making machine, the problem is solved for you). We essentially got lucky. On one of my first batches, I put the milk into a big heavy, cast iron Le Creuset pot for the incubation. That worked wonderfully, as the cast iron held the heat of the warm milk. I have had the pot in the oven and on the counter at room temperature and the yoghurt has set beautifully in both locations (yet slightly faster in the oven).
- I have experimented a little bit with different incubation temperatures. I have found with the starter yoghurt we use a starting incubation temperature of about 120ºF is ideal; yielding a creamy and full bodied flavor in the finished yoghurt. A starting incubation temperature of around 105ºF yielded a much tarter, less satisfying yoghurt. I am guessing that the reason for this is that the two different bacteria in my starter yoghurt reproduce the best at slightly different temperatures. This might explain why two really different tasting yoghurts (Fage and Alta Dena) can have the same two bacteria).
Note: the longer you let the yoghurt incubate, the more tart and thicker it will become. Unless you let the incubation temperature fall much below 100ºF, at which point the bacteria will stop reproducing and become dormant.
Step Four: Drain:
Although not really necessary, draining the whey out of the finished yoghurt makes a big difference in texture. Some recipes do not call for draining, but we found that the draining takes the yoghurt from a pourable, sort of lumpy texture, to one that is smooth and thick. It’s a taste thing. Also, if you do not drain, the whey left in the yoghurt may separate and you may need to stir your yoghurt a bit before eating.
To drain, line a colander with the cheesecloth, set over a pot or bowl deep enough to hold at least 4 cups of whey. Pour or scrape the yoghurt into the colander and drain until it has lost about a third its volume in whey -- about 3 to 4 hours.
Turn out the yoghurt into a large bowl and stir or beat it as smooth as possible with a wooden spoon (an electric mixer works quite well also). Store in the refrigerator for up to two weeks. I like to put the finished yoghurt into individual serving mason jars, so we can just grab one for breakfast.
Note: The longer you drain the yoghurt the stiffer and thicker it becomes. 3 to 4 hours of draining will yield a yoghurt that is very much as thick as a Greek yoghurt. But if you drain it longer still, 7-8 hours, you get a very thick yoghurt, close to yoghurt cheese. And if you drain the yoghurt for 12 hours, you actually get yoghurt cheese, which makes a very nice spread for bread or crackers.
Once your yoghurt is done, you can eat it plain or flavor it. I have used different sweeteners; honey and agave nectar worked well. I have also flavored the yoghurt with vanilla and different jams. All make for a nice change of pace from the plain yoghurt; but to be honest, plain is still our favorite -- mixed with some Grape-Nuts, it is a great breakfast.
Some More Basic Yoghurt Info
Yogurt Cultures & Their Properties:
I have found that the following are the basic bacteria found in most commercial yoghurts.
Lactobacillus bulgaricus - Tangy & Creamy
Steptococcus thermophilus - Tangy & Creamy
L. acidophilus - Sweet
L. delbrueckii - Mild taste
Bifidobacterium - Sweet
S. bulgaricus
S. lactis
L. casei
L. rhamnosus
Here is a list of which cultures are in some Commercial Yoghurts:
Fage = L. bulgaricus & S. thermopyilus.
Alta Dena = L. Bulgaricus & S. Thermopyilus
Dannon = L. Acidophilus
La Natura (Italian) = Bifidobacterium & L. Acidophilus
Horizon = All of above + L. casei
Stoneyfield Farm = L. bulgaricus, S. thermopyilus, L. acidophilus, bifidus, L. casei, and L. rhamnosus.
