Creating yogurt is one of the most simple fermentation processes that we humans facilitate. Making your own soy yogurt is ridiculously easy, so tasty, and super cheap (especially when making it from your own homemade soy milk). You'll never want to buy store bought soy yogurt again! Plus it reduces packaging waste and is totally customizable according to your tastes. After fermenting, you can add anything you want to it: sweeteners, fruit, lemon juice, spices, nuts and seeds, flavor extracts, granola, vegetables... seriously, anything.
Yogurts are one of my favorite ingredients to use in everything - dips and dressings (and all sorts of condiments), baked goods, deserts, smoothies, even marinating chicken. I make soy and other plant yogurts basically the same way I make dairy yogurt. The process is simple: heat milk, add cultures, incubate, enjoy.
Let's start with ingredients. Although there's a world of additives, all you actually need are two basic ingredients: soy milk and cultures.
Soy milk
For the absolute best yogurt ever, homemade soy milk really is the way to go. Not only does it offer fresher flavor with no additives, but it also yields better consistency and yogurty results. Some people have a difficult time making yogurt with store bought soy milk because certain additives affect the cultures. Making soy milk costs pennies to produce and takes minutes to whip up (check out my article on turning beans to milk). When I make soy yogurt I start by making soy milk. After heating the milk (step #5), I just let it cool to about 110F degrees and continue with the steps below.
Personal preference: Some people leave the okara, or pulp, in the soy milk when heating and continue to leave it in the yogurt as well. It gives a grainy texture to soy yogurt. Although it's not my preference, you might like it. It does offer additional protein and fiber.
Cultures
Fermentation happens when microorganisms (bacteria, yeast, etc) break down substances. Adding certain types of live bacterial cultures to milk is what makes yogurt. It works the same way with dairy and non-dairy yogurts alike. Unlike a bread starter, you can't just leave your milk out and hope that the right bacteria jump in. There are several strains of bacteria used for fermenting milks and you do have to initially introduce the right cultures. However, once you make your first batch, just use the last 1/2 cup of your yogurt to culture your next batch.
There are some choices here. The most commonly used starters include:
- A small store bought yogurt. You can use dairy yogurt as a starter, or if you're a vegan get soy or coconut. When choosing a starter consider which brand has the flavor and consistency that you like best. Your yogurt is likely to take on these characteristics. Some brands have only one or two bacteria, while others have several. This will affect your yogurt too. One other thing I do want to mention about using store bought yogurt is that for whatever reason the bacteria from these yogurts only continue reproducing for a limited amount of generations. What that means is: when using the last batch of your yogurt to culture your next batch, if you initially started with store bought yogurt, after a few batches the bacteria die off and won't ferment your milk anymore. At which point you'll need to buy another yogurt starter.
- Live probiotic supplements. These are the probiotics that come in capsules used for digestive health from the local pharmacy. Make sure the probiotics are alive or they won't ferment your soy milk.
- Probiotic cultures marketed just for making yogurt. These cultures come in vegan and non-vegan, and can be purchased from cheese-making suppliers.
- Heritage or heirloom cultures. If you know someone who has maintained a yogurt for a long period of time and has a healthy strain, ask them for a 1/2 cup of their yogurt. If you plan on making yogurt regularly, these are the strongest cultures that will continue to reproduce indefinitely. Take care of them and you'll never have to buy a probiotic or starter again.
Just for fun: In the past, I've always used probiotics or starter yogurt to inoculate my initial batch. However, I am currently in the process of researching and experimenting with plant-derived cultures and once I get that worked out I will definitely share in a future article.
As far as equipment goes, you'll need just a few things.
I know some people use a yogurt making machine, but that's just not my style. Why waste money on a one-trick-pony that just takes up precious kitchen real estate. Don't get me wrong, I love my kitchen gadgets, but if I can at all help it, they've got to be versatile (except my dishwasher). Luckily, it doesn't take much to make yogurt and I bet you've already got all the equipment you need on hand:
- Pot to heat the milk. Sometimes I use the double boiler method, with the milk in one pot that's set inside of a larger pot filled with water. This distributes heat and regulates temperature so that the milk is less likely to scorch on the bottom. Super useful especially if I'm doing other things while my milk is heating and aren't being vigilant about stirring.
- Stir spoon. I recommend metal and not wood. Wood is porous and any wild bacteria living in it may get into your milk and keep the desired cultures from growing strong.
- Thermometer. If you have a kitchen thermometer you can use it to make sure you're at the right temperatures.
- Container(s) for incubating. I've heard that yogurt can sometime react poorly with metal during incubating. In the past I've had issues with black specks forming when I used a stainless steel pot, which could have indicated unwanted bacteria or that the cultures reacted with the metal. Either way, now I use a ceramic crock with glass lid. I bought this beautiful crock at a thrift store many years ago. It was originally part of an electric crock pot, but the heating unit had broke and only the crock was left. It's perfect! Many people incubate directly in the glass jars that they intend to store them in, which also works very well.
- An incubator. This is the most complicated piece of equipment needed. Live bacterial cultures require a certain temperature range to thrive and reproduce rapidly, fermenting the yogurt along the way. To hold the right temp, here are a few options:
~ An oven. This only works during the summer or in warm climates. Pre-heat the oven to 110-120F degrees before making yogurt. When it's time to incubate, put yogurt in the oven with a lid on it, wrap it with a towel, and turn the oven off. For a gas oven: the pilot light may be sufficient enough to hold the temp. For an electric oven: leave the light on while incubating to help keep a warm environment. Don't open the oven until you're ready to remove the yogurt, this way heat won't escape. Do not use your oven for anything else while yogurt is in there. We tape a note to the door reminding us to stay away. We learned this the hard way when we accidentally baked a wheel of cheese I had drying the oven – not once, but twice. Fortunately, one of the wheels was a bel pasae and as it turns out, quite delicious when baked (leading to further experimentation, which I'll get to in future cheese articles). But I promise you that this will not work out for your yogurt.
~ An ice chest or cooler. Some people add heat packs or fill halfway with 110F degree water making a warm water bath. The warm bath method can be used in other containers too, like tubs, buckets, or a sink. Keep it closed during incubation. Hot summer day? Set the cooler in direct sunlight.
~ Beverage/soup thermos or insulated lunch bag. For small batches this works fine. Wrap it in a towel for added insulation.
~ Heating pad in a towel-lined box or ice chest. Use the lowest setting on the heating pad. This is my preferred method and the one I use regularly.
~ And, of course, you can choose to use a yogurt maker.
A note about cleaning equipment before use:
Many types of bacteria can ferment easily in your yogurt, including unwanted ones. Sterilizing all equipment, tools, incubator, and storage containers in advance is important. This way you control the cultures in your food. Because we make beer, cheese, and other fermented foods in our home we use a food grade sanitizer that Keith gets from a beer-making supplier. This particular sanitizer eventually degrades into sugar which feeds the cultures in the fermented food. In the past I've used vinegar (although this can affect the flavor of things), and just dipping tools in boiling water for a minute can work as well. Whatever you choose, make sure that not only are your tools cleaned and sanitized, but so is your work space (i.e. counter top).
Here we are! Let's make soy yogurt...
The instructions here are for getting your initial yogurt started and uses 4 cups of soy milk. Like I mentioned before, you can save 1/2 cup from this batch to use as the culture starter for your next batch, and follow these same steps.
1) Heat 4 cups soy milk on the stove, stirring often, until it reaches about 180-190F degrees or just as tiny bubbles are beginning to form. Don't let the milk boil. Since I make yogurt from fresh soy milk, after the milk heating step, I just continue with the yogurt making steps starting from here. If you're using a thickener, be sure to add it and whisk well before heating the milk.
2) Let milk cool to about 110-112F degrees (or slightly warmer than body temp), stirring occasionally so a skin doesn't form on the top. I often make an ice bath in the sink (just fill the sink 1/3 of the pot height with ice and water), place pot in ice bath and stir until temp is reached.
3) Now is the time to add cultures to the milk. If using a store bought or heirloom cultured yogurt, you'll need a 1/2 cup. If you're using a probiotic supplement, add 1-2 capsules. For yogurt starter culture, 1 packet. Stir well to distribute, then transfer the mixture to a non-metal container(s).
4) Time to let the magic happen. Place the cultured milk in your incubator setup. Allow to set, covered and undisturbed, for 8-12 hours. Longer means more tangy. Usually I make yogurt in the evening and it's ready in the morning.
5) It's yogurt! After time is up, stir and store. Keep in the refrigerator for up to one week, then eat and repeat.
FYI: When making dairy yogurt, the yellowish-liquid that separates out during the incubation time is called whey. A lot of people call the liquid that separates from their soy (and other plant) yogurts whey as well. But actually, it's really just water with a minute amount of soy.
Troubleshooting
Sometimes things just don't quite work out. Although yogurt is really simple there are a few of things that can go awry. Here's what to do...
Yogurt didn't curd or ferment?
If your yogurt is still just milk after the incubation period, check the temperature. Make sure that during incubation the temperature stays right around 110F-ish degrees. Bacteria thrive in certain temp ranges. Too high and they will die, too low and they'll be slow to reproduce and ferment. Use a kitchen thermometer and see where it's at. Adjust the temperature and check again in a few hours. If you're having trouble getting the cultures to grown and ferment, you can also try adding a little sugar as bacteria food to promote fermentation (1 tbsp should be fine) and allow to incubate longer.
Yogurt smells bad or has any kind of discoloration?
Do not use. That means there was some cross-contamination and unwanted bacteria has gotten into it. Compost it and start over, making sure all your equipment is sanitized and the yogurt is kept covered while incubating.
Yogurt is too thin?
Soy milk and cultures alone really do typically make a thick, creamy soy yogurt. However, certain store bought soy milks don't thicken well due to higher water content. I always recommend making your own soy milk. If you're having trouble getting a certain brand to thicken, then before heating the milk try mixing in agar agar, corn starch, arrowroot powder, tapioca flour, pectin, or another thickener. Start by adding 1 teaspoon and adjust from there as desired. To thicken just a slightly thin yogurt: line a colander with cheese cloth (I use unbleached cotton broadcloth for yogurts) and let the liquid drain off. The longer you drain the thicker the yogurt. I've let it drain in the refrigerator overnight before bottling for a more Greek style consistency.
Tell me: how did your soy yogurt turn out?
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