I have been making my own yogurt for about two years. I use Silk Unsweetened Plain Soymilk (the green carton). My results were stellar…once I got down how many hours to ferment a batch. Delicious, homemade vegan yogurt. And then, around November, everything changed. My yogurt would not thicken. What was going on?

Silk Changes Its Formula
Sometime last year, Silk changed the ingredients in its soy milk. They took out the carrageenan and added a new ingredient called gellan gum. This new ingredient for some reason interferes with the fermenting process. While the yogurt is fine to eat, it does not thicken. It tends to set on the outside but is swishy in the middle.
I contacted Cultures For Health where I purchase my yogurt cultures. What I am experiencing is a known issue. When soy milk with additives is used to make yogurt, it will not the thicken. The additives interfere with the process.
They seemed baffled that I had gotten good results with Silk. I shouldn’t have.
Three Solutions for Thicker Vegan Soy Yogurt
There are a couple of ways to get around this problem. As I said, the yogurt is edible. It just isn’t thick like you would expect. If you want thicker yogurt, you can try these things:
1. Use an agent such as pectin that will thicken the yogurt.
2. Buy only additive free soy milk for making soy yogurt.
3. Make your own soy milk with only water and soy powder that has nothing else added.
The Best Soy Milk for Yogurt
Using Silk has it’s advantages and disadvantages. While my yogurt is not thick, it is super creamy. Before my batches had a lot of curds (small lumps). Now they don’t.
I have tried other soy milk brands. I can attest to the fact that Westsoy Organic Unsweetened Soymilk original works. It only has soy beans and water. It thickens. It has a nice flavor when finished. But, it cost more. 32 ounces of Westsoy in the shelf stable container cost just a little less than 64 ounces of Silk in the refrigerator container.
My Solution to This Problem
I’ve decided to buy Westsoy when it is on sale, but I’ll stick with Silk as my regular soy base. I can put up with the thinner yogurt for the money it saves me. The alternative is making my own soy milk and we know that is not going to happen. It is hard enough getting me to make my yogurt each week.
If you are having less than satisfactory results with your homemade vegan soy yogurt, check the label. Certain ingredients can prevent your batch for setting correctly. Switch brands, make your own, or buy pectin.
Don’t know how to make yogurt? Here is my handy guide on How to Make Unsweetened Dairy Free Yogurt. It’s everything you need to know to make you own vegan yogurt.
Good to know, Melody. Thank you for sharing this. I haven’t tried soy milk yogurt yet, but I may one day. Now I know where to find help with it.
Kathryn, It is another reason to either make your own or buy products with as few (or none) additives. While my yogurt is very creamy now, it could use a little more thickness.
For drinking I prefer the Silk, organic brand. I have tried others and didn’t care for their taste. My question is, do the different brands of soy milk, when used for yogurt taste pretty much the same?
Thank,
Katy
Katy, I think they each give a different taste. I’ve used two different brands of soy milk for my yogurt and the batches tasted different. While I prefer Silk for drinking like you, the WestSoy made a more sour, flavorful yogurt which I liked better.
Thanks Melody. I think our local Sprouts carries the WestSoy. I will give it a try. I did find a large container of yogurt made out of cashew. It was plain, no added sugar or flavorings. The brand is Forager Project. It has live cultures in it so I may try using it to make my own soy yogurt.
I’ve been practising with different soy milk brands, too. I’m curious to hear have you noticed any other differencies between them: if using soy milk with additives, is there is more colour on the liquid sometimes or slightly bitter taste in the yoghurt itself?
I agree that natural soy milk is the best. I think it doesnt matter if has sugar on it (it is just a matter of taste). But I’m a little bit unsure if additives can also cause the liquid (whey) to turn a bit yellowish, in case there is separation. I haven’t been making good notes on this in the past, but with all my recent batches this has been so: whiter liquid when using “natural” soy milk. Recently I made a trial with 5 different milks, 2 of them natural and 3 with additives.
It also seems to be so that the yogurt made of vitamin-riched etc. soy milk tastes more bitter. I think those soy milks have good taste as such, so this is something that happens during the fermentation. I don’t know if this is caused by the additives or not. (The reason could also be that the process took longer and microbes didn’t have enough food. That’s basic biological fact of lactobacillicus. But as far as I can remember, I havent been fermenting those yoghurts exceptionally long.)
Thank you for your comments and questions! Let me see if I can answer your questions:
1. The color of the liquid (whey) turning yellow…I am not sure what affects this. I use Silk Unsweetened soy milk. I sometimes get the yellow you speak of and sometimes don’t. I don’t think it’s the additives in the milk.
2. The taste is affected by how long you culture your yogurt. The longer you culture the more sour the yogurt will be. I prefer mine sour, so I culture for 11 hours. But, if you prefer a more mild taste stick to 9 or 10 hours.
3. The temperature of the oven can also affect how the yogurt turns out. I was getting what I call “quick sand” yogurt. It set, but it’s runny in the middle. Then, I was getting too much whey liquid. I had one batch that was almost entirely whey on the bottom for an inch or more. I contacted the company I buy my cultures from and got the answer. My yogurt is over cultured…too warm when it’s fermenting.
I think I figured out why. I culture in the oven with the lights on. I was pushing my jar too close to the light. This week I moved the jar more to the center of the oven and I got very little whey.
Hope this helps with your yogurt results!
4. Can additives affect the yogurt? The answer is yes. The culture company I spoke of says that it can be difficult to get yogurt to set and thicken with some commercial soy milk. The additives can interfere with the process. It’s still good, it’s just not thick enough.
Overall quality can be affected by so many different factors. It’s a temperamental process as you know from your experience.
Thanks a lot for your reply. I made some more trials with plain soy milk (only water and beans) and indeed, even that soy yogurt develops yellowish whey if the fermentation time is exceptionally long or I add double the amount of starter. There is a slight bitterness, too.
But even then, this yogurt never gets this unpleasant bitter taste that I get when using fortified soy milk. I tried it again, too. This bitterness is present even when I have a short fermentation time and there is no whey, yet. (I’m using a yogurt maker, thermometer and pH-meter, so this result is to be trusted.)
My conclusion: There are some universal biological laws of lactobacillicus behaviour, but also a huge difference between different soy milks (as you have been saying). Just to advice – if there is anybody else reading this and getting not so perfect results: do try another milk, if may solve your problem!
Thank you coming back to report your results! Since I’ve gotten different results between simple soy milk (brand that is just soybeans and water) and soy milk that has more additives, I don’t doubt your conclusions. If you are getting a bitter taste there could be an additive that’s interfering with the process. If over or under culturing isn’t the cause, it has to be something with the milk itself.