Homemade soy milk was a rare treat for us because we lived in California and fresh soy milk can be purchased at almost every Asian grocery store in California. Even though fresh soy milk is very good, it does not compare to grandma's homemade soy milk. Fresh soy milk and homemade soy milk tastes nothing like the soy milk found in American grocery stores. I like the taste of Silk soy milk but when I drink it I don't expect it to taste like
real soy milk. I swear they do something to the soy beans to get rid of the soy flavor. It is either bland or vanilla-y. Silk also adds something called carrageenan to increase the viscosity and make it more milk-like. By adding the carrageenan, they make the soy milk less soy milk-like. For most Western taste, this works well because Westerners tend to drink soy milk as a cow's milk alternative.
I can't remember how I learned to make homemade soy milk. I think I was experimenting in the kitchen, found a bag of dried soy beans in my mom's pantry, called up my grandmother and asked her to walk me through the process. The process included a blender. I thought, "how did grandma make this when she lived in China?" I didn't ask.
I still use the same method for making soy milk. Last year while we were in San Diego, my aunt found a soy milk maker at 99 Ranch Market. She picked it up and held it tightly against her chest. She had been eyeing the soy milk maker for quite a while now. She said she saw it in a catalog for $100 and 99 Ranch had it for $50. She read the specs and deemed the 99 Ranch model superior to the catalog model. She said she would carry it on the airplane.
When we got home, I suggested that she test it out just in case there is a defect. We don't have 99 Ranch Markets in Colorado. My mom pulled out a 5-pound bag of soy beans. I forgot how much they swell up. I soaked all 5 pounds. We made the soy milk in batches as the machine would only hold about a cup or so of the beans at a time. The machine ground the soy beans, boiled the liquid and strained out the pulp. The first batch was pretty cool. It didn't make very much soy milk and it took quite a while to make the measly 4 cups. Still I proceeded to make batch after batch. We ran into trouble during the 5th batch. The machine ground up the beans but never heated up the water. We tried restarting, turning it off, unplugging it and cursing it. It never came back. We ended up having to make several gallons by hand.
I don't have exact measurements. I make it and judge by the opacity of the milk. I call it intuition
al cooking. My grandma never cooks with measurements. I asked her how to make fresh chow fun noodles. She said, "take a bag of rice flour, the one with the green writing
(or was it red?), and add two and half bags of water..." If you want a recipe for soy milk, go
here to Martha Stewart's website. I don't use her recipe but it sounds pretty close to my grandma's method.
Grandma's Homemade Soy Milk
yields 2 to 3 quarts1 pound dried soy beans
water
sugar (optional)
vanilla (optional)
1. Soak beans overnight or until soft. Rinse beans. (You can shell them if you want. I read that it makes the soy milk taste less beany but I happen to like the taste of the soy milk made with the shells.)
Soy beans before soaking:
Soy beans after soaking:
2. In batches, blend soy beans with water and pour into a large stock pot. (I don't measure the water. I just add enough to aid the blending.) Rinse out the blender with a little more water and pour into the stock pot. Check water to pulp ratio. You should have enough water so that you can easily stir it.
3. Bring to a boil, reduce to a simmer and continue to simmer for about 20 minutes. Be very careful and monitor the simmering soy milk. The soy milk has a tendency to foam and overflow. You may have to continually stir the soy milk to prevent it from overflowing.
This pot of soy milk nearly overflowed. Originally the pot was only 2/3 full.
Look at the foam on top. 
4. Let sit until cool enough to handle.
5. Set a strainer in a large bowl and line the strainer with cheesecloth (or in my case flour sack towel). Let the liquid drip and then squeeze the remaining liquid through the cheesecloth.
Don't toss the pulp. The pulp is high in protein, fiber and other nutrients. You can use it for many other dishes like meat balls, polenta, tuna salad, cookies, stif-fry, etc. I'll share some of my favorites later.
6. Add more water if soy milk is too thick. Optional: Add sugar and/or vanilla to taste. (I only added sugar.)
This is the way I was taught to make soy milk. I read other methods and many tell you squeeze the "milk" out of the soy pulp prior boiling the milk. This may be easier to do but I don't think you are able to extract enough of the "milk". By boiling and steeping the pulp, you achieve maximum extraction.
