Homemade Soy Milk

Soy is the one DIY milk on this site with a genuine food-safety step, not just a technique preference. Raw soybeans contain trypsin inhibitors — compounds that interfere with protein digestion and can cause real digestive upset — and raw soy milk also tastes strongly “beany” and grassy in a way cooking fixes. Every other DIY milk on this site (oat, almond, rice) is ready to drink straight off the strainer; this one genuinely is not. The simmering step below isn’t a “nice to have” the way a splash of vanilla is — it’s the difference between a safe, palatable milk and one that isn’t either. This recipe is the how-to companion to our guide on the best milk for coffee, which covers soy’s flavor, foam, and nutrition profile in more depth.

The Recipe

Ratio: 1 cup dried soybeans, soaked, to 6 cups fresh water — then simmered.

1. Soak 1 cup dried soybeans in plenty of water for 8-12 hours.
2. Drain and rinse. Rubbing off the loose skins as you rinse is optional and cuts down the beany flavor slightly.
3. Blend with 6 cups fresh water on high for 2-3 minutes until smooth and foamy.
4. Strain through a nut-milk bag into a large pot, squeezing well.
5. Simmer 15-20 minutes over medium-low heat, stirring often. It foams and can boil over — don’t walk away from the pot. This step deactivates the raw beans’ trypsin inhibitors and cooks off the raw, grassy flavor. Do not skip it.
6. Off heat, stir in salt and any optional vanilla or sweetener. Cool completely before refrigerating.

A batch this size makes about 6 cups (48 fl oz) of soy milk.

This batch, dried soybeans + salt (6 cups)~$1.10 total

Per 8oz cup, homemade~$0.18

Store-bought unsweetened soy milk, per cup~$0.47

Savings: about $0.29 per cup, roughly 62% cheaper than store-bought soy milk. Dried soybeans are genuinely inexpensive, and unlike almonds, straining and simmering don’t waste most of the bean’s value the way a nut’s fibrous pulp does. Assumptions: dried soybeans at ~$2.49/lb typical grocery/bulk-bin pricing, 1 cup (~7oz) dry soybeans per batch, yielding about 6 cups after straining and simmering. Store-bought figure is this site’s $0.47/cup unsweetened soy milk baseline (see src/lib/milk.ts, MILK_SOY_UNSWEETENED).

Getting It Right

• The simmer is mandatory, not optional. Raw soybeans contain trypsin inhibitors, compounds that block proper protein digestion and can cause real GI discomfort if consumed uncooked. Simmering 15-20 minutes deactivates them. This is a genuine food-safety step, unlike the “optional richness” tweaks on this site’s other DIY milks.
• Watch the pot. Soy milk foams aggressively as it heats and boils over easily — stir often and keep the heat at medium-low, not higher, to stay ahead of it.
• The beany flavor is real but fixable. Rinsing off the loose bean skins helps a little; the simmering step does the real work of mellowing it.

Storage & Shelf Life

Keeps about 4-6 days refrigerated in a sealed container — slightly longer than this site’s other three DIY milks, since the simmering step reduces bacteria the way pasteurization does for store-bought milk, even though this isn’t sealed or shelf-stable the way a carton is. Still treat it as fresh, not pantry-stable.

Swaps & Notes

• No stovetop patience for the simmer? There isn’t really a shortcut here — this is the one step on this page we won’t tell you to skip or shortcut, because it’s a real safety step, not a flavor preference.
• Okara (the leftover soybean pulp) is edible and used in some cuisines for baking or stir-fries, but it needs its own cooking to be palatable — treat it as a separate project rather than a quick stir-in the way oat or almond pulp is.
• Curious how soy stacks up against the other five milks this site supports? See our guide on the best milk for coffee for the full flavor, foam, and nutrition comparison, including soy’s real curdling risk in hot espresso.

Recipe Card Summary

Homemade Soy Milk

• 1 cup dried soybeans (soaked 8-12 hrs), 6 cups fresh water, pinch of salt (optional: vanilla/sweetener)
• Blend 2-3 min, strain, then simmer 15-20 min (required)
• Makes about 6 cups · Keeps 4-6 days refrigerated
• Cost: ~$0.18/cup vs. ~$0.47/cup store-bought (about 62% cheaper)

FAQ

Do I really have to simmer it, or can I skip that step?

You have to simmer it. Raw soybeans contain trypsin inhibitors that interfere with protein digestion and can cause digestive upset, and raw soy milk also tastes strongly beany and grassy. Simmering 15-20 minutes deactivates the inhibitors and cooks off the raw flavor — this is a genuine food-safety step, not a texture or flavor preference like the tweaks on this site’s other DIY milk recipes.

Why did my soy milk separate in the fridge?

Normal — soy solids settle out over time, the same way the other DIY milks on this site do. Shake before each use.

Is homemade soy milk actually cheaper than buying it?

Yes — about $0.18/cup homemade versus roughly $0.47/cup store-bought, a savings of about $0.29/cup (roughly 62%). It’s more affordable than store-bought but not as dramatically cheap as this site’s oat or rice milk recipes, since dried soybeans cost a bit more than oats or rice per batch.

Is it normal for soy milk to foam a lot while it simmers?

Yes, and you should watch for it — soy milk foams aggressively as it heats and can boil over if left unattended. Keep the heat at medium-low and stir often rather than walking away from the pot.