Have you ever wondered what happens to tofu if you freeze it? Or perhaps you've even tried freezing it, and been dismayed to find that it changes color and texture rather dramatically.

When you freeze a block of tofu, the white, creamy texture changes into a beige colored sponge with evenly distributed cells. This is because the water in the tofu expands and forms ice crystals. There's nothing wrong at all with frozen tofu though. It's a time honored way of preserving tofu. Freeze dried tofu is sold as kouya dofu (or kouya tofu) or kouri dofu (tofu)), and is a great long-keeping staple.

Here though I'm going to talk about fresh tofu that you freeze yourself, since I think for most people outside of Japan it's getting a lot easier these days to get fresh tofu, but freeze dried kouya dofu is still limited mainly to Japanese grocery stores. If you happen to overstock on fresh tofu or something though, freezing is a good way of keeping the excess. You just need to know how to deal with it for optimum flavor.

How to freeze tofu

Ideally, you want to drain the tofu out of the pack it comes in and put it into fresh water. But I have to admit that more often than not I just throw the whole unopened pack in a ziplock bag, and put it straight into the freezer.

What kind of tofu?

Silken or yakko tofu makes a finer textured frozen tofu, but any fresh tofu will work. (Interestingly, fried tofu doesn't change much in texture when you freeze it.)

How to defrost a block of frozen tofu

De-frost it as slowly as your time allows. Transferring it to the refrigerator a day before you need it is ideal. If you are in a hurry, defrost in the microwave (on the DEFROST setting) for about 3-4 minutes per 300g block. It's ok if it's still a bit frozen in the middle.

Once the water surrounding the tofu is melted, take the block out. It looks like this - a beige sponge.

It's sturdier than a fresh unfrozen tofu, but still rather fragile. Very carefully press down on top to squeeze out some of the moisture. Cut into slices.

Frozen tofu poached in vegetable bouillon

It looks like a sponge, and it really is a sponge - flavorless and ready to take on any seasonings and such that you want to throw at it.

My favorite way is to stew it gently in a stock or soup. The traditional combination of course would be something like the stewing liquid I used to cook the hijiki previously. But here I've poached the frozen tofu in a vegetable bouillon, just to show how versatile it is.

Ingredients for the bouillon

• 1 medium carrot
• A 20cm / 7 inch or so length of leek
• 1 celery stalk
• 1 tsp. dried thyme
• A handful of fresh parsley
• 4 cups Water
• 1/2 cup white wine
• Olive oil
• About 1 tsp. salt, or a vegetable stock cube
• Black pepper
• Up to 3 blocks of frozen tofu

Cut the carrot, leek, and celery into thin sticks. Sauté them in a hot pan with a little olive oil until lightly browned. Add water, wine, pepper, salt or stock cube, thyme and parsley and bring to a boil. Lower the heat to a simmer, and carefully add the tofu slices (add a little more water if there's not enough liquid). Simmer for at least 15 minutes.

(If you're using freeze-dried kouya dofu, soak it in water until soft and squeeze out the water before poaching. It will be firmer and spongier than tofu you freeze yourself, but still tasty.)

You can store this, liquid and all, in the refrigerator for a few days. You can eat the tofu just as-is, drained out of the liquid. It makes a very nice bento item. Or, turn them into tofu mini-cutlets or nuggets.

Frozen tofu mini-cutlets

• Slices of poached frozen tofu, drained and squeezed out lightly
• Cornstarch or potato starch (gluten-free kind if you are sensitive)
• Olive oil or butter (if you're not a vegan)

Coat the tofu slices lightly in the cornstarch. Heat up a pan with a little olive oil or butter (or other oil of your choice). Cook the tofu slices until golden brown on both sides. Optionally sprinkle with a little paprika and salt, or soy sauce.

Here's how it looks cut open. You can see the sponge-like texture, which is full of juicy vegetable bouillon.

These mini-cutlets or nuggets are really nice hot or cold, perfect for bento.