Old tofu has a firmer texture, a firmer texture, a yellow color, which is not fragile, and a firmer taste, while tender tofu is delicate, smooth and tender, with a white color, which is closer to tofu, easy to break, and has a tender and smooth feeling of breaking immediately.

Old tofu is north tofu, also called "brine tofu", which uses brine (magnesium chloride) as coagulant. Calcium and magnesium ions in brine combine with soybean protein to produce coagulation reaction, which makes tofu shape. After the tofu is formed, the old tofu should be squeezed for about 30 minutes by pressing tofu, so as to further drain the tofu, achieve the specified quality, and make the product firm and elastic. Therefore, old tofu has high hardness and rough texture.

Generally speaking, old tofu is suitable for cooking methods such as frying and stewing. Old tofu has less water content and large pores. It is most suitable for absorbing the umami flavor of soup, and also helps to stabilize the shape and is not fragile.