Tofu is made from curdling fresh soymilk with a variety of coagulants, such as nigari (derived from seawater), and then pressing the curds in a press, similarly to how cheese is made. The FODMAPs in soybeans are GOS and fructans and they are water soluble, so the more the tofu is pressed and condensed, the firmer it becomes and fewer FODMAPs remain. Monash University says that “Firm, drained” tofu is low FODMAP in 170 g servings. Soft and silken tofu is coagulated but not drained, so the FODMAP content remains higher. Avoid during your Elimination Phase, unless in the very small suggested amounts. Perhaps you will be able to add it back into your diet if GOS and fructans are not your triggers.