All three methods use hot liquid, but they solve different problems. Blanching is brief treatment, parboiling is partial cooking before a second method, and poaching is gentle cooking intended to finish delicate food.
Blanching is short and purposeful
Food enters boiling water or steam for a brief interval. The goal may be loosening skins, setting colour, reducing harshness or preparing vegetables for freezing. Cooling in ice water stops carryover when crispness and colour matter; it is unnecessary when the food goes straight into the next hot step.
Parboiling stops before doneness
Potatoes, rice or vegetables are partly cooked so roasting, frying or another method can finish them evenly. The correct stopping point belongs to the next step: potatoes for roasting need softened surfaces while their centres remain firm enough to handle.
Poaching finishes food below a boil
Eggs, fish, fruit and poultry can be cooked in liquid kept below a vigorous simmer. Lower agitation protects fragile structure and reduces the risk of toughening proteins. The liquid may be water, stock, milk, wine or syrup depending on whether it must also flavour the food.
Temperature words are visual shorthand
“Bare simmer” and “gentle poach” are not universal thermometer readings. Watch the liquid: few lazy bubbles and movement are different from a rolling boil, whatever number a particular recipe assigns.
