why a citric fruit rind is cooked several times to make a marmalade

Question

why the citric fruit rind is cooked several times to make a marmalade? i meaning boiled several times, its to reduce acidity or bitterness or what?

Answer 1

Speaking from a different dish: when I make citrus caramel I have to blanch the citrus peels a few times (three times mostly). It greatly reduces bitterness from the white part of the skin.

Here's Kenji-Lopez Alt's take on it.