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

We have a coffee tree we have been growing in our sun-room for 10 years. This year after we harvested the coffee cherries and hulled the beans, I decided to try making coffee cherry jelly. I didn't find any good recipes on the internet, so I decided to "wing it" and it turned out fantastic. This is what I did: I had about 2 cups of coffee cherries. I put them in a pan and covered them with about 3 cups of water. I brought them to a boil and let them simmer for about 30 minutes, then let them cool in the water. I put a strainer over a bowl and strained off the liquid from the coffee cherries and then squeezed the cherries to get all the juice out. Throw away the squeezed out coffee cherries and keep the liquid. The liquid will be a reddish-brown and be a bit cloudy, but don't worry, it will clear up as you make the jelly. Next, I measured the liquid and had about 2-3/4 cups. I added 1/4 cup of organic lemon juice to the liquid, stirred in 1/3 cup of powdered pectin. Stir to dissolve the pectin then bring it to a full boil. Use a really large pot for this because it will rise up when at a full boil. When at a full boil stir in 5 cups of sugar, all at once. Bring back to a full, rolling boil that can not be stirred down and boil like this for one minute. Take pot off the heat and spoon the jelly into clean jelly jars. It will make about 5 small jars of jelly. Once the sugar goes in, the jelly should turn clear. Skim off any foam that might form on top before pouring into jars. Allow to cool and set. The color will be a beautiful, chestnut red and the flavor is mild, almost like honey. Enjoy!

The book Putting Food By (Hertzberg) has a recipe:10 lbs. apples yields 1 pint pectin. Seems jam & jelly specific.