Here in S.C. I picked wild muscadine for jelly all my life. When mother could not find time to make jelly or was short on supply. She would cook the grapes squeeze the juice & freeze it. But never the whole grape cooked or uncooked. Later she would make up the jelly. You can make jam too, but I do not like the cooked hulls & the seeds are bitter. I now grow hybrid muscadine.

I boil and mash the grapes (and apples when I have them) in a pan, then take a bowl, set the colander in it. Pour boiling water over the pillowcase first, over the sink, and wring mostly dry once it's cool enough to touch, then set it in the colander, ladle the mashed fruit in (pour juice in too), then I take that pan, set the colander in it, pour any juice from bowl into pillowcase, take the pan, colander and case to where I hang it (over washer), hang the pillowcase from a sturdy wooden pants hanger with clips over the pan sitting on top of the washer. Leave the colander in the pan to break the fall if the pillowcase falls.

keepitlow, optimum boil time varies with altitude, with the grapes (more or less moisture depending on growing conditions, etc), your stove, your pan, a number of factors. I've gotten to the point where I can tell when jelly is thick enough by the way it looks and sheets off the spoon, but I started with a thermometer and then tested using a frozen plate when temps reached 218. I dab a bit on a frozen plate, stick it back in the freezer and wait a minute, then see how thick it is. After a few batches of pear taffy, I learned that if it was getting close I should turn the heat off while I tested, LOL, it takes only a minute to come back up to temps. So, unfortunately, there is no optimum boil time for everyone, it will vary and you will only find it through trial and error. (sigh) Yeah, I know... Annie

MCP, sounds like a 'work around' for Pomona pectin. That too is citrus based, but uses a small amount of calcium to set. I have never seen MCP here, must be regional. Too much sugar also makes a bland overly cloying sweet product. If I find something like that, I add acid blend and it helps to give back lost or disguised flavor to an overy sweet jam or jelly. The acid blend works realy well with grape, and is my 'secret ingredient', that beats all other grape jellies in bold flavor with good charater. The acid blend is 33% mix of citric, malic, and tartaric acid, which are naturally found in grapes. It can be bought in wine making supply stores and on the web. I usualy buy a pound or more per year and use it in fruit drinks to, especially with ones with artificial sweeteners that tend to have odd after tastes.