Hi, I found this out on the web that explains it pretty well. Somtimes I use Pectic enzyme and somtimes I don't.
""If you want to learn how to make wine, one of the first things you should do is learn about all of the different additives and chemicals that are used to make homemade wine. Pectic Enzyme is one of the most misunderstood additives.
This article will explain What is pecitic enzyme, why do I need it and how it works.
Let's back up a little and talk about grape jelly. MMMM! Everyone loves grape jelly and jam on a hot buttered biscuit. It always has a gooey, almost jello like consistency.
Did you ever wonder where that jello consistency comes from? Well, in jello, it comes from gelatin. But it fruit jams and jellies, a lot of the consistency comes from something called pectin.
Pectin is produced commercially as a white to light brown powder, extracted from citrus fruits, and is used in food as a gelling agent particularly in jams and jellies.
If you want to make your own wine out of grapes, peaches, strawberries or any other kind of fruit - you have to have a way of dealing with the naturally occuring pectin. The reason is that pectin can cause solids in your wine to clump together in a colliodal suspension and you'll end up with cloudy wine that won't clear no matter how long you leave it sitting in the secondary.
How to deal with it? Use something that EATS pectin! Pectic Enzyme loves to eat pectin.
The way to use pectic enzyme when making your own wine at home is to add about a 1/2 teaspoon per gallon of fruit juice before you start fermenting the juice.
While the fermentation is going on, the pectic enzyme will also be eating and dissolving the pectin. This will make your wine clear a lot faster and keep it from having suspended solids.""