Sometimes desirable, sometimes not, depending on your inclination. Pectin Stuff found in various berry-type things that causes hazey effects in wine. As this is dreadfully un-aesthetic, one adds pectolytic enzyme to rid oneself of it. The only ingredient that is more important than yeast or sugar. With skill and blending one can create a concoction that is quite palatable.
Raisins See sultanas.
A suggestion for something to ferment. Largely reduntant except when suffering imagination deficiency. Always remember Rule 1. Any wine that is pretty strong and very oxidised. The art of getting wine to flow through a plastic tube from one place to another.