The most common cause of haze in wine, especially fruit wine, is caused by pectin. Pectin is a natural carbohydrate that occurs in fruit and is used to thicken jelly and other products. If you boil the fruit initially to get better color or flavor for your wine, pectin haze is even more likely. You can add pectic enzyme at the beginning of fermentation to avoid pectic haze. In addition, many times you can clear a hazy wine by adding the pectic enzyme after fermentation, although prevention is the better solution.