It is generally recommended to leave the peel on when juicing an apple, according to VegNews. However, if the apple is not organic, cooks may peel it to reduce the risk of ingesting unwanted pesticides and other chemicals.
When juicing, simply core the apples to remove the seeds. Apples may also be quartered so that smaller slices are easier to push through the juicer chute.
Organic apples are considered best for juicing. These apples have not been exposed to the same high level of chemicals that is sprayed on traditional apples. Apples are among the most heavily treated and dirtiest crops, as stated by VegNews. If only traditional apples are available for use, the skins can be peeled before juicing. However, peeling does remove a lot of the apple's fiber and a large portion of its vitamin C. Without fiber, the resulting juice may not seem as filling compared to a juice made from apples with peels.
If opting to keep the peel on the apple, make sure to clean it well. Scrub the apple skin to remove as much dirt and contaminants as possible. If there are still leaves and a stem attached to the fruit, remove those as well before juicing.