Contrary to most fruits, grapes do not continue ripening once they are harvested. Grapes are often picked at their peak to ensure that they are sweet. To make a sweet grape juice you need to select grapes appropriately. Here are the tips for purchasing grapes. Color of the GrapesYou can tell how ripe and sweet a grape is by looking at its color. For the sweetest red grapes, ensure that you pick those with the deepest red color. The black grapes with the darkest color are highly flavored. When green grapes are ripe, they have a yellow-green color. Inspect the Stem and BerriesYou risk purchasing stale grapes if you do not critically check the stem and berries. Fresh grapes are firmly attached to the stem. The stem of fresh grapes is also flexible and green. You should not buy grapes that are weakly attached to the stem since they are likely to have decayed. Ensure that the Grapes have BloomBloom is the white powdery coating on the skin of grapes. It is an indicator of fresh grapes. Bloom aids in prevent the berries from decaying and losing juice through evaporation. Do not stress if the cleaning the berries does not remove the bloom; it is safe for human consumption. By inspecting the color, and stem of the berries, you avoid buying unripe and sour grapes. You should also check for the bloom to ensure that the grapes are juicy.