Pearls are manufactured from tapioca starch. They can also be made at home, but are very time-consuming to make. When purchased from a store, they will have one of several appearances :
Off-white / beige - these are almost entirely tapioca starch and yield pearls with the most natural texture. They take the longest to cook (1-2h preparation time) but maintain ideal consistency the shortest (3-4h). If the pearls are kept in water for too long, they will become soggy through to the centre.. When this type of pearl is added to a slush, it hardens the most quickly of all the types.
Tan - these also have a very high starch content, and the pearls have a natural texture. They require less time to cook (1h) but also become soggy if kept in a bath for more than a few hours.
Black with a white powder - these have additives which reduce the cooking time (20-40 min) and allow the pearl to cook to the centre sooner. The result is a more chewy consistency similar to jelly candy or Turkish delights.
Coloured with a white powder - these also have additives which reduce the cooking time.
For each type of pearl, the uncooked ball is not sweet. The raw pearls are added to boiling water. One may add sweetener (brown sugar, white sugar, honey, agave) at this point, but most don't. The pot is then covered and the pearls are cooked on medium-high heat. When the pearls are cooked to the desired consistency through to the centre, they are rinsed under cold water to lower the temperature inside each pearl to room temperature and stop the cooking process. A small amount of cool water is placed with the desired sweetener and the pearls, and the lot is mixed and allowed to stand. The pearls will soak up the sugar water thereby becoming slightly sweet. Brown sugar has the most noticeable effect.