If you enjoy eating boiled sweet potatoes like me, then here is a trick to make the potato sweeter, without adding anything. Sweet potato, sweeten during cooking because of an enzyme which reacts with the starch of the potato and breaks it down. The starch is broken down to maltose, a sugar made of two glucose molecules, and it is about 30% as sweet as table sugar. Soggy sweet potatoes convert as much as 75% of their starch to maltose and they taste like sugary jelly. This conversion from starch to maltose starts when the water temperature is 57c and stops when the rising heat denatures the enzyme at 75c. So for a really sweet potato, bake it slowly, rather than rapid cooking in steam or in pressure cooker. Rather than adding it to boiling water, add it in normal water and slowly raise the water temperature. The slower the rise, the sweeter it becomes.