of yam that turn black once it's new yam (just harvested yam). it's got something to do with exposure to air just the way apples turn brown once exposed to air. the older the yam gets (when it's stored in a yam barn for a long time), the less likely it is to turn black and the sweeter it gets (carbohydrate turning into sugar).
how much salt exactly are we meant to add, tea/tablespoon? 