text: since potatoes have starch in them, why don't they taste sweet after they are boiled?   starch doesn't taste sweet because stach is not a sugar. (take notes mashira).  starch is composed of lots of sugar molecules strung together, but because they are strung together out tongues don't detect them as being sweet.  boiling a potato loosens the starch up and makes it digestible, but it doesn't change the primary chemical structure. it starts out as starch and it is still starch after boiling. boiling doesn't convert it into sugar.  as dan says, you need to expose the starch to digestive enzymes to convert it to sugar.