The hydrochloric acid will break down the starch into sugars. 

Interestingly, your stomach performs this act every day (but without the heat!) so that you can break down (digest) the long starch molecules in your food into smaller simpler molcules.  These can then pass easily through the wall of your alimentary canal into your bloodstream.  This process is called digestion.

Or perhaps you are thinking about how hydrochloric acid modifies starch in food processing?  This is called acid hydrolysis.