Dextrins are the remains of starch molecules which have been broken down by heating, or by enzymes in the course of digestion. When starch is heated in dry conditions these products include pyrodextrins, which are brown in colour and have a characteristic flavour recognizable in bread crust and toast.
Again, excessive heating can yield black carbon.
© the Estate of Alan Davidson 1999, 2006, 2014 © in the Editor’s contribution to the second and third editions, Oxford University Press 2006, 2014.