Whisky is made by fermenting starch sugars from grains. The alcohol produced is distilled and matured in oak. There are several things that influence the final flavour of the single malt whisky
The barley itself: the type of grain is highly influential on the final flavour profile, it's why malt whisky and grain whiskies are in distinct categories.
The fermentation: During this crucial stage, aromatic compounds form, which add flavours ranging from tropical or ripe fruit to citrus or floral notes. It's not uncommon for distilleries to smell of banana bread and pina colada during fermentation.Maturation: Whisky takes on lots of flavour from the barrel including red fruit, raisins, nuts, smoke, toffee, toast, caramel and honey. The flavours in your final whisky can depend on the type of barrel seasoning used.