Bingo! And one excellent post reply. It's in the grape. A good quality grape will have it there for you. The above mentioned post about the Orange Peel, that is normally used for beer brewing as a flavor additive.Sauvignon Blanc usually has a considerable citrus character inherent in the varietal character. If you're using good quality fruit/juice it should result in a wine with some lemon/lime/grapefruit aromatics. You can also choose a yeast strain that is known for ester production. All the big yeast producers have strains tailored for aromatic wines. If you use one of these strains, ferment cool and are really careful about oxygen uptake, you'll be able to retain more of these delicate aromatics.