May 26, 2017 1:29 PM GMT
NYT: Winemakers employ a range of techniques to achieve desired properties and flavor profiles. The addition of sulfites, used as a preservative, must be listed on the label in order to notify individuals who might be allergic, yet more than 60 different additives can legally be used without being disclosed.
With regard to sugar, regulations vary by state. In California, for instance, added sugar is not allowed at any point in the winemaking process. There, winemakers may rely on unfermented grape juice to tweak the sweetness.