What important characteristic must be noted on the label during secondary maturation?

The key characteristic that must be noted on the label during secondary maturation is the change in barrel type. This is significant because the type of barrel used during aging can greatly influence the flavor and aroma profile of the whiskey. When whiskey undergoes secondary maturation, often in a different type of barrel than its initial aging, it can acquire new flavors and complexity that were not present during the first maturation.

Labeling this change allows consumers to understand how the whiskey has been crafted and how its taste profile might differ from other whiskies aged solely in traditional barrels. This practice aligns with transparency in labeling, which is crucial for informing consumers about what they are purchasing and the unique characteristics they can expect from the whiskey.

The other characteristics, although important, are not specifically required to be noted in the same way as the change in barrel type during a process of secondary maturation. Understanding these distinctions enhances a consumer's appreciation of the craftsmanship behind each bottle.