What is one of the characteristics required for 'garrafeira' red wines in Portugal?

The characteristic that 'garrafeira' red wines in Portugal must have a minimum aging of 30 months is important because this designation reflects a higher quality standard and specific aging requirements. For 'garrafeira' status, a red wine must be aged for at least 30 months, of which a minimum of 12 months must be in wood. This extended aging process allows the wine to develop complex flavors and aromas, which is a hallmark of premium Portuguese red wines.

The requirement for aging in the definition of 'garrafeira' is significant as it emphasizes the commitment to quality and craftsmanship in Portuguese winemaking. The lengthy maturation period helps integrate the tannins, enhance the wine's balance, and foster greater depth in flavor, showcasing the terroir and grape varietals used in production.

Although some other options present valid considerations in winemaking practices, they do not specifically relate to the 'garrafeira' classification as directly as the aging requirement does.