Extreme heat during grape ripening

Extreme heat spells during the late stages of grape ripening can lead to many difficulties in wine cellars. There is often a compression of harvest dates among different varieties, leading to a congestion in many cellars and a need to turn tanks over quickly. Key negative side effects of a heat wave that impact wine quality are:

• High brix without grape maturity (green tanins)
• Sunburn on fruit
• Low malic acid levels, resulting in difficult MLF
• Acid balance TA/pH out of normal range
• Low juice yields from dehydrated fruit
• High phenolic extraction during white grape processing
• Must/juices that are low in YAN, but high in protein content