Login
SUBSCRIBE TO OUR NEWSLETTER FOR UPDATES ON EVERY ARTICLE.

pTAN:IRPs

The protein-precipitable tannin to iron-reactive phenolic ratio (pTAN:IRP) is a useful metric for understanding extraction in skin-macerated wines. Iron-reactive phenolics extract readily from grape pulp whereas protein-precipitable tannins require alcohol, temperature, and movements to extract from the skins and seeds. Because of this, shorter macerations tend to have lower ratios whereas reserve-tier wines generally have higher ratios. pTANs generally account for 50-55% of extractable IRPs in skin-macerated wines. This ratio will fluctuate depending on fruit quality, most notably decreasing with hotter climates.

Protein-Precipitable Tannins: Iron-Reactive Phenolics (pTAN:IRPs)

  • <0.3 is low-efficiency extraction typical of shorter macerations and larger production volumes.
  • 3-0.4 is a moderately efficienct extraction typical of middle-tier wines.
  • 4-0.5 is a highly efficient extraction typical of premium and reserve wines.
  • >0.5 is heavily extracted typical for powerful wines.

For winemakers, these ratios are particularly useful for monitoring adherence to protocols and understanding the performance of vineyards across multiple vintages. We generally don’t place value between higher or lower ratios as a sign of quality, rather, we focus on pTAN:IRP as an indicator of extraction. Lower ratios benefit more delicate wine styles whereas high ratios benefit more concentrated wine styles. We can use the following variables to steer the type of extraction we desire based on the qualities of our fruit.   

  1. Timing: Tannins will not extract without alcohol present, so the pTAN:IRP ratio will only increase with maceration length. This is unless the fruit is severely heat damaged, in which case extended maceration actually decreases pTAN concentrations.
  2. Temperature: Higher temperatures increase the rate of tannin extraction relative to IRPs.
  3. Movement: Short and frequent pumpovers can moderate temperature distribution and decrease extraction. Long and infrequent pumpovers will exaggerate temperature gradients and increase extraction.