Final Report: June 30, 2021

Principal Investigator: Tim Donahue
Organization: Walla Walla College

Summary: Flotation is a technique of using compressed gas combined with fining agents (bentonite, gelatin) to clarify white wine juice. The predominant reason for using flotation is to clarify juice quickly (2-3 hours vs. 1-2 days) and that the clarification is done at room temperature, which creates a large energy savings over the refrigeration used in cold settling.

Post fermentation, wine was analyzed via- ETS Labs for:

  • Basic wine chemistry: pH, titratable acidity, volatile acidity, ethanol, free and total sulfur dioxide.
  • Wine phenolic chemistry: caffeic acid, caftaric acid, catechin, gallic acid, quercetin glycosides, tannin, astilbin, grape reaction product. quercetin aglycone.

Objectives and Experiments Conducted to Meet Stated Objectives: Floatation was done to observe modifications the phenolic makeup of a given white wine. Use of fining agents, along with an inert gas vs oxidative gas, can affect the phenolic makeup of the grape juice and subsequent wine. This investigated the way in which these different techniques can influence the makeup of grape juice and subsequent wine prior to fermentation.

Procedures to Accomplish Objectives: Fruit was hand harvested from Sagemoor Vineyards in Pasco Washington. Juice was separated into 3 treatments:

  1. Control: Riesling was cold settled using enzymes then racked for fermentation
  2. Treatment 1: Floatation using nitrogen as the compressed gas then racked for fermentation.
  3. Treatment 2 Flotation using oxygen as the compressed gas then racked for fermentation.

Was accomplished with QA-23 yeast and nutrient supplemented with di-ammonium phosphate at a rate of 1/g/L to add 220mg/L of nitrogen to the fermentation. Brix and temperature were monitored daily.

Major Research Accomplishments and Results by Objective: It was noted that there were differences in wine chemistry and phenolic makeup between all treatments, additionally, there was a pronounced sensory difference between the wines. This trial gives a multifaceted set of data to winemakers who are considering using floatation as a tool to modify their wines, and/or energy and time savings associated.

Read more by downloading the full report above.

Enology //