Juice Panel Analysis

QC Juice Panel

Parameters include:

Titratable Acidity (TA), pH, Brix, Glucose+Fructose, Malic Acid, Tartaric Acid, Potassium, Alpha Amino Nitrogen (NOPA), Ammonia, Yeast Assimilable Nitrogen (YAN)

This panel is great for:

• Quantifying vintage variation
• Making prefermentation adjustments (sugar, acidity, nutrients)

Sugar

The Parameters

Brix and Glucose+Fructose are analytical quantifications for the concentration of fermentable sugar in grape must.

Brix

• Brix is derived from refractometry and presented in units of degrees
• Degrees Brix and % Brix can be used interchangeably (Brix is % by weight in g/100g)
• Our Brix value is measured via refractometry, therefore it likely will not align with in-house Brix measurements derived from density (hydrometer/densitometer)

Glucose+Fructose

• Glucose+Fructose is based on enzymatic analysis and presented in g/L – this value can be easily converted to % by volume by moving the decimal one place to the left to give g/100mL

Turning Results into Action

• It’s common for winemakers to chose one sugar parameter – either Brix or Glucose+Fructose – to base their potential alcohol calculation on.
• Conversion rates vary from winery to winery. Since alcohol concentration can change during aging in cellar, submitting samples for alcohol analysis immediately after primary fermentation can help winemakers dial-in their conversion rate

Acidity

The Parameters

The primary factors influencing acidity in grape must are Titratable Acidity (TA), pH, Malic Acid, Tartaric Acid, and Potassium

pH vs. TA

• pH is the measure of the concentration of hydrogen ions in a solution
• TA measures the amount of titratable acids present in the must (Tartaric, Malic, Lactic, etc.)
• TA is often considered to correlate better with perceived acidity than pH

Tartaric Acid and Malic Acid

• If you are planning to put your wine through malolactic fermentation, knowing the ratio of Tartaric Acid to Malic Acid allows better prediction of the post-ML acidity shift

The Role of Potassium

• Potassium concentration can have a large influence on the TA and pH of a must
• Comparing two juice samples that have the same combined Tartaric Acid and Malic Acid values, the sample with higher potassium will likely have a lower TA value
• Samples with high TA and high pH likely have a high potassium concentration

Nutrients

The Parameters

The main sources of yeast assimilable nitrogen (YAN) in grape must are Ammonia and Alpha Amino Nitrogen (NOPA).

Ammonia

• The primary inorganic form of nitrogen in grapes is ammonium (NH₄⁺). By convention, it’s referred to as Ammonia (NH₃) and reported as of g/L of Ammonia

Alpha Amino Nitrogen (NOPA)

• Organic nitrogen in grapes comes primarily from amino acids (Alpha Amino Nitrogen, reported as of g/L of Nitrogen)

Yeast Assimilable Nitrogen (YAN)

• Converting the Ammonia value to g/L of Nitrogen and combining it with the NOPA value gives a total Yeast Assimilable Nitrogen value in units of g/L of Nitrogen
• YAN describes the Nitrogen available for yeast to use for proliferation

Turning Results into Action

• Though there are varying guidelines on nitrogen addition rates, the theme is generally the same: based on your Juice Panel YAN and the starting Brix, add an appropriate amount of Nitrogen to feed the yeast and promote a healthy fermentation
• Knowing the starting ratio of NOPA to Ammonia can also allow for a more targeted addition strategy