Measuring Malic Acids

We measure the concentration of Malic Acids in wine to monitor the malolactic fermentation. In the malolactic fermentation malic acids are converted to lactic acids – this helps to shape a wine style and character as well as its ageing potential. We use three methods to confirm the successful completion of the malolactic fermentation:

  • Chromatography which is time consuming,
  • Chemical Test which is only very approximative, and
  • OenoFoss spectral analysis which is expensive and has to be outsorced

Another accurate measurement of malic acids is possible with enzymatic test kits which use spectral analysis (similar to what we use for measuring phenolics) – however we do not employ it at this time

 

Paper Chromatography

Paper chromatography has been employed for decades to visualize molecules of different weight s in a solution. First tiny dots of the sample wines are placed along the bottom of a chromatography paper, then sides of the paper are clipped together so it forms a vertical cilinder, then the cylinder is placed into a jar which holds a chromatography solution and capilar forces push up the solution up to the top of the cylinder dragging with them the malic acid and lactic acid molecules. Malic acids being heavier than lactic acids will not travel as far up the paper. After a day standing in the chromatography solution, the paper is removed from the jar and dried. Once dried, traces of malic and lactic acids become visible at different heights of the paper. When there is no longer a trace of malic acids then the malolactic fermentation is complete. We use a test kit from MoreWine.com for this analysis (link

 

Chemical Test

Accuvin (www.accuvin.com) sells an economical kit to get approximative measurements of Malic Acids in wine. The kit includes sampler tips and test strips which change their color within 5 minutes of applying a 20 micro-liter sample. Matching that color with a reference chart allows to estimate the remaining malic acid concentrations [>500, 100-500, 30-100 and <30 mg/L]. The goal is to reach <30mg/L. The cost of the kit with 5 samples is around $30.

 

FOSS Spectral Tests

A OenoFoss analyzer provides estimates of malic acid concentrations through ultraviolet-infrared spectroscopy. The cost of the tool is prohibitive (>$35,000)  for a lab our size but nearby service providers (eg Fermentation Solutions) provide a test for around $30 which provides the following measurements: pH, Total Acidity in g/l, Malic Acid in g/l, Alcohol by Volume:, Glucose/Fructose g/l, Volatile Acidity in g/l. This is our backup

 

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Last updated: December 27, 2014