Fluorescence Spectroscopy Used by Winemakers

The nature of grapes for wine making affects the flavor, feel and color of the wine. Therefore, knowing its state during the maturing of these grapes is of paramount importance.

Fluorescence spectroscopy is beginning to take on a greater role in this process.

Most wineries have multiple brands and growing fields. Winemakers need to monitor these fruits for the phenolic content in the grape that will give it the desired color, flavor and mouthfeel.

The majority of wineries send out samples of their grapes for testing during the growth and harvest processes. Laboratories customarily use Gas Chromatography-Mass Spectrometry, Liquid Chromatography-Mass Spectrometry, and Fourier Transform Infrared Spectroscopy for these analyses.

Those types of instruments are expensive, pose significant difficulties in terms of calibrating the systems and maintaining calibration, and transferring calibrations to field locations and places where analysis is important.

There is also a significant work overload in terms of characterizing the grapes scientifically as its been delivered or prepared for wine making.

Instruments for each batch of grapes routinely evaluate all of these characteristics, including the pH and sugar content. The intention is to have a survey that's representative of the particular vineyard, as well as different locations in the vineyard.

The downside to conventional testing techniques are time and cost. It takes between 35 and 90 minutes to analyze a single sample in an independent laboratory using the conventional methods to fingerprint the grapes.  And it can cost up to $200 per sample. That makes it expensive for vineyards, especially small ones, to maintain this vigilance.

Enter fluorescence spectroscopy, a spectroscopy method used to analyze the fluorescence properties of a sample. Fluorescence spectroscopy can characterize the phenolic content in grapes and wine.

HORIBA Scientific recently patented an instrument called the Aqualog®, which makes this process faster and less costly. With the Aqualog, you can collect the entire composition of all the colored and phenolic compounds. The acquisition time is roughly 30 seconds. In less than a minute, operators can fully automate the analysis in terms of the phenolic identity and concentration.

The Aqualog acquires Absorbance, Transmittance and the fluorescence Excitation-Emission Matrices (A-TEEM) simultaneously. The Aqualog acquires EEMs up to 100 times faster than with conventional scanning fluorescence instruments.

HORIBA initially developed the Aqualog for water treatment facilities. But its portability, speed, functionality, flexibility, and cost are now appealing to several world-renowned winemakers across the globe. These winemakers have begun to adopt the technology, especially since the Aqualog’s portability and low cost allow winemakers to deploy it in multiple locations.

Most big wineries are dealing with multiple vineyards, often in different regions.  With the Aqualog, each region can have a laboratory that operates the instrument for quality control, as opposed to sending samples to one central internal or external contract laboratory and waiting for results. Laboratories can establish multiple units that have matching calibrations, and they can have these at convenient field locations.

Virtual libraries contain cataloged fingerprinting data of these grapes. Statisticians and winemakers evaluate the data to predict the flavor characteristics, storage, stability and blending operations.

Engineers often immediately relay the information resulting from the grape analysis to the growers. Growers use it to evaluate when to harvest, or hold off. It’s also used by the winemakers in terms of final processing, quality control and assurance, blending, bottling, and storage.

If a grape sample doesn’t meet the standards of its particular brand, it might influence a blending plan. The grape would go into another type of wine or another blend of something else the winery is making.