Take a typical Chardonnay. It’s rich, full-bodied and buttery.
Those qualities don’t happen by accident. It’s the combination of a variety of ingredients, and controlling those ingredients could be the difference between a celebratory toast and a glass of vinegar.
It’s also the reason that testing the grape harvest is so important as the grapes mature. But it’s been a laborious, expensive process.
Most wineries have multiple brands and growing fields. Each needs to be monitored for the ingredients in the grape that will give it the desired color, flavor and mouthfeel.
Wineries typically send out samples of the grapes to analytical labs to be tested on costly, hard to maintain equipment. The traditional devices are slow, and since so many samples must be run to monitor multiple harvests, it becomes an expensive and time-consuming process.
“Primarily it's a matter of cost, time and flexibility in terms of overall characterization of the wine,” HORIBA Scientific Aqualog Product Manager Adam Gilmore, Ph.D., said. “The conventional methods that most laboratories employ are things like Gas Chromatography-Mass Spectrometry, Liquid Chromatography-Mass Spectrometry, and Fourier Transform Infrared Spectroscopy. Those types of equipment are quite expensive. There are significant difficulties in terms of calibrating the systems and maintaining calibration, and transferring calibrations to field locations and places where analysis is very important.”
And there's always a significant work overload in terms of characterizing the grapes scientifically as they're being delivered or prepared for wine making. It’s a critical period in the winemaking process.
There are a lot of quality characteristics that the winemakers are interested in that relate to the color of the wine and the phenolic content – compounds that affect the wine’s taste, color and mouthfeel. Mouthfeel is usually referred to as silky, smooth, velvety and rough.
All of these characteristics, including the pH and sugar content, are routinely evaluated by instruments for each batch of grapes. The intention is to have a survey that's representative of the particular vineyard and different locations in the vineyard.
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 hundreds of dollars per sample.
A typical small winery would like to test each wine field location many times during the veraison, the wine making season, and the large wine companies have many different vineyards from which they are collecting grapes.Thus, it’s clearly expensive for most small vineyards, let alone very large vineyards and wine companies to have to manage a comprehensive characterization of all the key parameters.
HORIBA Scientific recently patented an instrument called the Aqualog®, which makes this process faster and less costly.
“With the Aqualog, you can actually collect the entire composition of all the colored and phenolic compounds,” Gilmore said. “And the acquisition time is roughly around 30 seconds. Further, in less than a minute, the analysis can also be fully automated in terms of the phenolic identity and concentration.”
The Aqualog is an instrument that acquires Absorbance, Transmittance and the fluorescence Excitation-Emission Matrices. (A-TEEM) simultaneously. EEMs are acquired up to 100 times faster than with conventional scanning PMT based fluorescence instruments. The Aqualog was initially developed for water treatment facilities, but its portability, speed, functionality, flexibility, and cost are now appealing to several world-renowned winemakers around the globe. These winemakers have begun to adopt the technology, especially since its portability and cost allow it to be deployed in multiple locations.
Most big wineries are dealing with multiple vineyards often in different regions. Each region may have a laboratory that can operate the Aqualog for quality control, as opposed to sending samples to one central internal or external, contract laboratory.
“It’s really about speed. Clearly we can do it much faster,” Gilmore said. “It's a solid state instrument that's fully externally validated with NIST traceability. Laboratories can thus establish multiple units that have matching calibrations, and they can have these at convenient field locations, as opposed to having to send everything to another laboratory and wait for results.”
How is all this characterization information used?
Generally, winemakers have something akin to laboratory information management systems (LIMS). It catalogs this fingerprinting information, and statisticians and winemakers evaluate the data to predict the flavor characteristics, storage, stability and blending operations.
The information yielded by the grape analysis is often immediately relayed to the growers to advise them 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.
“The HPLC (high-performance liquid chromatography) and LC (liquid chromatography) is really the primary discriminatory method for identifying the different phenolics and anthocyanins,” he said. “But day in and day out, for day-to-day operations, it's very difficult to train somebody in the field, or in a remote laboratory, how to maintain this (HPLC and LC) type of equipment.”
The Aqualog uses fluorescence, which produces orders of magnitude higher sensitivity compared to UV-Vis absorbance. And it also produces a molecular fingerprint in the form of the Excitation-Emission Matrix. Analysis of the A-TEEM data separates the spectrum in terms of the emission energy, as well as the absorption, which gives the user the ability to identify and create libraries with wide varieties of chemicals.
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 was making. Grapes are rarely thrown away.
The rate of sampling with the Aqualog is very fast.
“We can run hundreds of samples a day with the Aqualog,” Gilmore said. “They can be working in shifts around the clock.”
Wineries are finding out they can’t keep up with the samples with the costlier analytical tools or get the discriminatory phenolic profiles they want with simpler equipment such as UV-Vis absorbance.
“With the Aqualog, it’s a very simple standard operating protocol,” he said. “It can be automated with our auto-sampling systems. We can fully automate the data collection and analysis, and we can generate complete profile reports.”
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