Comparing the science of viticulture and winemaking to my academic and professional background in engineering and finance, I sense we are still in the dark ages. We know good wine when we drink it but we have very little scientific understanding of the chemical processes which lead to good wine. We have learned the importance of measuring certain physical and chemical characteristics of grape juice and wine mostly because we know what ranges they should be in to make drinkable wine and what to do if they are not. We do not understand most of the chemical processes leading to good wine and what and how to measure to optimize these processes. We know famous vignerons who have developed successful processes for their grapes leading to high-prized wines, but they themselves don’t understand the underlying science – they are artists who have refined their craft, based on recipes handed down over generations or based on processes they chanced upon.
The following questions and answers, working backwards from the bottle, highlight how little is currently understood by leading scientists in viticulture and enology:
- Exactly which chemical compounds in what combination in mature wine (phenolics and flavor compounds) create that wonderful combination of sensory experience in smelling, tasting and drinking great wine? We simply don’t know. We know which chemical create bad tastes and smells, and we know the composition of some of the chemicals which are associated with specific flavors
- Exactly how do certain cellaring processes (aging in barrels, adding woodchips, racking etc) change the chemical composition of wine? We don’t know, because we don’t know the chemical composition of wine in the first place, let alone the change therein. But we do know that certain cellaring techniques have led to wine which sells for a higher price.
- Exactly how are more or less successful processes in winemaking (enzyme addition, cold soak, fermentation, extended maceration, pressing) reflected in chemical processes extracting the “good” phenolics and flavor compunds from the grapes, and what should we measure to better guide us what to do, when and how much? We still rely mostly on the smell and palate of experienced winemakers and their past successes to guide us through the art and craft.
- What happens in the vineyard with respect to phenolics and flavor compounds in the grape? How can we make the vines produce the right phenolic composition in the grapes which then can be extracted in winemaking? We don’t know except that sunlight and irrigation affect the buildup of phenolics more than rootstock and temperature. But we know some viticultural practices which led to grapes which some winemakers have tended to pay high prices for.
So, my argument is: we still know (academically) very little of what exactly makes superb wines and why. We know a fair amount on what the acceptable ranges are for chemical properties we can easily measure; and we know how to intervene in the wine-making process to get these measures back into the acceptable measures. So science has helped us reduce the amount of bad wine that is made, but we still need to understand much more of the chemical processes for science to help us make outstanding wines.
This section describes the key chemical properties we endeavor to measure and the tools and methodologies we use to track the chemical properties of the grapes and wine. These tools have become very sophisticated and increasingly expensive as technology has progressed and industrial scalability has become important, As a consequence many wineries have decided to outsource this function to specialized providers (e.g. ETS, Enartis Vinquiry, Signature Labs etc.). Given our goal to keep the whole vineyard and winery process in-house we decided to maintain a laboratory which defies economic logic for the sake of understanding the whole picture.
While our laboratory is well equipped it is no match to the sophistication of equipment currently employed at top commercial and leading universities (mostly for various types of chromatography, spectrometry, nuclear magnetic resonance spectrometry etc.). Each of the following pages describes one laboratory analysis we do in-house:
- Brix: Brix is a measure of sugar content by weight in an aqueous solution. We measure Brix in berries in the vineyard (to track their maturity) and in the must during fermentation (to track the conversion of sugars into alcohol). The page explains how we use a simple Optical Refractometer to measure the sugar content of grapes and how we use Hydrometers to measure the sugar content of must during fermentation.
- Alcohol: We measure the alcohol content of wine with an Ebulliometer which compares the boiling temperature of the wine with the boiling temperature of water at a given atmospheric pressure point.
- pH: pH is a measure of acidity or alkalinity of a solution. Pure water has a pH of ~7, Wine is acidic and has a pH in the range of 3 to 4. We use a portable pH meter to measure the pH of juice, must or wine, and we use a benchtop pH meter to track changes in pH during a titration.
- Total Acidity: Total Acidity, also called Titratable Acidity, is the result of a test which measures the total amount of all acids present in wine (mostly tartaric, malic, lactic acids). We measure Total Acidity with a titration procedure.
- Volatile Acidity: Volatile Acidity refers to the steam-distillable acids present in wine (mostly acetic acids). We use a Cash Still to measure it. In small, barely detectable, amounts below 600 mg/L, Volatile acids are believed to add complexity, but above 1g/L they are considered spoiling the wine (vinegar)
- SO2: Sulfur Dioxide is added to must and wine as a preservative. Most wines contain sulfites, on average around 80 mg/L. We measure “free” SO2 using a method called aeration-oxidation, which is more time-consuming than other manual methods but more accurate.
- Dissolved Oxygen: Supply of oxygen is very important during fermentation and can be detrimental at any other stage of wine-making. We measure the dissolved oxygen in must during fermentation and monitor dissolved oxygen during cellaring with a specialized instrument
- Phenolics in Wine: Phenolics are organic chemicals in grapes and wines which are responsible for its taste, mouthfeel and color. In the past, they coul only be measured with an elaborate process in a wet laboratory. We use a platform developed by WineXray to measure a wine’s spectrum and from it calculate estimates of concentration of phenolic compounds.
- Phenolics in Grapes: We estimate the potentially extractable phenolics in grapes by pressing premature grapes and subjecting the skins to a warm alcohol extraction and then analyzing the simulate wine on the WineXray platform. This is very experimental still.
- Malic Acids: We use paper chromatography and a chemical test to check for the depletion of malic acids , to confirm that the malolactic fermentation has completed, i.e. all malic acids have been converted into lactic acids.
We supplement and cross-check the results from our own laboratory with outsourced analysis. The most helpful in this regard is a test battery performed by Fermentation Solutions on an OenoFoss spectral analyzer (http://www.foss.us/industry-solution/products/oenofoss/ ). It is available for less than $30/sample.