Wine is a product made from fruit produced on a growing medium, and it is for this reason that the final product is affected by the quality of both the grapes and the soil the grapes are grown in. Like all crops, the climate is also a determining factor. To realize a grape’s full potential, appropriate attention should involve the analysis of key chemical parameters that are central to a high-quality bottle of wine.
The first of these parameters is the ripeness of the grapes. This is evaluated via analysis of acidity, pH, and sugars through a ripening curve. The sugar accumulation curve follows a sigmoid-like trend. In the beginning of the process the increase is modest, then it increases and reaches its maximum when the size of the berry is maximum. In the final phase the accumulation of sugars undergoes a decrease and volatile and non-volatile aromatic compounds begin to accumulate.
The curve representing acidity adopts a more specular profile than that of sugars. Berries in the green phase have high levels of acidity but starting from the variation the content of organic acids decreases with the increase of sugars. A widely used ripening index is the sugar-acidity ratio expressed in tartaric acid. At the harvesting this ratio must be about 3 to 4. Technologic ripeness index indicates a particular level reached by the sugar content and the titratable acidity of the juice such as to allow the production of a given type of wine. Phenolic ripeness index is given by the sum of the concentrations of phenolic substances (anthocyanins and tannins) found in the skin and in the seeds.
After harvesting, the sugar level is decisive for making an alcohol yield forecast and to control the progress of fermentation in which the sugar is transformed into alcohol by yeasts (Saccharomyces cerevisiae). It is crucial to know, at this point, the level of primary amino nitrogen and ammoniacal nitrogen as the primary source of nitrogen for yeasts together with sugar. Little YAN (yeast assimilable nitrogen) would reduce fermentation, develop malodorous secondary products until fermentation end. Nitrogen must be adjusted at the beginning of fermentation with additions and maintained during consumption and then lowered towards the end as high nitrogen levels would negatively affect the final product in terms of taste and appearance. Monitoring is therefore necessary.
It is essential to stop fermentation only when the sugar is zero as sugar residues in wine would be a substrate for hundreds of other bacterial cultures that would create unwanted tastes and flavours. Leaving sugar unfermented would also lower the alcohol level, the primary purpose of fermentation.
When fermentation has completed, as well as measuring alcohol content, it is mandatory to measure volatile acidity (acetic acid) to ensure that the wine is not turning into vinegar.
Free sulfur ensures sterility, and it is for this reason that the limits of this are regulated by official guidelines.
A further determining parameter of red wine quality is the level of malic acid present. Malic acid is the source of red wine’s closed and astringent taste, and its conversion into lactic acid (which is tasteless), results in a more rounded flavor. As such, analysis of this parameter will reveal if malolactic fermentation has occurred or not – essential in maintaining an appropriate flavor.
Producing consistent, quality wines requires that growers and producers have access to all of these analytical results. Maintaining a laboratory with the capability to monitor these parameters is a complex, often daunting task for many wineries. Many wineries opt to send the samples out to commercial laboratories, but this delays the test results, limiting the ability of wineries to appropriately adjust harvest and production approaches in response to this analytical data.
Managing Key Parameters with AMS Alliance CFA
To help wine producers monitor and manage these parameters in-house, AMS Alliance provides specific continuous flow analyzers (CFA) and discrete analyzers for wine producers. These analyzers are supplied with dedicated reagent kits that have been specifically developed for the wine industry, including all the equipment and reagents required to immediately test critical parameters at various stages of the wine production process.
The Futura range of continuous flow analyzers (CFA) has been designed for a dedicated analysis of various specific parameters, possessing either routine or complex chemistries. Common parameters include total SO2, free SO2, volatile base, volatile acidity, urea, and sorbic acid.
Futura analyzers are also capable of analyzing up to 120 samples per hour. They can be configured for use with an autosampler, and in parallel with other Futura analyzers to allow for maximum throughput while analyzing several parameters simultaneously.
The Winechem line of discrete analyzers includes a range of fully automated analyzers, offering multi-parameter analysis and a range of 140 – 600 tests per hour able to easily accommodate testing requirements for small- to mid-sized farms to larger regional wineries.
It is possible to configure Winechem analyzers to run any combination of tests on each sample, making them an ideal investment for wine producers seeking to automate several tests and gain comprehensive results across the growing and production processes.
Selection OENO reagent kits are provided for the Winechem discrete analyzers for the following parameters:
- Acetic Acid
- Alpha Amminic Nitrogen
- Ammoniacal Nitrogen
- Calcium Ionic
- Citric Acid
- Colour 420-520-620
- D-Gluconic Acid
- D-Lactic Acid
- Free SO2
- Iron Ionic
- L-Ascorbic Acid
- L-Lactic Acid
- L-Malic Acid
- Pyruvic Acid
- Tartaric Acid
- Total Acidity
- Total Polyphenols
- Total SO2
For more information on this source, please visit AMS Alliance.
This information has been sourced, reviewed and adapted from materials provided by AMS Alliance.