Saturday, 18 January 2014


A culture of quality along with specific business programs must exist within a winery if quality control procedures are to be effective. Quality initiatives must be understood and practiced by all employees of the winery. From the workers handling the grapes in the field to the filling machine supervisors, all individuals involved have an equal part to play in maintaining the quality of the final wine. The successful winery realizes this and implements systems designed to naturally promote quality procedures at every point within the winemaking process.

When developing a business strategy or culture for quality management, it is important to take into account actual mechanisms for analyzing and adjusting the quality of the product. In the case of winemaking, it is critical to develop an analytical plan to capture critical production data at every critical process in the winemaking system. Likewise, it is important to then understand the very mechanisms that are used to modify or control the quality when deviations are discovered.

Building a manufacturing process that takes every administrative and operational variable into account is an extremely daunting task. Wineries must structure their operational systems accordingly so that wines: are produced economically, critical information is captured and recorded, quality is maintained and future growth is encouraged and not hindered. This mindset is important not only for producing a quality product but also for troubleshooting problems when they arise. A good mechanism and example would be traceable manufacturing codes associated with data recording systems. By recording all analyzed data into a winery database system, it becomes possible to associate production data with a specific bottling of wine. Using this mindset, wines returned as being defective can be traced back through the winemaking process by the use of manufacturing codes. This information is invaluable to the winery as the vintner can correlate data to determine exactly what caused the problem and apply a solution so that the problem does not happen again. Additional benefits to a properly designed analytical plan include learning from previous unexpected conditions.

The development of an analytical plan is meaningless without a clear understanding of the mechanisms from which data is collected. In the case of winemaking, these mechanisms are various properties that exist at various stages throughout the winemaking process. Specifically they include wine density, alcoholic strength, total dry extract, total acidity, pH, measurement of residual sugars, tartrate stability tests and protein stability tests.

Monitoring and recording the density of wine is a critical practice. Wine density on its own does not provide meaningful information concerning the quality on wine. The knowledge of density is important however as its value is used within the computation of various other quality control mechanisms. It is important to remember that dissolved sugars increase density where an increase in alcohol decreases density. Monitoring density can be achieved by the use of a hydrometer which in its simplest function consists of a float in a graduated cylinder. Density is determined by how far the float sinks into a specified amount of wine. Modern techniques for measuring density include the use of a computerized densitometer. A wine densitometer measures vibrations of a probe within a specified amount of wine.

As the name implies, alcoholic strength is used to measure the alcoholic content of the resulting wine. This is important, as wines with higher alcoholic strengths are more expensive. Alcoholic strength is perhaps the most important variable due to legal stipulations concerning the sale of wine. For example, it is a requirement within the European Union that a variance of only +/-0.5% be present against the alcoholic strength reported on the wine label. It is for these reasons that alcoholic strength is critically monitored. The actual mechanisms for determining alcoholic strength include the distillation method, an optical infrared method and a method where gas chromatography is utilized. When using the distillation method, a sample of wine is boiled and the resulting alcohol is condensed and thus separated from the wine. The density of the alcohol is then observed and from this density, the alcoholic content of the wine is determined. Modern practices of using infrared optics as well as gas chromatographers are largely displacing the traditional method of distillation. Gas chromatography is a preferred method as it not only can reliably provide alcoholic strength but can also provide a breakdown of the various types of alcohols found within wine. Finally, it is important to note that the alcoholic strength of wine is reported as a percentage by volume.

Measuring the total dry extract of wine involves measuring the sugars, glycerol, non-volatile acids, polyphenols, mineral salts and other non-volatile constituents under very specific conditions. The main benefits of this test are determining if dry wines have been diluted with water as well as approximating the sugar content of wine. More than anything else this test can be useful for determining if shady practices have been used to produce the tested wine.

The total acidity of wine is a measurement of the sum of acids found within the wine and is of significant importance. The production of a good quality wine requires the proper acid to sugar balance. Vintners will continually monitor the total acidity throughout the winemaking process and make small adjustments accordingly. It is important to remember that in the cases of acid to sugar balance, nature typically knows best and introducing dramatic changes to the balance can lead to disastrous results. The method for determining total acidity of wine is to use a process called titration. Simply put, titration is a laboratory method utilizing quantitative chemical analysis for the purpose of determining the concentration of a known component. The process of titration is a simple process for determining the total acidity of wine.

Measuring the pH of wine is a completely different test than measuring the total acidity of wine. pH is important as it characterizes the strength of an acid as shown on the pH scale. A substance with a pH of 0 may be considered extremely acidic while a substance with a pH of 14 may be considered extremely basic. In terms of winemaking, it is possible to have two wines with the same total acidity but different pH values. This is due to a buffering phenomenon caused by the natural salts within the wine. Due to this fact, monitoring the pH of a wine is essential as acid strengths control wine color, taste and storage abilities. Monitoring pH is a simple process with pH meters being readily available for this purpose.

Knowing the level of residual sugar in a wine is important for certain types of wine production. If a vintner is aiming to produce a dry white wine that is not sweetened, it is important to verify that very little residual sugar is present. Conversely, if a vintner is aiming to produce a white sweet wine, a higher concentration of residual sugar will be required. Determining the level of residual sugar is possible by the use of Fehlings titration or by the use of a high performance liquid chromatograph.

Tartrate stability tests and protein stability tests are conducted to determine if crystal formation and wine clarity are within limits. When performing a tartrate stability test, the electrical conductivity of the wine is measured at specific conditions. During the test if the conductivity of the wine increases, it can be deduced that any crystals are dissolving and the wine is stable. If the conductivity of the wine decreases, it can be deduced that the wine is not stable and must be put through the stabilization process again. Determining wine clarity is a simple test performed by heating a sample of wine to just above 176deg Fahrenheit (80deg Celsius) and then allowing the wine to cool to room temperature. If the sample of wine has developed clarity issues then additional fining is required.

Sources: Core Enology Group, GrapeHeaven, Brotherhood.

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