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Wine Quality Control Procedures

by Staff Writer - B. Shaughnessy | February 09, 2012

Viewing the amount of wine produced around the world presents the fact that winemaking is big business. And with the development of new wineries increasing exponentially, winemaking is becoming more and more competitive. The increasing amount of wine drinkers tends to support the ever-rising number of wineries. As with any competitive business, the product produced must be of good quality in order to appeal to potential customers. All wineries recognize this fact and successful wineries have gone to great lengths to ensure that the product produced is of the best possible quality.

In previous articles, winery centric business concepts and strategies were reviewed. In reviewing these articles, wineries focusing on quality must first organize their business practices to be conducive for the production of a quality product. In addition, it was reviewed that wineries must also integrate specific quality control systems into their operations. Finally, as reviewed in the article Wine Quality Control Mechanisms, a winery must develop an analytical plan to capture and monitor the quality of the wine throughout the winemaking process. Understanding the mechanisms used to collect data goes hand-in-hand with developing an analytical plan.

While the article Wine Quality Control Mechanisms described the mechanisms used for collecting important quality data, this present article describes the procedures to determine how much of an additive is required at a specific winemaking stage. It is important to remember that collecting data through an analytical plan and mechanism is necessary for determining if additives are required. In addition to this, the wine must be tested to determine any existing amount of additives already present within the wine. This is important, as the vintner must not exceed total prescribed amounts of additives within the wine. Finally, the vintner must also test for contaminates found within the winemaking processes. As is the case with data collected by the analytical plan and mechanisms, additive usage is also determined by the presence of contaminates. As reviewed in the before-mentioned procedures, determining the proper amount of additive to be used is critical for the quality of the wine.

Specific additives are reviewed in the article Wine Additives. As discussed within the Wine Additives article, sulfur dioxide is perhaps the most important additive found within the winemaking process. It is therefore critical that the wine is monitored to determine if the application of sulfur dioxide is required. Reviewing data captured from the analytical plan is required, but additional data in the form of the levels of free sulfur dioxide and total sulfur dioxide is required when determining the amount of sulfur dioxide to add.

The level of free sulfur dioxide represents the amount of sulfur dioxide that is available for the removal of oxygen from the wine. This level can be determined by a simple titration. A titration is a laboratory procedure utilizing quantitative chemical analysis for the purpose of determining the concentration of a known component. In the case of free sulfur dioxide, a solution of iodine is used to oxidize the sulfur dioxide in a given sample of wine. The result is a direct reading of the sulfur dioxide found within the wine sample.

While the method of using titration is simple, it has the tendency to provide erroneous readings. This is due to the fact that iodine reacts with more than just the sulfur dioxide. Additional compounds within the wine negatively affect the titration. For this reason, an alternate technique was developed to determine the level of free sulfur dioxide. The alternate technique is known as the aspiration method and involves forcing an air stream through a sample of wine. The air forced through the wine is then passed through a solution of hydrogen peroxide. This action oxidizes the sulfur dioxide to produce sulfuric acid. The sulfuric acid can then be titrated to give an accurate reading of the amount of free sulfur dioxide.

In addition to the level of free sulfur dioxide, knowing the level of total sulfur dioxide is also required. The level of total sulfur dioxide takes into account the free sulfur dioxide plus any bound sulfur dioxide found within the wine. The procedures for determining total sulfur dioxide are similar to the procedures for free sulfur dioxide, the only addition being treating the wine sample with an alkaline solution before testing.

Additives other than sulfur dioxide each have their own tests for determining their level of concentration within the wine. In the case of sorbic acid and ascorbic acid, an analytical process is used to determine if acid levels fall within legal stipulations. In the case of citric acids, analysis is much more complex and is only performed when legal stipulations require testing.

While using data from the winemaking analytic plan is important for determining if an additive is required, understanding and monitoring the presence of contaminates is also important for determining if an additive is required. This is because one of the base functions of an additive is to remove contaminates.

As sulfur dioxide is used to control oxidation, it is important to monitor the level of dissolved oxygen found within the wine. It is the goal of any winemaker to eliminate the presence of dissolved oxygen. To that end a simple meter has been developed that displays the amount of dissolved oxygen found within a wine sample. Using this data--as well as data concerning the levels of sulfur dioxide--the vintner can determine how much sulfur dioxide must be added to the wine.

Other contaminates include iron, copper and sodium. As with the procedures reviewed concerning sulfur dioxide, specific tests and equipment have been developed to monitor the levels of iron, copper and sodium found within wine. Depending on the levels encountered, the vintner can choose to remedy problems by the use of various additives or chemical removal processes.

An additional area that requires monitoring includes microbiological organisms and their presence of within the wine. In the case of winemaking this includes organisms such as yeasts. Typically yeasts are not a problem for a majority of wines. One exception to this rule is when a wine has had its fermentation stopped prematurely. In the case of sweet white wines, one does not want a second fermentation to occur within the wine bottle. This can occur if just one single yeast cell is introduced to the bottle of wine. Fermentation will begin again with the residual sugars being converted into alcohol. Fortunately there is a test for determining the presence of microbiological organisms. In this test, a sample of wine is passed through a special membrane. The membrane is designed to trap any microbiological organisms on its surface. After the sample has been passed through the membrane, the membrane is transferred to conditions conducive to rapid microbiological growth. After a period of about 3 days, any microbiological organisms present on the membrane will show extensive growth. If growth is detected then the resulting wine must be filtered. If growth is not detected, the wine is safe for bottling.

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    • DEMELASH ALIGAZ
      Jul 28 2016 5:43 PM
    • for individual purpose
    • THOMAS
      Mar 26 2017 7:44 PM
    • is there a taste change that's detectable between filtered and non-filtered wine ?. Does the wine label have to indicate this additional step ? is this situation going to effect following wine judgement regulation policy, for entering wine competitions ? You know what I'm trying to ask. I lack he proper terminology. Tx Thomas ... a little ole amateur wine maker

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