Automated Wet Chemical Analysis: Top Six Wine Spoilers

[hari-narayanan]

Wine is a product which dynamically evolves throughout the entire production process, starting from the grape harvest, fermentation process to bottling. Correct maturation of the grapes and management of alcoholic fermentation are two basic requirements to produce a quality wine. Rapid, real-time results are essential for ensuring a quality product. The list of necessary parameters for the oenologist to monitor the wine production from the juice to the bottling stage is very long and discussed in detail in the Analytical Guide for Beverage Testing eBook.

From the juice to the bottling stage, many different process critical parameters must be continuously monitored to maintain the brand signature and fulfill regulatory requirements. Monitoring and controlling the chemical reactions in the winemaking process is part of the science and artistry of producing an exceptional balanced product. From grape to glass, great winemaking starts with a commitment to quality. Wine’s unique attributes, like color, taste, and flavor, are all highly dependent on a series of chemical reactions and equilibriums throughout the various stages of winemaking.

Top Six Wine Spoilers

1. pH
   pH is critical in the relationship to microbial stability, interactions of phenolic compounds, and color expression. Wine color stability, potassium bitartrate stability (cold stability), calcium stability and molecular sulfur dioxide (SO2) levels are directly related to wine pH.

1. Volatile acidity—acetic acid
   Acetic acid is the main component of wine’s volatile acidity (VA). Acetic acid causes a sour taste to the wine and constant monitoring of it during the fermentation process is critical. High levels of acetic acid will indicate a level of spoilage bacteria and can render the wine as low quality. Acetic acid is involved in the metabolic processes during the ripening of fruit and is a key indicator of wine quality. Small amounts of acetic acid are always produced during and subsequent the alcohol fermentation which adds to the complexity of the wine production process.
   Volatile acid analysis, historically required distillation, can now be carried out reliably and accurately by the enzymatic photometric method

1. Total acidity
   Total acidity measures total available hydrogen ions in solution in wine or must. This measurement includes both the free hydrogen ions and the undissociated hydrogen ions from acids that can be neutralized by sodium hydroxide. Acids play a significant role in the taste, color and microbial stability of wine.

1. Residual sugar
   Monitoring of sugar levels at each stage of the winemaking process helps producers to make decisions that will influence the final composition and texture of the wine. For example, around grape ripeness, and when to stop fermentation. The total glucose and fructose concentration that remains after fermentation—the residual sugar— indicates how “dry” the finished wine is likely to be. Residual sugar is an important parameter to know, because wines that contain residual sugar need to be stabilized before being bottled to eliminate wine spoilage.

1. Residual L-Malic acid
   L-Malic acid is the most commonly assayed acid in winemaking, allowing the winemaker to assess grape ripeness and to quantify the progress of malolactic fermentation. Accurate determination of L-Malic acid is very important for monitoring the malolactic process and is the direct indicator of the completion of the process. L-Malic acid occurs naturally in grape must and is used as an indicator of ripeness. Malolactic fermentation (MLF) is a winemaking process involving a special bacterial strain that metabolizes the malic acid naturally found in grapes into lactic acid. The concentration below 1g/L can make the malolactic process very difficult, and it is for this very reason that an accurate analytical assay of this acid in the pre-fermenting phase is very important.

1. Free and total SO2
   Sulphites occur naturally as a by-product of yeast fermentation. Sulphites are used as an essential additive in the control of microbial contamination during aging and also to protect the wine against detrimental oxidative and enzymatic browning. Free and total sulfite is dependent on pH and the accurate and reliable determination is very critical from the product taste, stability and regulatory perspective. I will discuss in detail in my next blog on this topic.

How does consolidated wine analysis help prevent wine spoilage?

For effective control of the vinification process, it is highly recommended to carry out all necessary wet chemical analyses through an in-house laboratory with an easy-to-use system, so that oenologists can make rapid and timely decisions. The ability to measure and manage the levels of wine spoilers in juice or wine ensures a good final product. Effective quality monitoring during different production stages improves productivity and ensures consistent product. For this reason, for effective vinification process control, a tight quality control through in-house laboratory is recommended. Accurate determination of wine process-critical and spoiler’s analysis involves several analytical techniques such as titration, spectrophotometer, pH meter and HPLC, that requires highly skilled operators for day-to-day operation. It is important to use reliable analytical instrumentation which enables lab personal without technical or chemistry knowledge to carry out the routine juice and wine analysis. Thermo Scientific™ Gallery™ discrete analyzers together with ready-to-use system reagents makes the overall wine analysis simple, accurate and reliable. The ready-to-use wine reagents are specifically developed for cost-efficient and juice and wine analysis quality control. Gallery system reagents take away the guesswork for the oenologist and provides walkaway efficiency. The barcode reader improves the traceability and continuously monitors the reagent consumptions and provides real-time reagent information.

Want to learn how to avoid wine spoilage – Attend the upcoming webinar

Learn from Leah Lyon, Laboratory Manager, King Estate Winery, in Eugene, Oregon, how discrete analyzers and ready-to-use enzymatic reagents help consolidate the wine analysis, from juice to bottling.  Leah will present the importance of maintaining a meticulous quality control (QC) program, and the advantage of reproducible and reliable results for important harvest and post ferment decisions.

Register for the webinar

Reference:

1.    https://www.awri.com.au/information_services/technical_review/technical-notes/

2.    https://analyteguru.com/automated-wet-chemical-analysis-2-what-is-automated-discrete-analyzer/

3.     https://assets.thermofisher.com/TFS-Assets/CMD/brochures/in-73805-da-wine-testing-in73805-en.pdf

4.     https://assets.thermofisher.com/TFS-Assets/CMD/brochures/sn-73820-da-top-six-wine-spoilers-sn73820-e...

5.    https://assets.thermofisher.com/TFS-Assets/CMD/Reference-Materials/cs-64539-analyzer-napa-valley-win...