Wine Testing

Glossary of testing terms

CHEMISTRY

Ammonia/NOPA

This test determines how much nitrogen is available for the fermentation process. Ammonia is a readily available form of nitrogen for yeast nutrition. Ammonia is measured in conjunction with NOPA to obtain the Yeast Assimilable Nitrogen (YAN).
Method - Enzymatic assay

Brix

Brix is a measurement of the concentration of dissolved solids in a solution. This is equivalent to the amount of sugar in solution, where 1 degree Brix equals 1 gram of sucrose per 100 mL of liquid at a given temperature.
Method - Densiometer.

Calcium

Calcium is naturally found in grapes due to uptake from soil, and is used by grapevines as a nutrient. High concentrations of calcium can result in calcium tartrate instability in wine.

Citric Acid

Citric acid is present in small quantities in grapes. It can be consumed by lactic acid bacteria and converted into diacetyl. Citric acid testing is performed to meet regulatory or export requirements.
Method -Enzymatic assay.

Cold Stability test

We use a freeze/thaw method to determine the tartrate stability of your wine.

Ethanol

Alcohol affects a number of different things during production. Also known simply as alcohol, or grain alcohol, ethanol is the primary alcohol found in wine. Ethanol is a critical constituent of wine and is produced from sugar during fermentation.
Method - Gas Chromatography.

4-Ethylguaiacol (4-EG) / 4-Ethylphenol (4-EP)

Brettanomyces yeast are unique in their ability to readily synthesize the volatile phenols 4-ethylphenol (4-EP) and 4-ethylguaiacol (4-EG) in standard wine conditions. These compounds are useful for monitoring Brettanomyces and are an important component of Brettanomyces wine character.

Glucose + Fructose

Typically used to estimate the final alcohol level. Glucose + Fructose, also known as residual sugar after primary fermentation, measures the combined concentrations of the primary two sugars that are consumed by yeast during fermentation. In grapes, this value can provide an estimate of final ethanol concentration. As a product of photosynthesis, glucose and fructose are naturally found compounds in grapes.
Method - Enzymatic assay.

Haze Identification

This test assists identifying the cause of any clarification issues through microscopy and/or qualitative analysis.

Heat stability check

This test determines whether your wine is protein stable. If a haze is present post heating, the wine is unstable. We can then offer fining trials to determine the level of Bentonite required to stabilise the wine.

Malic acid

One of the major organic acids found naturally in grapes, malic acid contributes sharp green flavours to wine, similar to a sour apple. Malic acid concentration is an important component of the calculations necessary to make acid adjustments to must. This test is also useful for monitoring malolactic fermentation during which malic acid is converted enzymatically by bacteria to lactic acid.
Method - Enzymatic assay.

pH

pH levels have a large impact on the wine production process and should be closely monitored. As the nominal measure of a solution’s acidity, or hydrogen ion concentration, pH is a critical constituent of wine. pH can affect microbial activity, tartrate solubility, the interaction of phenolic compounds, and the efficacy of molecular SO2. Solutions with lower pH values are acidic, while those with higher pH values are basic.
pH is measured on a logarithmic scale, hence a wine with a pH of 3.0 is 10 times more acidic than a wine with a pH of 4.0.

Potassium

Potassium is found in grapes with levels increasing as the berries mature. Potassium is also found in certain chemical additions, such as potassium metabisulphite. Final concentrations in wine depend on addition rates of potassium containing compounds, as well as the amount of extraction from berries through pressing and maceration.

Reducing sugars / Residual sugars

Reducing sugars are defined as sugars which are capable of reducing other compounds. Residual sugar is a measure of all the fermentable sugars present. This test is often used after or near the end of fermentation to evaluate the dryness of a wine.The most common reducing/residual sugars are glucose and fructose.
Method - Enzymatic assay.

Resveratrol

The result from this test is often used as a marketing tool especially for wine destined to by consumed in the US market. Resveratrol is a stilbene from grape skin involved in grape disease prevention. It is considered important in studies on red wine and health.

Free Sulphur dioxide

Free sulphur dioxide is a measure of the amount of SO2 that is not bound to other molecules, and is used to calculate molecular SO2. Sulphur dioxide is used throughout all stages of the winemaking process to prevent oxidation and microbial growth. Excessive amounts of SO2 can inhibit fermentation and cause undesirable sensory effects.

Total Sulphur dioxide

Total sulphur dioxide is a measure of both the free and bound forms of SO2. Bound SO2 refers to SO2 molecules that are bonded to other compounds, primarily aldehydes, pyruvate, and anthocyanins. Sulphur dioxide is used throughout all stages of the winemaking process to prevent oxidation and microbial growth. Excessive amounts of SO2 can inhibit fermentation and cause undesirable sensory effects.

Tartaric Acid

The most prevalent organic acid found naturally in grapes, tartaric acid is commonly used to adjust the acid balance of must and wine.
Method - Enzymatic assay.

Terpenes

Aromatic compounds primarily derived from grapes.  The nature and quantity of terpenes varies between varieties and seasons.

Titratable acidity (TA)

TA is a measure of juice or wine acidity. It is the measurement that most closely corresponds to the sensory perception of tartness or acidity.  Results of this test are reported in terms of the predominant acid in grape, tartaric acid, which is the standard reporting convention in New Zealand.

Total Alcoholic strength

Total Alcoholic Strength is a calculation of the potential alcohol concentration if all remaining sugars were to be fermented. This test is used for regulatory and export purposes.

Volatile Acidity (VA)

Used as a measure of the potential presence of spoilage Organisms. it is a measure of the volatile acids in wine, primarily acetic acid. High concentrations of acetic acid can cause undesirable sensory effects similar to vinegar. This test is most useful for determining a baseline VA level and monitoring for any increases, which could indicate the presence of a spoilage organism.
Method - Enzymatic assay.

Yeast Assimilable Nitrogen (YAN)

Helps to guard against stuck fermentations or excessive sulphide production. Yeast Assimilable Nitrogen (YAN) is a measure of the total nitrogen including alpha amino nitrogen (NOPA) and ammonia (NH3).
Method - Enzymatic assay.