Enzymatic bio-analysis plays a vital role throughout the whole of the wine-making process:
Before the alcoholic fermentation begins, the nutritional status of the grape juice is
determined to ensure optimal growth conditions for the yeast. This includes an estimation of yeast available nitrogen as the product of free ammonia, primary amino nitrogen and
L-arginine, and the principle fermentable sugars D-fructose and D-glucose.
During the alcoholic fermentation, the level of acetic acid is monitored to detect infection by Acetobacter sp. and the level of urea is determined in order to establish whether the wine should be treated by the addition of urease to eliminate the risk of forming the carcinogen ethyl carbamate. Concentrations of acetaldehyde, ethanol, glycerol and succinic acid all rise throughout the alcoholic fermentation phase of the vinification process.
If it is elected to perform a malolactic fermentation, the falling level of L-malic acid and rising level of L-lactic acid are monitored. The falling level of citric acid can also be
determined.
Numerous analyses are performed in order to determine the quality, stability and
authenticity of wine after fermentation is complete, and include enzymatic assays for:
acetaldehyde, acetic acid, L-ascorbic acid, ethanol, ethanol/glycerol ratio, D-fructose,
D-glucose, D-fructose/D-glucose ratio, glycerol, D-gluconic acid, D-gluconic acid/ethanol ratio, D-gluconic acid/glycerol ratio, L- and D-lactic acid, L- and D-malic acid, D-sorbitol, succinic acid and urea.
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| analytet | Cat. No. | Analyte Significance | Advantages Of Megazyme Test Kits |
|---|---|---|---|
| Acetaldehyde | K-ACHYD | A sensory compound that adds flavour and complexity, but spoils wine at high concentrations |
AcDH supplied as a stabilised solution rather than a lyophilised powder, thus less wasted enzyme |
| Acetic Acid |
K-ACET K-ACETAF K-ACETAK K-ACETRM K-ACETGK |
A sensory compound that adds flavour and complexity in small amounts, but spoils wine at high concentrations. Produced naturally by yeast in small amounts and by spoilage organisms such as Acetobacter aceti in large quantities. This is the predominant of the acids comprising ~ 85 % volatile acidity (VA) |
All kits contain PVP to prevent tannin inhibition. K-ACET (manual, efficient) contains stable ACS suspension. K-ACETAF (auto) used to prepare very stable R1 and R2. K-ACETAK (auto) / K-ACETRM (manual) are very rapid acetate kinase (AK) based kits with excellent linearity. K-ACETGK is a new rapid, auto-analyser assay kit employing AK and phosphotransacetylase. Stable reagents |
| Ammonia |
K-AMIAR K-LARGE |
Most important inorganic source of Yeast Available Nitrogen (YAN) | Novel enzyme employed is not inhibited by tannins, endpoint reaction time ~ 3 min. Ideal for manual and auto-analyser applications |
| L-Arginine | K-LARGE | Most important amino acid in grape juice with respect to YAN | Simple and rapid test kit gives sequential values for ammonia, urea and L-arginine. No tannin inhibition |
| L-Ascorbic Acid | K-ASCO | Naturally present in small amounts; large amounts indicate addition for acidification (EU limit is 1 g/L) |
Ideal for both manual and auto-analyser applications. Reconstituted citrate lyase stable for > 6 months at -20°C. Stable reagents |
| Citric Acid | K-CITR | Naturally present in small amounts; large amounts indicate addition for acidification (EU limit is 1 g/L) |
Ideal for both manual and auto-analyser applications. Reconstituted citrate lyase stable for > 6 months at -20°C. Stable reagents |
| Ethanol | K-ETOH | Produced during alcoholic fermentation. Amounts > 17.5 % (v/v) indicate supplementation | Rapid reaction, stable reagents (AlDH supplied as a stable suspension) |
|
D-Fructose / D-Glucose |
K-FRUGL K-FRGLMQ K-FRGLQR |
Grape quality indicator. One of the two principle fermentable sugars of grape juice | Contains PVP to prevent tannin inhibition. Ideal for manual and auto-analyser use. Stable reagents |
| D-Gluconic Acid | K-GATE | Grape quality indicator for the production of certain wines | Rapid reaction, stable reagents |
| Glycerol |
K-GCROL K-GCROLGK |
Quality indicator of finished wine, important for “mouth feel” | Novel tablet format offers superior stability, rapid reaction |
| D-Lactic Acid |
K-DATE K-DLATE |
Produced predominantly by lactic acid spoilage bacteria | Rapid reaction, stable reagents |
| L-Lactic Acid |
K-LATE K-DLATE |
Produced predominantly from L-malic acid during malolactic fermentation | Rapid reaction, stable reagents. Ideal for manual and auto-analyser applications |
| D-Malic Acid | K-DMAL | Only present in significant quantities in adulterated wine |
D-MDH supplied as a stabilised suspension rather than a lyophilised powder, thus less wasted enzyme |
| L-Malic Acid |
K-LMAL K-LMALAF K-LMALMQ K-LMALQR |
Grape quality indicator. Very important grape acid, converted to less acidic L-lactic acid during malolactic fermentation |
All kits contain PVP to prevent tannin inhibition. 1. K-LMALR/L (manual) rapid reaction 2. K-LMALAF (auto) rapid reaction, excellent linearity 3. K-LMALMQ (manual, colorimeter based) 4. K-LMALQR (auto) liquid ready reagent |
| Primary Amino Nitrogen (NOPA) | K-PANOPA | Primary amino nitrogen (PAN) is the most important organic source of YAN | Novel kit, rapid reaction, stable reagents, simple format |
| D-Sorbitol | K-SORB | High levels indicate addition of fruit | Diaphorase supplied as a stabilised suspension rather than a lyophilised powder, thus less wasted enzyme |
| Succinic Acid | K-SUCC | Wine acid produced during fermentation | Rapid reaction (~ 6 min even at room temperature), stable reagents |
| Sucrose |
K-SUFRG K-SUCGL |
Added to increase the amount of alcohol. Use only permitted in certain situations | Added to increase the amount of alcohol. Use only permitted in certain situations |
| Sulphite |
K-SULPH K-TSULPH K-ETSULPH |
Sulphites are used as an essential additive in the control of microbial contamination during aging and to also protect the wine against detrimental “oxidative and enzymatic browning” | Choice of simple formats available, based either on liquid ready reagent chemical reactions (K-SULPH & K-TSULPH) or an enzymatic reaction (K-ETSULPH). Stable reagents |
| Tartaric Acid | K-TART | Occurs naturally in grapes and is one of the most prevalent organic acids. Key indicator of total (titratable) acidity (TA) | Stable liquid ready reagents. Simple, rapid chemical reaction for manual, auto-analyser and microplate formats |
| Urea | K-URAMR |
Source of YAN and precursor of the carcinogen ethyl carbamate. Over-supplementation with DAP can result in elevated levels |
Simple, very rapid (both urea and ammonia measured in < 10 min at room temperature) and sequential / efficient (only one cuvette required per sample) |