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ENARTIS NEWS POST-BOTTLING WINE DEFECTS: WHAT TO CHECK AND HOW TO PREVENT PART 1: WHITE AND ROSÉ WINES

The appearance of a problem in wine after bottling and/or cold test (we suggest 6 days at -4°C). If wine can be a big economic problem and damage your is unstable, use stabilizing colloids or a physical image. That is why it is recommended to take the time stabilization system. necessary to check wine and stabilize it before bottling. In the case of stabilization by physical systems (cold This is much less expensive and risky than having to treatment, electrodialysis, cation exchange resins), recall faulty bottles, open them, treat the wine and re-check the stability of the wine at the end of bottle again. The following are the most common treatment. problems that may appear in bottled white or rosé In the case of stabilizing colloids use (CMC, wines and how to prevent them. mannoproteins, metatartaric , KPA), run preliminary lab trials reproducing the process that HAZE & SEDIMENT the wine will undergo in the winery (clarification, PROTEIN HAZE sequence of filtration, etc.) to test the efficacy and Appearance: Whitish haze or amorphous sediment. determine the correct addition rate. Microscope observation helps identification. CALCIUM Causes: Wine exposure to high temperatures can Appearance: White , sandy precipitate. cause protein insolubilization; addition of negatively Calcium tartrate does not dissolve in hot water. charged colloids like metatartaric acid, CMC or KPA The presence of calcium tartrate crystals can induce or late tannin addition can react with wine proteins; the precipitation of . presence of residual lysozyme or fining proteins. Causes: Excessive calcium content: commonly, Prevention: Run preliminary bentonite fining trials concentrations above 80 mg/L in is and check the results with a protein stability test. If considered risky. Use of racemic : the a wine is going to be treated with stabilizing colloids calcium salt of the racemic form is much more or tannins, adopt a stricter stability limit. insoluble than the one formed by L-tartaric acid. MICROBIAL CONTAMINATION In presence of racemic tartaric acid, the risky Appearance: Whitish haze or amorphous sediment. concentration of calcium is much lower than the 80 mg/L mentioned above. In any case, calcium tartrate Sometimes presence of CO2 and off-flavors. Microscope observation helps identification. precipitation is unpredictable and may happen after Causes: Bad/insufficient microfiltration and years of ageing. presence of a growth substrate, mainly sugar or Prevention: Temperature has little effect on calcium malic acid. tartrate precipitation. For this reason, cold test and Prevention: Microfiltration suitable for wine Minicontact test are not effective for predicting composition; use antimicrobials: chitosan during calcium instability and cold stabilization is not a wine preparation for reducing wine microbial reliable method to prevent it. A way of reducing contamination, potassium metabisulfite and wine calcium content when above the risky limit potassium sorbate at bottling. consists of seeding micronized calcium tartrate. This accelerates the formation of crystals and their POTASSIUM BITARTRATE precipitation. Calcium tartrate seeding does not Appearance: White crystals, sandy precipitate. require chilling: treatment can be done at 10-15°C. Potassium bitartrate salt dissolves in hot water. Causes: Wine exposure to low temperatures. Prevention: Test for wine tartrate stability by Minicontact test (wine conductivity measurement) PINKING ATYPICAL AGEING Appearance: Salmon-red, blush color appearance Appearance: Loss of fresh and fruity aromas. in white wines. Appearance of an unpleasant sweetish aroma Causes: Light oxidation that may happen during (mothballs, soap, floor polish, antique wax, jasmine, bottling. Recent studies conclude that the compound acacia blossom, foxy) together with a yellow-orange responsible for the appearance of pinking in white color. wines is the anthocyanin malvidin-3-O-glucoside Causes: Formation of 2-aminoacetophenone present in small concentrations (~ 0.3 mg/L) in white by chemical oxidation of indole-3 wines produced under reductive conditions. (phytohormone present in grapes and intermediate Prevention: The first step is to check if wine can of yeast tryptophan metabolism). develop the defect. By forcing wine oxidation Prevention: Use of antiradicalic and antioxidant through hydrogen peroxide addition, it is possible compounds, particularly ascorbic acid. to estimate, visually or by measuring the increase of optical density around 500 nm, wine pinking LIGHT STRUCK susceptibility. In case of a positive result, removal Appearance: Loss of aromatics, discoloration and of pinking precursors from wine can be achieved appearance of unpleasant notes of garlic, onion and by fining with PVPP or carbon (high pinking boiled cabbage. susceptibility). At bottling, addition of ascorbic Causes: Exposure of wines containing more than acid in conjunction with SO2 and other antioxidant 100 µg/L riboflavin to light. In particular, blue light compounds is another effective solution. It is also waves create a condition of energetic overexcitation possible that pink color can be reversed by exposure in the riboflavin that transfers this energy to sulfur to UV light. amino causing their degradation and the appearance of the off-favor. SULFUR OFF-AROMAS Prevention: Treatment with decolorizing carbon Appearance: Off-aroma that, depending on the and specific bentonites can reduce wine riboflavin responsible molecules, can be described as rotten content below the risky limit. egg, burnt rubber, skunky, burnt match, asparagus, onion or garlic. OXIDATION Causes: Formation of sulfur compounds, namely Appearance: Color becomes gold yellow, brown.

H2S, mercaptans and disulfides, due to low wine Varietal and fresh aromas are lost, and wine redox potential. becomes evanescent. Bitterness appears. Prevention: Contrary to con¬ventional wisdom, Causes: First oxygen is solubilized into wine pre-bottling copper addition is not the solution. In during bottling, second oxygen is converted into + 2+ fact, it reacts with H2S and mercaptans but copper- free radicals by action of metals like Cu and Fe , mercaptan complexes are reversible and may be then free radicals oxidize wine aromatic and color responsible for sulfur off-aroma appearance after a compounds. few months. Moreover, copper catalyses reactions Prevention: during wine preparation for bottling, of oxidation leading to loss of aromatics and use oxygen scavenger like ascorbic acid and premature ageing. The addition of tannins with the hydrolyzable tannins that rapidly react with oxygen ability to buffer wine redox potential helps to limit and convert it into harmless forms before it can the decrease of redox and the appearance of the damage wine compounds. defect. Protein Microbial Atypical K bitartrate Ca tartrate Pinking Reduction Light struck Oxidation haze contamination ageing Powdered calcium Bentolit Super bentonite ✓ ✓ activated Natural sodium Pluxbenton N bentonite in granular ✓ form Sodium calcium Pluxcompact bentonite ✓ ✓ Bentonite of Pharmabent pharmaceutical ✓ ✓ quality Enoblack Compact pellet form Perlage decolorizing carbon ✓ ✓ Claril AF ✓ Preparation of potassium Sorbosol K sorbate, potassium ✓ metabisulfite and L-ascorbic acid Pure potassium Winy metabisulfite ✓ EnartisStab Micro (M) ✓ EnartisStab 20% solution of 20% Cellogum LV20 low viscosity CMC ✓ AMT Plus Metatartaric acid ✓ 10% solution of A-5D Zenith Uno K/SD potassium ✓ polyaspartate Pure micronized Enocristal Ca calcium tartrate ✓ Formulation made of ascorbic acid, Citrostab rH citric acid, potassium ✓ ✓ ✓ metabisulfite and tannin Citrosol rH ✓ ✓ Untoasted American EnartisTan SLI oak tannin ✓ ✓ ✓

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