El Dorado Home Wine Making Website - Home Wine Making Information and Wine Recipes


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Wineries of El Dorado County

Removing SO2 with H2O2:

One mole of peroxide (Mr=34) reacts with one mole of SO2 (Mr=64) to give one mole of Sulphate. Therefore 34/64g of peroxide can remove 1g of SO2, or to remove 10mg/L SO2 requires (34/64)*(10mg/L / 1000 mg/g) g/L H2O2. If you have a 30%w/v peroxide solution divide the g of H2O2 required by 0.3 to get mL required, or by 0.5 if you have a 50% solution. Generally, mL H2O2 = mg/L SO2 * 34/64000 * vol (L) / (%H2O2 soln/100). Add it very slowly with thorough mixing - remember it reacts with the molecular SO2 form which is present in very low concentrations, and so the SO2 equilibrium must be continually re-established as it is consumed in reaction with H2O2. If there is no free SO2, don't expect the total SO2 to drop!!

Adjusting to a pH:

Get 100mL of the wine or juice, and a 10% solution of the acid you will be using (eg 10g of H2Ta made up to 100mL with water in a volumetric flask). Put the pH probe in the sample with a magnetic stirrer, and with a 2mL graduated pipette titrate the acid solution into the sample until the desired pH is reached. Every mL of solution used equates to 1 g/L of the acid. If you are using something illegal like H2SO4, I suggest the same method, but make a 10% solution by pipetting 10mL of the acid into a 100mL volumetric flask and making it up to the mark with water.

What will my TA be after cold Stabilising:

Filter, and if necessary make a range of acid additions to samples, then stabilise them in the lab as you usually do for a cold stability test. Taste the samples and measure the cold stable TA and pH so that you know for sure what acid adjustment is best before cold stabilising.

Should I add Malic acid?:

1g/L of malic acid increases TA by 1.12g/L when expressed as tartaric acid. The taste is a bit harder and tarter than for tartaric, but malic is much cheaper. Up to 1g/L max. may be OK, but be aware that because of the fairly high pKa's of malic acid compared to tartaric, the effect on pH will not be nearly as significant, and if lowering of pH is the main goal, then malic is a waste of time. If a wine has more than 4g/L malic acid as an maximum, it will taste hard. Note also that when you buy commercial malic acid it is a 50/50 mix of L-malic anf D-malic acid, and if this is added to a wine that subsequently undergoes MLF, then half of the added malic (the D-malic half) will remain, unmetabolised. If you are monitoring MLF by paper chromatography this will always show up if the concentration is greater than about 0.2g/L. I wouldn't add malic to a red wine at any stage but that's just me. Sometimes adding malic may be a good thing to do. If you are making reds in a warm to hot climate, and you are picking with very low malics and the wine will be doing malo, then adding up to 4g/L of malic rather than just adding tartaric is a good thing. In this case the L-malic will be converted to the much softer lactic acid and the palate will be rounder and softer than if there was only a small amount of lactic and a lot of added tartaric - ie the balance in the final wine would be better.

How can I remove malic acid by chemical de-acidification?:

Typically high TA high pH musts have high malic acid levels, and double-salt deacidification is not good at removing malic acid in these musts. In order to remove malic and tartaric acid with calcium carbonate as a double salt, the malic and tartaric acids must be present in at least a 1:1 ratio. Therefore it is necessary to measure the malic acid level, and the tartaric acid level also if possible. Multiply the malic acid concentration by 1.12 to express it as tartaric acid equivalent (TA equivalent), then using this malic concentration, calculate the amount of CaCO3 required CaCO3 = Malic reduction x 2 x 0.67 (g/L)

Note: malic reduction is the amount of malic to remove, expressed as tartaric acid equivalent ie malic (g/L) x 1.12

the Volume to be treated is (Malic Reduction)/(Total MalicAcid) x Total Volume L

malic reduction and total malic acid are expressed as tartaric equivalents, as before

the amount of Tartaric to add = Volume to be treated x (Total Malic-Tartaric)

Tartaric should be added to the treatment volume before the CaCO3, and the juice should be added to the chalk. The pH should be maintained above 4.5, and formation of the double salt crystals should be checked under a microscope. The juice can be RDV filtered at the completion of the operation. So it's not easy, and it's not cheap, but it can be achieved. For a handy excel spreadsheet that summarises your deacidification options, click here.

Fining and fining trials?:

For red wines, over 90% of the time you will probably go for egg whites. Free range organic is best. Rates are generally anything from 0.5-5 whites per barrique (225L), or 0.1 g/L frozen egg white = 1 egg/ barrique. Gelatin may be an alternative in some cases - try Lafforte No. 1 Extra.

For clean white wines the best is isinglass at a rate between 2 and 15mg/L (usually 1-5mg/L), and this may be used with a silica-sol as a co-fining. Isinglass is difficult to dissolve, but use cold water as warm water causes denaturing and partial hydrolysis of the proteins and a reduction in effectiveness, and don't go for more than a 6% solution when you make it up - but the best bet is to actually follow the manufacturer's instructions.Get an electric drill with a stirrer! Most products have good instructions though, so read them. There are some liquid isnglass preparations available. Isinglass gives good clarification, and tends to give quite bright fruit and a smooth, round palate, but you may find you lose something from the nose.

For less clean, or older, more coloured whites, try casein or skim milk. Rates for casein would usually be between 10 and 50mg/L. The fining should be added very slowly through the mixing pump. The casein flocculates and precipitates as soon as it comes into contact with the acid enivronment of the wine, so slow addition and thorough mixing are essential. This property also means that over-fining (leaving residual unstable protein in solution) is not possible with milk/casein. This fining can also be very good for whites such as Gewurtztramiener that are often given skin contact.

For really rough whites, try gelatine (0.02-0.1g/L for a start), and use a silica-sol co-fining. Usually using 3 to 6 mL of 30%w/v silica-sol per gram of protein fining (gelatin in this case) is a good guide - trial it!

For juices that won't settle ie due to rot, people generally go for either Bentonite at 0.2-0.4 g/L (careful as this will slow down lees filtering), or a gelatine/silica sol fining (try 0.03-0.05 g/L gelatin for a start with 3-6mL (or even up to 10ml) silica sol for every gram of gelatin). Also make sure all of your other settling factors like solids generation in pomace handling, SO2 levels,enzymes, hygiene, cooling, settling time, convection currents etc are OK. Otherwise, do a lot of filtering!

To clarify whites after ferment, trial bentonite and isinglass together, adding the bentonite first to react with the proteins, then the isinglass acts as a co-fining to improve clarity. Sometimes reds coming out of barrel fail to clarify well (probably Pinot is the would have this problem more often than other reds). The best option to trial is Laffort No1 Extra Gelatine (about 50mg/L) with bentonite (about 100mg/L). Also look under the microscope, and if it looks like a high bacterial load might be the problem, trial lysozyme.

What is a good yeast for Sauvignon Blanc?:

VL3 is a good way to go (Laffort), R2 can also be good (Maurivin), and maybe try C19 (Leuvuline). VL3 can get quite stinky, but it has cysteine lyase enzyme activities that work to release specific Sauvgnon Blanc mercaptan based aroma compounds (notably 4-methyl-4-mercapto-2-pentanone which has aromas of cat urine, box tree/blackcurrant and broom). It tends to ferment quite fast in the first part of the ferment, but may slow down a lot in the second part - be careful about nutrient levels and temperatures! VL1 will release 3-mercaptohexan-1-ol which has passionfruit/grapefruit aromas. 90% of the precursor for this compound is found in the skins of Sauvgnon blanc. These yeasts for aromatic varieties are frequently selected because they produce enzymes that can produce or release flavour/aroma compounds from precursors that are often bound to glycosides or cysteine. To get the benefit of these enzymes, the temperature should be high enough (above 16 °C) for as long as possible, and fermentation with bentonite is likely to negate many of the benefits of these yeasts and the enzymes they produce. Also note that being sulphur-based aroma volatiles, copper addition, especially in conjunction with ascorbic, can lower the impact of the thiol based aroma compounds.

Is 'indigenous yeast' a good idea?:

Can be, but look at the big picture. Yeasts existing on the grape skins are likely to be be mostly Kloeckera, Hanseniaspora, Hansenula, Candida and Metschnikowia, depending on various environmental factors and spray programmes. Saccharomyces is unlikely to be present unless winery wastes are routinely spread in the vineyard from year to year. Saccharomyces will, however establish a population in the winery on equipment, in the building, in barrels, etc. Most of the vineyard yeasts will not survive beyond about 4% alcohol. Be aware of the pH, and the temperature and SO2 regime you chose, as these factors will affect the mix of flora that you start with. For example, yeasts such as Kloeckera and Candida have greater tolerance to low temperatures than Saccharomyces. Most of the VA forming yeasts are sensitive to even quite low levels of free SO2 whereas the apiculate yeasts are quite resistant, and of course lower pH's generally select more desireable microflora. Fermentation management may have to be modified as well. Monitoring the population under a microscope is a good idea. Almost certainly there will be two or more major species dominating different phases of the fermentation, but initial inoculum levels are low, so less cooling may be required, and the ferment will often go slower naturally. Despite the low inoculum, maximum cell numbers should usually be similar to in a normally seeded ferment, but obviously more cell divisions will be required. Nutrient supplementation, and aeration may be required to ensure a healthy population with sufficient survival factors. Highly clarified musts are not good candidates for natural fermentations. If the ferment starts with Kloeckera (which is very likely) the must can quickly become thiamine deficient for Saccharomyces as Kloeckera is particularly efficient at stripping juice of this vital nutrient. One common approach that provides a comprimise is to use a low inoculum (eg 50mg/L) of a selected yeast strain rather than 150-200mg/L recommended by the ADY manufacturers. Similarly with reds, some people wait until the cap starts to rise naturally before inoculating at a normal or reduced level. Because of the longer lag phase for natural ferments, some extra care should be taken with reds as conditions in the cap can be ideal for the growth of acetobacter (ie aerobic), but regularly wetting the cap, or provding good CO2 cover (from and adjacent ferment maybe?) should control this. For whites, be prepared for 4-7 days lag period before much happens, and a ferment that may last two months. Well managed natural ferments should generally go to dryness.

Does air get into a barrel through the staves?:

No. Not unless there is significant ullage so that the wood at the top dries out. Then you're really in trouble. Read Singleton 1995, AJEV. There will an air/wine interface at some point inside the stave where reactions will occur, but these reactions are highly unlikely to affect the bulk wine.

Diagnosing and Removing Reduced Sulphide Taints :

Never bottle a wine without first doing a copper trial on the blend!!! The best thing I've seen for fixing bad sulphide taints is a very cheap kit supplied by Pacific Rim Oenology in New Zealand, or The Wine Lab in the US. It is a very simple kit for doing the trials described by Zoecklein et al.(Wine Analysis and production 1995) that contains cadmium sulphate solution, copper sulphate solution, ascorbic acid solution, and also deodorising carbon. Most importantly it contains excellent documentation by Lisa Van de Water on the origins, characteristics, lab trials and practical cellar treatments relating to sulphides, mercaptans, and disulphides, and it is more thorough and complete than the Zoecklein text. Most simple H2S and mercaptan problems can be easily treated by copper treatment, but the more complex compounds are more of a problem, and they can make a wine smell like rotten cabage, coffee, sewage, burnt rubber and other various nasties. The lab procedure is described in Zoceklein, but the principle for diagnosing the presence of disulphides is to add ascorbic acid to the trial and leave it for a few minutes, then add copper sulphate solution. Ascorbic acid acts to lower the redox potential sufficiently to reduce the disulphides back to mercaptans, that can then be effectively removed by copper. In the cellar it is important to ensure there is at least 0.5mg/L molecular SO2 present in the wine before adding ascorbic acid, and ascorbic must be added before any copper. Because the reaction of disulphides to mercaptans is slow, the tank must be left 3-7 days after ascorbic addition before copper is added. In cases requiring ascorbic, a subsequent trial will have to be performed with low rate of deodorising carbon (0.02-0.08g/L) to remove any traces of sulphide complexes. The experience of Pacific Rim has shown that this step is crucial, as if it is omitted, the disulphides always return eventually. Carbon must be removed from the wine within one or two weeks by filtration or it will promote oxidation. This is a very brief glimpse at the kinds of details in the documentation supplied by Pacific Rim. If you have a serious sulphide problem I strongly recommend you get in touch with Pacific Rim for some detailed assistance, as done properly, quite impressive rescues can be performed. I would write more, but I don't have permission to reproduce the Pacific Rim documentation (I better ask, huh!).

Note when adding copper, the legal maximum is 1mg/L Cu++, but any addition of more than 0.5mg/L should be considered very high (and in fact, illegal in the US), and there is a risk of haze formation. If haze formation is a concern, add 0.1g/L citric acid as a chelationg agent.

How do I use Silver to get rid of Mercaptan?:

This is legal in some countries, and can be better than copper for removal of reduced/organic sulphur compounds, but really, read the previous section first. Silver ions can be used in the same range as that for copper ions, but usually less should be required (up to 1mg/L absolute maximum, but don't get it wrong!). The silver is used as Silver Nitrate and dissloved in distilled water, but immediately before addition to the tank it must be mixed with an excess of sodium chloride (uniodised salt) to produce silver chloride. This makes a milky looking solution that darkens rapidly upon exposure to light. Add this solution slowly to the tank with thorough mixing. Note that silver nitrate must not come into contact with your skin as it is Poisonous!!! Dissolve it in distilled water as town supply water often has chlorine added, and don't use iodised salt or you'll make silver iodide.

What do the different forms of Sulphur do?:

As you know when SO2 is added to a wine it exists in a pH dependent equilibrium between the molecular SO2 form, the HSO3-bisulphite form (both free SO2) and a tiny amout is present in the sulphite form SO3= form. The molecular form is the form primarliy responsible for anti-microbial activity, and it is estimated that this form should be present at about 0.825mg/L to prevent yeast growth. At pH 3.2 this equates to a Free SO2 of about 23. At pH 3.8, a Free SO2 of about 90 is required to give 0.825mg/L molecular SO2. This form is also responsible for the rapid reaction with H2O2 formed by chemical oxidation of phenols., and can thereby act as an anti-oxidant. (Click here for an Excel spreadsheet to convert between free and molecular SO2 as a function of pH.)

The bisulphite form is the predominant form in the range of wine and juice pH's. It is responsible for inactivation of PPO enzymes in juice (total addition of 50mg/L SO2 can reduce PPO activity by over 90%), it is an effective extractive agent for anthocyanins from red grapes, but bleaches them to a colourless form, and slows their polymerisation reactions with other phenols. It binds strongly with acetaldehyde that is formed by the oxidation of ethanol in wines, thereby making them appear fresher, and it binds with brown quinones or reduces them back to phenols, reducing browning in wines. The bisulphite addition products (especially with acetaldehyde) are mainly responsible for the bound SO2 fraction in wines. These products may have some anti-bacterial activity towards certain LAB, and some LAB that metabolise acetaldehyde and consequently release molecular SO2 can be inhibited or killed by bound SO2.

SO2 does not react with oxygen except in it's sulphite form. However, at wine pH this form is practically non-exisitant, and therefore oxygen consumption by SO2 in wines is also very minor and very slow. The reaction of molecular SO2 with H2O2 is the real anti-oxidation reaction of SO2 in wines, however this reaction is several times slower than the reaction of H2O2 with ethanol in model solutions. It does obviously occur in wines however, as free SO2 can successfully and predictably be removed by adding H2O2, and by maintaining free SO2 above about 10ppm, it is observed that wines do not become aldehydic. Most acetaldhyde that is formed by the reaction of H2O2 with di-hydroxyphenols will be bound by the abundant bisulphite form, so we don't notice the effects of oxidation. In juice, the main anti-oxidant activity of SO2 comes from the inactivation of PPO enzymes by the bisulphite form, and binding and/or reduction of brown quinones by the bisulphate form.

Hyperoxidation - How do I get it right?:

Look for the review by Schneider in the AJEV 1998, pp65-73. Hyperoxidation can be a very good idea for certain styles and situations, but the literature has contained mixed reports on how to do it and whether the results are worth it. Variations in O2 required and results achieved between musts are due to natural variations in PPO enzyme concentrations, pH, temperature, flavonoid and non-flavonoid phenol concentrations and glutathioene concentrations. Essentially you are seeking to use the natural PPO enzymes from the grape to rapidly oxidise the flavonoid phenols so that they can be precipitated as quinone polymers. To achieve this, no SO2 should be used, the juice should not be racked or clarified and no bentonite should be added. Any of these actions would reduce the PPO activity in the juice. Oxygen either as pure O2 (don't light a match near it!) or as filtered compressed air can be sparged into the juice in-line through a fine, sintered diffuser while either transferring or mixing the tank. In this case about 20-30mg/L O2 is required (density of oxygen is about 1.4 mg/mL, depending on temperature) so about 15-22 mL/L O2 is required). It is also possible to put the diffuser in the tank while it is mixing, and wait until degassing is seen at the surface - this means the juice is saturated (if pure O2 is used, not if air is used). Leave the tank for a half hour then do the same again - flavonoid phenol levels should be reduced to about zero after this. Don't be distressed if your juice is black! Now at least 2 hours will be required before further processing. It is important that the unsulphited juice be clarified by some means (settling and racking is OK) to less than 1% solids by weight to eliminate the precipitate. If SO2 is added or fermentation begun without proper clarification, the precipitate can be re-dissolved and reduced back to phenols, hence the process undone! If necessary for microbial reasons, SO2 can be added after clarification.

Alternatives to hyperoxidation may include whole bunch pressing, fining (of juice or added to the ferment) with PVPP or a protein such as gelatin, isinglass or casein, depending on your situation. Each processing technology has its trade-offs.

How do I reduce the amount of solids in my juice?:

From a drainer tank, don't start draining until the tank is full, and even then leaving it a while before starting to drain can help (four + hours is best, but then skin contact in the style is an issue), then drain slowly! Drain no faster than 3000L/hr for low solids. From a press, if possible apply the same rules, also do not roll the press while filling! Rolling the press is one of the worst things you can do, press programs should also have as little rolling as possible. Don't overfill the press either. The trade-off is smaller pressloads and longer processing time, but the benifit is lower juice lees volumes, and therefore reduced losses and downstream processing. If you want to try a higher solids ferment as a style tool, try not using pectinase enzymes, and ferment the cloudy juice.

Managing Methoxypyrazines in reds:

Excessive vegetal characters due to methoxypyrazines in Cabernet and Merlot wines can be a problem, especially in cooler areas. Obviously the place to get it right is in the vineyard, but if the fruit has to come in with green flavours you have to do your best to manage it. Certainly, fully destem the fruit. The skins contain a lot of the methoxypyrazines, but they also contain all the anthocyanins and a certain amount of flavonoid phenols that we want in the wine. I would probably opt to get the ferment up to temperature as soon as possible rather than cold soak (anyone got experience here?) and ferment at a reasonably high temperature (around 28°C) to blow off and break down as much as possible of the methoxyprazines. I think it is always important to work the cap hard and maximise transfer of phenols to the wine, so I wouldn't cut back on cap work or skin contact time, but I would try to minimise mechanical tearing and degrading of skins. It is definately worth getting in at least one aerative pumpover per day (one where air actually goes in as opposed to just CO2 coming out) so that some of the methoxyprazines might fall victim to oxidation reactions of one sort or another. Depending on style etc, it may be worth fermenting with oak chips (eg up to 2g/L Am Med+ Innerstave) mixed in with the cap, as this can help hide the greenness a bit. I haven't heard of any yeast strain that can influence the flavour/aroma profile of a red wine sufficiently to be of particular benefit to green fruit (but someone else may have?). It may be worth trying a Sauvignon Blanc yeast like VL3 and comparing this your trraditional red yeast on high methoxypyrazine fruit - it won't change the methoxypryrazines, but may help promote other aromas such as box wood/blackcurrant more. Extended post fermentation maceration may only serve to make things greener, and thus should be only used on ripe fruit. Likewise, pressings should also be kept separate as these will probably also be down the greener end of the flavour spectrum. If you can keep the wine warm (up to 26°C is no problem) for a couple of weeks after ferment while malo goes through (inoculate if necessary), preferably in barrels or on some form of oak (unless you already put lots of chips in the ferment of course), things should look a little better. From here on in I don't there's much else you can do except for possibly trial micro-oxygenation if you have the gear. Large scale air contact after ferment is unlikely to be of any benfit to the wine!

It's a Hell Year with loads of Bot. What do I do?:

Swear, and get everything in before it gets worse! Sort things out in the vineyards as far as possible, but there will always be some dirty fruit to deal with. For whites, obviously pasteurisation of the must is the best treatment for laccase, but for many winemakers this is not possible. The main things are to minimise skin contact, and get the juice as clean as possible. Draining and pressing can be very difficult, and screens can block. I don't know any good cure for this, just go slowly and carefully, and using enzymes that have some hemicellulase, cellulase and glucanase activity may help. Ascorbic additions won't be especially helpful if there is laccase activity, as it is a substrate for laccase. Temperatures must be kept low, and air excluded as much as possible if you are trying to fight oxidation.. For settling, a lot of people add bentonite - maybe 0.4 g/L depending how bad things are, or casein or skim milk, or do a trial to get a good rate for gelatine/silica sol. Filtering the juice is a good option if possible. All sorts of yeast and bacteria may be present on the mouldy grapes, and this can be dealt with by keeping SO2 up, temperature down, juice clean, and inoculating with a strong selected culture. The other problem that will raise it's head is oxidation by laccase. A good starting point is to do a lab trial to estimate the extent of laccase activity.in the juice (see Zoecklein et al Wine Analysis and Production 1995) - there is a kit available for this, but a spectrophotometer is required. And then to remember that the substrates for oxidation by laccase are phenols and oxygen. Phenols must be kept low, and although I haven't heard of people doing it, I would not exclude hyperoxidation as a possible strategy for some styles - provided wild fermentation can be kept in check and the juice can be well clarified at the end of the treatment. It is recommended to at least process without SO2 and allowing air contact to allow the laccase to consume much of the phenolic substrates, thereby protecting the wine later in its life. In this case add SO2 when racking clear juice to control the high populations of bacteria and yeasts that will have certainly established themselves on the mouldy fruit. Minimising skin contact and maceration, low temperatures, gentle handling, keeping fractions separate, and using appropriate finings on the fractions are main strategies for minimising phenols. Oxygen exclusion is usually by diligent use of inert gases - as cover and sparging, and by careful execution of jobs in the cellar. Laccase is very difficult to inactivate or remove except by HTST treatment. As you can all of the treatments may lower quality, by so will gray slimy rot and laccase, so the best compromise must be reached. At ferment time, do add nutrients, as the must is likely to be low in nitrogen and nutrients.

For reds it is trickier, because we want good extraction for quality wine, but the wine should usually be pressed early to minimise laccase extraction and rot characters. This is still assuming pasteurising facilities are not available. I would recommend getting the ferment up to temperature as soon as possible and working the cap reasonably hard, depending how nasty the rot is! Definately add plenty of tannins at the crusher - they have great antiseptic properties, and will help to make up for some of the structure that you won't be able to extract, and help to stabilise the colour a bit. Some people also put a low rate of bentonite into the ferment. Fermenting with lots of chips (2g/L+) can be a good idea too. Don't leave the wines on skins any longer than necessary, and you may consider re-using the healthy skins from any clean batches with juice/ferments/or wine from bot affected batches. These wines should also be cleaned from their lees quite early on. If you can do it, careful bunch selection in the vineyard and/or winery is tour best bet to make at least some good wine. If laccase is present, the best idea is to get the wine pasteurised when it is dry after being pressed, then inoculate for malo.

Rotory Fermenters?:

Yeah, sure, but I'd have a look at tipping tanks too. Check these babies out, made in 10 to 90 tonne capacities: www.taylormadenz.com/sl/tippingtanks.htm They can be used as very efficient white drainers, and red fermenters. The marc is easily tipped into the press after draining. Reds need to be pumped over. They might not be so good for some existing set-ups, but then rotary fermenters aren't always the best fit either. These are best if they can be in rows either side of a press that can move up and down the row on rails.

I've got some dodgey old wine left over from last year...

what can I do with it? Referment it with some juice from this year if possible to freshen it up. The yeast will metabolise the aldehydes etc. Depending on quality, style, and the amount, you can generally add a couple of percent of old wine to a ferment without noticing any negative effects at all. I don't know much about fermenting large amounts of old wine with small amounts of juice... Some people just do a yeast fining on old whites - take fresh yeast lees from a very recently finished ferment, and put them into the old wine to freshen it.

Do anthocyanins affect mouthfeel?

Anthocyanins are not reported to be tannic or bitter themselves, however it is useful to understand their role in shaping mouthfeel by their inclusion in polymers. As the tannin polymers grow by direct condensation and acetaldehyde mediated polymerisation they generally become less astringent and more hydrophobic, until they eventually reach a size where they precipitate out of solution. When anthocyanins join these tannin molecules, they effectively form terminal units, preventing further polymerisation at whichever carbon they bind at (C4,C6 or C8). By preventing the degree of polymerisation from increasing too much, and by including the anthocyanin's hydrophillic glucose moiety in the polymer, the prospects of the larger, more 'supple' tannins staying in solution and contributing positively to mouthfeel are greatly enhanced.

Got a spreadsheet for adjusting my reds when the grapes come in?

Yep. This is good for adjusting skin:juice ratio, sugar levels, and helps with pH adjustment. Click Here for an Excel spreadsheet for adjusting red musts.