Tannin I think is often misunderstood in fruit wines. Feared even. It is often talked of in terms of minimising tannin levels as if it should be totally removed from wine and wine making altogether. Often tannin it is actually added either as a pure additive, as tea or in oak chips when it is ageing. Oak chips provide “hydrolyzable tannins” that provide greater mouth feel with a softer taste to the harsher “condensed tannins” that are present in fruit juice in low quantities and more prevalent in some fruit skins, seeds and stems.
Both red and white grape wines have tannin present but it is far more prevalent in reds as it macerates on the fruit for longer. Little tannin is extracted aqueously but as the ethanol level rises so too does the extraction of tannin. Grape wines are the basis of fruit wines as the taste template we use as a reference. Home wine makers are beholden to those norms. Sadly not all fruit has the same characteristics of grapes so adding or managing tannin becomes important to replicate the balance between sweet, acidic sour and bitter tannin tastes of grape wines.
White fruit wine ingredients vary in tannin content. Elderflowers for example need tea added as the petals are naturally low in tannin. Gooseberries – the “hairy grape” has tannin present in the pips and skins so does not need any additives and I have found that pressing after an initial short maceration helps manage the tannin content to match that of a traditional white or rose wine. This is done two days into fermentation when the solids are removed, pressed then tossed away and the remaining wine happily sits in primary fermentation for a few days more.
Red fruit wines have more variance in finished tannin content due to personal preferences in taste and style as well as the initial tannin content of the fruit that makes them. Some people may want a full bodied tannic blackberry wine, a medium bodied blackcurrant or perhaps a light bodied almost rose elderberry wine made from a second run fermentation. The tannin levels vary between the base fruit but it can be managed to make the style of wine you want. Because of this tannin becomes far more about management than simply addition or removal as with a white wine.
Always plan ahead and have an idea of the wine you wish to make. Generally it is thought that high tannin content and low tasting acidity and higher alcohol content work with each other as a flavour profile. This means that an idea of the final ABV and initial sugar content derived from a hydrometer reading is useful. Fresher tasting younger style wines will need less tannin, but if you have a preference for full bodied wines, with both time and will power to age your wine more tannin can be present.
I can think of few fruit wines other than oak or walnut leaf wine and possibly some dandelion wines that use stems. Stems should always be removed from fruit as they are high in harsh tannins. This is especially so in something like elderberry or elderflower wine as the stems are toxic as well as tannic! A good eyeball and preparation of fruit will help you make a good wine.
After a style is in mind a recipe needs to match it. Blackberries have some tannin present in them and are a good example where the recipe can change the style of a wine. The berries left to themselves will create a traditional medium-bodied wine that could be drunk at nine months in age if you are very very lucky. Blackberries with a tea added will make a fuller bodied wine that will need 18 months ageing before it approaches drinkability.
Elderberries have the opposite problem and as they have a high proportion of thick skins and seeds compared to the juice they provide when crushed or pressed. When processing tannin rich fruit it is important not to break the seeds or pips as the interior has the harshest tasting tannins that could ruin a wine if extracted in large quantities. Blending in a foot processor or an extremely thorough press could crack the seeds and release it. There are several methods to control the amount of tannin extracted. Cold maceration allows an aqueous extraction of the least harsh tannins from the skins before the berries are crushed. In conjunction with removal of the fruit mid way through primary fermentation less tannin will be extracted. Pressing the fruit pre-fermentation then discarding half the skins and allowing those remaining to sit for the duration of primary fermentation could also work. This will allow the extraction of different tannins as the seeds will be exposed for far longer.
Alternatively whole elderberries could be left to ferment with months in bulk ageing to allow the tannins combine and fall out of suspension as sediment that is left behind when racking. This very much leaves it to chance. In addition or an alternative certain settling agents like gelatine or isinglass can be added to remove tannin when racked. It should be noted that tannin can also act as a natural settling agent combining with certain proteins as it ages and settling agents could interfere. Mechanical filtration though filter pads is a final way to remove tannin but that can also remove other flavour compounds… apparently… the jury is still out on that discussion.
Oaking a wine occurs neer the end of bulk aging just before bottling. This replicates the aging process in a wine barrel. Few white wines are aged in oak barrels but it is not unheard of and I may try it with my elderflower wine next year to simulate a Chardonnay style. Whites are generally unsuited to oaking with chips as the higher acidity (lower pH) conflicts with the tannin tastes. Typically less than 10g per litre of oak chips are added to either white or red wines and they can sit for a few days to three months extracting the oak flavour. A home made port is an exception as it is so rich and more than likely sweet it can with stand the high tannin extraction, ranging from 20 to 30g of oak chips added per gallon and resting for up to three months or more. Oak is not a tannin addition like tea and is not meant to provide the whole tannin content, merely to compliment it with a range of usually lighter tannins to add complexity as top notes. All oaked wines will need longer to age than an un-oaked wine of the same recipe as the tannin will gradually bind over time to create a rounded mouth feel and balanced taste.