Troubleshooting Your Wine

The faults and flaws and their analysis and resolution presented below are from my latest book, Modern Home Winemaking, where you can find additional information should you wish to explore these further.

POOR OR LIGHT COLOR IN REDS

DESCRIPTION

Red wine, even previously deeply colored, exhibits a very light color and subdued intensity.

CAUSES

If the (red) wine was already light-colored since the completion of fermentation, then there was insufficient extraction of anthocyanins during maceration and fermentation, or there was an anthocyanin deficiency due to a poor vintage, e.g., a rainy growing season.

If there was good color extraction but the wine is unexpectedly shedding color, then color was not adequately stabilized during maceration and fermentation.

Red wines also normally shed color during aging, but much more so if there is an anthocyanin–tannin imbalance. Anthocyanins are very unstable molecules and need to polymerize with tannins to become stable and exhibit their red color. If there is a large amount of anthocyanins, i.e., the wine has a deep-red color, but very little tannins, anthocyanins precipitate and wine loses some color.

Anthocyanins are also sensitive to pH; they exhibit a redder color at low pH and lose their red color as pH increases towards and beyond 4.0 — anthocyanins start becoming almost colorless. The difference in color due to pH is often very visible between free- and press-run fractions; the latter often has a higher pH due to a higher potassium content.

Blind, excessive sulfite additions too will bleach anthocyanins due to the high binding attraction between anthocyanins and SO₂.

ASSESSMENT

Color is assessed by visual inspection, naturally, but you can also taste the wine to assess its tannin profile. If the wine is richly colored but tastes unusually light and seems to lack body (due to low tannins), then the wine has an anthocyanin–tannin imbalance and is at risk of shedding some of its color during aging.

REMEDIAL ACTIONS

A simple way to restore the red color is to increase acidity, for example, by adding tartaric acid, if the wine’s acidity profile and tartrate stability status allow it; you do not want to create a taste imbalance or stability problem just to fix color. By acidifying, you are in effect lowering pH, and that causes anthocyanins to change from their more colorless form to their redder form.

Another simple way is to add cellaring tannins, particularly when there is a deficiency. Tannins stabilize color by polymerizing with anthocyanins.

If you are dealing with a variety or a poor harvest that have yielded poor color in spite of all extraction efforts, you can add exogenous anthocyanins, ideally to the must but it can also be added to wine. Commercial exogenous anthocyanins are natural dye obtained from skin extraction of red grape berries, but such products may prove to be very difficult to find.

PREVENTIVE ACTIONS

Richly colored red varietals that have had limited tannin extraction or hybrids with high protein content (which will precipitate larger amounts of essential tannins) will need an extra dose of tannins at crush and during fermentation to balance anthocyanins and stabilize color.

Before bottling, you can also add gum arabic — a protective colloid — to prevent flocculation of anthocyanins and anthocyanin complexes in young red wines meant for early consumption. It is not recommended for wines destined for aging as desirable polyphenol reactions would be inhibited; the wine can then take on a milky appearance that can affect its normal clarity.

Following are techniques to increase color extraction and improve color stability:

Destem grapes at crush; potassium-rich stems increase pH.

Run off approximately 10% of juice at crush to increase the skin-to-juice ratio to improve color in low-anthocyanin varieties, such as Pinot Noir and St. Croix.

Use macerating enzymes at crush.

Add sacrificial grape or oak tannins at crush, and do a second tannin addition to lock in color when it has peaked.

Consider doing a pre-ferment cold soak to get an extended maceration to extract more color.

Ferment at warmer temperatures in the range 25–30 °C (77–86 °F).

Increase frequency of punchdowns or consider doing pumpovers if you have a good pump; these improve polyphenol extraction and polymerization.

Supplement with inactivated yeast derivative nutrients to augment tannin-complexing polysaccharides.

Inoculate with an appropriate yeast strain suitable for the variety and desired wine style.

10.

Watch out for large acidity drops, for example, in high-malic wines during MLF, which can cause pH spikes.

11.

Coferment with a teinturier, such as Alicante Bouschet or Marquette.

12.

Coferment complementary white and red varieties, for example, Viognier with Syrah, to increase color intensity and stability, and for copigmentation to shift color towards purple.

13.

Consider adding pasteurized, crushed and destemmed grapes, such as Allgrape Pack, when making small volumes from lightly colored juice.

14.

Process free- and press-run fractions separately; blend only if similar.

15.

Consider freezing must (or buying frozen must); the freezing process ruptures grape skin cell walls and releases more anthocyanins.

16.

Use SO₂ judiciously as it can bleach anthocyanins.

Troubleshooting Your wine