Home made wine normally clears on its own, although it can take a long time – up to a year for some wines. However, some wines can develop a stubborn haze of tiny particles that simply refuses to clear, and your wine stays cloudy no matter how long you wait. Hazes are usually caused by pectin, starch or protein. Pectin and starch are broken down using enzymes at the start of the wine making process, whereas proteins are removed later using inexpensive substances known as ‘finings’.
What causes haze in wine making?
Most hazes are caused by one of three things: pectin, starch or protein.
Pectin is a compound present in many fruits, and is what makes home made jam set so nicely. Pectin hazes are much easier to prevent than to treat, which is why recipes for wines made from high-pectin fruits (such as plums) will always tell you to add pectolase. Pectolase is an enzyme that breaks down pectin and is best added right at the start, when the fruit is pulped. Problems occur when wine makers use older or incomplete recipes that don’t mention this. Pectin hazes can also happen unexpectedly when inexperienced wine makers decide to boil or steam-juice fruit, rather than scalding it. If you do this, adding the enzyme once things have cooled down is a good idea for all fruit.
If you suspect a pectin haze, bring the wine up to room temperature and degas it so that it doesn’t froth. Add pectolase (amount) and leave the wine for 48 hours to see if clearing has started. If not, treat with finings (below) and move to a cool place to clear.
Starch haze is common in wines made from cereal grains and root vegetables, and is likewise usually prevented by adding amylase (an enzyme that breaks starch down into sugar) at the start of the recipe. If you think you may have a starch haze, bring the wine up to room temperature and degas it before adding amylase (amount). If clearing has not started within 48 hours then treat with finings (below) and move it back to a cool place to clear.
Protein hazes are less predictable than starch and pectin hazes, and the causes are complex. They won’t clear with enzymes, so protein hazes have to be treated with finings. There are several different types on the market, but for effectiveness and ease of use you can’t beat two-stage fining gels such as Youngs Wine Finings. After making sure the wine is properly degassed and cool, the two sachets are added in order. If you already degassed before enzyme treatment, there’s no need to do it again. Sachet A (Kieselsol, a silica gel) binds to the protein, and an hour later you add sachet B (chitosan) which speeds up clearing and mops up any free Kieselsol. The wine should be clear 24 hours later, but benefits from standing for a couple of weeks to let the sediment compact, making for easier racking.
Note that chitosan is not suitable for vegans, as it is a by-product of the fishing industry (it is derived from the shells of shrimp and crabs). Bentonite, a natural clay, is a suitable alternative although it makes a notoriously ‘fluffy’ sediment that takes two rackings to remove, unless you have a supremely steady hand.
The pros and cons of fining in wine making
Fining can rapidly clear hazy wine. Even if a wine appears clear, dissolved proteins can sometimes precipitate later to form a sediment. If you practice bulk storage this isn’t a problem because you simply rack again, but if you like to bottle your wine it can really spoil the effect. However, fining wine alters its flavour slightly, particularly if you use too much.
With the exception of kit wines supplied with finings, never fine a wine that hasn’t been given a chance to clear naturally. That means at least six months in a cool place (preferably over winter) and three rackings. If that doesn’t do it, fine away!
Filtering in wine making
Don’t confuse fining with filtering, even though filter manufacturers are quite keen for you to see filtration as a natural extension of the fining process. Only wines that are already clear are suitable for filtration, and I’ll deal with it in a separate article (to follow).