Why is my beer hazy?

Unless you’re making a wheat beer or a NEIPA, generally, clear beer is what you’re after. A lot of forums and internet advice talk about sure-fire ways to remove hazes and when they fail, brewers can reach their wit’s end. Here, I’m going to describe the root causes of haze and how to reduce it.

Proteins

Proteins give both body and foam to beer, but the ones involved in haze aren’t the ones involved in foam. (There is an exception to this, which I’ll discuss later). Proteins involved contain a high levels of an imino acid (not amino) called proline. This is important because it’s one of the amino acids that yeast don’t need and don’t take up, meaning that there are a lot of these proteins that hang around.

Polyphenols

These guys are pretty complex, so hang on and I’ll try and make it as user friendly as possible. These will come from both malt and hops and they aren’t all bad. Only about 10% of them are an issue and that’s the flavonoid groups and even then, only 30% will double up to become dimers and trimers. These are a problem because they have two or more OH ends that react to these proline rich proteins. During mashing and boiling they will polymerise through oxidation and become reactive to proline. At this point, they are referred to as tannins and should probably be referred to as such in the literature, but “polyphenols” seems to have stuck.

Polysaccharides

The first two are fairly well-known and many products exist to remove one or the other, which I’ll discuss later. Polysaccharides, however, is not as well known, mostly because it tends to be much more of a home brewer (or inexperienced brewer) problem, but a problem nonetheless. There are no products that exist to get rid of them once they exist in your beer. There are a few subclasses of them, so let’s get to it:

  1. β-glucans and pentosans– these exists in all malt, though well modified malt will tend to have less of it, particularly well-modified European ale malts. They come from barley cell walls and exists in abundance in wheat and unmalted barley. A protein rest will usually take care of these, but care must be taken to avoid disturbing the mash bed. Doing so will shear the cell walls and β-glucans and pentosans will make it into your wort. Overly hot sparge water will also cause β-glucans to gelatinise and make it into your kettle
  2. α-glucans (aka starch) will become a problem if your mash rest is too short or if it is too long and is allowed to cool as it will re-gelatinise. If you’re unsure whether conversion is complete, do a quick iodine test and make sure your mash tun is well-insulated.
  3. Mannans are bits of yeast cell wall. If you’re using old, unhealthy yeast or shearing it (unlikely in a home setup as it tends to happen during centrifuging) you can end up with mannan hazes.
  4. Oxalic Acid is a big contributor to haze, as well as gushing. This happens when brewers think they’re doing the right thing by using only RO water to mimic Plzen water for those Czech Pilsners. Oxalic acid needs to be precipitated by sufficient calcium in the mash and the boil, otherwise it forms crystals that will cause haze, as well as nucleation sites which will cause gushing.

Lesser causes, but still problematic can be:

Metals

If you’re brewing with well water or you have rust somewhere in your system, especially iron or copper, it will oxidise and turn chill haze into permanent haze

Finings

Overuse of gelatin can cause haze, especially with temperature changes. Using PVPP without a filter will also cause haze as PVPP adsorbs tannins, but doesn’t precipitate them out.

Freezing

Freezing will compound haze problems. When making Eis beers, it’s important to freeze slowly to allow hazes to form and precipitate out and not become trapped in huge complexes.

Collapsed foam

Once foam proteins have been used up, they will not be able to become active again. If you’ve seen lacing on the side of a glass, you know that foam can become solid and those solids can fall back into your beer. In the glass, that’s not a problem, but when you’re transferring from fermenter to another vessel, make sure that you do so slowly enough, or under pressure, to avoid creating foam that will cause a haze in your beer.

I’ve purposefully left out a lot of other haze causes because they generally do not affect the home brewer – specifically lubricants, machine oils, isomerised hop products, silica gels and PGA foam stabilisers. However, if you’re having haze problems this can be a good place to start. Now lets get into finings.

Available to the enthusiast are a handful of options and they will target protein, polyphenols or yeast, but nothing else – those have to be solved via optimisation of your process.

  • Gelatin and isinglass: These target yeast cells and will precipitate them fairly quickly. They aren’t vegetarian, so you may need to take that into consideration. Silica hydrogels are a replacement for these and they work very well, but generally aren’t available to the home brewer. Gelatin does not work as well as isinglass and the stuff you buy at the grocery store isn’t as high in collagen as gelatin made specifically for brewers.
  • PVPP and Gallotannic acid (Brewtan B) target polyphenols. PVPP isn’t suitable for use without a filter whereas gallotannic acid will precipitate polyphenols.
  • Combination products, such as BrewBrite will precipitate both as it’s a mixture of PVPP and carrageenan will work without a filter. It has a narrow temperature range and will not work once frozen.
  • Proline-specific enzymes (Brewers Clarex, Clarity Ferm) These are enzymes that hydrolise proline containing proteins. Although it’s specific to proline, overuse can cause foam stability issues. It has the added advantage of reducing gluten to 10ppm which considered “gluten reduced” or even “gluten free” for most health agencies. It’s usually suitable for people who have gluten sensitivities, but not for celiacs or people who are allergic to gluten.

While filters exist for home brewers, they don’t work particularly well for what home brewers use them for, which is getting clear beer. Breweries will filter to polish a beer that a home brewer would consider already clear in order to make it more shelf stable. DE filters may be used before that, but that’s usually considered “rough” filtration and involves expensive and difficult to handle materials at a small scale. I don’t recommend buying home brew filters because they’re not designed for rough and fine filtration, even the dual ones. They will clog quickly or you will require multiple filter runs, increasing the risk of oxidation. Concentrate on process to eliminate polysaccharide haze and judiciously use finings for the rest.