Copied with permission from https://www.arishtam.com/product-page/aristam-homebrewing-guide and https://www.amazon.in/Arishtam-HomeBrew-Probiotics-Indias-homebrew-ebook/dp/B07WSXSCQY
hanks to photo blogging: Cloudiness and other visual flaws are the first thing people are observing. A newbie who is hesitant to taste a home-brew will be scrutinizing for visual flaws to bail out.
However, in the past, this was not the case. Until about 200 years ago, glassware was a luxury and people drank out of wooden or metal cups. As a result, people historically did not bother about the color and clarity much. Till about 15th Century, nobody even wrote about techniques to minimize haze. Prevention of vinegar formation and remedying watery ferments lacking body was the main obsession of oenologist and zymologist (wine and beer brewing scientists) of the era. Today, however, focus is on minimizing haze and sediments.
Beverages are colloidal solution which have particles floating in them due to Brownian motion. Haze or scattering of light is caused by them. Therefore, the brew master often carries a torchlight with him to measure it (Tyndall effect). Laboratories use turbidity sensors to measure them. If all these particles are removed, the brew will thin out (watery, lacking body). If all suspended particles were allowed all of them, then we might get bready notes, excessive malty tastes along with a murky drink. So, getting the right balance for the style is the key.
The easiest way to get rid of the haze is patience. Over time, most suspended particles settle down, leaving behind a clear broth. Talk to any artisanal winemaker from Europe, their heirloom recipe usually requires a year of ageing to get the right clarity. Cold crashing (keeping the fermenter at 4oC for a day or two) slows down the particle velocity and helps accelerate the natural sedimentation process. Industrially, a centrifuge removes these particles. At home (often just before a competition), I keep sealed plastic bottles in the washing machine to centrifuge out the haze.
A more scientific analysis involves root causing the nature of the floating haze and then remedying them.
Yeast: It is usually accompanied with bready taste. Most common in beers, as they are not aged but can be detected in young wines too. One can dissolve a teaspoon of gelatin in half a cup of warm water and pour it in the beer (or wine) and cold crash (store at 4OC for 24-48 hours). Gelatin causes the yeast cells to bind together and accelerates sedimentation.
Pectin: It is the binding substance which keeps the cells of the fruits together. Wine makers use pectinase enzyme (0.01 to 0.04gm per liter) to break cell wall down. The easiest way to test Pectin haze is by taking a few drops of must (fruit juice) or wine and pour them in 90% isopropyl alcohol glass. Pectin will form a gel at the bottom of the glass. Please do not confuse pectinase enzyme with pectin that is added in jams and jellies to make it thick.
Chill haze: As the name suggests, certain beers (and few young meads and fruit wines) become turbid at low temperatures only. This is because of long chain proteins in the final beer which coagulate at low temperatures. Tannins and polyphenols (from husk and hops) also precipitate at low temperatures. Altering the protein rest (breaking down long chain proteins) in the wort is what home brewers can do to avoid this haze. A proper whirlpool and trub separation in the kettle also helps. Use of kettle fining agents like carrageen, Irish moss along with a long rolling boil in the mash kettle helps in removing this problem.
Starch haze: The easiest way to detect this is pouring a few drops of tincture iodine in the beer. Certain fruit wines (especially banana and pineapple also have shown starch residue). Use of amylase enzymes in fruit wines and proper mashing technique in beers is remedies them.
Oxidation: Tannin in wines and protein in beers oxidizes on contact with oxygen. This oxidation is accompanied with many other faults/ problems (for more details read chapter on oxidation).
Tannins: They are also called as wine proteins. Although most wines lack adequate tannins and hence wine makers need to add them additionally for color, some of the natural tannins are attributed to haze. Beer makers use kettle fining agents to manage protein levels, wine makers use egg white (0.07gm/L) in red wine or Casein (0.5gm/L) to white wines to reduce the brown tint and bitterness. Industrial Beer brewers, use of silica gel (0.3gm/L) is used to remove the protein and PVPP (0.5gm/L) for the tannins.
Refermentation: Turbidity due to inadequate pasteurization or preservatives in wines cause this. As a result, the yeast/ microbes start fermenting the residual sugar in back-sweeten wines. This will increase the alcohol content, reduce the sweetness and cause turbidity because of suspended yeast. Proper sterilization of bottles (especially for sweet wines) and use of potassium sorbate helps overcoming this problem. Another technique is making port wine: Adding some brandy to make the wines too strong (>20%ABV) for yeast activity. Sparkling wines should be aged to clear off the refermentation turbidity.
Centrifuge and filtration is the preferred industrial technique used for clearing wines and beers today. However, filtering a cloudy liquid will only result in a clogged filter, which can be a nightmare for a hobbyist. If we are using electrical pumps, this choking of filters will cause leakage and bursting of pipe joints. (A mess to clean, could lead to oxidation exposure as well as unnecessary delays). Also in spite of the best efforts to clean, there will be some organic debris left in the filter pads which can introduce contamination. It is advisable to keep the pads soaked in spirits or food grade disinfectants when not in use to prevent mold infestation.
Electrolytic method is another preferred fining technique in wines (and certain style of American beers and lagers). Bentonite slurry removes positively charged haze particles (1/4 to 1gm per liter) and Isinglass (made from fish bladders) removes positively charged (0.01 to 0.03gms per liter). Kiesesol (1/3 ml/L).
Newer and powerful fining agents are being discovered as home brewing is gaining popularity. However, excessive use of fining agents could ruin the batch by stripping away the color and body (mouthfeel) from the wines and beers. This is probably the reason why aged and naturally cleared wines still command a premium.