Turbid beer: It is a beer that has a certain amount of […]
Turbid beer: It is a beer that has a certain amount of live yeast in the finished product and has a turbidity of 2.0 to 5.0 EBC turbidity units.
Unless the beer style requires a certain degree of turbidity (except wheat beer, turbid IPA, some dark beer), in fact, beer is still scored by color, luster, and transparency.
Beer turbidity is divided into biological turbidity and non-biological turbidity.
1. The fermentation process pollutes other microorganisms, causing the temperature of beer death to rise
2. The Pu value of the finished beer sterilization is too low, that is, the water temperature of the sterilization machine is low or there are dead spots in the spray, and the yeast and contaminated bacteria are not killed
For biological turbidity, we can completely avoid it through strict process hygiene. (If there is biological turbidity, it is very difficult to recover, that is, the beer is infected with bacteria and the beer is spoiled. Solution: Pour out the wine, do a good job of hygiene and rebuild)
The substances that cause non-biological turbidity in beer are mainly proteins, peptides, polyphenols, polysaccharides and hop resins. The main forms of turbidity include protein-polyphenol turbidity, dextrin turbidity, polysaccharide and protein-polyphenol complex precipitation, inorganic substances Precipitation, hop resin turbidity, etc.
Protein and polyphenol turbidity:
The protein in beer mainly comes from malt, and the proteins that cause beer turbidity are gliadin and β-globulin; the polyphenols in beer come from bark and hops, and the polyphenols that cause beer turbidity are mainly derived from flavan hydroxyl groups Other phenols can only be polymerized into polymers to have an effect on beer turbidity; protein and polyphenols form turbidity mainly due to the oxidation and polymerization of heavy metals. According to its different formation, it can be divided into the following situations:
True protein turbidity (sterilization turbidity): Because the pH of beer is similar to the isoelectric point of protein, and the protein content is high, the protein water film in the beer is destroyed during sterilization and heating, making it denatured and solidified, and appears flake, flocculent, and lumpy. Or the turbidity formed by suspended particles.
Cold turbidity: The beer stored at low temperature (0°C) will lose gloss and haze, but when the beer is heated to 20°C or higher, its turbidity will decrease or disappear. This is called cold turbidity or reversible turbidity. This is because there are more β-globulins and δ-gliadins in wort and beer, which form hydrogen bonds with water at a suitable temperature and are water-soluble. When the temperature is low, the hydrogen bonds combined with water break and then Polyphenols are hydrogen-bonded to form small particles and precipitate, because the hydrogen bonds formed with polyphenols are connected by weak hydrogen bonds. When the beer is heated to above 20°C, the weak hydrogen bonds are broken. At this time, the beer loses light and disappears, and the protein combines with water to form an aqueous solution.
Permanent turbidity (oxidative turbidity): After the beer is stored for a period of time, the polyphenol component anthocyanins and proteins in the beer are oxidized and polymerized to form oxidized polyphenols and polymerized proteins, respectively. These two polymers form larger proteins through covalent bonds -Polyphenol polymer particles precipitated from the beer, which appeared turbid at first, but slowly settled on the bottom of the bottle after standing still to form a thin layer of loose sediment, and the wine body gradually returned to clear and transparent, this turbidity It is irreversible.