Muddy 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 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, gloss, and transparency.

Beer turbidity is divided into biological turbidity and non-biological turbidity.

Biological turbidity;

1. The fermentation process contaminates other microorganisms, causing the temperature of beer death to rise
2. The Pu value of finished beer sterilization is too low, that is, the water temperature of the sterilizer is low or there are dead spots in the spray, and the yeast and contaminating 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 and do a good job of hygiene.)

Abiotic turbidity;

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. (Welcome to consult beer equipment: 18363068887)

1. Protein and polyphenol turbidity:

The protein in beer mainly comes from malt, and the proteins that cause the beer to produce turbidity are gliadin and β-globulin; the polyphenols in beer come from bark and hops, and the polyphenols that cause beer to produce 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:
1.1. 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, The turbidity formed by lumps or particle suspensions.
1.2 Cold turbidity: The beer stored at low temperature (0℃) will lose gloss and haze, but when the beer is heated to 20℃ 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 its light and the protein combines with water to form an aqueous solution.
1.3 Permanent turbidity (oxidative turbidity): After the beer is stored for a period of time, the polyphenol components anthocyanins and proteins in the beer are oxidized and polymerized to form oxidized polyphenols and polymerized proteins, respectively. These two polymers form a larger size through covalent bonds. The protein-polyphenol polymer precipitates particles from the beer, which first appears turbid, but slowly settles on the bottom of the bottle after standing still to form a thin and looser sediment, and the wine body gradually returns to clear and transparent. Turbidity is irreversible.

The solution to protein turbidity:
1. Selection of brewing materials: barley with thin skin and low protein and polyphenol content should be used, although protein affects the foam and improves the taste. Appropriate control. If the sugar is not enough, you can add some refined sugar and other auxiliary materials.
Control the appropriate degree of pulverization of raw materials to completely pulverize the wheat husks and prevent excessive polyphenols from entering the wort.
2. Control of water hardness for saccharification: carbonate hardness <5 degrees dH, non-carbonate hardness: 3-5 degrees dH, alkalinity should be small, control Fe2+, Cu2+ ions should be less than 0.5ppm, reasonable control of Ca2+, Mg2+ concentration.
3. Saccharification temperature control: protein decomposition should be appropriate, mainly to control the high, medium, and low molecular weight proteins of the wort within a reasonable range. Generally, the normal protein decomposition temperature (50°C) is used for the malt with better dissolution. Malt can be decomposed by low temperature and long-term proteolysis, and protease can be added to increase proteolysis, or it can be mixed with malt with better solubility. During the saccharification process, the wort iodine detection reaction should be strengthened to prevent the beer dextrin and polysaccharide turbidity caused by incomplete saccharification. Control the dissolution of polyphenols. The condensation of malt polyphenols and protein in the malt mash is very weak. It is not easy to remove during the filtration and boiling of the wort. The beer is brought into the beer and affects the stability of the beer. This weak reaction makes the polyphenols even during fermentation. After the pH in the liquid drops, part is separated, and the other part is precipitated due to the accelerated condensation with the protein due to oxidative sunlight after the sake is filtered. Therefore, it is necessary to control the dissolution of polyphenols during saccharification. Generally, formaldehyde is added in the saccharification process. Way.

Properly lowering the PH value of the mash can reduce the dissolution of polyphenols and also benefit the action of proteases.
4. Wort filtration: After the saccharified wort enters the filter tank, it should first stand still for 10 minutes, and then reflux until the wort is clear, and then start to filter. Control the water temperature of the spent grains at 76°C and pH 6.0-6.5. It is generally required to control the residual sugar between 1.5-2.0 to control the dissolution of polyphenols.
5. Wort boiling: When boiling, the protein in the wort is easily separated from the tannins in the hops to reduce the content of coagulable nitrogen in the wort; the boiling strength is generally required to be 8% while adjusting PH5.1-5.3, if necessary, add edible tannins, carrageenan, etc. to promote protein condensation and precipitation, and control the boiling time at 60-90 minutes.
6. Precipitation cooling: Fully remove hot coagulum and shorten the wort cooling time as much as possible.
7. Oxygenation control during fermentation: the oxygenation of wort is controlled at 6-8mg/L, the temperature of entering the tank is 8-9℃, the number of yeast in the full tank: 1.5-1.8×107/mL, so the wort Fast rise, fast acid production, and fast pH drop, which can effectively coagulate and precipitate the protein in the fermentation broth; drain the condensate for 24 or 36 hours when the tank is full, and the main fermentation temperature is 10-11°C. After the diacetyl is qualified, try your best Keep the mash calm, that is, when the temperature of the fermenter is controlled, the upper temperature is required to be equal to or slightly higher than the lower temperature to facilitate the precipitation of proteins and yeast, and to remove yeast and sediment in time to avoid yeast autolysis; it can also extend the storage time appropriately , In order to fully separate the condensed solids.
Use fresh and robust yeast to make fermentation and pH drop quickly, and promote protein-polyphenol complexes to form precipitation
8. Control the oxygen content in the wine body during the sake process to prevent the sake from oxidation.
9. Two-tank fermentation: As the yeast is redispersed in the fermentation broth during the inversion process, it is not only conducive to diacetyl reduction, but also the yeast will adsorb some phenolic substances during the precipitation process.

2. Polysaccharide turbidity:

The main manifestation is the turbidity of the beer after sterilization, and when the beer is cooled to room temperature, it reconstitutes and the wine body becomes clear and transparent. The reason is the presence of dextrin or polysaccharide crystals in beer.

3. Inorganic precipitation:

Heavy metals, silicon oxides, calcium oxalate, etc. are also factors that cause non-biological turbidity. The heavy metals in beer mainly come from water and pipeline containers. There are two reasons for the turbidity: integration with the active groups of proteins and polyphenols to form precipitates; as a catalyst to promote protein-polyphenol oxidation and turbidity. The silicon oxides or silicates in beer are mainly derived from bark, water, clarifiers, and filter aids. They form micelles during beer storage and cause siliceous precipitation. Calcium oxalate precipitation is mainly due to the reaction of Ca2+ in brewing water, wheat husks, and gypsum added in saccharification with calcium oxalate, an intermediate product of fermentation metabolism, to form precipitation.

4. Hop resin is turbid:

After sterilization, a layer of flocculent, silky brown floating particles appear on the bottle neck (commonly known as "black neck") on the beer liquid surface, which is mainly a complex of oxidized hop resin and protein.