Views:8517 Author:Site Editor Publish Time: 2020-12-24 Origin:Site
During brewing, wort boiling is a complex process of physical and chemical changes. These changes are complex and difficult to take into account all the favorable conditions at the same time. To a large extent, it needs to be mastered according to the type of products and operating experience.Now let's go and learn about wort boiling.
First of all, do you know why the wort is boiled?
01 enzyme inactivation
In order to maintain the consistency of wort composition and fermentation, the function of amylase should be stopped and the proportion of fermentable sugar and dextrin in wort should be stabilized.
02 Wort sterilization
By boiling, eliminate all kinds of fungi in wort, especially lactobacillus, avoid spoilage during fermentation, so as to ensure the quality of the final product.
03 Protein denaturation and flocculation precipitation
During the boiling process, some proteins which are denatured by heat and flocculated by binding with tannins are precipitated to improve the abiotic stability of beer.
04 Evaporated water
To vaporize excess water in the wort mixture so that the wort is concentrated to the desired concentration.
Malt uesed for Brewing
01 lowers the pH of the wort
When wort is boiled, the pH value of wort is further reduced due to the addition of hops, the formation of acidic melanin and the acidifying effect of calcium and magnesium ions in water, etc., which promotes the precipitation of B-globulin in wort and the decrease of pH value of finished beer, which is beneficial to the biological stability and non-biological stability of beer.
02 Formation of reducing substances
In the boiling process, wort color gradually deepened, formed some complex components of reducing substances, such as reducing ketone, enhanced the antioxidant ability of wort, these substances have a great effect on maintaining the beer flavor stability and non-biological stability
03 Evaporation of undesirable volatile components
During the boiling process, some of the original and newly formed vapour-volatile components of the wort are steamed, including some of the unsavory hydrocarbons in the hop oil, such as geronene.
01 Wort boiling time
Determine the wort boiling time, according to the wort boiling intensity, master the wort mixing concentration, so as to achieve the final required wort concentration in the prescribed boiling time.
The wort boiling time has a great influence on the beer properties. Under normal pressure, the boiling time of light beer (10%~12%) is generally controlled at 1.5~2h, and the thick beer can be appropriately extended. When boiling under pressure of 0.11~0.12MPa, the time can be reduced by half.
Reasonable prolongation of boiling time is beneficial to protein solidification, hop utilization and reduction of substance formation, but not to foam performance.
Excessive extension of boiling time, not only economic unreasonable, wort quality will also decline. For example: wort color, rough taste, reduced bitterness, poor foam, etc., for light beer, the impact is more serious.
Relationship between wort boiling time and concentration:
More than 14
02 Wort boiling strength
When the wort is boiling, the water evaporated per hour is equivalent to the percentage of mixed wort, namely the boiling intensity: the boiling intensity is closely related to the thermal conductivity of the boiling pot, modeling, heating area, steam pressure, wort evaporation area, boiling method, etc.
Valuation of wort boiling strength:
The intensity of wort（%/h）
The intensity of wort（%/h）
At the same boiling time and pH, the boiling intensity is the determinant of how well the protein sets. Different boiling intensity, different transparency of wort, different amount of coagulate nitrogen, but too high boiling intensity has no good effect.
Relationship between boiling strength and solidification Nitrogen content in wort:
Appearance of wort after boiling
Coagulated nitrogen content 12% wort mg/100ml
Wort is not clear enough, protein condensation poor
The wort is clear, and the protein coagulates are precipitated as elements
Wort is clear and transparent, protein coagulant is flocculent, grain size is large, precipitation is quick
Wort clear and transparent, protein condensation, large particles, rapid precipitation
03 PH value
PH value is closely related to protein coagulation, color and flavor of wort.
The protein in wort is most unstable at its isoelectric point and is easy to coagulate and precipitate. The isoelectric points of various proteins in wort are different, therefore, they are precipitated first and then at different pH values. The ideal pH for wort boiling is 5.2, but this is difficult to achieve under normal conditions and even more difficult to achieve with hard water saccharification. Generally can be in the beginning of saccharification or wort boiling, take the way of acidification, make its pH value lower. With a pH of 5.2~5.6, proteins can generally achieve a good degree of coagulation. The better the protein condensation, the better the non-biological stability of beer.
The interaction between polyphenols and proteins is also an important aspect of protein condensation and precipitation. The lower the pH value of boiled wort, the more readily the polyphenols such as tannins and anthocyanins react with proteins to precipitate, thus reducing the color of wort, improving the taste of beer, and increasing the non-biological stability of beer.
A lower pH value, while favorable for protein condensation, is unfavorable for the isomerization of -acid in hops, thus reducing the utilization of hops.It is ideal to have the wort's pH value in the range of 5.2~5.4 when boiling.
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