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Homebrew Equipment – The Relationship Between Malt Concentration And Alcohol
2022-03-28How is the Kind Fruit Beater?
2022-04-01
Hydrogen Sulfide In Beer
Hydrogen sulfide is one of the major sulfides in beer, which has a large impact on beer flavors, and its flavor value is also lowered (5 ppm). The effect of hydrogen sulfide to beer flavor has a double effect, that is, when the trace is present, it can constitute a special style of a brewable beer flavor, and excessive excessive taste is not conducive to beer.
1, the main source of hydrogen sulfide
The sulfide in the beer, part from the raw material, may also form some volatile sulfide (mainly in hydrogen sulfide) during malt production and hydrazine, but these sulfides are in the boiling process of wheat sauce. Evaporated to remove it. Non-volatile organic sulfides contained in wheat sauce include sulfur amino acid, biotin, sulfide, and sulfur-containing protein, peptide, and the like, with a total content of about 5omg / L.
Volatile sulfides in the beer are mostly formed during the fermentation process. The metabolism of yeast on sulfide first utilizes organic sulfides, and the sulfate ions are rarely utilized in the presence of metabolic organic sulfides, as inorganic sulfur needs to be energy and nitrogen sources.
2, formation of hydrogen sulfide
- Bay on the decomposition of sulfur-containing
- Most of the hydrogen sulfide in the beer mainly comes from yeast on sulfur amino acid (semi-amino) and sulfate and sulfite and intermediate products when the yeast synthesis methionine is suppressed.
- Yeast uses sulfate formation
- After sulfate into human yeast cells, under the catalysis of ATP-sulfated enzymes, first, after three phospologic gland, after a series of enzymatic reactions, it becomes a sulfite. The sulfite is an intermediate product, further after reduction of sulfite reductase, hydrogen sulfide is formed. Methionine has inhibitory effect on ATP monase and sulfite to limit the decomposition of sulfate. Phalable acid also inhibits sulfite reductase.
- Decomposition of semi-amine formation H2S
- Most of the hydrogen sulfide in the wheat sauce from yeast to the assimilation of sulphate, and the amount containing semino is relatively small. The semi-amine was decomposed by yeast chloride, and methionine had an inhibitory effect on semi-amino deronidase, thereby affecting the decomposition of semi-amine. Most of the half of the hydrazine is cleaved when the wheat sauce is boiled, and the number remaining in the cold wheat juice is extremely small, so the decomposition of semi-amine is not hydrogen sulfide.
3, factors affecting hydrogen sulfide formation
- e hydrogenation rate of different yeast is not the same, and the hydrogenation rate of the hydrogen sulfide of the following yeast is much higher than the above yeast. A strain of hydrogen sulfide can be born by a method of mutation. At the same time, in the process of yeast metabolism, the yield of hydrogen sulfide is parallel to yeast metabolism, the higher the growth rate of yeast, and the higher the yield of hydrogen sulfide.
- Wheat component
- The pantosis can inhibit the formation of hydrogen sulfide from two aspects, first inhibiting the sulfite reductase, followed by a cofactor of methionine biosynthesis, so it can also indirectly inhibit hydrogen sulfide production. Therefore, ryptic acid should contain sufficient pantothenic acid to ensure yeast growth and the biosynthesis of methionine. However, in general, the content of pantothenic acid in wheat is sufficient.
- Wheat and saccharification should strictly prevent excessive protein decomposition, because methionine in wheat can inhibit ATP-sulfate enzymes, so that sulfate can be limited, and methionine can still restore sulfite reductase and cysteine dehydroid group Enzyme.
- Threonic acid, glycine and other amino acids can inhibit the synthesis of methionine, so their presence can result in more hydrogen sulfide.
- The active matrix of cysteine as a cysteine can stimulate hydrogen sulfide, and it can induce an ATP-sulfate enzyme, which increases the utilization of sulfate to promote hydrogen sulfide.
- Even if the amino acid composition in the wheat saurate is constant, the methionine can also be consumed quickly, and relatively many other amino acids will also inhibit the synthesis of methionine, and excite hydrogen sulfide.
- Metal ions also have an effect on the production of hydrogen sulfide, generally considered to increase the formation of hydrogen sulfide by copper and zinc ion.
- Fermentation
- In the early stage of fermentation, since the presence of methionine can inhibit the production of hydrogen sulfide. When the wheat is fermented to a residue of 50bX, hydrogen sulfide is the highest. When the fermentation continues, other amino acids are also consumed, the formation rate of the sulfide is lowered again.
4. Measures to reduce hydrogen sulfide content
- (1). The sulfur amino acid in the wheat is mostly from malt, and if the auxiliary feedstock is used to replace some malt, the content of hydrogen sulfide in the beer can be reduced.
- (2). In the past, people believe that copper-made wheat sauce boil pot and pipelines, making the beer flavor. Practice has proved that the hydrazine contains copper ions, and the H2S content in the beer is indeed low. However, the harm of copper ions on the stability of beer flavors is also serious, people are still unwilling to contain too much copper ions in the wheat.
- (3). Cold, thermocoagulant separation of wheat juice, sulfide content, can reduce hydrogen sulfide during fermentation.
- ⑷. Slow fermentation of low temperature or low inoculation can reduce the amount of H2S.
- ⑸. The high-alcoholic liquor added during reservoir tends to have more hydrogen sulfide.
- ⑹. When fermentation is completed, an antioxidant such as sulfite is added, or a reservoir with a 50 ° C sterilized, it is easy to cause more H2S.
- ⑻. In the reservoir, with a large amount of CO2 emissions, most of the volatile H2s can be excluded. Generally speaking, the final content of H2S in the beer can be controlled in the range of 0 to Loug / L. However, polish (coliform, fermented monocans), etc., will contain a large amount of hydrogen sulfide.
- ⑼. Beer has been bactericidal, especially the extension of sterilization, will increase the H2S in large quantities, even more than 1 to the H2S content after filtration, so that the sterilization beer has an inconspicuous beer taste. However, after a period of placement, the H2S concentration will gradually disappear to the concentration or less preceding before unfind.
