Brewing knowledge Flashcards
Brettanomyces
Yeast, produces phenolics and esters (barnyard, leather, spice, tropical fruit), and amylase enzymes that break the bonds in dextrins. Strong diacetyl reducer (often pitched with pediococcus). Long and warm fermentation, 2-6 weeks at 21-26°C. Loves wood barrels.
Pediococcus
Souring bacteria, can generate a pH>3 . Produces lactic acid, more slowly than Lactobacillus, but sharper and more complex. Resistant to hops. Grows best at warm temperatures (18-29°C). Facultative anaerobe. Produces a lot of diacetyl. Used in Belgian lambics and American Sours.
Saccharomyces Pastorianus
Lager yeast. Named in honor of Louis Pasteur. Ferments at 10-13°c. Better fermentation of maltotriose than ale yeast.
Lactobacillus
Souring Bacteria, used in yogurts and sausages. Grows best at 32-46°c, but adapts to lower fermentation temperatures. Only consume a small amount of sugars (only glucose, fructose and maltose). Facultative anaerobe. Excretes proteolytic enzymes to obtain amino acids. Inhibited by hops. Some strains are homolactic, some are heterolactic.
Yeast
Eukariotic single-cell fungus. 5-10 microns, 10 times the size of a bacteria. 6000 genes, 16 chromosomes. Cell-wall made of carbohydrates. Each cell buds between 20 (lagers) and 30 times (ales).
What are the conversion ratios of sugars by the yeast?
48% in ethanol, 46% in CO2, 5% in new cells, 1% in other compounds.
Saccharomyces Cerevisiae
Brewer’s yeast. By fermentation, it converts carbohydrates to carbon dioxide and alcohols. Ferments better at 18-21°c. Saccharomyces reproduce by the asymmetric division process known as budding. It is not airborne.
In what order do the yeast cells consume the different sugars of the wort?
Glucose, fructose, sucrose, maltose, matotriose.
Acetobacter
Bacteria, mainly in aerobic conditions, oxidize ethanol to carbon dioxide and water, resulting into vinegar.
Obligate aerobe.
Enzymes
Special proteins created by a living organism to catalyse chemical reactions. They are like machine tools, their active site is shaped to hold specific substrates: they can bind molecules together, or break them appart.
pH
Potential of hydrogen. Chemical variable denoting a solution’s acidity or alkalinity through the concentration of hydrogen ions (the more hydrogen ions, the more acid).
Logarithmic scale, from 1 to 14.
Calcium and magnesium react with phosphates to lower the pH, and bicarbonate raises the pH. Kilned malts lower the pH, pale malts raise it.
Vicinal diketone (Or VDK)
Group of flavor compounds, most notably 2,3-butanedione (diacetyl) and 2,3-pentanedione. Strain dependent in a healthy fermentation, they can be a sign of improper fermentation/contamination by lactobacillus.
Not produced by the yeast: during synthesis of amino-acids valine and isoleucine, yeast cells secrete alpha-acetolactacte and alpha-acetohydroxybutyrate, which then break down into VDKs. During maturation, yeast cells metabolize VDKs as an energy source.
Diacetyl (2,3-butanedione)
One of the VDKs. Buttery flavor. During the synthesis of amino-acids valine, yeast cells excrete alpha-acetolactate which then breaks down into diacetyl. It is then metabolized by the cell as an energy source.
2,3-pentanedione
One of the VDKs. Buttery flavor. During the synthesis of amino-acids isoleucine, yeast cells excrete alpha-hydroxybutyrate which then breaks down into 2,3-pentanedione. It is then metabolized by the cell as an energy source.
Acetaldehyde
Produced in the early stage of fermentation, it is later reduced into ethanol. Aroma of green apple. If the yeast is not sufficiently active, acetaldehyde may stay in the finished beer.
It is also the immediate product of the metabolism of alcohol in the human body.
During standard fermentation, acetaldehyde and carbon dioxide are produced in equal amounts.
Isoamyl acetate
Key ester, present in all beers. Fruity aroma: banana, pear. Particularly present in Bavarian-style wheat beers (weissbier)..
4-vinyl guaiacol
Flavor compound, tastes like clove. Comes from the conversion of ferulic acid by the yeast. Gives a distinctive flavor to Weissbier and Wit.
Dimethyl Sulfide (DMS)
Organic sulfur-containing molecule. Smells like cooked corn and cabbage. Heat sensitive, lost to a great extent to kilning. Comes principally from the precursor S-methylmethionine that develops into the embryo of barley during germination. SMM is broken down to DMS during the hot wort stand, so cool the wort ASAP.
Factors of production: High levels due to high concentration in malt and extended hot wort standing.
Pyruvate
Compound formed by yeast cells during fermentation, at the end point of the glycolytic break down of glucose. Pyruvate is then transformed into Co2 and acetaldehyde, which is then converted to ethanol.
Glycogen
Major carbohydrate in yeast cells, it serves as a store of biochemical energy. 20% to 30% of the yeast dry weight. Yeast cells use it during the lag phase, when growth is limited, and convert it to lipids. Low glycogen: diacetyl, acetaldehyde and sulfur dioxide at the end of fermentation.
Lag phase
Period of 3 to 15h between pitching and beginning of fermentation. Yeast cells absorb oxygen to produce important compounds like sterols, that they need for membrane permeability. Keep the temperature down to prevent the production of VDKs precursors.
Alpha-acetolactacte
Precursor of the VDK Diacetyl excreted by the yeast cells during synthesis of amino-acid valine.
Alpha-hydroxybutyrate
Precursor of the VDK 2,3-pentanedione excreted by the yeast cells during synthesis of amino-acid isoleucine.
Sterols
Types of cholesterol that form part of the yeast’s cell wall membrane: they make it permeable for the transfer of sugars into the cell, of alcohol out of the cell, and make the cell more alcohol tolerant.
Yeast cells use oxygen to synthesize sterols during the aerobic phase. The level of sterols is a strong viability indicator.
Beta-glucans
Highly viscous glucose polymers derived from the cell wall of the barley endosperm. They are degraded by beta-glucanase, but this enzyme is heat sensitive and is easily destroyed during kilning or mashing. Excess amount of beta-glucans can cause problems with filtration and haze.
A different beta-glucan is found in the cell walls, affording rigidity.
Beta-glucanase
Enzyme that hydrolyses beta-glucans. Synthesized during malt modification. Heat sensitive, easily destroyed during kilning/mashing. When brewing with flaked barley or oats, which contain a lot of beta-glucans, one can begin with a low mashing temp. (40-50°c) and add a microbial or fungi glucanase.
Polymer
Material made of long repeating chains of molecules called monomers.
Ex: proteins are natural polymers made up of amino acids.
Ion
An atom or molecule that has gained or lost one or more of its valence electrons, giving it a net positive or negative electrical charge. There is an imbalance in the number of protons (positively charged) and electrons (negatively charged).
Cation
Cations are ions that carry a net positive charge because the number of protons in the species is greater than the number of electrons.
Anion
Anions are ions that carry a net negative charge, because there are more electrons than protons.
Ethanol
Primary end product of anaerobic fermentation of certain micro-organisms like Saccharomyces, from the conversion of small carbohydrates like glucose or maltose. Boiling point at 78,4°c. In the beer, it reacts with carboxylic acids to produce esters.
Ethyl acetate
Major ester produced by yeast found in both beer and wine, formed by the reaction between ethanol and Acetyl Coa. Depending on its concentration, goes from “fruity” to “solventy”. To control its production: low temperature, high pitching rate, high oxygen rate.
Hydrogen sulfide
Gas, smells of rotting eggs. Produced by the normal metabolism of the yeast cells, when they processe sulfate ions to produce amino acids cysteine and methionine.
Cause: low nitrogen levels.
Hydrogen sulfide
Gas, smells of rotting eggs. Produced by the normal metabolism of the yeast cells, when they process sulfate ions to produce amino acids cysteine and methionine.
Can combine with carbonyl compounds to produce mercaptan.
Cause: low nitrogen levels.
Amino acids
Building blocks, they usually fonction as monomers to form larger molecules: a chain of many amino acids is called a polypeptide, which can bond to form proteins.
Fusel alcohols
By-products of ethanol fermentation, they give the beer its “alcoholic” taste and warming sensation. They are more present in high gravity beers, because of the stress inflicted upon the yeast.
Phenols
Aromatic compounds characterized by a hydroxyl group attached to a carbon atom. Usually an off-flavor (clove, band-aid, medicinal, smoky).
Some polyphenols like tannins found in malt and hops can contribute to mouthfeel and astringency.
Chlorine and bromine can combine with phenols to create chlorophenols and bromophenols.
4 Vinyl Guaiacol, produced by the decarboxylation of ferulic acid by the yeast, is a phenol.
Esters
Largest group of flavor compounds found in beer. Fruity aromas. Formed by the reaction between organic acids and alcohols created during fermentation. Most significant esters: isoamyl acetate (banana), ethyl acetate (solvent), ethyl caprilate (apple), ethyl caproate (apple/anis) and phenylethyl acetate (rose/honey).
Ale strains, high temp., low oxygen content, high gravity, high FAN and zinc: a lot of esters.
Free amino nitrogen (FAN)
The measure of individual amino acids, ammonium ions, and small peptides, resulting from the degradation of proteins found in the malt (High adjunct beer: FAN deficiency). FAN is used to assess the nitrogen yeast cells utilize for growth and proliferation, and it’s an excellent index for the prediction of a good fermentation.
Nitrogen
Second to sugar, the most important macronutrient required for yeast, used to accomplish its metabolic activities, particularly the synthesis of new amino acids and, hence, proteins.
Used to purge oxygen or push the beer, but also to produce nitrogenated beer (fine and stable bubbles, no flavor).
Stout
A distinctive type of British beer developed as a strong version of Porter. Dark ale, made with roasted malts, chocolate and coffee flavors. Ex: Guinness.
Autolysis
Self-destruction of yeast cells: release of hydrolytic enzymes causing the disintegration of the vacuolar membrane. Cause: heat, extensive re-pitching, bacteria, pH, high alcohol, high carbonation.
Consequences:
- Flavor change (meaty, sulfury, bitter taste) because of the amino acids and nucleotides released in the process. Rise of the pH if yeast is in high concentration.
- Enzymatic digestion: the proteases that are released will digest the proteins in the beer. Reduction of head retention and foam, haze and over-carbonation (the newly released enzymes can cause re-fermentation).
Proteins
Nitrogenous organic compound made of linear polymers of 20 different amino acids. Vast array of functions: structural components of cells, enzymes that catalyze reactions, DNA replication, transport of molecules…
In brewing: they break down starches into small sugars, they reduce large molecules into amino acids, they provide haze, foam and texture to the beer.
Lautering
Separating sweet wort from spent grain.
Proteolysis
Breakdown of proteins into peptides and eventually amino acids.
Yeast nutrients
Carbohydrates, amino acids, vitamins, and minerals essential for the yeast vitality and viability.
Zinc
Key component at the active site of several yeast enzymes, most notably alcohol dehydrogenase. Beneficial to beer foam stability and cling, probably through an involvement in the bridging of hydrophobic polypeptides with iso-alpha acids. The Reinheitsgebot forbids German brewers to add it to the wort.
Reinheitsgebot
Decree issued by the Bavarian Duke Wilhelm IV in 1516. Barley, hops, and water were the only ingredient authorized to brew beer.
Modification
Chemical breakdown of proteins and starches that reside naturally in grains, and are too complex for the brewer to use in their natural state.
Starches are converted to small sugars like glucose or maltose. Proteins are converted to peptides or amino acids.
Endosperm
Largest tissue of the barley grain, it acts as a food storage for the embryo. It contains the starches we break down into sugars during mashing.
Aleurone layer
Layer of living endosperm cells that encloses the outer surface of the starchy endosperms of cereal grains. It produces a wide range of hydrolytic enzymes that contribute to the modification of the starchy endosperm.
What are the different steps involved in malting?
- Steeping of the grain in water, up to 2 days. The barley absorb water and activates enzymes (to break down proteins and carbohydrates) and hormones (to start the growth of the plant).
- Transfer to the germination room, and aeration for 4 to 6 days. The enzymes produce malt sugars, soluble starch, and amino acids.
- Drying of the grain into a kiln during 2 to 4 hours. It kills the embryo and preserves its nutrients for beer making. The enzymes become dormant and modification stops. Later, they will be reactivated by heat and moisture during mashing.
What’s the difference between two-row and six-row barley?
The kernels of six-row barley are generally smaller than those of two-row barley, giving six-row kernels a greater husk-to-endosperm ratio, so more polyphenols and enzymes.
Most of the world besides USA uses six-row barley only for livestock feed, not for beer. And most brewers consider that two-rows barley has a greater extract value (+1-2%).
Diastatic power
The total activity of malt enzymes that hydrolyze starch to fermentable sugars, measured in °Lintner (°L). Diastase is the mixture of enzymes responsible for degrading starch.
What are the enzymes contributing to starch degradation?
Alpha-amylase, beta-amylase, limit dextrinase, and alpha-glucosidase.
Beta-amylase is the driving force in this process.
Original gravity
The measure of the solids content originally in the wort, before alcoholic fermentation has commenced to produce the beer, expressed as the density above that of distilled water.
Maltose
Maltose is a di-saccharide, derived from the breakdown of starch during the mashing process mostly by beta-amylase. It represents around 40% of the total carbohydrates in the wort.
Terpenes
Hydrocarbon chains found in all organisms, and especially in hop essential oils. The most common and important terpenes are myrcene, caryophyllene, humulene… but they are so water insoluble that they rarely survive into finished beer unless added during dry hopping.
Important oxygenated terpenes include linalool and geraniol (floral characteristics), limonene and alpha-terpineol (citrus characteristics).
Trehalose
Sugar consisting of two molecules of glucose. First thought to be a reserve carbohydrate like glycogen, it mainly functions as a membrane stabiliser and protectant for yeast cells under stress.
Lipids
Biomolecule that is soluble in nonpolar solvents, and hence not in water. Ex: waxes, oils, sterols, glycerides…
Yeast lipids (mostly phospholipids and sterols) are found along with proteins in the cell membranes, and lipid synthesis is an important part of yeast reproduction.
In finished beer, too much lipids can affect foam stability.
Carbohydrates
Biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms. In biochemistry, they are synonyms of saccharides. Carbohydrates perform numerous roles in living organisms. Polysaccharides serve for the storage of energy (e.g. starch and glycogen) and as structural components (e.g. cellulose in plants and chitin in arthropods).
Fatty acids
Subcategory of lipids.
Fatty acids
Subcategory of lipids. They are essential elements in yeast metabolism, as long chain unsaturated fatty acids are used to create other lipids such as sterols in cellular membranes. Brewers will promote their synthesis by aeration of the wort, oxygen being required for the desaturation of the molecules.
On the other hand, they negatively affect the organoleptic stability of beer during aging, through the breakdown of unsaturated fatty acids such as linoleic and linolenic acids into staling compounds such as (E)-2-nonenal (cardboard flavor).
New studies suggests that an addition of olive oil to yeast during storage can supply yeast with the fatty acids it needs for cell wall construction and good fermentative capacity. Oleic acid, a fatty acid contained in olive oil, may be capable of supporting yeast health without the destabilizing oxidative effects of wort aeration.
Vorlauf
Recirculation of the wort over the grain bed, to filter particles such as lipids from the grain’s embryo, and phenolic compounds from the grain’s husk, and prevent them from being boiled in the kettle.
Polyphenols
Molecules containing one or more aromatic rings and two or more hydroxyl (OH) groups attached to aromatic rings. They are derived directly from malt and hops and are often involved in haze formation in finished beer. They have no aroma, and their major gustatory impact is a perception of astringency, as the result of polyphenols combining with proline-rich proteins in our saliva to form insoluble complexes.
Hot break
Hot Break comprises proteins and polyphenols that coagulate during the wort boil, eventually clumping together in large enough chunks to break out of solution and fall to the bottom of the kettle. To facilitate it, brewers can add hops or carrageenan.
Maltotriose
A carbohydrate comprising three linked glucose molecules and accounts for 15 to 20% of the total carbohydrate content. Most brewer’s yeast can metabolize it, after the more easily absorbable sugars.
Maltodextrins
Glucose polymers present in wort after mashing.
The side bonds of starch amylopectin are not digested by either alpha or beta amylase. The parts of the starch molecule containing these side bonds form the basis of the important unfermentable dextrins.
High mash temperatures promotes the presence of dextrins in the wort by inhibiting alpha and beta amylase.
They contribute to the FG of the beer and generate palate fullness, some sweetness, and calorific content.
Saccharification
Conversion by enzymes of starches into sugars and dextrins during the mashing process. To be susceptible to digestion by enzymes, the starches in barley malt must first be gelatinized (at 61°C-65°C). They are then broken down by alpha amylase (hydrolysis of starches into dextrins) and beta amylase (digests dextrins into fermentable sugars).
Lower saccharification temperatures will favor the production of fermentable sugars by beta amylase, whereas higher temperatures will favor the production of unfermentable sugars and dextrins by alpha amylase.
Amylases
Most of the activity of diastase can be attributed to the activities of alpha and beta amylase, and, to a lesser extent, gamma amylase. Their concerted action produces balance of simple fermentable sugars—glucose, maltose, and maltotriose—and larger unfermentable dextrins roughly in a 3:1 proportion.
A pH-promoting general amylase activity is around 5.3.
Beta amylase
Barley contains appreciable levels of latent beta amylase (glucan 1,4-alpha maltohydrolase), which is located in the endosperm. In the absence of other enzymes, beta amylase is unable to degrade starch granules, but it is able attack amylose, dextrins, and soluble starch chains in solution.
pH optima: 5.1–5.3
Temperature optima: 60°C–65°C
Alpha amylase
Alpha Amylase (ptyalin) is a major mash enzyme which digests starch, a large polymer of glucose, into smaller units, exposing it to further digestion by beta amylase.
Barley does not contain alpha amylase (glucan 1,4-glucanohydrolase), it develops in the grain during malting. Copious quantities are synthesized in the aleurone layer that surrounds the endosperm, and in the endosperm as a response to gibberellic acids secreted by the embryo.
Alpha amylase is an endo-acting enzyme (endoglucanase) in malt and catalyzes the hydrolysis of internal alpha 1,4-glycosidic bonds at random within the starch molecule. Such an attack is slower on short-chain dextrins, is slower near the chain ends, and does not occur in the vicinity of alpha(1→6) branch points. Thus, unlike beta amylase, alpha amylase acting alone can attack starch granules and will steadily degrade them to a complex of sugars (including dextrose), maltose, oligosaccharides, and dextrins during mashing.
Alpha amylase requires calcium ions (Ca2+) for activity (add gypsum).
pH optima: 5.3–5.7
Temperature optima: around 70°C
What are the four four beta acid analogues in hop resin?
Lupulone, adlupulone, colupulone, and prelupulone.
Lupulone
One of four beta acid analogues in hop resin. Lupulone levels vary across hop varieties from roughly 30% to 55% of total beta acids.
What’s the difference between alpha and beta acids in hop resin?
Beta acids are very similar to their alpha acid counterparts, except that beta acids have a third prenyl group attached to the center ring. It prevents beta acids from isomerizing, thus iso-beta acids are not created. Furthermore, beta acids are virtually insoluble in wort, and only trace levels can be found in beer.
When beta acids oxidize into hulupones, however, which happens as hops age, they become wort soluble and confer bitterness.
Adlupulone
One of four identified beta acid analogues in hop resin. Adlupulone levels are low (10% to 15% of total beta acids) but consistent across different varieties.
Hulupulone
Oxidation products of hop beta acids. Beta acids are fairly reactive with oxygen and can oxidize to a set of compounds called hulupones, each of which is derived from its beta acid analogue; for instance, cohulupulone comes from colupulone.
The bitterness conferred by hulupones is considered coarse… or is it?
Colupulone
One of four beta acid analogs in hop resin. Colupulone levels vary across hop varieties from roughly 20% to 55% of total beta acids.
Prelupulone
One of four beta acid analogs in hop resin.
Cohumulone
One of five alpha acid analogs in hop resin. Cohumulone levels vary between roughly 20% and 50% of total alpha acids, depending on variety.
Most hop analyses will specifically show a cohumulone percentage, because brewers believe iso-cohumulone contributes a rougher, harsher quality of bitterness than other iso-alpha acids. Traditional aroma hops tend to be low in cohumulone, whereas some bittering varieties have higher levels, and breeders are favoring new cultivars with low cohumulone levels.
What are the five alpha acid analogs in hop resin?
Cohumulone, adhumulone, humulone, prehumulone, and posthumulone.
Myrcene
Monoterpene, essential hop oil, the most plentiful hydrocarbon of the hop oils. It develops in the hop cone after beta caryophyllene and humulene, and it is therefore an indicator of the hop’s ripeness. Herbaceous aroma, distinctively “hoppy”, the most potently aromatic. Very volatile, sensitive to prolonged boiling: dry hop, to keep it in the beer.
What happens when hops oxidize?
When hops oxidize, alpha acids, including cohumulone, change their molecular makeup, producing isobutryic acid, which has a distinctive rancid, sour, cheesy odor.
Adhumulone
One of five identified alpha acid analogues in hop resin. Adhumulone levels in hops are typically constant at 15% of the total alpha acid content across all varieties.
Only slight differences in molecular structures differentiate all analogues of the alpha acids. In the case of adhumulone, the side group of the molecule is 2-methylbutyryl. Oxidation of hops leads to cleavage of this side group and the production of 2-methylbutryic acid, which has a distinctive, pungent odor similar to Roquefort cheese.
Humulone
One of five alpha acid analogues in hop resin. Humulone levels vary across varieties, between roughly 20% and 50% of total alpha acids.
Posthumulone
One of five alpha acid analogues in hop resin. It only plays minor roles.
Prehumulone
One of five alpha acid analogues in hop resin. It only plays minor roles.
Alpha acids
Principal components in lupulin, the resin of the hop cone, and main bittering agent in hops. They reside in the soft-resin fraction of the lupulin, which is soluble in hexane. Alpha acid analogues include prehumulone, posthumulone, humulone, cohumulone, and adhumulone. When isomerized to isohumulones (iso-alpha acids) through the boiling process they become soluble in water, and bring bitterness to beer. The unit of measurement for bitterness is International Bitterness Units (IBU).
Iso-alpha acids
Thermally induced isomers of alpha acids and principal source of bitterness in beer. The isomerization from an alpha acid into an iso-alpha acid is a chemical process (heat and time dependent) that maintains the alpha acid’s original material composition but essentially rearranges the compound’s molecular structure, altering its chemical properties and reactions. Iso-alpha acids are intensely bitter and have a human detection threshold in beer of approximately 6 to 7 ppm.
Humulene
Sesquiterpene, highly volatile and hydrophobic component of the hydrocarbon fraction of essential hop oil. Hops containing a lot of it tend to be floral, herbal, and spicy in character (ex: Hallertauer Mittelfrüh, U.K. Kent Golding).
Hops
Hops are the flowers or “cones” of Humulus lupulus, and provide beer with its backbone of bitterness, increases its microbiological stability, helps stabilize its foam, and greatly influences its taste and aroma.
Hops are perennial herbaceous plants that live 10 to 20 years, maintaining a perennial root, called a rhizome, a carbohydrate storage structure that is also found in ginger and the iris plant. Each spring the rhizome sprouts a mass of bines that wrap clockwise around anything they contact.
Only seedless female hop cones are used in the brewing industry.
Essential oils
An essential oil is a concentrated hydrophobic liquid containing volatile chemical compounds from plants. Essential oils are generally extracted by distillation, often by using steam.
Essential oils
An essential oil is a concentrated hydrophobic liquid containing volatile chemical compounds from plants. Essential oils are generally extracted by distillation, often by using steam. These hydrocarbons are very volatile and do not survive the boiling process, and so their detectable presence in a finished beer would be due to late-hopping in the kettle, dry-hopping, or addition of a “late hop” extract. Essential oils are also lost during the storage of hop cones.
What are the main essential oils found in hop cones?
Myrcene, Humulene, Caryophyllene
Caryophyllene
Sesquiterpene, highly volatile and hydrophobic component of the hydrocarbon fraction of essential hop oil. β-Caryophyllene is a main flavor constituent of black pepper, which was used as a beer adulterant in bygone years; it produced “heat” on the palate that the buyer was meant to mistake for alcoholic strength.
Adenosine triphosphate (Atp)
Molecule that is a universal energy store. It comprises one xylose sugar, the adenine base, and three phosphates. One of the phosphates is linked through a high-energy bond which, when split, fuels reactions such as biosynthesis, transportation, etc.
ATP is generated in catabolic processes such as glycolysis (“sugar breakdown”). In turn, ATP is consumed in reactions that demand an input of energy, e. g., the biosynthesis of cellular materials in anabolic reactions.
The detection of ATP can be used as a rapid test for the hygiene status of equipment and products, through ATP bioluminescence. Wherever there is or has been growth of microorganisms the soil will contain ATP.
Calcium sulfate
Critical component in the measurement of permanent water hardness. Calcium sulfate is one of the primary salts used for the improvement of calcium levels in beer, to this effect: they lower the pH, preserve mash enzymes, increase extract yield, improve yeast growth and flocculation, accelerate oxalate removal, and reduce color.
The sulfate ion in this compound is generally thought to promote a drier, more bitter beer.
Calcium sulfate
Gypsum. Critical component in the measurement of permanent water hardness. Calcium sulfate is one of the primary salts used for the improvement of calcium levels in beer, to this effect: they lower the pH, preserve mash enzymes, increase extract yield, improve yeast growth and flocculation, accelerate oxalate removal, and reduce color.
The sulfate ion in this compound is generally thought to promote a drier, more bitter beer.
To Burtonize
To improve one’s brewing water via the addition of calcium sulfate, to promote a drier, more bitter beer. Common for the production of pale ales and India pale ales.
Burton-on-Trent, England is the classic source of water with a high calcium sulfate content, caused by the region’s large gypsum deposits.
Calcium chloride
One of the primary components in the measurement of permanent water hardness. It is believed to promote a palate fullness, sweetness, or mellowness within the flavor profile of beer. Dortmund, Germany, is an example of a water source that has a high calcium chloride content.
Acidification
The process of lowering the pH of a solution until it falls below pH 7.00, through the use of acids, acidic salts, or microbial fermentations. Average malts when mashed will result in a pH of about 5.65–5.75, usually above the optimum for the enzymes (5.40).
Sulfuric and phosphoric acids, lactic acid, acidic salts like calcium chloride, calcium sulfate (gypsum), and magnesium sulfate (Epsom salts).
Acidification
The process of lowering the pH of a solution until it falls below pH 7.00, through the use of acids, acidic salts, or microbial fermentations. Average malts when mashed will result in a pH of about 5.65–5.75, usually above the optimum for the enzymes (5.40).
Possible adjuncts: sulfuric and phosphoric acids, lactic acid, acidic salts like calcium chloride, calcium sulfate (gypsum), and magnesium sulfate (Epsom salts).
Maillard reaction
A type of non-enzymic browning that adds color and flavor to food. It is the result of a complex series of chemical reactions between the carbonyls of reactive sugars (pentoses reacts more than hexoses) and the amino groups of amino acids, at higher temperatures, low moisture levels, and under alkaline conditions.
It occurs during kilning and gives it color to the malt, but also in the kettle (and also during decoction mashing).
Aldehydes
Organic compounds produced by the removal of hydrogen from (i.e., oxidation of) alcohols. Conversely, the reduction of aldehydes leads to the production of alcohols. In a brewing context, the best known of these reducing reactions is the reduction of acetaldehyde to ethanol. Aldehydes tend to be highly flavor active: acetaldehyde (green apple), E-(2)-nonenal (cardboard).
Oxidation
Oxidation occurs when an atom, molecule, or ion loses one or more electrons in a chemical reaction. Oxidation doesn’t necessarily involve oxygen! Originally, the term was used when oxygen caused electron loss in a reaction. The modern definition is more general.
Reduction
Reduction is the gain of electrons or a decrease in oxidation state by an atom in a substance. The greater the degree of reduction, the lower the oxidation state of a given atom. A reduction always occurs in tandem with an oxidation. One reactant is reduced (gains electrons or decreases in oxidation state) as another is oxidized (loses electrons or increases in oxidation state).
Reductants in beer protect it to a certain extent from the ravages of oxidation (ex: products of the Maillard reaction, melanoidins).
Polyphenols, sulfhydryls, nitrogen compounds, and hops also contribute to reduction potential.
CO2 Conditioning
CO2 will dissolve quite readily in beer, with solubility increasing with decreasing temperature. The content of CO2 in a beer is often expressed in terms of volumes of gas at standard temperature and pressure per volume of beer or in grams of CO2 per liter of beer (one volume of CO2 is equivalent to two grams of CO2 per liter).
Cask-conditioned beers: 1.2 vols
Keg beers: 2–2.6 vols
Bottled and canned beers: slightly higher
Knowledge of the precise level of CO2 in a keg beer is important in that gas pressure in the dispense line from keg to tap needs to be adjusted to the level of the beer in the container to prevent excessive foaming.
Gibberellins
Gibberellins are a group of complex chemical compounds that have positive effects on plant growth and development, and are regarded as natural plant hormones. The compound gibberellic acid is used in the malting industry to increase alpha amylase production and accelerate endosperm modification.
Calcium oxalate
Calcium Oxalate ("beer stone") is a crystalline deposit formed by calcium reacting with oxalic acid. Oxalic acid is released from malt during mashing. It is known to harbor microorganisms if not properly removed via the use of an acid during the cleaning cycle.
By insuring there is enough calcium in upstream processing then one can insure calcium oxalate forms and precipitates in tanks and not in kegs and bottles where it can create nucleation sites (an so, gushing).Melibiose
Melibiose is a sugar that appears in the fermenting beer as the result of an enzymatic degradation of raffinose. In lagers, melibiose eventually disappears broken down by yeast thanks to the enzyme alpha galactosidase, whereas in ales it remains intact: convenient marker sugar for determining whether a beer was fermented by a top- or a bottom-fermenting yeast strain.
Alkalinity
The ability of a solution to resist a change in its pH value when acids are added. Three key ions: hydroxide ion, carbonate ion, bicarbonate ion. In water, they react with acidic substances to form salts. They are acid reducers, they increase water’s pH value.
Alkalinity is often reported as either milligrams of bicarbonate. Brewing waters: don’t exceed 100 mg bicarbonate/l, but 50 mg/l is much better.
Antioxydants
Oxidation is defined as the loss of electrons. Antioxidants function by interfering with the siphoning of electrons from molecules. They may do this by themselves being preferentially oxidized, thereby preventing other materials being oxidized; by blocking the action of oxidizing systems; or by donating electrons.
Ex: polyphenols, phenolic acids, and Maillard reaction products and enzymes, ascorbic acid (vitamin C), sulfur dioxide (metabisulfite).
Anthocyanogens
Group of polyphenolic compounds that provide most of the tannins that are important in terms of beer stability. Their polymerization is a first step on the path to haze formation: the colloidal stability of beer is inversely related to the concentration of anthocyanogens in wort. If they end up in finished beer, they may be converted into tannins and then interact with proteins to give unwanted hazes.
What are the two main causes of haze in beer?
Haze in beer can be formed by either of two main factors: biological (bacteria and yeast) or non-biological agents (starch, polyphenols and proteins).
What are the two types of non-biological hazes in beer?
Non-biological haze can be amorphous (e.g., starch based) or colloidal (proteins and polyphenols i
Colloidal haze
Beer colloidal haze is generally the result of protein molecules within the beer joining with polyphenols to form molecules large enough to cause turbidity. Two strategies can be employed by a brewer to control colloidal haze: decrease the protein level in the beer (most common method) or decrease the polyphenol content in the beer.
Tannins
Complex polyhydroxy phenols that are soluble in both water and ethanol. They come in two basic groups:
- Hydrolyzable: hydrolysis can turn them into glucose and phenolic acids.
- Condensed: stable compounds made up of several flavonoid phenols that are polymerized with each other. Tannins are capable of binding and precipitating proteins.
The amount of tannin in the average finished beer is usually no more than 150 to 330 mg/l. About two-thirds of this is derived from the husk material of barley and about one-third from hops.
When consumed, the saliva proteins coagulate and it ceases to be a lubricant in the mouth.
What are the two important yields brewers are concerned with?
- Brewing material efficiency (BME): the measure of the amount of extract that is actually delivered to the fermenter compared to the amount of extract that is theoretically extractable from the grist.
- Hop utilization: the measure of the amount of bitterness, as measured in International Bitterness Units (ppm of iso-alpha acid), contained in the beer versus the amount of alpha acids of the raw hops that was added to the kettle.
What are the various functions of the boil?
- Inactivation of residual enzymes from the mash
- Isomerization of bittering hop α-acids
- Sterilization of the wort
- Removal of unwanted volatiles
- Precipitation of unwanted proteins as “hot break”
- Concentration of the wort
What are the different methods to produce a high-gravity wort?
- Mashing a big grain bill at a low water-to-grist ratio
- Double mashing
- Adding some good quality malt extract to the wort
