Brewing knowledge Flashcards
1
Q
Brettanomyces
A
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.
2
Q
Pediococcus
A
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.
3
Q
Saccharomyces Pastorianus
A
Lager yeast. Named in honor of Louis Pasteur. Ferments at 10-13°c. Better fermentation of maltotriose than ale yeast.
4
Q
Lactobacillus
A
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.
5
Q
Yeast
A
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).
6
Q
What are the conversion ratios of sugars by the yeast?
A
48% in ethanol, 46% in CO2, 5% in new cells, 1% in other compounds.
7
Q
Saccharomyces Cerevisiae
A
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.
8
Q
In what order do the yeast cells consume the different sugars of the wort?
A
Glucose, fructose, sucrose, maltose, matotriose.
9
Q
Acetobacter
A
Bacteria, mainly in aerobic conditions, oxidize ethanol to carbon dioxide and water, resulting into vinegar.
Obligate aerobe.
10
Q
Enzymes
A
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.
11
Q
pH
A
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.
12
Q
Vicinal diketone (Or VDK)
A
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.
13
Q
Diacetyl (2,3-butanedione)
A
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.
14
Q
2,3-pentanedione
A
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.
15
Q
Acetaldehyde
A
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.
16
Q
Isoamyl acetate
A
Key ester, present in all beers. Fruity aroma: banana, pear. Particularly present in Bavarian-style wheat beers (weissbier)..
17
Q
4-vinyl guaiacol
A
Flavor compound, tastes like clove. Comes from the conversion of ferulic acid by the yeast. Gives a distinctive flavor to Weissbier and Wit.
18
Q
Dimethyl Sulfide (DMS)
A
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.
19
Q
Pyruvate
A
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.
20
Q
Glycogen
A
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.
21
Q
Lag phase
A
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.
22
Q
Alpha-acetolactacte
A
Precursor of the VDK Diacetyl excreted by the yeast cells during synthesis of amino-acid valine.
23
Q
Alpha-hydroxybutyrate
A
Precursor of the VDK 2,3-pentanedione excreted by the yeast cells during synthesis of amino-acid isoleucine.
24
Q
Sterols
A
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.
25
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.
26
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.
27
Polymer
Material made of long repeating chains of molecules called monomers.
Ex: proteins are natural polymers made up of amino acids.
28
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).
29
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.
30
Anion
Anions are ions that carry a net negative charge, because there are more electrons than protons.
31
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.
32
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.
33
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.
34
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.
35
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.
36
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.
37
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.
38
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.
39
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.
40
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).
41
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.
42
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).
43
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.
44
Lautering
Separating sweet wort from spent grain.
45
Proteolysis
Breakdown of proteins into peptides and eventually amino acids.
46
Yeast nutrients
Carbohydrates, amino acids, vitamins, and minerals essential for the yeast vitality and viability.
47
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.
48
Reinheitsgebot
Decree issued by the Bavarian Duke Wilhelm IV in 1516. Barley, hops, and water were the only ingredient authorized to brew beer.
49
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.
50
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.
51
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.
52
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.
53
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%).
54
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.
55
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.
56
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.
57
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.
58
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).
59
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.
60
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.
61
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).
62
Fatty acids
Subcategory of lipids.
63
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.
64
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.
65
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.
66
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.
67
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.
68
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.
69
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.
70
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.
71
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
72
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
73
What are the four four beta acid analogues in hop resin?
Lupulone, adlupulone, colupulone, and prelupulone.
74
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.
75
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.
76
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.
77
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?
78
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.
79
Prelupulone
One of four beta acid analogs in hop resin.
80
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.
81
What are the five alpha acid analogs in hop resin?
Cohumulone, adhumulone, humulone, prehumulone, and posthumulone.
82
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.
83
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.
84
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.
85
Humulone
One of five alpha acid analogues in hop resin. Humulone levels vary across varieties, between roughly 20% and 50% of total alpha acids.
86
Posthumulone
One of five alpha acid analogues in hop resin. It only plays minor roles.
87
Prehumulone
One of five alpha acid analogues in hop resin. It only plays minor roles.
88
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).
89
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.
90
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).
91
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.
92
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.
93
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.
94
What are the main essential oils found in hop cones?
Myrcene, Humulene, Caryophyllene
95
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.
96
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.
97
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.
98
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.
99
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.
100
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.
101
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).
102
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).
103
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).
104
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).
105
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.
106
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.
107
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.
108
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.
109
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).
```
110
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.
111
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.
112
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).
113
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.
114
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).
115
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
116
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.
117
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.
118
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.
119
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
120
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
121
What is the standard pitching rate for ales?
0.75 billion cells per liter per degree Plato.
122
What is the standard pitching rate for lagers?
1.5 billion cells per liter per degree Plato.
123
How much of the potential bitterness is found in the final beer?
Only 25 to 30% of the potential bitterness is actually developed or found in the final beer.
124
Where in the hop cone are located the hop oils?
In the lupulin glands.
125
By how much should we multiply the gravity fall to obtain the ABV?
0.129
126
What's the normal level of carbonation for cask ales?
2 grams per litre.
127
What's the normal level of carbonation for kegs and bottled/canned beers?
4 to 5 grams per litre.
128
What's the difference between cask ales and keg beers?
Cask ale is dispensed from casks containing live yeast and requires a period of time to settle in the cellar. It is served from a hand pump on the bar.
Keg beer is filtered in the brewery and partly carbonated to allow dispense under pressure.
129
What's a lauter tun?
A vessel for separating the wort from the solids of the mash. It normally has a slotted, perforated floor, also called a false bottom, which holds the spent milled grains. Mashing occurs in a separate mash mixer, and the mash is then transferred by a pump to the lauter tun.
In some breweries, a single vessel serves as both the mash and the lauter unit.
130
Crabtree effect
A metabolic control in yeast whereby pyruvic acid is converted into ethanol rather than carbon dioxide and water in the presence of oxygen. In many microbes oxygen initiates the Pasteur effect where glucose is digested to carbon dioxide and water.
131
Melanoidins
Brown and flavorsome pigments found in malts and malt products. Their structure varies and, in general, melanoidins from darker malts have higher molecular weights than those from pale malts (which are usually more aromatic).
They are formed by Maillard reactions, by the combination of simple sugars and amino acids. This reaction is accelerated by heating and mostly occurs during boiling. Melanoidins are good oxygen scavengers and can protect wort against oxidation and staling.
132
Mercaptans
Distinctive flavour compounds with the aroma of skunk. Produced by the photolysis of a side chain of iso alpha acids and the subsequent reaction of this with sulphur containing thiol radicals to produce 3-methyl-2-butene-1-thiol. Exposing beer to light, particularly by using clear glass bottles, will initiate this reaction although specially treated hop oil, Tetra hop, will stabilise the iso alpha acid.
133
Polymerase chain reaction (PCR)
A molecular biology procedure whereby a single piece of DNA may be extracted from a sample and multiplied extensively to demonstrate the presence of a particular gene or organism. Currently being developed as an identification procedure for yeasts and beer contaminants but also to distinguish barley and hop varieties.
134
Zymonomas mobilis
A pernicious bacterial contaminant of beer. Zymonomas mobilis is the major species found and produces very distinctive vegetal off flavours as well as some lactic acid so rapidly spoiling beer. The bacteria grows particularly well with glucose and sucrose and is most likely to contaminate primings or beer primed for cask conditioning.
135
What are the desirable pH levels at the different steps of the brewing process?
* Brewing liquor should be around pH 6.2 to 6.8 • Start of mash pH 5.6
* Pre-boiled wort pH 5.3
* Post boil wort pH 5.1
* Finished beer pH 4
136
Why are acidic conditions favored during brewing?
```
Acid:
- Favors enzyme action
- Increases mash yield
- Precipitates proteins
- Precipitates oxalates
- Decreases extraction of tannins
- Increases flocculation
But:
- Decreases isomerization of hop acids
- Decreases color and flavor extraction from malt
```
137
Why is alkalinity bad for brewing?
```
Alkalinity:
• Uses up acidity
• Extracts tannins and oxalates from the mash
• Destroys enzymes
• Stops yeast flocculating
• Lowers mash yield
• Decreases free amino-acids
• Extracts more color and flavors from malt
• Increases hop utilisation
```
138
What are the 6 causes of colloidal haze?
```
Microbiological infection
Calcium oxalate
Beta-glucan
Protein
Polyphenols
Tannins
```
139
What's the minimum proportion of Pale ale / Lager malt in a recipe?
At least 75%, to provide enough diastatic power.
140
What's the volume of a UK barrel?
One UK barrel is 163.58 litres.
141
What's the volume of a US barrel?
One US barrel is 117.3 litres.
142
Head Retention
The ability of the beer to retain a nice foamy head for a long period of time. The inclusion of proteins and dextrines enhance the body and head retention of finished beer, as well as isohumulones from hops.
Household soap and lipids will however decrease head retention.
143
What is the risk with using high proportions of sugar adjuncts in the wort?
Sugar adjuncts provide only carbohydrates and if used at high levels will result in wort lacking in amino acids and this may lead to poor yeast growth causing tailing fermentations and poor yeast crops.
144
What happen to yeast cells when they age?
Both cell and vacuole sizes increase with age.
145
What can cause hydrogen sulfide and sulfur dioxide in beer?
Extended maturation time, yeast autolysis, insufficient evolution of carbon dioxide.
146
What factors influence the production of fusel alcohols in beer?
High wort oxygen levels, high free amino acid levels.
147
What is the difference between T45 and T90 hop pellets?
T90: 1 lbs whole cone hops = 0.9 lbs (0.4 kg) of pellets
T45: 1 lbs whole cone hops = 0.45 lbs (0.2 kg) of pellets
T90 pellets have more plant material in addition to the cones: T45 pellets are more concentrated.
148
Describe simply the endosperm of the barley grain
The endosperm of the barley corn comprises cell walls consisting of glucans encasing proteins and starch granules.F
149
What's the objective of the malting process?
Malting is a controlled germination which starts the degradation of structural glucans and proteins while activating enzymes which will yield the fermentable sugars.
150
Why should glucans level should be low in the mash?
To prevent wort and beer viscosity leading to run off and filter problems.
151
What is the temperature optima for alpha-amylase?
70-74°c
152
What is the temperature optima for beta-amylase?
58-65°c
153
What is the temperature optima for peptidase?
45-50°c
154
What is the temperature optima for beta-glucanase?
45°c
155
Gelatinization
Starch molecules are tightly packed within granules surrounded by polysaccharide and protein cell walls: the starch can only be degraded once its internal structure has been disrupted by the absorption of water: that's gelatinization.
It leads to an increased viscosity of the mash, before the starch gets liquefied by amylolytic enzymes.
Temperature optima for malt starch: 64°c.
156
Why do brewers add gypsum to the brewing water?
The calcium ions from gypsum react with phosphates derived from the malt to reduce the mash pH (to acidify) and so enhance enzymic activity.
157
How do brewers remove the undesirable bicarbonate ions to raise the mash pH?
Boiling, acid addition, demineralization.
158
What is the minimum calcium ppm for brewing water?
At least 60ppm.
159
What's the best crush for malt milling?
30% husk, 40% coarse grits, 20% fine grits and 10% flour
160
What’s the difference between homolactic and heterolactic fermentation?
In homolactic fermentation, end product is lactic acid. (E.g.: souring milk with lactobacillus lactis).
In heterolactic fermentation, end product is ethanol and CO2 in addition to lactic acid.
161
What is the difference between homolactic and heterolactic fermentation?
In homolactic fermentation, end product is lactic acid. (e.g.: Lactococcus).
In heterolactic fermentation, end product is ethanol and CO2 in addition to lactic acid. (e.g.: Leuconostoc).
162
What is the pathway of ethanol production by yeast cells?
1. Maltose is hydrolyzed into glucose by the yeast maltase.
2. Glucose is converted into pyruvate by glycolysis
3. Pyruvate is decarboxylated into acetaldehyde and CO2
4. Acetaldehyde is then reduced to ethanol by alcohol dehydrogenase
163
How do we calculate the amount of water we need to liquor back?
(Gravity / Target gravity) x actual volume - actual volume = Liquor back water
164
What is the cell count in the beer at the end of fermentation?
Ideally below 1 million cell per ml.
165
Why should we get rid of the yeast not too long after the end of fermentation and maturation?
To avoid meat and shit flavor that appear with autolysis.
166
What is the adequate pitching rate for an average gravity beer?
10 million cells per ml.
167
What is the adequate viability for pitching yeast?
At least 95% viable cells.
168
What’s the protocol for acid washing yeast cells?
1. Cool yeast to 4 degrees C.
2. Add ortho-phosphoric acid to bring pH to 2.1 and stir.
3. Leave for 60mn max.
4. Add to cooled wort in FV to quench reaction.
169
What substance is used to test yeast cell viability?
Methylene blue.
170
Give the normal cell count for the three stages of fermentation.
Start: 10 million cells / ml
Middle: 50 million cells / ml
End: 1 million cells / ml
171
How much IBUs are usually needed to inhibit Lactobacillus?
As few as 8 IBUs (but some strains are more resistant).
172
What does it mean when we say a bacteria is facultatively heterofermentative?
The bacteria will perform homolactic fermentation in conditions of abundance of nutrients, and in heterolactic conditions in poor conditions.
173
What’s the difference between titratable acidity and pH?
* pH only measures the free hydrogen ions, therefore in weak acids not all the acidity is measured.
* Titratable acidity measures all hydrogen ions (associated and dissociated).
174
What are the 4 methods of sour beer production?
- Pre-boil souring
- Sour Mash
- Kettle souring
- Post-boil souring
175
Why do brewers use sour mashing with caution?
The low pH produces a low mash enzyme effect.
176
What are the advantages of kettle souring?
- Speed: souring of the wort within days of inoculation.
- Hops do not inhibit lactobacillus as they haven’t yet been added.
- pH and TA are easy to monitor
- Souring can be stopped by boiling the wort.
177
What are the temperature range for souring?
Between 42 to 48C.
178
What’s the gravity threshold for lactobacillus souring?
1.040
179
What is the taste threshold for diacetyl?
Ales : >0,3mg/l
| Lagers : >0,1mg/l
180
How much bicarbonate is sodium carbonate?
Sodium carbonate is 73% bicarbonate.
181
How much sulfate is calcium sulfate?
Calcium sulfate is 56% sulfate.
182
How much chloride is calcium chloride?
Calcium chloride is 64% chloride.
183
How much calcium is calcium sulfate?
Calcium sulfate is 23% sulfate.
184
How much water is calcium sulfate?
Calcium sulfate is 21% water.
185
How much calcium is calcium chloride?
Calcium chloride is 36% calcium.
186
What is the Tinseth Formula for calculating IBU?
IBU = (Vol. hops in gr. x Alpha acids x Decimal AAU x 10)/Batch Vol.
187
In the Tinseth Formula, what does "Decimal AAU" stands for?
Decimal Alpha Acids Utilization, which is used by the Tinseth method to express the utilization of hops as a function of boil time and wort gravity.
188
What are IBUs?
International Bitterness Unit, scale which accurately describes the bitter content of beer. Direct measurement of the concentration of isohumulones, the bitterness-causing chemical component of beer. The scale is given as a number, representative of the parts per million of isohumulone in the sample.
189
Why does the IBU scale is sometimes not in accordance with the perceived bitterness?
The bitter taste of beer can be masked through additional flavours and malts, so the IBU value may not be totally representative of the consumer’s perceived bitterness taste.
190
How can we calculate the future EBC of a recipe?
(Malt vol./Batch vol.) x 100 = ?
( ? x Malt EBC) / 10 = EBC contribution for this malt
We do this calculation for each malt of the grist, then add all the EBCs to have the final EBC.
191
What is the minimum proportion of diastatic malts in a recipe?
A brewer should at least provide 75% of pale or lager malt.
192
How do we calculate the degrees of fermentability when designing a beer?
ABV / F factor = Degrees of fermentability
193
How do we calculate the OG when designing a beer?
Degrees of fermentability x (100 / 80) = OG
In this exemple, we have 80% fermentable sugars. This proportion depends on the temperature of the mash.
194
How do we calculate the amount of malt we need to attain our OG?
OG x Vol. Batch = the Litre degrees we want.
BUT mashing vessel are not 100% efficient, so we need more malt:
Litre degrees / Efficiency = the extract we aim for.
```
E.G.
I am doing 25L of a 1.039 OG beer, with 100% PA malt (305°L/KG).
39 x 25 = 975 liter degrees.
If my efficiency is 75%:
975 / 75 x 100 = 1300°L.
```
1300 / 305 = 4.26kg of PA Malt.
195
What are the most common sulphuric compounds found in beer?
Dimethyl Sulphide
Hydrogen Sulphide
Sulphur Dioxide
Thiols
196
What off flavor comes from dimethyl sulfide?
Boiled cabbage
197
What off flavor comes from hydrogen sulfide?
Rotten eggs
198
What off flavor comes from sulphur dioxide?
Struck matches
199
What off flavor comes from thiols?
Skunk, lightstruck
200
What are the 3 main factors of DMS production ?
Lightly killed malt, yeast production during fermentation, and hot wort air exposure.
201
Where do the polyphenols come from?
They arise from the polymerisation of phenols present in the wort.
Avoid last runnings from the mash tun, below 1.007, as they are high in polyphenols.
202
What is the main ingredient of Isinglass Finings?
It is obtained from the swim bladders of fish.
203
What substance brings herbal and woody flavor, and is most notable in noble hops?
Humulene.
204
In hops, what substance brings citrus and pine aroma in beer?
Myrcene.
205
What is the difference between humulene and humulone?
Humulene is one of the components of the essential oil from the flowering cone of the hops plants.
Humulone is one of five alpha acid analogues in hop resin.
206
What bittering substance can we use to remove the risk of "skunking" or "light struck beer"?
Reduced pre-isomerised extracts (or Tetra hydro-iso-alpha acids, Hexa hydro-iso-alpha acids). They are used in beer bottled in clear glass.
207
Appart from removing the risk of skunking, what is the other benefit of reduced pre-isomerised extracts?
Tetra and Hexa hydro-iso-alpha acids are also very foam positive.
208
Where are situated the resins and essential oils of the hop plant?
In the cone, and more precisely in the lupulin glands.
209
What are the parameters that affect hop utilization?
- Gravity of the wort
- Degree of agitation in the copper
- Duration of the boil
- Wort pH
- Alpha acids content
- Addition rate
210
What is the temperature range for the use of peracetic acid?
5°c to 40°c.
211
What does CIP mean?
Cleaning in place.
212
What is temporary hardness?
Temporary hardness is water hardness due to the presence of calcium and magnesium carbonates and bicarbonates, which can be precipitated by heating the water, leaving water that is softer upon cooling.
213
What is permanent hardness?
Permanent hardness refers to the mineral content in water that is not possible to remove through boiling. The hardness is typically caused by the presence in water of magnesium sulfates and/or calcium sulfate that do not undergo precipitation at increased temperatures.
214
What is the desirable pH for brewing liquor?
Around 6.2 to 6.8
215
What is the desirable pH at the start of the mash?
5.6
216
What is the desirable pH for pre boil wort?
5.3
217
What is the desirable pH for post boil wort?
5.1
218
What is the desirable pH for beer?
4
219
What are the results of low calcium levels in brewing?
Poor fermentation, poor alpha amylase activity, poor hop isomerization, poor yeast flocculation.
220
Why should we use calcium salts instead of magnesium salts to correct the water profile of the brewing liquor?
Because magnesium salts impart a harsh bitter metallic taste, because more is required to neutralise acid, and they also have a laxative effect.
221
When we condition brewing water to increase alkalinity, where should we add sodium bicarbonate?
In the HLT.
222
When we condition brewing water to decrease alkalinity, where should we add phosphoric acid?
In the HLT.
223
When we condition brewing water to increase calcium levels, where should we add calcium sulphate?
In the mash. But usually, calcium levels are above what we need because of the previous addition of calcium chloride and calcium sulphate.
224
When we condition brewing water to increase sulphate levels, where should we add calcium sulphate?
In the mash.
225
When we condition brewing water to increase chloride levels, where should we add calcium chloride?
In the mash.
226
In what order should we condition water before brewing?
- Alkalinity : in the HLT, with sodium bicarbonate or phosphoric acid.
- Sulphate : in the mash, with calcium sulphate.
- Chloride : in the mash, with calcium chloride.
- Calcium : in the mash, but usually needless.
227
What is the moisture level of stored dry barley?
12% moisture.
228
At what temperature is ale malt kilned?
100°c.
229
At what temperature is lager malt kilned?
84-85°c.
230
What is the specificity of crystal malt production?
After steeping, crystal malt is stewed in a closed system that doesn’t allow moisture to escape: the starch interiors of the grains are broken into sugars by amylase enzymes in the barley. Kilning then dries the grain, darkens the husk and caramelizes some of the sugar inside, which brings its distinct flavor to the beer.
231
What is the specificity of roast barley production?
It is kilned unmalted, making it one of the darkest grain (just after black malt), and is characterized by an intense, coffee-like roasty aroma.
232
What is the pH range that produce the highest level of fermentable sugars?
Between 5.4 to 5.5.
233
What small vessel is used to maintain even flow from the mash tun to the kettle?
An underback.
234
What are the 5 phenomenons that happen during fermentation?
- Cells sedimentation
- Gravity fall
- Increase in ABV
- Increase in carbonation
- Flavour change
235
What can we use to restrict the number of micro-organisms in finished beer?
Sulphites (SO2) (but with caution as 5-15mg/L are naturally produced by yeast and through isinglass additions).
236
What are the causes of permanent haze?
The presence of active forms of oxygen, but also metal ions (tin, lead, copper and iron), causing the proteins and polyphenols to create permanent covalent bonds.
237
What makes a haze reversible?
A haze is reversible when the proteins and polyphenols are loosely linked by hydrogen bonding.
238
To avoid colloidal haze, what should be the maximum nitrogen level in the grist material?
1.7% as a guide.
Ales: 1.45%-1.55%
Lagers: 1.6%-1.7%
239
What is PVPP (Polyvinylpyrrolidone) used for?
It is a polyphenol absorbant used to achieve colloidal stability.
240
What are silica hydrogels used for?
They are used as colloidal stabilizers, preventing haze formation through protein removal.
241
What is the increase in moisture from stored barley to fully hydrated barley in a steep tank?
From 12% to 45%.
242
What are the different steps involved in malting?
Drying, storage for dormancy, steeping, germination, kilning.
243
What are the pH levels of wort and beer?
5.3 and 4.0 respectively.
244
Why do some mash systems need a progressive increase in temperature?
Enzymes to digest Beta glucan, protein and starch have different optimal temperatures.
245
What is the first step of germination?
Germination starts by the embryo releasing gibberellin hormone to stimulate enzyme synthesis in the aleurone layer.
246
What is the main use of flaked maize in the grist bill?
Flaked maize can be used to decrease colour in a light ale.
247
In the realm of cleaning agents, what do we call "builders"?
They are the basic active ingredients of detergents, and they increase their cleaning power.
Alkaline builders: potassium or sodium hydroxide, they help to increase the dispersion of organic soils.
Acidic builders: phosphoric or nitric acid, they remove mineral stone, scaling and biofilm.
248
What substances are used as alkaline builders?
Potassium or sodium hydroxide, they help to increase the dispersion of organic soils.
249
What substances are used as acidic builders?
Phosphoric or nitric acid, they remove mineral stone, scaling and biofilm.
250
In the realm of cleaning agents, what do we call "surfactants"?
They lower surface tension, allowing efficient wetting of the surface, and breaking down the interface between water and oils and/or dirt.
251
In the realm of cleaning agents, what do we call "water conditioners"?
They are important parts of detergent, they bind inorganic cations in the water (calcium, magnesium...) that would otherwise produce scale or reduce detergent effectiveness, in a complex that is soluble in water. They are divided between sequestering and chelates (the latter create much greater bonds).
252
What is the difference between chelates and sequestering agents?
They all bind inorganic cations in the water (calcium, magnesium...) that would otherwise produce scale or reduce detergent effectiveness, but chelates create much greater bonds.
253
In the realm of cleaning agents, what do we call "oxidizing agents"?
They are used as a cleaning booster in manu alkaline detergents. Oxidation is needed to remove burnt on protein and biofilm.
The most common and effective oxidizing agents are hydrogen peroxide and sodium hypo-chloride based products.
254
What are the most common and effective oxidizing agents?
The most common and effective oxidizing agents are hydrogen peroxide and sodium hypo-chloride.
255
What are the most potent micro-biocidal cleaning chemicals available?
Peracetic and peroxyacetic acids. They are fast acting, don't foam, require no rinsing and are non-polluting.
256
How do peracetic and peroxyacetic acids work as a disinfectant?
They destroy the enzyme apparatus of the micro-organisms cells by oxidation.
257
What is the difference between disinfecting and sterilizing?
Disinfection kills 99.99% of the micro-organisms. Sterilization is the complete obliteration of all forms of life.
258
What are the 4 factors to be taken into consideration when we want to achieve optimal soil removal?
- Temperature
- Time
- Mechanical effect
- Concentration
259
Why do we clean?
- To avoid contamination and keep product integrity
- To maintain processing efficiency
- To maintain shelf life of the product
- To maintain safe working conditions
260
What is the difference in temperature use between caustics and acids?
Acids are used cold
| Caustics are used hot
261
Where is disinfection required in the cleaning process of a brewery?
In the heat exchanger, in the fermenters and in all the cold pipes.
262
What are the 3 risks associated with hypochlorite use?
- Pitting corrosion
- Chlorophenolic taint
- Acid + chlorine = chlorine gas, very toxic!
263
What does PPE stand for?
Personal protective equipment.
264
What does CCSHH stand for?
Control of substances hazardous to health regulations.
265
What does MSDS stand for and how do we use it?
Material safety data sheets, that we receive from our suppliers to tell us about the risks from each substance.
266
At what temperature is Vienna malt kilned?
At 115°c, to produce a 7-10 EBC color. It is used as 15% of the grist in German beers.
267
At what temperature is Munich Malt kilned?
At 115°c.
268
At what temperature is Melanoidin malt kilned?
At 130°c.
269
At what temperature is Biscuit malt kilned?
At 160°c. It is used in lagers and brown ales to intensify roast character.
270
What is the Cabot torrefaction ?
The grains are heated at 100°c using steam, and blown through a heated atmosphere. This disrupts the grain structures and gelatinizes the starch granules (//pop-corn). Usually used for wheat and barley.
271
Why do sugar adjuncts cause fermentation problems if used in high levels?
They only provide carbohydrates and not enough amino acids. It can lead to poor yeast growth.
272
What is the moisture content of hops after kilning?
10% moisture.
273
What are the Kolbach Index and SRN ratio?
They are used to measure malt modification. The higher the %, the higher the modification. A well modified malt should be >38%.
274
What is the temperature optima for viscosity reduction by beta-glucanase?
40-45°c.
275
What is the temperature optima for protein reduction by proteases?
50-54°c.
276
When should we use a protein and beta-glucan rest?
When the malt is poorly modified.
277
How much kappa carrageenan should we add 10 minutes before end of wort boiling?
25-35mg/L.
278
To what end do we add kappa carrageenan at the end of the wort boiling?
The kappa carrageenan gel react with hot and cold proteins, facilitating their removal due to binding increasing weight and losing buoyancy.
279
What at the sources of lactic acid in sour beer?
Lactobacillus and Pediococcus.
280
What at the sources of acetic acid in sour beer?
Acetobacter and Brettanomyces.
281
What is the typical rate addition of auxiliary finings?
3.5ml/L.
282
What is the composition of auxiliary finings?
Acidified solution of alginates, polysaccharides or silicates, negatively charged.
283
What are the difference in use of alginates, polysaccharides or silicate based auxiliary finings?
- Alginate and polysaccharide based: use at least 4 hours before isinglass finings.
- Silicate based: can be use after of before isinglass.
284
What does HACCP stand for?
Hazard analysis critical control points.
285
What is the point of HACCP?
It deals with hazards to consumer health from the product we make, identifying the points in operations where they can occur, and implementing controls and periodical reviews.
286
In the HACCP system, what is a pre-requisite?
```
It is an expected practice, part of the overall food safety plan.
E.G.:
- Supplier quality assurance
- Training protocol
- Hygiene
```
287
In the HACCP system, what is a CCP?
Critical control point. When a process does not totally eliminate a grave hazard to an acceptable level, it becomes a CCP. It is the last chance to control a process before the product is presented to the consumer.
288
Where does the grassy off-flavor come from?
From Hexen-1-ol, found in poorly stored malts and badly dried hops.
289
Where does the butterscotch off-flavor come from?
From diacetyl, produced by bacterial/wild yeast contamination, or incomplete maturation.
290
Where does the vegetable off-flavor come from?
It comes from S-methylmethionine, naturally present in barley, which breaks down into dimethyl sulfide. It can also come from contamination by short rod bacteria.
291
Where does the clove off-flavor come from?
It comes from eugenol, which is released by wild yeast.
292
Where does the medicinal off-flavor come from?
It comes from sterilant contamination, or infection by enteric bacteria.
293
Where does the cheesy off-flavor come from?
It comes from valeric acid, which is released in oxidized hops.
294
Where does the papery off-flavor come from?
It comes from trans-2-nonenal, which is found in oxidized hops.
295
Where does the baby sick off-flavor come from?
It comes from butyric acid, released by bacterial contamination.
296
Where does the light struck off-flavor come from?
It comes from mercaptans and iso-pentenyl that are produced during the degradation of the hop acids by light;
297
Where does the sour off-flavor come from?
It comes from acetic or lactic acid released by bacterial contamination.
298
How gluten free beers are produced?
- Using the enzyme called Brewers Clarex, which breaks down the proteins that are responsible for triggering bowel symptoms.
- Using gluten-free grains such as sorghum, quinoa, buckwheat, rice or millet.
299
What is Stokes Law?
Stokes law predicts that large dense particles will settle faster than small light ones, and any particle will settle best in a low density and low viscosity liquid.
300
Why is the use of sulphur dioxide to enhance shelf stability problematic?
Because it is not very effective at the pH of beer, and also because 1 out of 100 people is sulphite-sensitive.
Isinglass and auxiliary are preserved with sulphites, and it will take the level of beer just below the legal limits.
301
What is the negative effect of filtration?
EBU and colors are reduced by 10%, and aroma compounds even more.
302
Can filtration totally get rid of colloidal haze?
No, it has been demonstrated that colloidal particles approximately 0.5-1 micro-meter play a major part in beer haze formation. Many of them will remain after the filtration.
