BJCP National · Lesson 14 · Technical pool (P0) · 8 days to exam
Three technical-pool areas flagged as weak on 2026-08-07, put in priority order. Yeast is first and it is not a tie: the five selection considerations question has already been missed twice on live mocks. Water and hops are volume problems, and both have a spine that collapses the volume.
The question asks for five selection considerations – the criteria you use to choose a strain. Not four yeast families, not named strains, not styles. The failure here has never been knowledge; it has been answering a different question. Prescriptions 2026-07-28-P0-1 (nothing written) and 2026-07-30-P0-1 ("question asks for five SELECTION CONSIDERATIONS; answered with four yeast FAMILIES … the fifth slot is empty").
One sentence of ground first, because it usually opens the answer. Ales use top-fermenting Saccharomyces cerevisiae; fermentation by-products such as fruity, estery flavors are usually evident and make up a significant part of the ale profile. Lagers use bottom-fermenting S. pastorianus, whose colder fermentation reduces or eliminates esters, giving a cleaner-tasting beer. [src: Study Guide, Ales/Lagers overview]
| # | Consideration | What it is, and what it buys you |
|---|---|---|
| 1 | Attenuation | Apparent attenuation = the strain's ability to decrease wort original gravity upon fermentation, listed as a percent. Ale yeasts 69–80%, lager yeasts 67–77%; a higher-attenuating strain ferments more of the wort sugars. Style lever: body and dryness of the finish. [src: Study Guide, Yeast] |
| 2 | Flocculation | The yeast's ability to settle out of the beer on completion of fermentation; varies significantly with strain. Powdery (Frohberg) lager yeast stays suspended longer and attenuates more; break (Saaz) type flocculates readily and attenuates less. Style lever: clarity – and note it is coupled to attenuation, so one choice moves two things. [src: Study Guide, Yeast] |
| 3 | Fermentation temperature | Ale yeast works best at 55–75 °F (13–24 °C), lager yeast at 46–56 °F (8–13 °C) – California Common lager yeast excepted, 58–68 °F (14–20 °C). The causal link to remember: ale yeasts produce esters because they require higher temperatures to remain active. Temperature is not a parameter sitting next to the flavor profile – it is what produces it. [src: Study Guide, Yeast] |
| 4 | Alcohol tolerance | How well a strain continues to ferment as alcohol concentration rises. Most lager yeast up to about 8% ABV; some ale strains up to 12%. Style lever: whether a strong wort finishes at all. [src: Study Guide, Yeast] |
| 5 | Fermentation by-products | Yeast produces and metabolizes esters (fruity, sweet aroma), fusel alcohols (harsher, solvent-like), diacetyl (buttery) and sulfur compounds (e.g. hydrogen sulfide, rotten-egg). German weizen strains generate high clove-like phenols and banana/bubblegum esters. This is the slot where POF+ / POF− lives. [src: Study Guide, Yeast] |
Two minutes on the clock: name the five yeast selection considerations, and give one style consequence for each.
Write it, do not think it. This one failed twice as a retrieval problem, not a comprehension problem – reading it again will not fix it. Half-answers count as misses.
Attenuation (body and dryness of the finish) · Flocculation (clarity, and it moves attenuation with it) · Fermentation temperature range (it is what drives ester and phenol expression) · Alcohol tolerance (whether a strong wort finishes) · Fermentation by-products including POF+/POF− (clove phenols in Weissbier vs a clean lager)
On 2026-07-30 the answer listed four yeast FAMILIES instead of considerations and timed out with the fifth slot empty. Forty minutes earlier in that same mock, an 18 °C ferment was chosen specifically for its ester and phenol profile – so consideration 3 and 5 were being applied correctly while the list itself could not be produced. Recite the list, not the concept.
Water reads as an unstructured pile of facts until you give it a spine. It has four vertebrae, and they are worth rehearsing in this order.
Calcium is the most important cation in brewing: essential for reducing the mash pH to the target 5.1–5.5 range (needed for starch and protein breakdown). It also keeps oxalate salts in solution – they form haze and gushing if they precipitate – reduces tannin extraction, and aids protein coagulation in the hot and cold breaks. [src: Study Guide, Ions in Brewing]
Bicarbonate (HCO3−) is the most important anion because it determines the alkalinity of the brewing water. It neutralizes acids from dark and roasted malts, reacts with calcium to reduce hardness, and promotes the extraction of tannins and coloring compounds. [src: Study Guide, Ions in Brewing]
| Ion | Effect |
|---|---|
| Sulfate | Accents hop bitterness and dryness at high concentrations, as at Burton. |
| Chloride | Enhances sweetness at low levels; high levels hamper yeast flocculation. |
| Sodium | Accents sweetness at low levels, salty at higher – part of Gose. |
| Magnesium | Yeast nutrient at 10–20 ppm; harsh and mineral above that. |
[src: Study Guide, Ions in Brewing]
When the water is too alkaline, mash pH can be reduced by adding lactic or phosphoric acid to the brewing liquor when brewing pale-colored beers. It can also be adjusted with acidulated malt, produced using lactic acid generated by the naturally occurring lactobacillus on the grain. Third, the natural acidity of toasted, caramel and roasted malts lowers mash pH: using a dark crystal or roasted malt for 20% of the grainbill can drop pH by about 0.5, usually enough to reach the proper level for starch conversion. The source notes that this need to include higher-kilned malts "played a role in the development of several historical beer styles" – which is the hinge into the city table below. [src: Study Guide, mash pH]
Sulfate plays no significant role in the brewing process itself, but it accents hop bitterness and dryness at high concentrations – so its ranking is the cheapest way to hold the whole table. More sulfate = drier, more assertive bitterness. Less sulfate = mellow, smooth bitterness.
Burton 820 ≫ Vienna 216 > Dortmund 120 > Edinburgh 105 > Munich 79 > Dublin 54 > London 32 > Plzen 4 ppm, Famous Brewing Waters table in the Study Guide, from Palmer, How to Brew.
| City | Water → style |
|---|---|
| Plzen | Very low hardness and alkalinity let the proper mash pH be reached with only base malts; combined with the lack of sulfate this yields the rounded malt character and mellow hop bitterness of Czech Premium Pale Lager. |
| Dortmund | Higher level of all minerals lets brewers of Dortmunder Export and German Pils make pale lagers that are bolder, drier and lighter in color than their Czech counterparts. Not "smoother and rounder" – that is the Plzen line. |
| Munich & Edinburgh | Remarkably similar water. The darker malts used for amber and dark German lagers and Scottish ales balance the carbonates and acidify the mash for a very smooth malt character; relatively low sulfate gives mellow hop bitterness. |
| Vienna | Calcium too low to balance the bicarbonate for a sufficiently low pH with pale malts; kilning malt at higher temperatures added color and acidity, giving birth to the reddish-amber Vienna Lager. |
| Dublin | Calcium/bicarbonate imbalance even greater than Vienna's, leading to Irish Stout (high percentage of roasted barley and malts); its relatively high IBU is softened by low sodium, chloride and sulfate. |
| London | Bicarbonate nearly twice its calcium, so brewers used more dark malt to balance mash pH; high sodium and low sulfate smooth the flavor of brown British beers such as Dark Mild and English Porter. |
| Burton-on-Trent | Calcium 352 and sulfate 820 far higher than any other city listed, but the calcium is nearly balanced by the bicarbonate (320) – this let brewers make British Bitters lighter in color than London ales. High sulfate and low sodium (44) give an assertive, clean hop bitterness. |
[src: Study Guide, Famous Brewing Waters]
Burton-on-Trent water, in one clause – which is right?
If you keep one thing from water, keep the three-point contrast. Say it.
Three cities, one clause each, in sulfate order.
Plzen, very soft (Ca 10, SO4 4, HCO3 3): base malts alone reach the proper mash pH, and the lack of sulfate yields the rounded malt character and mellow hop bitterness of Czech Premium Pale Lager. Dortmund, all minerals high: bolder, drier and lighter in colour than the Czech counterparts. Burton, extreme calcium and sulfate: assertive, clean hop bitterness, and Bitters lighter in colour than London's.
These three are the poles; Vienna, Dublin, London, Munich and Edinburgh all sit as consequences of the same two variables – calcium/bicarbonate balance and sulfate level. Derive, do not memorise eight paragraphs.
Blocks 1 and 2 are mechanism – understood once, they hold. Block 3 is pure recall and is normally the one that leaks. Read all three once, then drill only the block that actually failed; there is no value in re-reading a block you already have with eight days left.
The lupulin resin of the hop cone contains alpha acids and essential oils, which contribute the characteristic bitterness, flavor and aroma associated with hops in beer. Bitterness arises from the alpha acids – humulone, cohumulone and adhumulone, in proportions that vary by variety – which are isomerized into iso-alpha acids in a vigorous boil, making them much more soluble in the wort and increasing their bitterness. The essential oils contribute flavor and aroma and consist of dozens of compounds; many are volatile and do not survive extended boil times, so flavor and aroma hops are generally added during the last 30 minutes of the boil. [src: Study Guide, Hops]
Aroma hops are generally lower in alpha acid but contribute desirable flavor and aroma; bittering varieties are higher in alpha acid with less-refined flavor and aroma; some are dual-purpose. The finest aroma hops are the noble varieties: Saaz, Spalt, Tettnanger and Hallertauer Mittelfrueh. [src: Study Guide, Hops History]
AAU/HBU (weight in ounces × alpha-acid percent) is the simplest, but describes potential bitterness without accounting for the many factors that determine actual bitterness. IBU is the concentration of isomerized alpha acids in the finished beer (mg/L or ppm) and is more precise. BU:GU (IBU divided by the last two digits of OG) characterizes style balance. [src: Study Guide, Bitterness from Hops]
| When added | What you get |
|---|---|
| 60–90 min | Isomerization requires a vigorous boil; bittering hops are most efficient at yielding iso-alpha acids in this window. |
| 10–40 min | Flavor hops – less bitterness, retain some essential oils for characteristic flavor. |
| at or near end of boil | Little or no bitterness, some flavor and aroma. |
| during / after fermentation | Dry hops – fresh hop aroma, little or no bitterness. |
| first wort | Hops added to the first sweet-wort runnings from lautering (higher pH) and kept through the boil give a smoother, more refined bitterness plus fresh hop flavor and some aroma. An old German method used for hop-centered styles like Pilsener. |
Utilization tops out at about 30% in the home brewery and is often lower. It is reduced by: shorter boil, lower boil temperature, higher wort gravity, whole hops vs pellets, higher hopping rate, hop bags, older hops, lower wort pH, more flocculent yeast and filtering. [src: Study Guide, Bitterness from Hops]
| Style | Varieties and descriptors |
|---|---|
| British ales | Native varieties: East Kent Goldings, Northern Brewer, Challenger, Fuggles. Goldings – earthy, peppery, lemon-like. Fuggles – earthy with cedar/tobacco/floral notes. Challenger – tea-like earthiness with light citrus. |
| Czech Premium Pale Lager | Saaz – the style is partially defined by its characteristic spicy Saaz aroma and flavor. |
| German pale lagers | Tettnanger, Hallertauer Mittelfrueh, Spalt – slightly peppery or woody spiciness with a soft floral or light citrus character. |
| Altbier | Subdued hop aroma and flavor with a clean bitterness from low-alpha Spalt. Dunkles Bock and Munich Helles similarly benefit from the soft bitterness of low-alpha noble varieties. |
| American Pale / Brown Ale | Cascade, Centennial, Columbus, Chinook. Cascade and Centennial – grapefruit and floral (Centennial a little more floral). Columbus and Chinook – high-alpha, assertive pine/resin, herbal, light citrus. |
| American IPA / Double IPA / American Strong Ale | Generous New World hops: Amarillo (orange-blossom), Citra (orange-rind plus tropical: mango, passion fruit, pineapple), Simcoe (grapefruit, pine, tropical), Mosaic (blueberry, tangerine, pineapple, peach). Region of cultivation matters as much as variety. |
[src: Study Guide, Varieties]
Which of the three hop blocks actually failed for you – lupulin, extraction, or varieties?
Do one cold pass over all three, then answer honestly. The point of this lesson is to stop drilling the blocks you already have.
Blocks 1 and 2 are causal chains – if you can explain why aroma hops go in late (volatile oils) and why first wort hopping is smoother (higher pH), you have them and you should stop. Block 3 is a lookup table with no internal logic, so it is the only one that decays, and it is the one that earns repeated passes.
Eight days is enough to fix one leaking block properly and not enough to re-cover three. Spend the passes where the decay is.