Volatile acidity in a wine is measured chiefly as
Answer: A
Volatile acidity is dominated by acetic acid and is therefore a direct measure of spoilage by acetic acid bacteria and, to a lesser extent, by certain yeasts. Tartaric and malic acids come from the grape and are not volatile.
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The cereal most commonly used to brew beer is
Answer: B
Barley is preferred because it malts well, is rich in the enzymes needed to convert its own starch, and retains a husk that acts as a natural filter bed during lautering. Rice and maize appear as adjuncts rather than as the main grain.
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Malting barley is essentially a process of
Answer: C
The grain is steeped and allowed to germinate so that enzymes develop and the starch reserves begin to be mobilised, then dried in a kiln to arrest the process and fix the flavour. No fermentation takes place at this stage.
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The chief purpose of malting is to develop
Answer: D
Correct answer: Enzymes able to convert starch into fermentable sugar
Barley grain is nearly all starch, which yeast cannot ferment. Malting germinates the grain just far enough for it to produce the amylases that break that starch down, then arrests the process by kilning before the seedling consumes the reserves. The enzymes survive to do their work later, in the mash.
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Mashing in brewing refers to
Answer: A
Correct answer: Holding milled malt in warm water so enzymes convert starch
Mashing holds the crushed malt at around 63 to 68 degrees, the range in which the amylases developed during malting work fastest without being destroyed. Over an hour or so they convert the starch into maltose and other fermentable sugars, and the sweet liquid drawn off is the wort.
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Wort is best described as
Answer: B
Correct answer: The sugary liquid extracted from the mash before fermentation
Wort is to beer what must is to wine: the unfermented sugary liquid the yeast will act upon. It is separated from the spent grain, boiled with hops, cooled, and only then pitched with yeast.
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Boiling the wort with hops serves to
Answer: C
The boil isomerises the hop resins to give bitterness, drives off unwanted volatiles, coagulates protein and destroys the organisms present in the wort. Starch conversion happened earlier in the mash and no yeast is present until the wort has cooled.
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Hop compounds contribute to the microbiological stability of beer because they
Answer: D
Iso-alpha acids from hops are antibacterial against many Gram-positive organisms, which is one reason the spoilage flora of beer is narrow. The organisms that do spoil beer, notably certain Lactobacillus and Pediococcus strains, are precisely those that have become hop resistant.
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Ale is produced using yeast described as
Answer: A
Correct answer: Top fermenting, working at warmer temperatures
Ale yeast, Saccharomyces cerevisiae, works at 15 to 22 degrees and rises with the foam to the top of the vessel. The warmth encourages ester formation, which is why ales carry fruity notes that lagers do not. The fermentation is also quicker, finishing in days rather than weeks.
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The yeast used to brew lager is
Answer: B
Correct answer: Saccharomyces pastorianus
Lager is brewed with Saccharomyces pastorianus, a hybrid of S. cerevisiae with the cold-tolerant S. eubayanus. It ferments at 8 to 14 degrees and settles to the bottom, producing few esters and so the clean character lager is valued for. S. cerevisiae is the ale yeast, while Brettanomyces and Zygosaccharomyces are spoilage organisms.
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