The word must applies to
Answer: C
Correct answer: Unfermented grape juice
Must is the winemaking term specifically; the corresponding brewing term is wort. Neither applies to lees, which is the sediment, or to the foam on a fermenting beer, which is the barm or kraeusen.
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The residual sweetness of a beer depends chiefly on
Answer: D
Attenuation measures how much of the fermentable extract the yeast has used, so a highly attenuating strain leaves a drier beer and a poorly attenuating one a sweeter beer. Hops affect bitterness and kilning affects colour and malt character.
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Which is true of both wine and beer fermentation?
Answer: A
The central conversion is the same in both, performed by Saccharomyces under anaerobic conditions. Where they differ is in how the sugar is obtained, since barley must be malted and mashed while grapes supply it directly.
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Which best explains why fermented beverages keep longer than the raw materials they are made from?
Answer: B
Correct answer: Alcohol and acid together exclude most organisms
Fermentation converts a sugary, near-neutral liquid that would spoil in days into one holding 5 to 14 per cent alcohol at a pH around 3 to 4, and few organisms tolerate both conditions at once. The addition of hops in beer and sulphur dioxide in wine narrows the field further. Preservation by fermentation is the oldest use of the process.
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Which vessel material has traditionally been used to mature wine and to influence its flavour?
Answer: C
Oak barrels contribute vanillin, tannin and other compounds while permitting a slow ingress of oxygen that matures the wine. They are also, unfortunately, a favourite refuge of Brettanomyces, which is one reason barrel hygiene matters.
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Which measurement would a brewer use to follow the progress of a fermentation?
Answer: D
As sugar is converted to alcohol the liquid becomes less dense, so gravity readings taken over time show how far fermentation has gone and when it has finished. Colour, bitterness and kilning are all fixed before the yeast is pitched.
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Sulphur dioxide is more effective against wine spoilage organisms at
Answer: A
The active molecular form predominates at low pH, so the same total addition is far more effective in a high-acid wine than in a low-acid one. This is why winemakers adjust the dose according to the pH of the wine rather than using a fixed rate.
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Which of the following would NOT help prevent spoilage of bottled wine?
Answer: B
Correct answer: Leaving a large air space in each bottle
Head space means oxygen, and oxygen is what the acetic acid bacteria and film yeasts need - so a large air space invites precisely the spoilage the other three measures guard against. Filtration removes the organisms, minimal head space starves them of oxygen, and sulphur dioxide is both antimicrobial and antioxidant.
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Beer with a low hop rate and low alcohol is more vulnerable to spoilage because
Answer: C
Beer resists spoilage through several barriers at once, and lowering both the hop compounds and the alcohol removes two of them, widening the range of organisms able to grow. Such products need correspondingly stricter hygiene and processing.
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Which organism would you expect to find in a healthy, actively fermenting wine?
Answer: D
Correct answer: Saccharomyces cerevisiae
S. cerevisiae is the wine yeast, and finding it in large numbers in an actively fermenting vat is exactly what is expected. The other three are spoilage organisms: Acetobacter makes vinegar, Brettanomyces gives barnyard and medicinal phenols, and Pediococcus sours the wine.
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