The role of salt in a vegetable fermentation is best described as
Answer: C
Salt-tolerant lactic acid bacteria continue to grow at concentrations that check many Gram-negative spoilage bacteria, so salting tilts the competition in their favour. It supplies no nutrient, sterilises nothing and has no direct effect on pH.
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Too little salt in a vegetable fermentation is likely to result in
Answer: D
Insufficient salt lets softening organisms and other competitors grow alongside the lactic acid bacteria, so the texture goes and spoilage follows. It is excess salt, not shortage, that holds back the lactic acid bacteria and encourages the pink yeasts.
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Too much salt in a sauerkraut fermentation tends to
Answer: A
Above the intended range the lactic acid bacteria are slowed while more salt-tolerant yeasts, including the pigmented ones responsible for pink kraut, are relatively favoured. The fermentation becomes sluggish rather than faster.
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Fresh-pack or quick-process pickles differ from fermented pickles in that they are
Answer: B
Quick-process pickles are packed in an acid solution and heat processed, so no fermentation takes place and no microbial succession occurs. They can be made in hours rather than weeks, and taste of vinegar rather than of lactic fermentation.
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Kimchi resembles sauerkraut microbiologically in that both are
Answer: C
Kimchi is a salted vegetable fermentation driven by the same families of lactic acid bacteria, with Leuconostoc prominent in the early stage as in kraut. The seasonings and the vegetables differ, but the microbiology follows the same pattern.
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Vegetables suitable for lactic fermentation must supply
Answer: D
The bacteria can only make acid from sugar, so a vegetable low in fermentable carbohydrate will not acidify properly however carefully it is salted. Cabbage and cucumbers both carry enough for the purpose in their juice.
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Blossoms and plant trash are removed from cucumbers before brining because they
Answer: A
Flowers in particular carry moulds rich in pectin-degrading enzymes, and those enzymes survive to soften the pickles even after the mould itself has gone. Cleaning the fruit is therefore a control measure against softening rather than a cosmetic step.
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Keeping fermenting vegetables submerged beneath the brine chiefly prevents
Answer: B
Moulds and film yeasts need oxygen, so denying them a surface to grow on prevents both the softening enzymes they bring and the loss of acid they cause. The lactic acid bacteria are unaffected because they do not require air.
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Which organism would you NOT expect to find carrying out a sound sauerkraut fermentation?
Answer: C
Correct answer: Acetobacter aceti
Acetobacter is an aerobic acetic acid bacterium: it needs air, which a sound fermentation excludes, and it would produce vinegar rather than lactic acid. The other three are the successive lactic acid bacteria of the kraut fermentation, appearing in order as the acidity rises.
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The characteristic flavour of sauerkraut owes much to
Answer: D
The mixed products of the Leuconostoc stage, acetic acid among them, give kraut a complexity that lactic acid on its own would not. A fermentation that skips straight to the homofermentative stage tastes noticeably flatter and harsher.
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