Sauerkraut is produced by the fermentation of
Answer: A
Sauerkraut is salted shredded cabbage left to ferment in its own juice, the name meaning sour cabbage. Cucumbers give pickles, grapes give wine and soya beans give products such as soy sauce and tempeh, each with a different microbial community.
Please log in or register to report this question.
The fermentation that produces sauerkraut is carried out chiefly by
Answer: B
A succession of lactic acid bacteria converts the sugars of the cabbage to lactic acid, dropping the pH far enough to preserve the vegetable. Acetic acid bacteria make vinegar, moulds are spoilage organisms here, and yeast fermentation gives alcohol rather than acid.
Please log in or register to report this question.
Salt is added to shredded cabbage for sauerkraut at a concentration of about
Answer: C
Around 2 to 2.25 per cent by weight draws juice out of the cabbage by osmosis and selects for salt tolerant lactic acid bacteria while holding back competitors. Much more than this suppresses the desirable bacteria as well, and much less gives a soft product.
Please log in or register to report this question.
The immediate effect of salting shredded cabbage is to
Answer: D
Salt withdraws water and dissolved sugars from the plant cells, creating the brine in which the fermentation takes place and which excludes air. It does not sterilise the cabbage, which is exactly the point: the natural lactic acid bacteria must survive to do the work.
Please log in or register to report this question.
Sauerkraut fermentation must be conducted under conditions that are
Answer: A
Keeping the shredded cabbage submerged excludes oxygen, which favours the lactic acid bacteria and denies moulds and film yeasts the surface they need. Exposure to air is the usual cause of surface growth and of the softening that follows it.
Please log in or register to report this question.
The organism that initiates sauerkraut fermentation is
Answer: B
Leuconostoc mesenteroides grows first because it tolerates the salt and starts at the near-neutral pH of fresh cabbage juice. It is also the least acid tolerant of the group, so it stops once its own acid has accumulated and hands the fermentation on.
Please log in or register to report this question.
Leuconostoc mesenteroides is described as heterofermentative, which means it produces
Answer: C
A heterofermentative organism yields a mixture, here lactic acid together with acetic acid, ethanol and carbon dioxide. The gas flushes oxygen from the vat and the acetic acid contributes to flavour, which is why the early phase matters to the final product even though it is brief.
Please log in or register to report this question.
The high final acidity of sauerkraut is produced chiefly by
Answer: D
Lactobacillus plantarum is homofermentative and considerably more acid tolerant, so it continues working long after Leuconostoc has stopped and carries the acidity to its final level. Rhodotorula is a spoilage yeast and Bacillus has no part in a sound fermentation.
Please log in or register to report this question.
A homofermentative lactic acid bacterium is one that produces
Answer: A
Homofermentative organisms channel almost all the sugar they use into lactic acid, which is why they reach higher acidities. Heterofermentative organisms split the sugar into several products, so less of it ends up as acid.
Please log in or register to report this question.
Carbon dioxide produced early in sauerkraut fermentation is useful because it
Answer: B
The gas flushes air out of the vat, which suppresses moulds and film yeasts and protects the vitamin C and the colour of the cabbage. It is a waste product, not a nutrient, and dissolving in water it acidifies very slightly rather than raising the pH.
Please log in or register to report this question.
