If a sauerkraut fermentation is conducted at an unusually high temperature, the likely result is
Answer: A
Warmth favours the lactobacilli, which overrun the Leuconostoc stage before it can contribute its mixed products, so the flavour is sharper and less rounded. Higher temperatures also raise the risk of softening and of spoilage organisms.
Please log in or register to report this question.
Lactic acid bacteria are able to grow in a salted vegetable brine partly because they
Answer: B
Their salt tolerance is what lets the process work: at the concentrations used, many Gram-negative spoilage organisms are checked while the lactic acid bacteria continue. Salt is not a nutrient and is not metabolised by anything.
Please log in or register to report this question.
Lactic acid bacteria used in vegetable fermentations are best described as
Answer: C
They are Gram-positive, non-sporing and notably acid tolerant, which is what allows them to keep working in the acid they themselves generate. Their inability to form spores is why heat processing destroys them readily.
Please log in or register to report this question.
Oxygen is excluded from a vegetable fermentation mainly to
Answer: D
Aerobic organisms at the surface oxidise the lactic acid, letting the pH climb until spoilage bacteria can grow, and moulds add softening enzymes as well. Lactic acid bacteria themselves are unbothered by the absence of air.
Please log in or register to report this question.
Compared with the fresh vegetable, properly fermented sauerkraut has
Answer: A
Correct answer: A much lower pH and a longer keeping quality
The bacteria convert the cabbage’s sugar to lactic acid, taking the pH from around 6 to below 4. That acidity is the preservative, and it is why sauerkraut keeps for months where fresh cabbage keeps for days - the same transformation that makes it sour makes it stable.
Please log in or register to report this question.
Vitamin C in cabbage survives sauerkraut fermentation relatively well because
Answer: B
Ascorbic acid is destroyed chiefly by oxidation, and a submerged fermentation under carbon dioxide with a low pH offers little opportunity for that. This is one reason kraut was historically valued on long sea voyages.
Please log in or register to report this question.
Which of these would most likely cause an entire sauerkraut batch to fail to acidify?
Answer: C
Excess salt inhibits the lactic acid bacteria themselves, so little acid is produced and the batch is open to spoilage and to pink yeasts. Submersion, cool temperatures and fine shredding all favour a sound fermentation rather than hindering it.
Please log in or register to report this question.
The chief practical reason for shredding cabbage finely before salting is to
Answer: D
Correct answer: Release juice quickly and give the bacteria access to sugar
Shredding ruptures the cells so that the salt can draw the juice out promptly, forming the brine in which the fermentation takes place. The bacteria need that sugary liquid, and they need it quickly - a slow start is what allows spoilage organisms to establish themselves first.
Please log in or register to report this question.
In a cucumber fermentation, salt equilibration between brine and fruit matters because
Answer: A
Salt diffusing into the cucumber and water diffusing out bring the inside and the brine to the same concentration, and until that happens conditions inside the fruit differ from those outside. Uneven salting gives uneven fermentation and defects.
Please log in or register to report this question.
Which change would you expect during a normal cucumber fermentation?
Answer: B
The bacteria consume the sugar of the fruit and excrete lactic acid, so the titratable acidity climbs while the pH falls to about 3.3. A finished fermentation has little or no sugar left, which is part of why it then remains stable.
Please log in or register to report this question.
