fermented vegetables

Question 1

what are the cell populations on raw vegetables?

Answer 1

10^4-10^6 CFU/g

Question 2

to begin which organisms are most populous

Answer 2

mesophilic organisms (LAB is present later)

Question 3

spoilage of vegetable fermentations

Answer 3

• occurs when the brine is no longer present
• Spoilage bacteria result in the deterioration of the vegetable material due to the elaborate destructive enzymes produced (proteases, lipases, amylases, nucleases, etc.)

Question 4

general fermentation process

Answer 4

• organic acids diffuse into the brine
• results in lower pH
• As the vegetable cells die, sugars diffuse into the brine resulting in the rapid growth of LAB

Question 5

are bacteriophages a problem in vf?

Answer 5

NO because vf do not typically use a starter culture

Question 6

Leuconostoc mesenteroides

Answer 6

• important in the initiation of the fermentation of several vegetables
• grows more rapidly than other LAB over a range of temperatures (5-35C) and brine concentrations (0-5%)
• heterolactic fermentation of vegetable sugars, typically sucrose, fructose, and glucose and produces carbon dioxide and acids (lactic and acetic) (The carbon dioxide replaces air and provides the anaerobic conditions favorable for the stabilization of ascorbic acid and the natural color of the vegetables)
• will grow until an acidity level of 1.5-2.0% is achieved
• does not grow in temperatures above 22C

Question 7

Lactobacillus plantarum

Answer 7

• homofermentative LAB
• can survive the elevating lactic acid levels
• In most vegetable fermentations Lb. plantarum will outcompete other LAB
• 2% acidity and above

Question 8

Lactobacillus brevis

Answer 8

Will continue fermenting after L. plantarum until an acidity level of 2.5-3% is obtained, and there is no sugar left vegetables

Question 9

what is the microorganism cascade general

Answer 9

Leuconostoc mesenteroides, lactobacillus plantarum, lactobacillus brevis

Question 10

in the first 24 h for sauerkraut which compounds are formed?

Answer 10

CO2, lactic acid (lesser acetic acid)

cuz it starts with heterofermentative

Question 11

optimum temperature for sauerkraut

Answer 11

18-22C - optimal
Below 7.5C fermentation time can be up to 6 month, flavor good
18-22C fermentation time is ~20 days, optimal flavor
32-36C fermentation time is 10 days, flavor is poor

Question 12

why is salt added to sauerkraut?

Answer 12

to extract juice from the plant, making sugar and nutrients more available
to reduce spoilage organisms

Question 13

why is the core removed?

Answer 13

core is rich in sucrose which Lm will metabolize to dextrose - slimy texture

Question 14

why does sauerkraut have a diphasic growth curve?

Answer 14

The shoulder at ~8 days is when the heterofermentative LAB die, and the second growth curve (diphasic growth) is created when the homofermentative bacteria become dominant

Question 15

is there still sugar present in the final sauerkraut

Answer 15

yes, the acidity is the limiting factor, not the sugar content
-The fermentation end point (21 days) includes mannitol and acetic acid at ~1% each and lactic acid at ~2%

Question 16

heterolactic stage

Answer 16

• produces lactic and volatile acetic acid

- HeteroLAB convert fructose to mannose

Question 17

relationship between pH and titratable acidity

Answer 17

The increases in titratable acidity corresponds to a decrease in pH

Question 18

which bacteria decrease in S in the first few days of fermentation?

Answer 18

enterobacteriaceae

aerobes and LAB increase

Question 19

temperature of kimchi

Answer 19

18C for a few days and then refrigerated at 1-2C

allows only heterolactic fermentation to occur (kimchi is not as sour as sauerkraut)

Question 20

which vitamin increases in K and S?

Answer 20

B