6- Fermented vegetables

Question 1

What is the LAB responsible for the initiation of sauerkraut?

Answer 1

leuconostoc mesenteroides

Question 2

What is the more acid tolerant LAB that carries fermentation of sauerkraut when the Leuconostoc dies because of a too acidic environment

Answer 2

Lactobacillus plantarum

Question 3

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

Answer 3

Lactobacillus brevis

Question 4

T or F : Unlike dairy fermentations, bacteriophages can be a problem for vegetable fermentation

Answer 4

false

Question 5

Complete : the best quality sauerkraut is produced between _____ , since this temperature favors the growth of ____

Answer 5

18-22˚C L. mesenteroides (heterofermentative)

Question 6

why is salt added to sauerkraut?

Answer 6

To extract cabbage juice from the leaves to make the sugars and nutrients from the plant material readily available to the LAB To keep non-LAB from spoiling the cabbage. LAB are resistant to moderate amounts of salts, non-LAB are less resistant

Question 7

Why is there a biphasic growth of titrable acidity

Answer 7

because of the rapid in acid due to the increase of the L.mesenteroid followed by another increase in acid due to the L.plantarum

Question 8

T or F : homofermentative LAB can produce mannitol

Answer 8

false, only heterofermentative (l.mesenteroid)

Question 9

Why is there a decrease in the color of cabbage if you don’t pump the oxygen out at the begining of the fermentation?

Answer 9

because of the oxydation of ascorbic acid.

Question 10

What is the temperature that kills most LAB?

Answer 10

41 ˚C.

Question 11

What is the purpose of fermeting pickle in the sunlight?

Answer 11

The UV radiation from the sunlight kills aerobic surface yeasts

Question 12

What is the cause of air pockets in cucumbers?

Answer 12

the respiration of cucumber can lead to CO2 and the decarboxylation of malate and the production of CO2 by the lb.plantarum.

Question 13

why does a fermentation of sauerkraut done at T > 22˚C will lead to a lower quality sauerkraut

Answer 13

because there will be no L.mesenteroid (no heterofermentative microorganisms)

Question 14

what organisms will be responsible for the bulk of fermentation

Answer 14

the lactobacillus plantarum

Question 15

until what acidity does the lactobacillus plantarum will ferment sugars in sauerkraut

Answer 15

above the acidity of 2.0%

Question 16

what are the main sugars in cabbage ?

Answer 16

glucose and fructose

Question 17

slower is the fermentation time in sauerkraut, the better is the _____

Answer 17

flavor

Question 18

why do you need to remove the core when making sauerkraut?

Answer 18

core contains sucrose that can lead to dextran formation by L.mesenteroides resulting in slimy texture

Question 19

what is the goal of removing the oxygen ?

Answer 19

Removing the oxygen favors the growth of LAB, over the growth of molds

Question 20

what does the MRS agar selects for

Answer 20

the aerobes

Question 21

in the sauerkraut fermentation ____ is rapidly used while ___ increases and takes some time to be used

Answer 21

sucrose glucose

Question 22

why is there a biphasic growth in the titratable acidity in sauerkraut?

Answer 22

because of the L. mesenteroid switching for the L.plantarum

Question 23

why is there no manitol production after 8 days

Answer 23

because the L.mesenteroids are responsible for the formation of mannitol from fructose

Question 24

why is there an increase in ethanol and acetic acid after 28 days

Answer 24

because the spoilage microorganisms will increase ethanol an actic acid

Question 25

what is the limiting factor of the sauerkraut fermentation

Answer 25

ACID : There is still sugar in the final sauerkraut, acid accumulation is the limiting factor.

Question 26

why is there a gre brown color in kraut sometime

Answer 26

because of the decrease in ascorbic acid

Question 27

•Most commercial sauerkraut products are pasteurized and then canned, killing all of the LAB (any heating above __ will kill most LAB)

Answer 27

41C

Question 28

•Kimchi has___ acid while kraut as ___ acid

Answer 28

0.6 % kimhci

2% kraut

Question 29

how is the acid reduced in kimchi fermentation

Answer 29

•The ingredients are packed into jars and held in “kimchi refrigerators” which provide a temperature of 18C for a few days followed by cold refrigeration (1-2C)

Question 30

•Vitamin ___ content increases

Answer 30

B

Question 31

True or F : •Vitamins C and A are increased during sauerkraut and kimchi fermentation

Answer 31

False theyr are maintained

Question 32

why are pickle fermented in light

Answer 32

•The UV radiation from the sunlight kills aerobic surface yeasts (next slide)

Question 33

what is the compound used in pikle fermentation to maintain the crisp

Answer 33

calcium chloride

Question 34

pickle tipically undergo homo or heterofermentation, why?

Answer 34

•The high salt concentrations favor homofermentative LAB

Question 35

how are the bloaters reduced

Answer 35

potassium sorbate or acetic acdi are used to limit growth of organisms in purged fermentations

Question 36

•Most commercial cucumber fermentations rely on the growth of LAB naturally present on the cucumber, although the trend is now starting to be to use a ___ starter

Answer 36

Lb. plantarum starter

Question 37

•At the end of the fermentation there may be ___ lactic acid, a pH of___ and no residual sugar

Answer 37

1. 5%
2. 0 pH

Question 38

In the secondary fermentation that spoils cucumbers the pH ___ the lactic acid ___, and propionic and butyric acids are formed – which causes the product to stink

Answer 38

increase
decrease

Question 39

in olive fermentations, as the pH drops below 6, LAB colonize then dominate the fermentation specifically ___

Answer 39

Lb. plantarum

Question 40

why is the fermentation of black olive slower?

Answer 40

because there is no NaOH treatment : Antimicrobial phenolic compounds dissolve into the brine, slowing fermentation and diffusion of sugars out of the olives is slower in black olives