Fermented vegetable products

Question 1

The primary commercial fermented vegetable products in Canada include:

Answer 1

• cucumber pickle (can be acidified, pasteurized and refrigerated)
• Olives
• Sauerkraut

Question 2

Prior to fermentation, fresh fruit and vegetables harbor a variety of microorganisms including (3):

Answer 2

aerobic spoilage microflora, as well as yeasts and molds

Question 3

Brining the vegetables (adding salt) results in the production of __________________by LAB

Answer 3

organic acids, and a variety of antimicrobial compounds by LAB

Question 4

LAB are initially present on fresh vegetables in (higher or lower) numbers compared to other mesophilic organisms

Answer 4

lower

Question 5

Explain what happens during vegetable fermentations (organic acids…..)

Answer 5

• During the fermentation, organic acids diffuse into the brine, and the low pH that results, influences microbial growth in the vegetable material
• As the vegetable cells die, sugars diffuse into the brine resulting in the rapid growth of LAB
• In the absence of brine, spoilage microbiota are able to grow
• Spoilage bacteria result in the deterioration of the vegetable material due to the elaborate destructive enzymes produced (proteases, lipases, amylases, nucleases, etc.)

Question 6

_____________ are important in the initiation of the fermentation of several vegetables

Answer 6

Leuconostoc mesenteroides

Question 7

Name a few characteristics of L.mesenteroides

Answer 7

1) grows more rapidly than other LAB over a range of temperatures (5-35) and brine concentrations (0-5%)
2) carries out heterolactic fermentation of vegetable sugars typically glucose sucrose and fructose and produces CO2 and acid (lactic and acetic)
3) The carbon dioxide that it produces replaces air and provides anaerobic conditions favorable for the stabilization of vit c and the natural color of vegetables

Question 8

L. mesenteroides will grow until an acidity level of ______ is achieved

Answer 8

1.5-2.0%

Question 9

If the temperature is above ______ L. mesenteroides will not grow, and this will be detrimental to the development of the fermentation

Answer 9

22C

Question 10

___________ are able to survive the elevating lactic acid levels and produce exclusively lactic acid from the remaining sugars

Answer 10

Lb. plantarum

Question 11

Lb.plantarum will grow above an acidity of ____

Answer 11

2%

Question 12

Why will Lb.plantarum outcompete other LAB at the end of the fermentation reaction?

Answer 12

due to its higher acid tolerance

Question 13

__________ will continue fermenting after Lb.plantarum until an acidity level of 2.5-3% is obtained and there’s no sugar left in the vegetables

Answer 13

Lactobacillus brevis

Question 14

TRUE OR FALSE: Bacteriophages are a problem for vegetable fermentation

Answer 14

FALSE

Question 15

Explain the relationship between vegetables fermentations, starter cultures and phages

Answer 15

Vegetable fermentations do not typically use starter cultures, but if phages are present and inhibit one strain of LAB, another resistant indigenous strain will grow instead.

Question 16

If given _________ conditions, at approximately ___C, and ____% salt concentration, LAB dominate the microbial community able to grow on the sugars from the cabbage

Answer 16

anaerobic
22
2-3%

Question 17

TRUE OR FALSE: High-quality sauerkraut can be produced without a starter culture if the conditions are correct

Answer 17

TRUE

Question 18

During the first 24-48 hours what will be produced from the salted cabbage (sauerkraut fermentation)? (3)

Answer 18

• CO2
• lactic acid
• acetic acid

Question 19

Explain the relationship between sauerkraut quality and temperature

Answer 19

• Temperature is important, the best quality sauerkraut is produced between 18-22C, since this temperature favors the growth of L. mesenteroides
• Generally, lower temperatures produce higher quality sauerkraut
• Higher temperature can produce sauerkraut in 7-10 days but it will be of lesser quality, LAB don’t grow as well during fast fermentation producing a much less complex flavor

Question 20

Why are the outer leaves removed in sauerkraut fermentation?

Answer 20

To lower the non-LAB bacterial load

Question 21

Why do we remove the core of the cabbage in sauerkraut fermentation

Answer 21

Because the core contains high levels of sucrose which can lead to dextran formation by L.mesenteroides resulting in a slimy texture

Question 22

Give me the 2 reasons why we add salt in sauerkraut fermentation:

Answer 22

1) To extract the cabbage juice from the leaves to make the sugars ans nutrients from the plant material readily available to the LAB
2) To prevent non-LAB from spoiling the cabbage, non-LAB are less resistant to high amounts of salt

Question 23

Why removing the oxygen is important in sauerkraut fermentation?

Answer 23

Because it favors the growth of LAB over the growth of mold

Question 24

What happens to sucrose, fructose and glucose during sauerkraut fermentation?

Answer 24

• sucrose remains at low levels
• fructose is rapidly used
• glucose increases for the first few days

Question 25

What happens to titratable acidity during sauerkraut fermentation?

Answer 25

- it increases rapidly - slows - then increases again but at a slower rate

Question 26

What causes the increase in mannitol at the beginning of the fermentation reaction of sauerkraut?

Answer 26

the decrease in fructose | -Heterofermentative lactic acid bacteria use fructose as an electron acceptor converting it to mannitol

Question 27

The fermentation end point of sauerkraut (21 days) includes mannitol and acetic acid at ~_% each and lactic acid at ~_%.

Answer 27

1 | 2

Question 28

There is still sugar in the final sauerkraut, ___________ is the limiting factor

Answer 28

acid accumulation

Question 29

What happens to the concentration of ascorbic acid during the first days of fermentation if the oxygen in the head space is not pumped out?

Answer 29

the ascorbic acid concentration decreases because it is oxidized by dissolved oxygen from the head space

Question 30

What is the relationship between sauerkraut color and ascorbic acid concentration?

Answer 30

If ascorbic acid remains high the sauerkraut retains a light straw colour, if the ascorbic acid decreases the kraut has a grey/brown colour.

Question 31

Most commercial sauerkraut products are pasteurized and then canned, killing all of the __________________

Answer 31

LAB (any heating above 41C will kill most LAB)

Question 32

What are the 2 primary ingredients in Kimchi?

Answer 32

- Chinese cabbage | - Asian radishes

Question 33

Is kimchi more or less acidic than sauerkraut ?

Answer 33

less

Question 34

Explain the main steps in kimchi fermentation: (6)

Answer 34

1) Cabbage is cut in half 2) Cabbage is soaked in 5-10% brine to wilt the cabbage 3) Cabbage is drained 4) Paste of red pepper is added 5) The ingredients are packed into jars and held in kimchi refrigerators at temp 18C for a few days 6) Cold refrigeration (1-2C)

Question 35

Why is kimchi less acidic?

Answer 35

Because the fermentation allows the heterolactic fermentation to take place, but halts the reaction before the homofermentative stage occurs

Question 36

White kimchi contains no _______

Answer 36

red pepper

Question 37

what is special about Traditional kimchi?

Answer 37

it has the diphasic heterofermentative and homofermentative pattern of LAB succession

Question 38

____________ content increases during sauerkraut and kimchi fermentation

Answer 38

vitamin B

Question 39

___________ and ________ are maintained during sauerkraut and kimchi fermentation

Answer 39

vit c and vit a

Question 40

Are all pickles fermented pickles?

Answer 40

no some can be pasteurized and canned in acid

Question 41

In cucumber fermentation, the UV radiation from the sunlight kills what :

Answer 41

aerobic surface yeasts

Question 42

Cucumber fermentations typically undergo ___________ fermentation, which does not result in the production of carbon dioxide

Answer 42

homolactic

Question 43

In cucumber fermentation: the high salt concentrations favor _______________ LAB

Answer 43

homofermentative

Question 44

Some LAB have inducible malolactic enzymes that converts _____ to ________

Answer 44

malate | lactate and CO2

Question 45

CO2 can cause _______ in cucumber fermentation

Answer 45

bloaters (this happens when bacteria produce internal gas pockets in fermented cucumbers)

Question 46

What is done to prevent bloater formation in cucumber?

Answer 46

cucumber fermentations are purged with air to remove excess CO2 from the tank

Question 47

__________ or ________ can be used to limit the growth of aerobic organisms in air purged fermentations

Answer 47

potassium sorbate or acetic acid

Question 48

What is the new trend in cucumber fermentation?

Answer 48

the use of Lb.plantarum starter culture that does not decarboxylate malic acid (no bloaters)

Question 49

What happens if a secondary fermentation occurs in fermented cucumbers? (pH, lactic acid,etc)

Answer 49

pH increases lactic acid decreases propionic and butyric acids are formed (stink)

Question 50

What are the 3 principle types of commercial olives:

Answer 50

1) green table olives (fermented) 2) natural black olives (fermented) 3) canned ripe black olives (not fermented)

Question 51

Explain the treatment of green table olives:

Answer 51

1) strong base treatment 1-3 % NaOH 2) the strong base reduces bitterness, decreases natural antimicrobial activities of the phenolic compounds 3) makes skin of the olive more permeable to allow sugars to diffuse out during fermentation 4) olives are washed with 10% NaCl

Question 52

In what way the fermentation of natural black olives is different from the fermentation of green table olives ?

Answer 52

they do not receive NaOH treatment prior to brining

Question 53

Explain the steps in natural black olives fermentation:

Answer 53

1) They are picked in a ripened state and have a softer texture than green table olives 2) Fermentation is a much slower process with black olives because of the lack of NaOH treatment: - Antimicrobial phenolic compounds dissolve into the brine, slowing fermentation - Diffusion of sugars out of the olives is slower in black olives 3) As a result this fermentation can take months to complete