6- Fermented vegetables Flashcards
What is the LAB responsible for the initiation of sauerkraut?
leuconostoc mesenteroides
What is the more acid tolerant LAB that carries fermentation of sauerkraut when the Leuconostoc dies because of a too acidic environment
Lactobacillus plantarum
______ (LAB) will continue fermenting after L. plantarum until an acidity level of 2.5-3% is obtained, and there is no sugar left vegetables
Lactobacillus brevis
T or F : Unlike dairy fermentations, bacteriophages can be a problem for vegetable fermentation
false
Complete : the best quality sauerkraut is produced between _____ , since this temperature favors the growth of ____
18-22˚C L. mesenteroides (heterofermentative)
why is salt added to sauerkraut?
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
Why is there a biphasic growth of titrable acidity
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
T or F : homofermentative LAB can produce mannitol
false, only heterofermentative (l.mesenteroid)
Why is there a decrease in the color of cabbage if you don’t pump the oxygen out at the begining of the fermentation?
because of the oxydation of ascorbic acid.
What is the temperature that kills most LAB?
41 ˚C.
What is the purpose of fermeting pickle in the sunlight?
The UV radiation from the sunlight kills aerobic surface yeasts
What is the cause of air pockets in cucumbers?
the respiration of cucumber can lead to CO2 and the decarboxylation of malate and the production of CO2 by the lb.plantarum.
why does a fermentation of sauerkraut done at T > 22˚C will lead to a lower quality sauerkraut
because there will be no L.mesenteroid (no heterofermentative microorganisms)
what organisms will be responsible for the bulk of fermentation
the lactobacillus plantarum
until what acidity does the lactobacillus plantarum will ferment sugars in sauerkraut
above the acidity of 2.0%
what are the main sugars in cabbage ?
glucose and fructose
slower is the fermentation time in sauerkraut, the better is the _____
flavor
why do you need to remove the core when making sauerkraut?
core contains sucrose that can lead to dextran formation by L.mesenteroides resulting in slimy texture
what is the goal of removing the oxygen ?
Removing the oxygen favors the growth of LAB, over the growth of molds
what does the MRS agar selects for
the aerobes
in the sauerkraut fermentation ____ is rapidly used while ___ increases and takes some time to be used
sucrose glucose
why is there a biphasic growth in the titratable acidity in sauerkraut?
because of the L. mesenteroid switching for the L.plantarum
why is there no manitol production after 8 days
because the L.mesenteroids are responsible for the formation of mannitol from fructose
why is there an increase in ethanol and acetic acid after 28 days
because the spoilage microorganisms will increase ethanol an actic acid
what is the limiting factor of the sauerkraut fermentation
ACID : There is still sugar in the final sauerkraut, acid accumulation is the limiting factor.
why is there a gre brown color in kraut sometime
because of the decrease in ascorbic acid
•Most commercial sauerkraut products are pasteurized and then canned, killing all of the LAB (any heating above __ will kill most LAB)
41C
•Kimchi has___ acid while kraut as ___ acid
0.6 % kimhci
2% kraut
how is the acid reduced in kimchi fermentation
•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)
•Vitamin ___ content increases
B
True or F : •Vitamins C and A are increased during sauerkraut and kimchi fermentation
False theyr are maintained
why are pickle fermented in light
•The UV radiation from the sunlight kills aerobic surface yeasts (next slide)
what is the compound used in pikle fermentation to maintain the crisp
calcium chloride
pickle tipically undergo homo or heterofermentation, why?
•The high salt concentrations favor homofermentative LAB
how are the bloaters reduced
potassium sorbate or acetic acdi are used to limit growth of organisms in purged fermentations
•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
Lb. plantarum starter
•At the end of the fermentation there may be ___ lactic acid, a pH of___ and no residual sugar
- 5%
- 0 pH
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
increase
decrease
in olive fermentations, as the pH drops below 6, LAB colonize then dominate the fermentation specifically ___
Lb. plantarum
why is the fermentation of black olive slower?
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
