Fermented Vegetable Products Flashcards
(54 cards)
What are some common vegetable fermentation products?
sauerkraut, pickles, olives, kimchi, fermented radish, fermented mustard leaves
What are the microorganisms found naturally on fresh fruit/veg?
spoilage aerobic microbes, yeasts, molds, LAB
True/False: LAB are the dominant microbe on fresh produce
False; actually in lower numbers than other mesophiles
What allows LAB to outcompete other microbes?
Adapted for high sugar environment
creates organic acids, antimicrobial compounds, lowers pH
What causes mushy sauerkraut?
Spoilage organisms (break down plant material)
sterilization/heat treatment
What is the importance of brining? (3)
salt break down cabbage to release sugars (feed LAB)
released juices create anaerobic environment (prevent spoilage/oxidation)
salt inhibit spoilage microbes
What is the notable species in most veg ferments? What conditions can it withstand?
Leuconostoc mesenteroides (LAB) grows rapidly large range of conditions (5-35C, 0-5% brine, up to acidity 1.5-2%)
What is the metabolism of L. mesenteroides?
heterolactic convert sugars (suc, fruc, gluc) -> CO2, acetic and lactic acid
Vegetable fermentations should be done below ____. Why?
22C
L. mesenteroides does not grow well in higher temperatures -> less flavor molecules produced -> lower quality product
What makes L. mesenteroides important to the beginning of vegetable fermentation?
create acidity (prevent spoilage) produce flavor compounds
What happens once L mesenteroides has acidified the product to 2%? What microbe takes over?
L. mesenteroides is inhibited
Lb. plantarum takes over (LAB)
What microbe is dominant at the end of the veg ferment, and why? Why does the ferment stop?
Lb brevis
superior acid tolerance
sugars have been consumed
True/False: a veg ferment that has not reached absolute completion (sugars depleted) can be safely consumed and stored
True
When is a vegetable ferment usually halted and deemed ready?
After Lb. plantarum log phase ends (before Lb. brevis)
Two preparations of sauerkraut have a pH of 2.2% and 3%. What are the dominant species in each?
2.2%: Lb. plantarum
3%: Lb. brevis
List the dominant species in a veg ferment in order:
Beginning: L. mesenteroides
Middle: Lb. plantarum
End: Lb. brevis
True/False: phage infection is of big concern in vegetable fermentations
False; not a concern. If one species targeted, another will take over (not monoculture like dairy)
(higher/lower) temperatures will produce better quality sauerkraut, but (higher/lower) temperatures produce faster sauerkraut
What is the best range?
lower
higher
18-22C (20 days time)
What is the sugar content of cabbage?
What % salt should be added?
2.5% glucose, 2% fructose
2-3%
Why are the leaves and core of cabbage removed?
leaves may contain more non-LAB bacteria
core high in sucrose, L. mesenteroides convert to dextran -> slimy
Are the pathogens (enterobacter) on the raw vegetable of concern?
No. killed off (5 log decrease in first few days) by acid, salt
True/False: glucose and fructose continue decreasing through the veg ferment
False; glucose will actually increase in first few days (then decrease)
Why does glucose levels increase in the first few days of sauerkraut fermentation?
slow release from cabbage
What happens to acid content during cabbage fermentation? Is this reflected by pH?
increase, slows, keeps increasing at slower rate
yes, corresponds to pH
