Fermented Vegetables

Question 1

Explain the general Process of Vegetable Fermentation

Answer 1

So you begin with fresh fruit and vegetables which already harbor a variety of microorganisms included aerobic spoilage microflora as well as yeasts and molds.

• The pop is moderate
• Brining vegetables results in the production of organic acids and a variety of antimicrobial compounds by LAB.
• organic acids diffuse into the brine and this results in low pH that influences microbial growth
• as vegetable cells die, sugars diffuse into the brine resulting in rapid growth of LAB
• in the absence of brine, spoilage microbiota are able to grow.

Question 2

explain why it is important that vegetables be fermented in the presence of brine?

Answer 2

without brine spoilage microbiota are able to grow. They will deteriorate the vegetable material due to elaborate destructive enzymes.

Question 3

What are leuconostoc mesenteroides, why are they important in the fermentation of vegetables?

Answer 3

1. They initate fermentation of several vegetables
2. they grow more rapidly than other LAB over temp range and brine concentration.
3. carry out heterolactic fermentation. pH drops –> 1.5-2%
4. above 22C L mesenteroides will not grow

Question 4

What happens to L. mesenteroides and other LAB when acidity reaches greater than 2%?

Answer 4

their growth is inhibited and the growth of homofermentative microbes are favored. Lb plantarum can survive elevating acid levels and produce exclusively lactic acid from the remaining sugars. It will outcompete other LAB.

Question 5

What happens at the end of the log phase for Lb plantarum?

Answer 5

there is little sugar left and the vegetable ferment is at an acceptable quality to be served or canned. Lactobacillus brevis will then take over and continue fermenting until acidity = 2.5-3% and NO sugar is left.

Question 6

Explain why bacteriophages are not a problem in vegetable fermentations?

Answer 6

They dont typically use starter cultures (contrast to dairy where if it infects starter culture than fermentation fails). In veg, if phages are present and inhibit one strain of LAB another resistant strain will grow instead.