Vegetable fermentation

1. VEGETABLE
FERMENTATION

2. FERMENTATION OF CUCUMBERS TO
PRODUCE PICKLES USING THE BRINE
PROCESS
INTRODUCTION
 Fermentation is by definition an anaerobic process i.e.
takes place in the absence of oxygen. It is done on numerous
foods to preserve as well as to modify flavour.
 Vegetables are a group of foods that can also be preserved or
modified by fermentation.

3. INTRODUCTION CONT…
 The fermentation process for vegetables can result in
nutritious foods that may be stored for extended periods, i.e.
1 year or more without refrigeration.
 One of the ways that can be used to preserve vegetables is
the production of pickles.
 Pickles are fermentation products of cucumbers and they are
produced using various processes, however, the most
commonly used is the brine process.

4. REQUIREMENTS FOR FERMENTATION
 Lactic acid bacteria (LAB)
 A source of nutrients for metabolism: the fermenters require
carbohydrates, either simple sugars such as glucose and fructose or
complex ones such as starch or cellulose.
 The energy requirements of microbes are very high. Limiting the amount
of substrate available can reduce the rate of fermentation.
 Brine i.e. strong salt solution-provides a suitable environment for the
growth of lactic acid bacteria and it also withdraws juice from the
cucumbers and make a favourable environment for fermentation.
 Optimum temperature i.e. 21◦C

5. FERMENTATION PROCESS
 The washed cucumbers are placed in large tanks and brine is added.
 The cucumbers are submerged in the brine, ensuring that none floats on the surface.
This is essential to prevent spoilage by aerobic bacteria and yeasts.
 LAB tolerate high salt concentrations, which gives them an advantage over less
tolerant species. This allows lactic acid fermenters to begin metabolism, which produces
acid, which then further inhibits the growth of non-desirable organisms.
 Leuconostoc spp. tolerate high salt concentrations, which makes them ideal to start the
lactic acid fermentation.
 Cucumbers contain glucose and fructose at about 1% each; these undergo
homofermentation typically by naturally occurring lactobacillus plantarum.

6. Process cont….
 The LAB that are naturally present on the cucumbers are tolerant of the salt and
can ferment the extracted sugars and nutrients to a variety of end products, such as
lactic acid, carbon dioxide and lesser amounts of other components. These end
products give pickles their characteristic flavour.
 Fermentation begins as soon as brine is formed and it can be seen by bubbles of
carbon dioxide gas that are given off by the bacteria.
 It takes place between 1 and 4 weeks depending on the temperature, pH and
strength of salt solution.
 During fermentation, visible changes take place which are important in the
progress of the process.

7. Process conti…
 The colour of the cucumber surface changes from bright green to a dark olive
green as acids interact with the chlorophyll.
 The interior of the cucumber changes from white to waxy translucent shade as air is
forced out of the cells.
 The specific gravity of the cucumbers also increases as a result of the gradual
absorption of salt and they begin to sink in the brine rather than floating on the
surface.
 The completion of fermentation is noted when no bubbles appear on the surface of
the brine.

8. INTERACTION OF MICROORGANISMS
 The interactions of the groups of microorganisms during the fermentation of the
cucumber results in the elimination of fungi, indicator organisms i.e. E. Coli and
Salmonella/ Shigella at different stages of fermentation period.
 The gram positive Coccus-Leuconostoc mesenteroides predominates in the first
stages of the pickle fermentation. This species is more resistant to changes and
tolerates higher salt concentration than the subsequent species.
 As fermentation proceeds and the acidity increases, lactobacilli start to take over
from the Cocci.
 The active stage of fermentation continues for between 10 t0 30 days, depending
upon the temperature of fermentation.

9. STARTER CULTURE FAILURE
 The starter culture generally consists of the normal mixed
biota of cucumbers i.e. Leuconostoc bacillus species.
 However, starter culture failure occurs when the LAB consume
all the nutrients required for their metabolic activities.
 In the case of starter culture failure, a starter juice from a
previous fermentation may be added to speed up the
fermentation.

10. BIOCHEMICAL PRODUCTS GENERATED
 The LAB that are naturally present on the cucumbers are tolerant of the salt and
can ferment the extracted sugars and nutrients to a variety of end products such as:
i. lactic acid
ii. Acetic acid
iii. Carbon dioxide and lesser amounts of other components.
 These end products give pickles their characteristic flavour.

11.  Some lactic acid bacteria have a malolactic enzyme that converts malate to malate
to lactate and carbon dioxide.
 This reaction occurs intracellulary and results in the uptake of a proton thereby
increasing internal cell pH.

12. SAFETY AND SHELF LIFE OF THE FINAL
FERMENTED PRODUCT
 Clean glass jars with lids are preferred type of packaging for
pickles.
 Small quantities of pickles can be packaged in polythene
pouches that are sealed with a heat sealer.
 The shelf life of the pickle after the completion of
fermentation is 1 year or more…

13. REFERENCES
 Jay et al. (2005), Modern Food Microbiology, 7th Edition
 Ray B & Bhunia A, (2007), Fundamentals of Food Microbiology, 4th Edition.

14. THANK YOU!