PICKLING
An important food preservation system combines salting to selectively control microorganisms and fermentation to stabilise the treated food materials.
the oldest, and most successful, method of food preservation known to humans
The process when applied to vegetables is called pickling.
When applied to meat it is called curing.
a major form of preservation because it:
(1) yields desirable organoleptic qualities;
(2) provides a means for extending the processing season of fruits and vegetables;
(3) requires relatively little mechanical energy input.
salt, temperature, and anaerobiosis creates environment necessary for a successful lactic acid fermentation.
Within just a few hours, lactic acid bacteria will begin to grow, a lactic acid fermentation will commence, and the number of competing organisms will decline.
Salt
growth repressing : on microorganisms by limiting available water and dehydrating protoplasm, causing plasmolysis.
26.5 % sodium chloride at room temperature corresponds to saturation concentration.
Salometer degree( a scale used in pickling industry)
0 % NaCl —– 0 degree
2.65 % NaCl—10 degree
26.5 % NaCl—100 degree (No free water available for microbial growth
Salt for pickling.
Impurities or additives can cause problems.
Salt with chemicals to reduce caking should not be used as they make the brine cloudy.
Salt with iron impurities can result in the blackening of the vegetables.
Magnesium impurities impart a bitter taste.
Carbonates can result in pickles with a soft texture.
Important microorganisms in plants:
I- Pseudomonas, Bacillus, Chromobacterium, Enterobacter, Escherichia, Flavobacterium
II- Lactobacillus, Leuconostac, Pediococcus
We support group II and supress group I
Less research on fermented vegetables compared to other fermented foods
-because cheap,
-produced at small scale by traditional methods
-very little public health problems occured.
The lactic acid fermentation of vegetables depends not on any single organism, but rather on a consortium of bacteria
Eventually, the initial microbial population gives way to other species that are less sensitive to those inhibitory factors.
Microbial ecologists refer to these sorts of processes as a succession.
Lactic acid fermentations
are carried out under three basic types of condition:
I-dry salted
II-brined
III-non-salted.
I- Dry salted fermented vegetables
the vegetable is treated with dry salt.(3%)
The salt extracts the juice from the vegetable and creates the brine.
vegetable washed in potable cold water and drained.
placed in a layer of 2.5cm depth in container (a barrel or keg).
Salt is sprinkled over the vegetables.( repeated until the container is three quarters full.)
compress the vegetables to assist the formation of a brine, fermentation starts and bubbles of carbon dioxide begin to appear.
Fermentation=f( temp) : one and four weeks
Fermentation is complete: no more bubbles, then pickle can be packaged in a mixtures of vinegar and spices or oil and spices
SAUERKROUT FERMENTATION
It is a perfect example of microbial succession .
Shredding cabbage: ( sugar 2.4-6.4 %, if it is too high product will be too acidic) ( In turkish style cabage is divided into four rather than slicing)
Washing : to reduce chromogens (coloring bacteria) and to wash out contaminating yeast and mold.
Salting : Optimum salt conc. is 2.5 % (evenly distributed)
3.5 % salt will support pediococcus,
1 % salt will support Leuconostoc mesentroides.
Pressing: To make it anaerobic
Mirobial Succession
1-enterobacter ( gas producer) and erwinia
( produces cellulases and pectinases )
2- L. Mesentroides : produces lactic acid ( 0.7 % ) PH drops and this will suppress growth of gram(-) bacteria. It also produces mannitol ( bitter taste) which can only be utilised by L. Plantarum. By this way it supports growth of L. plantarum.
3- L. Plantarum grows to produce more acid
( 2 %) and using mannitol reduces bitterness.
Further growth of L. pentoaceticus may increase acid to 2.5 %
temperature control is one of the most important factors in the sauerkraut process.
A temperature of 18º to 22º C is most desirable( optimum temp. range for the growth and metabolism of L. mesenteroides. )
Temperatures above 22ºC favour the growth of Lactobacillus species.
Packaging and processing
thermally processed, at about 75°C, prior to packaging in cans or jars. (commercially sterile and are stable at room temperature.)
There is also a market for non-pasteurized, refrigerated sauerkraut that is packaged in glass jars or sealed plastic bags (polybags). ( antimycotic agents, such as benzoate and sulfite salts are added)
Sauerkrout defects
High temperature: suppresses Leuconostoc( which produces desired flavor compounds)
-too long fermentation: favor gas forming L. Brevis.
-Soft krout: due to faulty fermentation, exposure to air and excessive pressing.
-dark brown or black krout: air exposure, uneven salting ( salt burn) or high temperature.
-Pink krout: coused by red asporagenous yeast growth
– slimmy or ropy krout: caused by encapsulated varieties of L. Plantarum ( edible but not salable)
Kimchi
the Korean version of sauerkraut is called kimchi.
Kimchi is usually made from cabbage, but other vegeta-bles, including radishes and cucumbers also used.
Garlic, green onion, ginger, and red peppers are among the typical ingredients, but fish, shrimp, fruits, and nuts, can also be added.
II- Brine fermented vegetables
Brine : used for vegetables which contain less moisture.
strong brine draws sugar and water out of the vegetable.
salt concentration should not fall below 12 salometer
the microbial populations = f( the concen. of salt, temp. of the brine, the availability of fermentable materials and the numbers and types of micro-organisms present at the start of fermentation.
rate of the fermentation=f( concentration of salt, temperature.)
Most vegetables can be fermented at 12.5o to 20o salometer
about 40o salometer, homofermentation, dominated by L. plantarum.
(about 60o salometer) the lactic fermentation ceases only acetic acid, by acid-forming yeasts, is observed.
A-Pasteurized Pickles
(Fresh-packed pickles )
Vegetables which are fresh or only partially fermented may be preserved by the addition of vinegar or acetic acid and subsequent pasteurization.
Vinegar : alone is not sufficient to insure product safety, and so requires an additional form of preservation such as heat or refrigeration.
The steps involved in producing pasteurized or ‘fresh-pack’ pickles are the following:
• slice, cube, or dice product;
• place in clean container;
• mix water, salt, vinegar, sugar, spices and bring to boil;
• add hot brine to container;
• seal and pasteurize.
The pasteurization process inhibits polygalacturonase, the enzyme responsible for pickle softening.
Enzyme activity may also be controlled through use of appropriate salt concentrations.
CaCl2 and KAl(SO4) added to brine to aid in firming cucumber pickles
Pasteurized pickled products have steadily gained in popularity( very different flavor and texture)
B-Refrigerated Pickles
latest development: direct acidification and addition of sodium benzoate or another preservative.
non-fermented pickles, the preservative takes the place of pasteurization
a crisp, crunchy texture and bright green color.
refrigerated pickles have a shorter shelf-life than fresh-packed pickles.
C-Fermented Pickles
cucumber fermentation; (1) salt stock; (2) genuine dill; and (3) overnight dill.
(1)Salt stock
fermentation in 5–8% ( salt conc. increased 1%/week up to 16 % salt) until all fermentable sugars have been converted to acids. ( can be stored for several years)
quick leaching in warm,43-54 C, water, 10-14 hrs to 2–2.5% salt
make up the largest percent of fermented pickle products.
processors acidify and purge tanks after brine is added.
Acidification inhibits the growth of acid-sensitive Gram-positive and Gram-negative bacteria and, therefore, favors the growth of lactic acid bacteria.
Purging decreases the incidence of bloating.
BLOAETER DAMAGE ( HOLLOW CUCUMBER)
due to high level of gas production.
Reasons:
large cucumbers (with thick skin)
higher fermentation temperatures ( which supports growth of gas producing bacteria such as coliforms, heterofermentative lactic bacteria and yeast ).
Preventing:
-Inoculating with L. Plantarum
-purging out produced CO2 with nitrogen gas
-using small size cucumbers
(2)Genuine dill pickle
fermented in 4–5% salt, to which dill weed, garlic, and other spices have been added.
3–6 weeks for fermentation to reach completion,
where the lactic acid content is 1.0–2.5% and the salt content is 3–3.5%.
not require desalting
thightly closed, can be kept 12 months, otherwise film yeast will grow and utilize lactic acid( addition of 0.1 % potassium sorbate is helpful to reduce this risk).
(first) Enterobacter clocea, (second) Leuconostac mesentroides, (third) Lactobacillus plantarum
Dill (dereotu)
(3)Overnight dill
soaking cucumbers in to 20 salometer degree solution ( containing salt, vinegar, dill )
very little or no fermentation, only taste changes due to replacement of some plant juice with solution.
product must then be refrigerated: keep < 6 months
TOMATO PICKLE
same procedure with cucumber pickling.
Green tomatoes are used .
When color turns from green to cream
color it is the right time to end process
PEPPER PICKLE
7 kg pepper + 300-400 g acetic acid
+ 5 % salt solution
In only salt solution color will be darker,
in acetic acid solution color will be yellow(desired)
Foodelphi.com Science of Food Engineering