May 19, 2007
Mr. Happer
Sophie Lin
Biology
The Effect of Sunlight, Time, and Salt Concentration
on the Rate of Fermentation of Kimchi
Introduction
A)
Background
Kimchi is a delicacy of the Korean culture, a fermented mixture of
Chinese cabbage, radishes, red pepper, garlic and ginger. It is very important
to learn the most effective conditions for Kimchi fermentation that will help
companies to produce Kimchi at the best quality. Fermentation is
furthermore an important process to learn about. In today’s world, there is
an immense market of products that use fermentation to alter the appearance
and/or flavor of foods and beverages such as beer, buttermilk, cheese, wine,
vinegar and yogurt
B)
Goals
My goal for this experiment is to see a steady trend of the rate of
fermentation of cabbage though time, and a significant difference of the
results between different variables. Through my results, I want to learn more
about the process of fermentation, and the negative affects of time, light, and
salt concentration on fermentation.
General Expectations and Models
(a) My expectation is that the salt will increase the acidity of the cabbage,
decreasing the pH level. If salt is added to the cabbage, the salt will cause
osmosis to occur between the cabbage cells and the outside environment.
Thus, water would be excreted from the cells to balance out the
concentration. This process would kill all the cells except for the anaerobic
cells; cells that do not depend on oxygen from the water for cellular
respiration to create ATP. This suppresses the growth of other aerobic
bacteria that may rot the cabbage. With the absence of water therefore
oxygen, the cells would have to resort to fermentation. The more salt
added to the environment, the more water is expelled from the cabbage
cells, resulting into a faster rate of fermentation to meet the energy need of
the cells. The faster the rate of fermentation, the more lactic acid is
released, making the greater acidity.
Greater concentration of salt→ greater rate of osmosis
Greater rate of osmosis→ less water in cell
Less water in cell→ less oxygen
Less oxygen→ less rate of cellular respiration
Less rate of cellular respiration→ greater rate of fermentation
Greater rate of Fermentation→ Release more lactic acid
Release more lactic acid→ Greater acidity of cabbage cells
Greater Acidity→ Less pH level
Greater concentration of salt→ less pH level
(b) I expect that the more time the cabbage is exposed in non-oxygen
conditions and concentrated salt, the more the acidity will increase. The
byproduct of fermentation is lactic acid. As long as the fermentation
continues, the lactic acid will accumulate, resulting to an increasing level
of acidity.
(c) I expect that the sunlight would overheat many of the cells and kill many
anaerobic cells, thus the rate of fermentation would decrease, causing less
lactic acid. The cabbage cells in the cupboard though, would have more
acid since most bacteria like to grow in damp, dark, cool places, and there
would be more bacteria growing to create lactic acid.
C) Variables
1) Constant Variables
(a) Amount of cabbage in the bag
(b) Type of Salt
(c) The type of Ziploc bag
2) Independent Variables
(a) Time
(b) Sunlight (Temperature)
(c) Salt Concentration
3) Dependant Variables
(a) The pH level of the water excreted from the Kimchi (acidity)
(b) The rate of fermentation
II)






Materials
16 Small Ziploc bags
2 large Ziploc bags
56g of Chopped cabbage
Scale
40 g of Noniodized salt
Electronic pH measurer
Method and Procedures
ACIDITY
1) Separate chopped cabbage
in sixteen bags of 35 grams of cabbage in Ziploc bags
2) Separate the sixteen bags into two groups, label half of them WINDOW and half
of the CUPBOARD
3) Label the WINDOW bags, A to H
4) In bags A, B, C, and D, add 5 grams of salt to each bag
5) In bags E, F, G, and H, add 15 grams of salt to each bag
6) Make all of the WINDOW bags airtight
7) Label the CUPBOARD bags, A to H
8) In bags A, B, C, and D, add 5 grams of salt to each bag
9) In bags E, F, G, and H, add 15 grams of salt to each bag
10) Place the CUPBOARD bags in two large Ziploc bags, to conceal the air (four
small bags in each big bag)
11) Make the bags airtight
12) Place WINDOW bags on window sill
13) Place the CUPBOARD bags in two large Ziploc bags, to conceal the air (four
small bags in each big bag)
14) Make the bags airtight
15) Place CUPBOARD bags in a CUPBOARD
16) After one day, measure all the ph level of the each bag of cabbage by:
a. Placing the electronic ph measurer in the liquid of the kimchi
b. Rinsing the measurer in distilled water after each use
c. Writing the results on a table
17) Measure the ph level of every single kimchi bag each day at regular intervals for
two weeks
18) Graph Data
19) DO NOT EAT
III) Results
A) Qualitative Observations
B) Quantitative Observations
The Effect of Salt, Light, and Time on the pH of Kimchi
DAY 2
Sunlight pH
A 5 ml of salt
6
B 5 ml of salt
C 5 ml of salt
6
6
D 5 ml of salt
6
E 20 ml of salt
5
F 20 ml of salt
5
G 20 ml of salt
5
H 20 ml of salt
5
DAY 5
Sunlight pH
Cupboard
pH
5
4
Cupboard
pH
A 5 ml of salt
5
5
B 5 ml of salt
C 5 ml of salt
5
4
5
4
D 5 ml of salt
5
6
E 20 ml of salt
5
5
F 20 ml of salt
5
4
G 20 ml of salt
6
6
H 20 ml of salt
5
4
Sunlight pH
Cupboard
PH
A 5 ml of salt
4.5
4.6
B 5 ml of salt
C 5 ml of salt
4.6
4.5
4.6
4.4
D 5 ml of salt
4.6
5
E 20 ml of salt
5
5.2
F 20 ml of salt
5.2
5.2
G 20 ml of salt
5
7.2
H 20 ml of salt
5
5.2
DAY 7
DAY 9
Sunlight pH
Cupboard
PH
A 5 ml of salt
4.4
4.6
B 5 ml of salt
C 5 ml of salt
4.3
4.4
4.5
4.5
D 5 ml of salt
4.6
5
E 20 ml of salt
5.2
5.25
F 20 ml of salt
5
5.2
G 20 ml of salt
5.2
7.7
H 20 ml of salt
5.1
5.3
C) Data Processing and Analysis
IV)
Discussion
V)
Appendix I: Scientific Terminology
 pH pH is a measure of the concentration of hydrogens ions (= H+) (= protons) in a
solution
 Fermentation an acid produced by glucose-burning cells when these cells have an insufficient
supply of oxygen The scientific meaning of fermentation is the energy-yielding
anaerobic metabolism of a nutrients, such as sugars, without oxidation. Fermentation
converts these nutrients mainly into lactic acid, acetic acid, and ethanol.
 Lactic Acid Bacteria A large group of beneficial bacteria that have similar properties and all
produce lactic acid as an end product of the fermentation process. They are widespread in nature and
are also found in our digestive systems. Lactic acid bacteria have been used to ferment foods for at
least 4000 years eg yoghurt, cheese... They may also be responsible for food spoilage.












Lactic Acid Fermentation- A type of fermentation carried out by lactic acid bacteria
in which sugar (eg lactose, glucose, pentose) are converted either entirely (or almost
entirely) to lactic acid (homolactic fermentation) or to a mixture of lactic acid and
other products (heterolactic fermentation).
Anaerobic microorganisms-Their survival does not depend on the availability of
oxygen
Actobacillus Plantarum -in the late stage, this could affect the ripening of kimchi.
L. Brevis- in the late stage, which could affect the ripening of kimchi.
Streptococcus faecalis- actively grows in the early stage of fermentation
Leuconostoc mesenteroides- actively grows in the early stage of kimchi
fermentation, thereby producing lactic acid and carbon dioxide which could acidify
kimchi and create an anaerobic state to suppress the growth of aerobes.
Pediococcus pentosaceus- in the late stage, which could affect the ripening of
kimchi.
Acid-A solution that has an excess of H+ ions. It comes from the Latin word acidus
that means "sharp". (As time passes, our kimchi became more acidic)
Bacteria- Beneficial bacteria found in food after fermentation are capable of
producing so many enzymes necessary for the building up and breaking down of
organic compounds
Base-A substance that yields hydroxyl ions when dissolved in water.
NAD+ is nicotinamide adenine dinucleotide.-It serves as an intracellular oxidizing
agent (a.k.a., electron acceptor).
Oxymosis
NADH:


NADH is reduced NAD+.
NADH serves as means by which cells transfer reducing power around (a reducing
power intermediate) similar in concept to the way cells employ ATP as an energy
intermediate.


VI)
Appendix II: Key Concepts, Models, "Big Ideas"




Lactic acid fermentation produces no gas, which is unusual among fermentation
pathways.
Lactic acid is an acid and therefore sour to the taste.
Fermentation, the process
Anaerobic byproduct production:
o Fermentation includes all metabolic processes that do at least three* of the
following:
 release energy from a sugar or other organic compound
 do not require molecular oxygen
 do not require an electron transport system
 use an organic compound as the final electron acceptor.

The BIG idea
Bacteria such as lactic acid bacteria produce ATP without the presence of oxygen by
fermentation. The by product of the fermentation contributes to the taste of a food. Some
bacteria help change the flavor and appearance of food and suppresses the growth of
other non-helpful bacteria which could grow under such conditions..
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/P/pH.html
http://www.mansfield.ohiostate.edu/~sabedon/biol1095.htm#substrate_level_phosphorylation