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Transcript
The Fermentation of Food
Chapter 22
The good, the bad,
and the smelly
What food or beverage comes to mind when you
hear the word fermentation?
Fermentation in History
Louis Pasteur: Page 341
 Hypothesised that certain
bacteria was spoiling wine.
 Suggested that wine be
heated to kill bacteria.
 Pasteurization of milk.
Making Use of Fermentation



Extended shelf life of food (ex. Cheese)
Eases Digestion (ex. Wild rice)
New [better] flavours (ex. Chocolate)
The Fermentation Process


Cell Respiration – cells of your body need
energy they get it through this process.
Oxygen is required during the last stage of
respiration.
Respiration Processes

Aerobic respiration
VS

Anaerobic respiration
What is the difference?



Fermentation is sometimes called anaerobic
respiration.
Early stages of respiration can occur without
oxygen.
Without oxygen respiration cannot continue.



Fermentation splits complex organic
compounds into simpler substances.
Sugar is changed to carbon dioxide and
alcohol.
What causes this process to occur in foods and
beverages? Page 343
Sources of Bacteria


Occur naturally in plants – cucumbers and
cabbage have bacteria on them when they are
harvested.
Microorganisms found on these are called
native or indigenous microorganisms.

Added to food products – lactic-acid bacteria.
–
–

Streptococcus thermophilus
Lactobacillus bulgaroicus
Produced commercially.
–
Preserved through drying, freeze drying, or
concentrating and freezing.
Bacterial Fermentation
Four types
1. Lactic-acid
2. Acetic-Acid
3. Carbon-dioxide
4. Proteolytic (least
common)
bacteria
1. Lactic-Acid Bacteria
Used in production of yogurt, sour cream,
cottage cheese, cheddar cheese, dill pickles,
olives, sauerkraut, and vanilla
 Glucose is converted into lactic acid and
energy
Formula:

bacteria
C6H12O6 → 2HC3H5O3 + Energy
Glucose
Lactic Acid
2. Acetic-Acid Bacteria



Produces Vinegar
Two steps involved
First step – sugar from the fruit is fermented to
ethyl alcohol (yeast makes this happen).
Second step – acetic-acid bacteria attack the
alcohol that was produced.
–
Ethyl alcohol combines with oxygen, oxidation
occurs.
3. Carbon-dioxide


Yeast Fermentation – process converts
glucose into ethyl alcohol and carbon dioxide.
During fermentation – yeast grows and
produces carbon dioxide at different rates.
–
Temperature is critical


Too cool fermentation will not take place.
Too hot will kill the yeast.


Yeast needs sugar to produce carbon dioxide
(Feeds the yeast)
Salt will cause the fermentation to slow down.