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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 Processes
Aerobic respiration
Anaerobic respiration
What is the difference?
Fermentation is sometimes called anaerobic
Early stages of respiration can occur without
Without oxygen respiration cannot continue.
Fermentation splits complex organic
compounds into simpler substances.
Sugar is changed to carbon dioxide and
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
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
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
C6H12O6 → 2HC3H5O3 + Energy
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
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.