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CAN THO UNIVERSITY
COLLEGE OF NATURAL SCIENCES

THEMATIC REPORT

ROLES OF BACTERIA IN FOOD
GUIDANCE LECTURER:
PhD. Nguyễn Thị Phi Oanh

STUDENT PERFORMANCE:
Trần Chí Linh
B1303493
Nguyễn Thị Hồng Lẹ
B1303491
Trần Thị Ngọc Loan
B1303494
Võ Thị Quyền Qúy
B1303603
Võ Chí Linh
B1303
Nguyễn Thành Luân
B1303


THE STRUCURE OF REPORT

I

THE CONCEPT OF FOOD AND BACTERIA

II

THE EFFECTS OF BACTERIA ON FOOD

III

INTRODUCTION OF LACTIC ACID BACTERIA

IV

APPLICATION OF BACTERIA IN FOOD

V

CONCLUSION


I. CONCEPT OF FOOD AND BACTERIA

1. Food

• Food is any substance consumed
nutritional support for the body.

to

provide

• Food is usually of plant or animal origin, and contains
essential nutrients, such as fats, proteins, vitamins,

or minerals.
• The substance is ingested by an organism and
assimilated by the organism's cells to provide
energy, maintain life, or stimulate growth.


I. CONCEPT OF FOOD AND BACTERIA

2. Bacteria
• Bacteria were among the first life forms to appear on
Earth, and are present in most of its habitats.
• Bacteria inhabit soil, water, acidic hot springs,
radioactive waste and the deep portions of Earth's
crust.
• Bacteria also live in symbiotic and parasitic
relationships with plants and animals.
• They are also known to have flourished in manned
spacecraft.


II. THE EFFECTS OF BACTERIA ON FOOD

1. Good bacteria
• Some bacteria possess properties that can benefit food
production or conversion.
• Many food-grade bacteria are used to produce a variety of
fermented foods from raw animal and plant materials.
• The acidic, and in part organolytic, properties of
fermented products result from the fermentative activities
of these bacteria .

• Foods such as ripened cheeses, fermented sausages,
sauerkraut and pickles have not only a greatly extended
shelf life compared to the raw materials from which hey
are derived, but also aroma and flavor characteristics
contributed directly or indirectly by the fermenting
organisms.


II. THE EFFECTS OF BACTERIA IN FOOD

2. Bad bacteria
•

Microbial contamination of foods can have many undesirable
consequences ranging from spoilage to foodborne illness.





III. INTRODUCTION OF LACTIC ACID BACTERIA

1. Lactic acid bacteria
• The colonies are small round,
glossy – clear, opalescent or
yellow of cream; or colonies are
large round, outstanding,
opalescent. Also colonies have
sour smell of acid
• LAB need nitrogen from some acid

amin, vitamin, growth substance,
and some mineral. The best
carbon that they growth are small
glucoses, alcohol.
Figure 7. The colonies of LAB
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III. INTRODUCTION OF LACTIC ACID BACTERIA

2. Lactic fermentation
Lactic fermentation is anerobic metabolism from sugar to lactic
acid by some lactobacilli: Bacterium lactic, Bacterium delbriski,
Bacterium casei,…


III. INTRODUCTION OF LACTIC ACID BACTERIA

a. Homofermentative pathway
Lactic acid is main product (90 - 98% in fermentation products total),
subproducts are ethanol, acid acetic, CO2.
C6H12O6
2C3H6O3
(Glucose)
(Lactic acid)
b. Heterofermentative pathway
Only 50% glucose was created lactic acid. Subproducts are ethanol, acid
acetic, CO2 . It can interact each other to create smell ester.
C6H12O6
2C3H6O3 + C2H4(COOH)2 + CH3COOH + C2H5OH + CO2 + H2
(Glucose)

(Lactic acid) (Succinic acid) (Acetic acid) (Ethanol)


III. INTRODUCTION OF LACTIC ACID BACTERIA

3. Classification of LAB
According to fermentation method, Lactobacilli includes two species:
Homolactic and Heterolactic bacteria.
a. Homolactic bacteria
Homolactic bacteria are lactic bacteria create main products are lactic acid
in glucose fermentation process. There are two genera take part in this
fermentation process: Lactobacillus and Streptococcus.

Figure 9. Lactobacillus bulgaricus



III. INTRODUCTION OF LACTIC ACID BACTERIA

Some Lactic bacteria species in Homolactic bacteria


III. INTRODUCTION OF LACTIC ACID BACTERIA

b. Heterolactic bacteria
Heterolactic bacteria are lactic bacteria create a little lactic acid in glucose
fermentation process. Other some subproduct are ethanol, acid acetic... Like
Homolactic bacteria Lactobacillus and Streptococcus have some common
species: Lactobacillus brevis, Streptococcus fulcalis, and Streptococcus
cumoris.

Figure 10. Lactobacillus brevis

www.brewingscience.com

enfo.agt.bme.hu


IV. APPLICATION OF BACTERIA IN FOOD
1. Fish sauce
• Uneviscerated fish is mixed with salt and placed in fermented tanks

about six month.
• Streptococcus, Micrococcus and Bacillus speces are involved in this
fermentation process.
• This product is dark couloured with a distinctaroma.


IV. APPLICATION OF BACTERIA IN FOOD
2. Kim Chi
• Kim chi is the fermented napa
cabbage
• Kimchi is processed with various
seasonings, such as red pepper
powder, garlic, ginger, green onion,
fermented seafood (jeotgal), and salts,
at low temperatures.
• Lactic acid bacteria and included
several species of the genera
Lactobacillus, Leuconostoc and

Weissella are involved in this
fermentation process.


IV. APPLICATION OF BACTERIA IN FOOD
3. Soy sauce
• Soy sauce is the mixtrure of soybeans, wheat, salt and water.

• The wheat-soy mixture is exposed to specific strains of mold
called Aspergillus oryzae or Aspergillus soyae, which break
down the proteins in the mash.
• Further fermentation occurs through addition of specific
bacteria (lactobaccillus) and yeasts which enzymatically react
with the protein residues to produce a number of amino acids
and peptides.
• These protein derivatives all contribute flavor to the end
product


IV. APPLICATION OF BACTERIA IN FOOD
4. Yogurt
• Yogurt is made by fermenting many types of milk with lactic acid
bacteria.
• The good bacteria most commonly used as probiotics are lactic acid
bacteria, such as lactobacillus bulgaricus, lactobacillus acidophilus, L.
animalis and L. casei, the probiotic Bifidobacterium strains B. animalis
and B. lactis, Streptococcus thermophilus .
• To turn milk into yogurt, these bacteria ferment the milk, turning the
lactose sugars in the milk into lactic acid. The lactic acid is what causes
the milk, as it ferments, to thicken and taste tart.

V. CONCLUSION

• Food, bacteria and humans have an intimate relationship with each other
very interesting for a long time, before both the record of history.
• Food not only has nutritional value for humans but also the ideal culture
medium for the growth of bacteria.
• Fermented by bacteria that can lead to the ability to preserve food instead
of food spoil.
• Therefore, people have long been promoted:
Study rules of bacterial activity with the relevant food.
The study method using the friendly bacteria to food processing.
Research methods to control the harmful bacteria, prevention of food
spoilage.
Research test methods bacteria in foods, identifying food safety standards.


V. CONCLUSION

• Bacteria can be used to turn raw food into your favorite food, such as
cheese, pickles, yogurt, the tofu (bean curd powder), sausage, sauce, fish
sauce, soy sauce, noodles, noodles, yeast cake .... bacteria can directly affect
food quality and human health.
• In terms of benefits, the nutrient-rich foods are essential for humans.
• The growth of bacteria in food can lead to either safety or to help preserve
the food spoil.
• This depends on the relationship between bacteria and food storage
conditions.
• Therefore, people need to continue to improve the understanding of the

bacteria to be able to exploit the benefits tubers them up.


REFERENCES

1.
2.
3.
4.

Michael P., J. Meng, 2006. Bacteria in Food and Beverage Production,
Prokaryotes,1:797–811.
Tran Minh Tam, 2000. Microbiological technology applications. Agriculture
Publisher, TP. HCM.
Dong Thi Thanh Thu 19, 2003. Biochemical applications. National University
Publishing House, TP.HCM.
Nguyen Duc Luong, 2006. Microbiological technology. National University
Publishing House, TP. HCM.


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