Lactic acid fermentation and mixed-acid fermentation are two types of fermentation processes. Lactic acid fermentation involves the conversion of glucose into lactic acid and cellular energy by lactic acid bacteria like Streptococcus. Mixed-acid fermentation is carried out by bacteria like E. coli and produces three different acids - acetic, lactic and succinic acids. Fermentation processes are important in food preservation and enhancing safety and flavor through the production of acids or alcohol during the breakdown of materials like milk, vegetables, barley and crops.

1. LACTIC ACID
FERMENTATION
MIXED-ACID
FERMENTATION
IMPORTANCES OF
THE FERMENTATION
KOAY BOON KEAT TONG KAI LOON
GAO LE EE CAI FENG
EMMANUEL JUDE JIMY VINCENT YATIN
JUMAAIAH BINTI TAASA TUTTYCIA MITCHEL ANAK SEAT

3. - biological process by which glucose and other 6C sugars are
converted into cellular energy and the lactic acid.
- lactic acid bacteria = gram-positive non-spore forming
bacteria (cocci or rods)
- classified into two fermentative patterns
=> homofermentative pathway (lactic acid)
=> heterofermentative pathway (lactic acid + ethanol + CO2)

4. - Undergo by bacteria such as Streptococcus sp. and some
types of Lactobacillus sp.

5. - Undergo by bacteria such as Leuconostoc sp. and some types
of Lactobacillus sp.

6. - used by mixed-acid fermenters such as Escherichia coli
- formed 3 different acids – acetic, lactic and succinic from
fermentation of glucose
- ethanol, CO2 and H2 also formed during the fermentation

8. Lactose (milk) + lactic acid
bacteria → Lactic acid
Two bacteria:
Streptococcus thermophilus
Lactobacillus bulgaricus
Importances:
makes the milk more acidic
causing the proteins in milk to coagulate

9. Bacteria involved:
Lactobacillus kimchii, Lactobacillus sakei were
common.
Stage ❶
☞vegetables are submerged in a brine.
Stage❷
☞Lactose + sugars lactic acid.
Importances:
classic tangy flavour
preserve food.

10. Benefits of Fermentation
Benefit Raw material Fermented
food
Preservation Milk Yoghurt, cheese
Enhancement of
safety
-Acid production Fruit Vinegar
-Acid and alcohol
production
Barley Beer
Improvement of
flavour
Vegetables Kimchi
Enhancement of
nutritional value
Milk Acidophilus yoghurt

11. Agricultural crops
 Make silage
 exposure of crops to lactic acid bacteria
 fermentation activity
 lowers pH on the surface of the crop
 preventing colonization of unwanted microorganisms