This document provides information about fermentation processes used in food science and nutrition. It discusses various types of fermentation including alcoholic fermentation carried out by yeast and lactic acid fermentation carried out by lactic acid bacteria. Key microorganisms involved in different fermentations are described along with their uses in producing foods like yogurt, cheese, bread, wine and others. Fermentation pathways and conditions required for different microbes are also summarized.

1. Course Title: Principles of Food Science and Nutrition
Course No: FDSN 101
Credit hours: 2(2+0)

2. Fermentation in food processing is the process of converting
carbohydrates to alcohol or organic acids using
microorganisms—yeasts or bacteria—under anaerobic
conditions.
 Fermentation usually implies that the action of
microorganisms is desired.
The science of fermentation is known as zymology or
zymurgy.

7. • ALCOHOLIC FERMENTATION
• LACTIC ACID FERMENTATION

8. • The breakdown of simple sugars into alcohol is normally referred to as alcoholic
fermentation.
• Yeasts, usually Saccharomyces sp, e.g. cerevisae or bayanus, are used to produce
ethanol from carbohydrates and very small amounts of other organic compounds.
• This conversion can be represented by the following equation:
C6H12O6 =2C2H5OH + 2CO2
(Glucose)= (Ethyl alcohol)+ (Carbon dioxide)

9. • In ethanol fermentation, the pyruvate produced through
glycolysis is converted to ethanol and carbon dioxide in two
steps.
• First, the pyruvate releases carbon dioxide to form a two-
carbon compound called acetaldehyde.
• Next, acetaldehyde is reduced by NADH to ethanol, thereby
regenerating the NAD+ for use in glycolysis.
• Overall, one molecule of glucose is converted into two
molecules of carbon dioxide and two molecules of ethanol.
• Ethanol fermentation is typically performed by yeast, which is a
unicellular fungus.

10. • Alcoholic fermentation usually results in the production of beverages such as
wine, beer vodka etc. and rising of bread dough.
• The substrates used for fermentation include honey, cereal grains, sap of palm,
fruit juices, grain malt, that contain sugars that can be fermented and are
converted to ethanol by yeast.
• During the process equal amount of carbon dioxide (CO2) is also produced
as a side product and this process is carried out under anaerobic conditions.

11. .
• Lactic acid fermentation is a metabolic process by which
glucose and other six-carbon sugars (also, disaccharides of
six-carbon sugars, e.g. sucrose or lactose) are converted
into cellular energy and the metabolite lactate, which is
lactic acid in solution.
• It is an anaerobic fermentation reaction that occurs in
some bacteria and animal cells, such as muscle cells.

12. • In lactic acid fermentations sugars are transformed to lactic acid by lactic acid organisms such as
Leuconostoc, Streptococcus, Lactobacillus bacteria.
• Lactic acid is the most important compound result from this reaction.
• Lactic acid producing bacteria are most significant bacteria used in food fermentation and production.
• Sour milk is one of the most ancient lactic acid fermented food in which the lactic acid bacteria will convert
the milk sugar known as lactose to lactic acid resulting in sour or fermented milk.
• Dairy products for example yogurt, cheese, butter and sour milk are also produced. Lactic acid
fermentation is used for the preservation of different vegetable foods .
• The best example is of sauerkraut, produced by the action of LAB on cabbage.

13. • There are two main types of lactic acid fermentation: homolactic and heterolactic.
• In homolactic acid fermentation, NADH reduces pyruvate directly to form lactate. This
process does not release gas. Overall, one molecule of glucose is converted into two
molecules of lactate.
• In heterolactic fermentation, some lactate is further metabolized, resulting in ethanol
and carbon dioxide via the phosphoketolase pathway.

16. • The organisms that one encounters most widely in these processes are undoubtedly the yeasts,
notably Saccharomyces, and lactic acid bacteria.
• It is important to note in passing that if these organisms ‘stay’ from where they are supposed to be,
then they are spoilage organisms with a ruinous nature.
• For example lactic acid bacteria have a multiplicity of values in the production of many foodstuffs,
including cheese, sourdough bread, some wines and a very few beers. However, their development
in the majority of beers is very much the primary source of spoilage.

18. Yeast:
• S. cerevisiae, namely, brewer’s yeast or bakers yeast
• Yeasts are heterotrophic organisms whose natural habitats are
plant tissues, including flowers and fruit.
• They are mostly obligate aerobes, although some (such as
facultative anaerobes. They are fairly simple in their nutritional
requiring a reduced carbon source, various minerals and a
and vitamins
• Focusing on brewing yeast, the term S. cerevisiae is properly
yeasts and it is spherical or ellipsoidal.
• Brewing yeast reproduces through budding

19. • Yeasts are predominant in several fermented foods prepared from ingredients of plant
as well as animal origin.
• The diversity of foods in which, yeasts predominate ranges from alcoholic beverages
such as wines (e.g., fruit, palm and rice wines), cereal based leavened products (e.g.,
sourdough and idli), milk products (e.g., cheese and dahi) and condiments such as soy
sauce and papads.
• Many yeast strains have been selected from the natural fermentation and successfully
utilised as starter culture for industrial food production.
• They have a significant impact on food quality by improving the taste, flavour, texture,
nutritive values, reduction of anti-nutritional factors and improving the functionality
(health promoting properties).

20. • The most notable species within this genus is L. lactis, which is
most important in the production of foodstuffs such as yoghurts
and cheese.
• It is often co-cultured with Leuconostoc. There are two sub-
species of L. lactis: cremoris, which is highly prized for the flavour
it affords to certain cheese, and Lactis, in particular L. lactis ssp.
lactis biovar. diacetyllactis, which can convert citrate to diacetyl, a
to diacetyl, a compound with a strong buttery flavour highly prized
in some dairy products., beers.
• The carbon dioxide produced by this organism is important for eye
formation in Gouda.

21. • These are heterofermentative cocci.
• Capable of producing lactic acid, CO2 and aromatic compounds (ethanol and acetic
acid) from glucose.
• These organisms are normally used along with lactic acid bacteria (LAB) in multiple or
mixed strain cheese starter cultures, which produces flavour compounds.
• Leuconostoc cremoris
• Leuconostoc citrovorum
• Leuconostoc dextranicum
Leuconostoc

22. • Found in the gut of infants, intestines of man, various animals and honeybees.
• These organisms are generally used in preparation of therapeutic fermented milk products in combination
with yoghurt, acidophilus milk
• Bifidobacterium bifidum, Bifidobacterium longum, Bifidobacterium infantis, Bifidobacterium breve, etc.
Bifidobacterium:

23. • These are mostly pathogens
• Uses - Streptococcus thermophilus is a food
organism, with Lactobacillus delbrueckii ssp.
Bulgaricus used in the production of yoghurt.
• It is used in starter cultures for certain cheeses
[Parmesan]
Streptococcus:

24. • Moulds are used for the manufacture of some semi soft cheese varieties and in some
fermented milk products.
• Moulds enhance the flavour and modify slightly the body and texture of curd.
• White mold is used in manufacture of surface mould ripened cheeses like Camembert and
Brie cheeses.
Eg: Penicillium camemberti, Penicillium caseicolum, Penicillium candidum
• Blue mold is used in manufacture of internal mould ripened cheeses like Roquefort, Blue
Stilton, Danish blue, Gorgonzola and mycella cheeses
Eg: Penicillium roquefortii
Moulds

25. • Other molds Mucor rasmusen – used in Norway for the manufacture of
ripened skim milk cheese.
• Asperigillus oryzae – used in Japan for the manufacture of Soya milk cheese
Soya milk cheese
• Geotricum candidum– used in the manufacture of Villi a cultured product of
cultured product of Finland.
• The mould grows on the surface of the milk to form the white velvety layer

26. • rod-shaped
• Present in- mucous membranes of the human[the oral cavity,] also found in
foodstuffs, such as plants, meats and milk products.
• Example- Lb. delbrueckii ssp. bulgaricus is a key starter organism for yoghurts
organism for yoghurts and some cheeses.
• lactobacilli involve in other fermentations, such as sourdough and fermented
sausages, for example, salami
• Disadvantage - they can spoil beer and either fresh or cooked meats, etc.
Lactobacillus

27. • These bacteria are only weakly proteolytic and lipolytic, which means that
they are quite produce ‘mild’ pungent flavours.
• They are also naturally present in the intestine and the reproductive tract, so it
is necessary to add probiotics and prebiotics in the food to increase the level
of lactic acid bacteria in the gut.
• Joseph Lister isolated the first lactic acid bacterium in 1873.

28. • Lactococcus lactis is a species of great significance in the
fermentation of milk products.
• TYPE-Gram-positive organisms
• SHAPE- rod-shaped, cocci (spherical) or coccobacilli.
• TEMPERATURE - mesophilic, [but some can grow at
temperatures (4◦C) and as high as 45◦C.
• pH - 4.0–4.5, [but certain strains can tolerate and grow at
as low as 3.2]
Lactococcus

34. Batch
It is a technique for large
scale production of
microbes or microbial
products in which, at a
given time , the fermenter
stopped and the culture is
worked up.
Fed-batch
In this , the fresh aliquot of
the medium is continously
or periodically added,
without the removal of the
culture fluid.
Continuous
It is continous culture or
processing in which the
growth of the organism is
controlled by the
availability of growth
limiting chemical
components of the
medium.

35. Alcoholic Lactic acid
•Homolactic:
•Lactic acid
•Lactobacillus/
Streptococcus
• Eg: Yogurt
• Heterolactic:
• Lactic acid +
ethanol + CO2
• Leuconostoc
• Eg: Kimchi
Propionic Butyric acid
•Butyric acid,
acetic acid,
butanol,
isopropanol,
acetone,
ethanol +
CO2, H2
• Clostridium
butyricum
Formic acid
•Mixed acid:
•Lactic acid +
acetic acid +
succinic acid +
ethanol +
formic acid
(gives CO2
•Escherichia
•Butanediol:
•2,3-
butanediol,
lactic acid,
acetic acid,
ethanol,
formic acid
(gives CO2 +
H2)
Acetic acid
• Acetic acid,
gluconic
acid, kojic
acid
• Acetobacter
• Ethanol + CO2
acid
• Saccharomyces •Propionic acid +
cerevisiae acetic acid +
• Eg: Beer CO2
•Propionibacteri
um
•Eg: Swiss
cheese
•Klebsiella

39. 1. The use of mild conditions of pH and temperature which maintain (and
often improve) the nutritional properties and sensory characteristics of
the food.
2. The production of foods which have flavours or textures that cannot be
achieved by other methods
3. Low energy consumption due to the mild operating conditions
4. Relatively low capital and operating costs
5. Relatively simple technologies.