Flavour is the sensory impression of food or other substance determined by chemical sense of taste and smell. Flavour can be characterized as plants, amimal, microbial, enzymatic. . Microbial bioprocess has advantageous over plant cell culture such as high yield, low cost, independent on seasonal variation.

1. Microbial metabolites as
flavouring agents
SUBMITTED BY : SARABJIT KAUR

2. Flavour

3. Flavour Sensations

4.  Alcohols (-OH)
 Aldehydes (-CHO)
Dicarbonyls (-CO-)
 Esters ( -COOR)
Lactones ( )
 Methyl ketones(-COCH3)
 Phenolic compounds
Short to medium chain free fatty acids
Sulphur compounds
Compounds responsible for the aroma of the food
products

5. Classification of flavours on the
basis of sources
NATURAL
FLAVOURS
MICROBIAL
FLAVOURS
SYNTHETIC
FLAVOURS
ENZYMATIC
FLAVOURS
•Vanilla
•Cinnnamic acid
•Limonene
•Menthol
•Camphor
•Eucalyptol
•Cinnamaldehyde
•Eugenol
•Isoamyl acetate
Flavours
•Diacetyl
•Lactones
•Esters
•Alcohols
•Methyl ketones
•Benzeldehydes
•Ester
•Terpenes
•Vanilla
• Allylpyrazine
•Methoxypyrazines
•2-Isobutyl-3-
methoxypyrazine
• Acetyl-L-pyrazines
•2-Acetoxy pyrazine
• Aldehydes

6. Natural Flavours

7. I. Natural flavours
• Natural flavors contains the flavoring constituents derived from a spice,
fruits, vegetables, similar plant material, edible yeast, meat, seafood,
poultry, eggs, dairy products.
(i) In plants-
• Plants can synthesize, accumulate and emit volatiles that act as aroma and
flavor molecules due to interactions with human receptors.
• Natural flavours present in different parts of plants -
i. Bark- Cinnamon,
ii. Bud- Onion, garlic,
iii. Root-Carrot,
iv. Leaf - Coriander, Curry leaf
• They are commercially important for the food, pharmaceutical, agricultural
and chemical industries as flavorants, drugs, pesticides and industrial
feedstocks.

8. ii. Animal based flavours- such as meat
• Raw meat - salty, metallic with slightly sweet
aroma
• Cooked meat- meaty flavor notes due to bis-(2-
methyl-3-furan) disulfide, formed by interactions
between Maillard reaction products and lipid
oxidation products
Plant species Compounds Products
Oryza sativa (Rice) 2-acetyl -1-pyruvate Basmati flavour
Allium sativum (Garlic) Thiols Garlic
Allium cepa (Onion) Phenolics Onion
Vanilla planifolia
(Vanilla beans)
Vanilla(4-Hydroxy-3-
methoxybenzaldehyde)
Vanillin

9. Biosynthetic pathway of natural flavours

10. Limitations of natural flavours
• Low abundance of the volatiles
• Flavours are affected by plant type, geographical
location, seasonal restriction
• High cost

11. Synthetic flavours
• Synthetic (or artificial) flavors are complex mixtures of naturally occurring
flavor compounds to either imitate or enhance a natural flavor.
• In the 1800s, a German chemist was the first to develop synthetic aromatic
chemicals of fruity odour.
• In 1858, Vanillin was first crystallized from an alcoholic extract of vanilla
beans by Gobley
• By the end of the 19th century, production of synthetic flavors shares a
global market.
• These mixtures are formulated by flavorists to give a food product a unique
flavor and to maintain flavor consistency between different product
batches.
• Produced by fractional distillation and additional chemical manipulation of
naturally sourced chemicals, crude oil or coal.

12. Chemical flavours used for food flavouring
• Chemicals : Flavours
• Allylpyrazine Roasted nut
• Methoxypyrazines Earthy vegetables
• 2-Isobutyl-3-methoxypyrazine Green pepper
• Acetyl-L-pyrazines Popcorn
• 2-Acetoxy pyrazine Toasted flavours
• Aldehydes Fruity
• Alcohols Bitter
• Esters Fruity
• Ketones Butter, caramel
• Pyrazines Caramel
• Phenolics Smokey

13. Health Risks of Synthetic Flavours
• Brain tumors, cancer, depression, DNA damage, allergies,
kidney problems, high blood pressure.
• Nowadays, the consumer has developed a ‘chemophobia’-
attitude towards synthetic compounds, especially when
related to food and its products.

14. • Since time immemorial, man has unwittingly used microorganisms to
produce flavours while preparing fermented foods and drinks.
• Around the turn of 20th century that the relationship between the typical
desirable flavour of fermented foods and beverages, and the
microorganisms involvement became recognised.
• A wide range of microorganisms is known to produce flavour compounds
from simple nutrients via de novo synthesis, e.g. sugars, alcohols, etc.
• Provide characteristic flavour to fermented products such as in wine ,beer,
yogurt, butter ,bread, fruity and nutty flavour.
• In most cases the de novo fermentation processes can be boosted by
supplying a limiting intermediate or precursor molecule, which is otherwise
limiting the yield, to the culture.
Microbial flavours

15. Microbial flavours Microorganisms Compounds
Butter flavour Lactococcus lactis Diacetyl
Cocconut like, buttery,
creamy, sweet and nutty
Candida tropicalis,
Trichoderma viridae
Lactones
Fruity flavour Pichia anomola Esters
Nutty and roasted flavour Corynebacterium
glutamicium
Pyrazines
Organoleptic properties Saccharomyces cereviase Alcohols
Vanillin Vanilla planifolia Vanilla
Natural fruit flavour Phanerochaete
chrysosporium
Benaldehydes
Microbial flavours

16. Biosynthetic pathway of Microbial flavours

17. Diacetyl (Butane-2,3-dione)
• Diacetyl is a byproduct formed in the curd, butter, cheese ,
milk , bread, coffee, brandy, rum.
• It also is manufactured as a component of artificial butter
flavoring that is used in butter-flavored microwave
popcorn, candy, baked goods and cake mixes
• The FDA currently classifies diacetyl as “Generally
Recognized as Safe” (GRAS) for consumption.

18. Biosynthetic pathway of Diacetyl
production
• Substrate : Whey media, lactose peptone medium, with 1% citrate as
inducer
• Organisms : Lactococcus lactis , Lactobacillus sp., Streptococcus
thermophilus and Leuconostoc mesenteroids
Biosynthetic pathway

19. Lactones( D-glucono-1,5-lactone lactonohydrolase )
• The microbial bioprocess of lactone synthesis was first established
in the early 1980s.
• Microbial lactones are produced by the β-oxidation of hydroxy fatty
acids.
• They contribute to the aroma of butter, cheese and various foods and
fruits.
e.g.- i. Cyclopentadecanolide is responsible for the musk like odor of
angelica root oil.
ii. Phthalides are responsible for the odors of celery and lovage oils.
iii. Raw milk does not contain free lactones, appear after heating.

20. Biosynthetic pathway of lactones
production
• Organisms:
Trichoderma viridae,
Cladosporium suaveolens
Candida tropicalis
Yarrowia lipolytica.
• Fruity , coconut like , buttery,
creamy, sweet and nutty.

21. ESTERS (-COOR)
• Volatile esters are responsible for the fruity character of fermented beverages
and constitute a vital group of aromatic compounds in beer and wine.
• Maarse and Visscher (1989) listed 94 esters formed in beer during primary
fermentation.
• A study conducted by Saerens et al. (2007) to evaluate the fermentation
parameters with ethyl ester production using yeast strain.
• Observations-
i. Higher level of unsaturated fatty acids - decrease in ethyl ester production
ii. Higher carbon or nitrogen content - moderate levels in ethyl ester
production.
iii. Limited level of medium chain fatty acids – leads to increase in ethyl ester
production
Conclusion-
The precursor availability is the major limiting factor in ethyl ester
production. So, the expression level and activity of the fatty acid
biosynthetic enzymes therefore appear to be prime targets for flavour
modification by alteration of process parameters

22. Biosynthetic pathway of Ester
production
• Substrate : Barley malt
• Organisms: Saccharomyces ,
Henseniaspora guilliermondii and
Pichia anomola
Biosynthetic
pathway

23. Ester products
• Ethyl butyrate ester has
large market demand
• Fruit-flavoured products:
• Beverages
• Candies
• Jellies, jams
• Baked good
• Wines
• Dairy products :
• Cultured butter,
• Sour cream
• Yogurt and chesse.

24. Pyrazine((7R)-7-methyl-6,7-dihydro-5H-
cyclopenta)
• Constituents of peas, coffee, c apsicum peppers and wines at concentration as low
as 0.00001 ppm.
• The synthesis of pyrazine was first recorded by Laurent in 1844, the compound was
proved to be tetraphenylpyrazine
• In 1912 – 1916 Louis-Camille Maillard observe the colour changes on mixing
amino acids and sugars
• Pyrazines is a heterocyclic, N2 containing compound formed during roasting of
food through Maillard reaction.
• Modern cooking do not favour pyrazine formation, so need to supply natural
pyrazine with roastyflavour
• Has interesting anticancer as well as antituberculosis activities.

25. BROWNING IN THERMALLY PROCESSED
FOODS: THE MAILLARD REACTION

26. Flavour and Colour in the
Maillard Reaction
H2O
rearrangement
NHROH
OOH
H
OH
OH
Amadori intermediate
carbonyl compounds
 H2O
 RNH2
O
O
H
O
O
O CHO
HO
O
OOH
O OH
O
O CHO
O OH
O
amino acids
FLAVOUR
COMPOUNDS
MELANOIDIN
PIGMENTS
H
O
OH OH
OHOH
OH
R NH2+
reducing sugar amino
compound
Amino acid
or
proteins

27. Biosynthetic pathway of Pyrazine((7R)-7-
methyl-6,7-dihydro-5H-cyclopenta) production
• Organism: Corynebacerium glutamicum.

28. Biosynthetic pathway of Alcohols (-OH)
production
• Theses complex alcohols and derived esters has organoleptic
properties.
• Organisms: Saccharomyces cerevisiae , Hansenula anomala,
Kluyveromyces marxianus.
Methyl phenyl
acetate
2-phenyl ethanol Phenylacetic acid

29. Alcohols products
• 2-phenylethanol is
most relevant aroma
compounds give rose
like smell.

30. Vanillin(4-hydroxy-3-
methoxybenzaldehyde)
• It is the immature fruit of the orchid Vanilla planifolia
and is cultivated as a vine .
• Vanilla extract contain more than 250 chemical
compounds extracted through percolation method.
• It is the second most expensive spice in the world
• In 1997,the H&F Florasynth began the production of
vanillin identical to natural one by process consist of
two steps leads to ferulic acid turns into vanillin

31. Biosynthetic pathway of Vanillin
production
• Vanillin flavour
• Organisms:
– Pseudomonas putida
– Aspergillus niger
– Corynebacterium glutamicum,
– Corynebacterium sp.,
– Arthrobacter globiformis
– Serratia marcescens .
Vanilla beans

32. Production of Vanillin from Caffeic acid
•A two step bioconversion by filamentous fungi to transform Ferulic acid
to vanillin by Aspergillus niger.
• Vanillic acid reduced to vanillin by Pycnoporous cinnabarinus.

33. Applications
• Febrifuge: Vanilla essential oil an effectively reduce
fevers by fighting infections
• Anti-carcinogenic: The anticarcinogenic property of
vanilla oil comes from its antioxidant properties.
• Antioxidant: This property of vanilla essential oil
solve many problems

34. Vanillin products
Ice cream Perfumes
Cookies
1. Used in flavouring in
sweet foods
• Cookies
• Muffins
• Cakes
• Icecreams
• Softdrinks
• Beverage ,
2. Non-food users
• Perfumes,
• Pharmaceuticals

35. Benzaldehyde
• Benzaldehyde is the second most important Flavour molecule after vanillin.
• Benzaldehyde was first extracted from bitter almonds in 1803 by the
French pharmacist Martres.
• In 1832 German chemists Friedrich Wohler and Justus von Liebig first
synthesized benzaldehyde
• It is mainly in the form of glycosides in cherry, laurel, peach contain
significant amount of amygdalin.
• Occur naturally in bitter almond oil.
• Used as a flavoring and fragrance in food, cosmetics, pharmaceuticals, and
soap and is "generally regarded as safe" (GRAS) by the US FDA.

36. Biosynthetic pathway of Benzaldehyde
production
• Made up of
benzene ring with a
formyl substituent.
• Bitter almond
Flavour
• Organisms :
– Pseudomonas
putida
– Trametes
suaveolens
– Polyporous
tuberaster
– Bjerkandera
adusta
– Phanerochaete
chrysosporium
.
Metabolism of L-phenylalanine by Trametes suaveolens

37. Benzaldehyde Product
• Consumption of
Benzaldehyde
approximately 7000 tones
per year as product of
almond and cherry

38. Methyl ketones
• Methyl ketones are important flavor components, especially
of blue cheeses
• Penicillium roqueforti produces 2-pentanone, 2-heptanone
and 2-nonanone
• Contributing to the flavor of fresh butter.
• They also have applications as biofuels, owing to their
reduced, aliphatic carbon chains
• Methyl ketones can be produced from the fatty acid β-
oxidation pathway

39. Methyl ketones
• Organisms :
– Agaricus bisporus,
– Aspergillus niger
– Penicillium roqueforti
– Trichoderma viridae

40. Methyl ketone products
• Application:
• blue cheese and fruit
flavours

41. Solid state fermentation
• Solid state fermentation process occuring in
the absence or near-absence of free water.
• SSF employ natural raw material as carbon
source such as cassava,barley,wheat bran, rice
bran,sugarcane bagasse, various oil cakes,fruit
pulp,corn cobs,seeds, coffee husk,

42. Solid state fermentation

43. Flavours produced by microbial bioconversion of the
precursor

44. Advantages of SSF
•Process is simple
•Cost effective
•Less Effluent release,reduce pollution
•Aeration process is easy
•Easier downstream processing

45. Conclusion