food chemistry

1. FOOD
CHEMISTRY
PRESENTATION
Anisha Raj
A14312616105
‘B.TECH [FOOD TECH.]

2. CLASSIFICATION
OF LIPIDS

4. What are lipids?
 Lipids, together with carbohydrates, proteins and nucleic acids, are one
of the four major classes of biologically essential organic molecules found
in all living organisms; their amounts and quality in diet are able to
influence cell, tissue and body physiology.
 Unlike carbohydrates, proteins and nucleic acids they aren’t polymers but
small molecules, with a molecular weights that range between 100 and
5000, and also vary considerably in polarity, including hydrophobic
molecules, like triglycerides or sterol esters, and others more water-
soluble like phospholipids or very short-chain fatty acids, the latter
completely miscible with water and insoluble in non polar solvents.
The little or absent water-solubility of many of them means that they are
subject to special treatments at all stages of their utilization, that is in the
course of digestion, absorption, transport, storage and use.
 They may be classified based on their physical properties at room
temperature (solid or liquid, respectively fats and oils), on polarity, or on
their essentiality for humans, but the preferable classification is based on
their structure.

5. A) Simple lipids:
 Simple lipids are the esters of
fatty acids with various alcohols.
They are further classified as ;
1) Triglycerides( fats and oils)
 These are the esters of fatty acid
with glycerol.The fats and oils that
are widely distributed in both
plants and animals are chemically
triglycerides or
triacylglycerides.They are
insoluble in water and not- polar in
nature and commonly known as
neutral fat.
Note: R is same for simple oils and
fats
 R is different for mixed oils and
fats
 Oilsand fats are considered as
lipids which on hydrolysis produce
long chain monocarboxylic acid
and glycerol.

6. Oils fats
1.The glycerides which
exist in liquid form at room
temperature are known as
oils.
2.≥The degree of
unsaturation of fatty acid
residue in oil is higher.
3.Oils are the triglycerides
of unsaturated fatty acids.
1.The triglycerides which
exist in solid form at room
temperature are known as
fats.
2.The degree of
unsaturation of fatty acid
residue in fat is lower.
3.Fats are the triglycerides
of saturated fatty acids.
Difference between fat and oil:

7. 2) Waxes:
 Waxes are the ester of long chain saturated and
unsaturated fatty acids with long chain alcohols.
waxes are considered as the lipid which on hydrolysis
produce long chain fatty acids and long chain
alcohols.
 Waxes→hydrolysis→long chain fatty acids+ long chain
alcohols
 In the case of plankton (aquatic plants) waxes is the
chief storage form of metabolic fuel . Biological waxes
have a variety of applications in the pharmaceutical,
cosmetics and other industries.
B) Complex Lipids:
On the basis of composition complex lipids are further
classify as:
1) Phospholipids
2) Glycolipids

8. 1) Phospholipids:
 These are complex lipids
containing phosphoric acid .They
also contain nitrogen base and
other substances and they are
mainly deposited in the brain
and nervous tissue.They are also
present in cytoplasmic
membrane due to which they
are involved in cellular activities.
They are classified into two
groups:
Glycerophospholipids
Sphingophospholipids
 Glycerophospholipids:
They are most abundant
phospholipids . They contain 2
fatty acids esterified with first and
second hydroxyl group of glycerol.
the third hydroxyl group of
glycerol forms an ester linkage
with phosphoric acid.

9.  Glycerophospholipids are
further divided into
following groups:
A) Phosphatidylcholine(
Lecithins):
 It is widely distributed in
the body mainly in the
liver. In this
phospholipids, collin is
present as the base
which prevents the
deposition of abnormal
fat in the liver. It is also
the major constituents of
acetyl choline.

10. b) Phosphatidylethanolamine
(cephalin ) ;
The base ethanolamine
is present which occur
together with lecithin
and connected with the
brain. It is also present
in RBC.

11. c)
Phosphatidylserine:
The base amino acid
serine is present. It has
similar function with
lecithin.

12. d)
Phosphatidylinositol:
 It contains inositol as
the base instead of
nitrogen base. It is
mainly found in
plants and nervous
tissue. Some
hormones such as
oxytocin, vasopressin
are modified through
phospholipids.

13. e) Phosphatidylglycerol:
 In this
phospholipids, two
molecules of
phosphatic acids
are held by the
addition of glycerol
to phosphate
groups. It is found
in the inner
membrane of
mitochondria.

14. f) Phosphatidylethanolamine
(plasmalogens)
 In this
phospholipids, fatty
acids are linked
with carbon and
glycerol by an ester
linkage. Generally,
unsaturated fatty
acid is linked at
carbon.

15. Functions of phospholipids:
 Phospholipids are constituents of an important group of
compound lipids that perform a wide variety of functions:
 Phospholipids in the associations with proteins form the structural
components of a membrane and regulate membrane
permeability.
 Phospholipids in the mitochondria are responsible for maintaining
the conformation of electron transport chain components and
thus cellular respiration.
 Phospholipids participate in the absorption of fat in the intestine.
 Phospholipids are essential for the synthesis of different proteins
ie. lipoproteins and thus participate in the transport of lipids.
 Accumulation of fat in the liver can be prevented by phospholipids
,hence they are regarded as the lipo protein factor.
 phospholipids participate in the reverse cholesterol transport and
thus help in the removal of cholesterol from the body.
 Cephalins are the important group of phospholipids participate in
the blood clotting.
 Phosphatidylinositol are involved in signal transmission across
membrane.
 Phospholipids act as an agent for lowering surface tension.

16. 2) Sphingophospholipids:
 These are compounds
formed by one molecule of
long chain fatty acids and
two molecules of long chain
amino alcohol sphingosine or
one of its derivative and
their polar bond alcohols.
They are found in the brain
or nervous tissue. On the
basis of composition
Sphingolipids are two types:
a) Sphingomyelin:
 It is the simplest and most
abundant lipid which
contains phosphocholine or
phosphoethanolamine as the
polar head region. It is
present in the animal cell as
myelin sheath which
surrounds the nerve cell.

17. b) Ceramides: It is
composed of
sphingosine molecule
and fatty acids:

18. 2) Glycolipid:
 It is the combination of lipid and carbohydrates which lack
the phosphate group. It contains C 24 fatty acid molecule
such as cerebric acid, lignoceric acid. It is mainly of two
types:
a) Cerebrosides
b) Gangliosides
 Sulfatides are also the class of glycolipids which are similar
to cerebrosides except the 6th carbon of glucose and
galactose is bonded with sulphuric acid. They are present
in the myelin sheath.
a) Cerebrosides: It is the simplest form of glycolipids.
Glucose and galactose are present as carbohydrate residue.
Generally, carbohydrate chain of 2-20 units is present.
b)Gangliosides: It is a derivative of cerebroside and contains
one or more molecule of N- acetyl neuraminic (NANA) . It is
predominantly present on grey matter of the brain and
neutralized tetanus toxins.

19. Function of glycolipids:
 glycolipids are essential components of all
membranes in the body.
 They are located primarily in the outer layer of
the plasma membrane where they interact with
the extracellular environment.
 They play a role in the regulation of cellular
interaction, growth, and development.
 They are antigenic and determine blood group of
an individual.
 They also serve as cell surface receptors for
cholera and diphtheria as well as for certain
viruses.
 It forms the structural component of nervous
tissues.

20. C) Derived Lipids:
 These are the lipids containing
cyclopentane rings and are
complex fat soluble molecule with
four fused rings.
 Steroids are compounds containing
a cyclic steroid nucleus namely
Cyclopentanoperhydrophenanthren
e (CPPP). It consists of a
phenanthrene nucleus to which a
cyclopentane ring is attached .
There are several steroids in the
biological system including
cholesterol, bile acids, vitamin
D,sex hormones etc. If the steroids
contain one or more hydroxyl
group it is commonly known as the
sterol (means alcohol).
 The most common sterol found in
animal tissue is cholesterol which
consists of
Cyclopentanoperhydrophenanthren
e ring with OH group at carbon
number three and the double bond
between carbon number 5 and 6.

21.  It is solid at room temperature, insoluble in water and
occurs rarely in higher plants. The cell membrane of
eukaryotes consists of cholesterol.
 It is the precursor of a large number of important steroids
including bile acids, sex hormones, vitamin D etc.
Cholesterol is synthesized by the liver and secreted in the
blood. It is equally distributed in serum and plasma.
 The normal blood cholesterol level is 130-250mg/dl. But
cholesterol level is determined by metabolic functions
which are influenced by heredity, nutrition,endocrine
functions and integrity of vital organs like liver,kidney etc.
If the cholesterol level falls below normal value the
condition is called hypocholesterolemia. This condition is
seen in hyperthyroidism acute
infection,anemia,malnutrition etc. If the cholesterol level
exceeds normal value the condition is called
hypercholesterolemia.
 This condition is seen in hypothyroidism infection, poorly
controlled diabetes mellitus,chronic hepatitis,nephrotic
syndrome, obstructive Jaundice. Thus the determination of
blood cholesterol level is the important diagnostic
parameter from the clinical point of view.

22. Function of steroids/ cholesterols:
 It serves as a structural component of the cell
membrane which determines the shape of a cell
membrane .
 cholesterol functions as an insulating cover for the
transmission of electrical impulses in the nervous
tissue.
 It is the precursor of a large number of equally
important steriods which include the bile acids, sex
hormones and vitamin D.
 The low concentration of cholesterol in female may
lead to sterility ,so cholesterol play important role in
fertility .
 The excess cholesterol in the body leads to
cardiovascular diseases.
 Steroids are the precursors of Vitamin D which
maintains the serum calcium level.