Food additives are substances added to improve flavor, texture, color, and preserve food, with a broad definition allowing for any substance that alters food characteristics. Antioxidants, a key category of food additives, prevent oxidative deterioration and extend shelf life by acting against free radicals and reactive oxygen species. These additives can be classified as natural or synthetic, with various mechanisms of action to combat rancidity and preserve nutritional quality.

1. Definition
Classification
Functions
Dr.Shakila

2. Definition
 Food additives are substances which are added
to food to:
 either improve the flavor, texture, colour or chemical
preservatives, taste, appearance or function as
processing aid.
 A broad definition of “food additive” is
 “any substance the intended use of which results,
directly or indirectly, in it’s becoming a component
of or otherwise affecting the characteristic of any
food, and which is safe under the condition of its
use.”

3.  chemical substances added to foods to improve
flavour, texture, colour, appearance and
consistency, or as preservatives during
manufacturing or processing.
 Herbs, spices, hops, salt, yeast, water, air and
protein hydrolysates are excluded from this
definition.

4.  The broadest practical definition of a food
additive is any substance that becomes part of a
food product either directly or indirectly during
some phase of processing, storage or packaging.

6. Need for Food Additives
 Provide protection against food spoilage during
storage transportation, distribution or processing.
 Concept of “convenience” foods.
 To colour foods, add flavor, impart firmness, and
retard or hasten chemical reaction in food.
 To maintain the nutritional quality of food,
 to enhance stability with resulting reduction in
waste,
 to make food more attractive, and
 to provide efficient aids in processing, packaging
and transport

15. Classification
 1. Anti-oxidants
 An anti-oxidant is a substance added to fats and
fat-containing substances
 to retard oxidation, and thereby prolong their
wholesomeness, palatability, and, sometimes,
keeping time.
 Antioxidants as food additives are used to delay the
onset of or slow the pace at which lipid oxidation
reactions in food processing proceed.
 According to Rule 58 of PFA rules (1955), an
antioxidant has been defined as a substance which
when added to food retards or prevents oxidative
deterioration of food

16. Antioxidants
Many nutrients are
antioxidants.
Examples include:
• Vitamin A
• Vitamin C
• Vitamin E
• Anthocyanins
• Beta carotene
• Catechins
• Ellagic acid
• Lutein
• Lycopene
• Resveratrol
• Selenium
 A food
additive, which
prolongs the
shelf-life of
foods by
protecting
against
deterioration
caused by
oxidation.

17.  Antioxidants are used to preserve food for a
longer period of time.
 Antioxidants act as oxygen scavengers.. as the
presence of oxygen in the food helps the
bacteria to grow that ultimately harm the food.
 In the absence of antioxidant food additive,
oxidation of unsaturated fats takes place
rendering to foul smell and discoloration of food.

18.  The classification of antioxidants is based on the
oxidation steps they prevent or interfere with.
 Classifying antioxidants can be done depending
on their function or on their nature.
 Depending on their function, there are:
 Primary antioxidants also known as radical
scavengers, oxygen scavengers, metal chelators,
quenchers of high energy species,
hydroperoxides decomposers, and antioxidant
regenerators.
 ascorbic acid and its derivatives, tocopherols, the
esters of gallic acid, erythorbic acid and its sodium
salt, BHA, BHT and other substances THBP and

19.  Secondary antioxidants (substances with
antioxidant action but that have other functions as
well).
 Sulphur dioxide and sulphites as well as lecithin
are secondary antioxidants.
 Antioxidants can also be grouped into two
classes:
 Natural antioxidants and Synthesis antioxidants
 The natural antioxidants present in foods inhibit
formation of anti carcinogenic Nitrosamines.
 Vitamin c or Ascorbic acid (fruits and
vegetables) Vitamin E or tocopherols (grains,

20.  For e.g., Enzymatic browning in cut fruits and
vegetables is due to enzymatic oxidation of
phenolic substances.
 Antioxidant like Vitamin C can prevent this
browning.
 Citric acid & phosphoric acid increase the
effectiveness of ascorbic acid in this process.
 Tocopherols (TCP) are natural AA, as well as a
series of compounds with different structures that
can be found in plants (flavones).

22.  Synthetic antioxidants :
 These are most effective antioxidants and are
synthetic chemicals, approved by Food and Drug
Administration for addition to foods,
 eg: BHA (Butylated hydroxy anisole),
 BHT (butylated hydroxy toluene),
 TVHQ (tertiary butylated hydroxy quinone) etc .

23.  Besides the above-mentioned compounds,
there are also substances that can strengthen
the action of primary antioxidants.
 Such compounds as lactic acid and lactates,
citric acid and citrates, tartric acid and tartrates,
etc.

24. Mode of action of antioxidants
 In general, the antioxidants act by the
following routes·
 Chain breaking reaction which act in
lipids to trap free radical.
 By reducing concentration of reactive
oxygen species (ROS)
 By scavenging initiating radicals ego
superoxide dismutase which act in the
lipid phase to trap superoxide free
radicals .

25.  Antioxidants in general protect cells in our body
from damage from free radicals.
 Free radicals are unstable molecules that can
damage cells.
 This cell damage may increase risk of cancer,
heart disease, cataracts, diabetes, or infections.
 Free radicals may also affect brain function

26.  Oxygen, which is an indispensable element for
life can, under certain situations, have severe
deleterious effects on the human body.
 Most of the potentially harmful effects of the
oxygen are due to the formation and activity of
number of chemical compounds, known as
reactive oxygen species (ROS).

27. Reactive oxygen species
 Reactive oxygen species
is a collective term that
includes all reactive
forms of oxygen, that
participate in the initiation
and/or propagation of
chain reaction.
 Many such reactive
species are free radicals
and have a surplus of
one or more free floating
electrons rather then
having matched pairs
and are therefore,
These reactive oxygen
species can be combated
with the involvement of
antioxidants of both
exogenous and
endogenous origin.
Antioxidants are a group
of substances which,
when present at low
concentration in relation
to oxidizable substrates,
significantly inhibit or
delay oxidative
processes, while often
being oxidized
themselves

28. Free radicals…
 Free radicals represent a class of highly reactive
intermediate chemical entities whose reactivity is
derived from the presence of unpaired electron in
their structure, which are capable of independent
existence for very brief interval of time.
 Sources of free radicals:
 Internal sources
 External source
 Physiological Factors

29.  Internal sources:
 These can be enzymatic reactions, which serve as
a source of free radicals.
 These include those reactions involved in the
respiratory chain.
 External sources:
 These include non-enzymatic reactions of the
oxygen with organic compounds.
 Physiological Factors
 Mental status like stress, emotion etc. and
disease conditions are also responsible for the
formation of free radicals

30. radicals
 If free radicals are not inactivated, their
chemical reactivity can damage all cellular
macromolecules including proteins,
carbohydrates, lipids and nucleic acids.
 Their destructive effect on protein may play a role
in the causation of diseases, like cataracts.
 Free radical damage to DNA is also implicated in
the causation of cancer and its effect on LDL
cholesterol is very likely responsible for heart
disease.
 Free radicals are also responsible for ageing

31. Mechanism for the formation
of free radicals
 Free radicals can be formed by three ways :
 By homolytic cleavage of covalent bond of normal
molecule, with each fragment retaining one of
paired electrons.
 X : Y X* + Y*
 By the loss of single electron from normal
molecule.
 X : Y X++ Y-
 By addition of single electron to normal molecule.
 X + e- X-

32.  Antioxidant constituents of the plant material act
as radical scavengers, and helps in converting
the radicals to less reactive species.
 A variety of free radical scavenging antioxidants
is found in dietary sources like fruits, vegetables
and tea, etc.
 Antioxidants are of interest to the food industry
because they prevent rancidity in food ;
 Antioxidants are also of interest to biologist and
clinicians because they may help to protect
human body against damage by reactive oxygen
species (ROS).

33.  Oxidation shortens the
shelf life of foods by
affecting taste, odor
and color, and by
changing the texture
and functionality.

34.  Fats tend to spoil due to rancidity.
 Oxidative rancidity is catalyzed by temperature,
very low humidities, UV, presence of trace
minerals (cu, Fe & co) & degree of unsaturation .
 Oxygen susceptibility increases with the way
the unsaturated fatty acids are distributed in the
glycerol moiety.
 Natural oils & fats are less prone to oxidation due
to the presence of antioxidants like tocopherols.
 Refined oils are prone to rancidity

35.  Generally oxidative rancidity occurs in oils having
a high degree of unsaturation
 Oxidation forms:
 Peroxides and hydroperoxides followed by
aldehydes, ketones & acids which are responsible
for off odours and off flavours associated with the
rancid fats.

36. H H H H H H
 H-C-C = C-C-H + a quantum of energy H-C-C =C-
C- H +H *
H labile Unsaturated fatty
acids free radical
H H H H H H H H
 ii) C-C = C-C-H +O2 -C-C = C-C-H
* H o-o*
Free radical Activated peroxide

37.  A free radical formed marks the beginning of a
self perpetuating chain reaction leading to the
formation of hydroperoxides.
 Hydro peroxide is very unstable decomposing
into compounds of shorter carbon chains.
 They include fatty acids, aldehydes & ketones
which are volatile and which contribute to the
unpleasant odour to rancid fats.
 Oxidation may be catalysed by the enzyme
lipoxygenase as well as heat, light & certain
metals like cu, Fe.
 These are called prooxidants, as they promote

38.  Common example:Fe from Hb catalyses rancidity
in cooked meats.
 Oxidation of linoleic acid forms an aldehyde
called 6-Nonenal which is responsible for the off
odour during the process of flavor reversion.
 Autocatalytic oxidative rancidity occurs in fats due
to enzyme lipoxygenase

39.  Antioxidant molecules generally replace UFA as a
source of labile hydrogen to unite with a free
radical to form an activated peroxide.
 In this process the molecule of antioxidants is
oxidized instead of another fatty acid.
 Thus antioxidants prevent oxidative chain
reaction.

40.  AH + ROO” ROOH + A”
 RH + A” AH + R”
Incapable of initiating the chain
complex
 AH + ROO” (ROO”AH) Non-radical
product
 A” + R”/ROO” RA + ROOA
 R” – free radical (any species capable of
independent existence that contains one or more
unpaired e)
 AH – antioxidant

41. Synthetic antioxidants
 The most common synthetic antioxidants are:
 BHA – Butylated Hydroxy Anisole BHT –
Butylated Hydroxy toulene Propyl gallate (PG)
 Tetiary butyl hydroquinone (TBHQ)
Thiodipropionic acid
 Dilauryl thio dipropionate