Chemical preservatives, preservation by ionizing radiations

1. OBT554
Unit 5
Dr K.Geetha
Associate Professor, Dept of
Biotechnology, Kamaraj College of Engg
& Tech, Madurai

2.  To increase shelf life and to make food
attractive various chemicals are added to
food.
 Main categories of food additives are food
colours, flavours and sweeteners,
antioxidants, fat emulsifiers, stabilizing
agents, flavour improvers, food
preservatives, nutritional supplements like
minerals, vitamins, amino acids.
 Except for nutritional supplement, no other
additive has any nutritional value.

3.  Food preservatives are the substances when
added to food is capable of inhibiting, retarding
or arresting the process of fermentation,
acidification or other decomposition of food by
the growth of microbes.
 Examples: Sodium benzoate, salt of the ascorbic
acid and propionic acid etc.
 Food preservatives are classified into two groups
– Class I and Class II.

4.  It should not be harmful to human being.
 It should inhibit the growth of microorganism
even if it is used in traces.

5.  Chemical preservatives are food additives,
which are specifically added to prevent the
deterioration or decomposition of a food.
 Chemicals are used to inhibit the factors
causing spoilage.
 These are also used to complement other
food preservation techniques.

6.  In food preservation, the added chemical preservatives may be grouped
into two classes.
 Class I preservatives:
Includes the use of sugar, salt, spices, acetic acid (vinegar) and
alcohol, and is considered to be relatively safe to humans.
 Class II preservatives:
Includes the use of benzoic acid, sulfur dioxide, nitrates and nitrites
and a variety of neutralizers, firming agents and bleaching agents and
is considered to be relatively safe to humans, but within the permissible
doses prescribed by the food regulatory bodies of the country because
higher concentrations can be a health hazard.

7.  have to be used only at a dosage level which is
needed for a normal preservation and not more
 a new addition of preservative in order to stop a
microbiological deterioration already occurred is not
recommended
 The use of chemical preservatives MUST be strictly
limited to those substances which are recognised as
being without harmful effects on human beings'
health and are accepted by national and international
standards and legislation.

8.  Factors related to the chemical preservatives:
 chemical composition
 concentration
 Factors related to micro-organisms:
 micro-organism species
 initial number of micro-organisms in the treated
product
 Specific factors related to the product to be
preserved
 product chemical composition;
 influence of the pH value of the product
 physical presentation and size of product

10.  Citric acid: fruit juices; jams; other sugar preserves;
 Acetic acid: vegetable pickles; other vegetable products;
 Sodium benzoate: vegetable pickles; preserves; jams;
jellies; semi-processed products;
 Sodium propionate: fruits; vegetables;
 Potassium sorbate: fruits; vegetables; pickled products;
jams, jellies;
 Methyl paraben: fruit products; pickles; preserves;
 Sulphur dioxide: fruit juices; dried / dehydrated fruits
and vegetables; semi-processed products.

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