This document discusses food preservatives, including natural preservatives like salt and sugar and chemical preservatives. It provides examples of common chemical preservatives like sodium benzoate and potassium metabisulfite. The document also outlines criteria that effective preservatives should meet and lists advantages and disadvantages of various preservatives. Qualitative and quantitative methods for analyzing preservatives in food are described, including titration. Common antioxidants used to prevent food from oxidizing are also identified.

1. BY AJAY KUMAR
1ST SEM
DEPARTMENT OF ANALYSIS

3. Theycontain acertain chemical composition which
controls microorganismsgrowth
They are mainly of 2types
Natural Preservatives
Examples :- Salt , Sugar , lemon juice ,spice
Chemical Preservatives
Examples :- Organic and Inorganic foods like Sodium Benzoate,
Potassium Meta bisulphate , CitricAcid

4. Natural Preservatives
Salt
It returns water through osmosis process in food product thus it
changes composition of food
Asa result, no freewater is left for microorganisms to grow
Sugar
It absorbs freewater from food product thus restricts growthof
microorganisms
Oil and Spices
They form a layer over the food product hence it forms a layer
between air and microorganisms , thus restricting them

6. Preservatives should meet the following criteria:
 (i) can inhibit the growth of a wide range of micro-organisms
 (ii) should be non-toxic to humans
 (iii) should not be expensive
 (iv) should not affect the flavour, taste or aroma of the food
product
 (v) should not promote the development of resistant micro-
organisms
 (vi) should kill rather than inhibit the micro-organisms

8. s. no
PRESERVATIVES METHOD
ADVANTAGES
DISADVANTAGES
1
Benzoic Acid and
Sorbic Acid
Overlapped HPLC -
PDA
Preservatives Can
Causes Disinfectant
Preservatives Can
Causes Anti Microbial
Action
Preservatives Can
Prolong Shelf Life
It Increases The Bulk
of The Compound
It Acts Bacterostatic
And Bacterositic
It Prevent Oxidation
Of Product
It Prevent
Degradation Of
Product
Preservatives Can
Causes Cancer
Preservatives Can Have
Allegric Reaction
Preservatives Can Have
Hyper Senstive
Reaction
Preservatives Causes
Cardiovascular Disease.
Benzoic Acid Causes
Skin And Eye Irritation
Preservative cause
Diarrhea And Nausea
It Causes Skin Allergy
2
Sodium Benzoate
and Potassium
Benzoate
HPLC
3 Benzoic Acid UV
Spectrophotometry
4 Sorbic Acid
UV
Spectrophotometry
5
Sodium, Potassium
Salts Of Nitrates
And Nitrites
Colorimetry
6 BHT And BHA HPLC
7
Methylparaben And
Propyl Paraben
HPLC
8 Copper Sulfate GCMS
9
Benzoic Acid and
Sorbic Acid
Capillary
Electrophoresis

9.  Qualitative Methods
 (A) Ferric Chloride Test: Acidify the food product with
HCl (1+3) and extract with diethyl ether.
 Evaporate the solvent on a hot water bath removing last
traces of solvent under a current of air.
 Dissolve the residue in few ml of hot water and add few
drops of 0.5% ferric chloride solution.
 Salmon colour precipitate of ferric benzoate indicates the
presence of benzoic acid.

10. (A) Titrimetric Method:
 Reagents:
 1. Chloroform -distilled
 2. Hydrochloric acid (1+3)
 3. Sodium hydroxide (10%)
 4. Standard sodium hydroxide solution (0.05N)
 5. Saturated sodium chloride solution.
 Preparation of Sample:
 (A) Beverages and liquid products:
 Mix the sample thoroughly transfer 100 gm of the sample into a 250 volumetric flask, using
saturated sodium chloride solution.
 Make alkaline to litmus paper with 10% sodium hydroxide solution and make upto volume
with saturated sodium chloride solution.
 Shake thoroughly and let it stand for 2 hrs.
 Filter the sample and use the filtrate for determination.

11. (B) Sauces and Ketchups:
 Add 15 gm salt to 150 gm of weighed sample and
transfer into volumetric flask.
 Rinse with saturated sodium chloride solution,
 Add 15 gm pulverized sodium chloride and then add
10 ml of 10% sodium hydroxide solution and make up
to 500 ml volume with sodium chloride solution.
 Let it stand for 2 hrs with occasional shaking.
 Filter and use the filtrate for determination.

12. Determination:
 Pipette 100 ml to 200 ml of the filtrate into a 250 ml separatory
funnel.
 Neutralize to litmus paper using hydrochloric acid (1+3) and add 5 ml
excess
 Extract carefully with 40, 30, 30 and 20 ml portions of chloroform.
 Transfer the combined chloroform extract in to a separatory funnel
 wash it free from mineral acid by shaking gently and rinsing with
water.
 Drain off the water phase.
 Dry the chloroform layer over anhydrous sodium sulphate and distil
off the solvent.

13.  Remove the last traces of the solvent under a current of air at room
temperature.
 Dry the residue overnight or until no residue of acetic acid is
detected if the product is a ketchup.
 Dissolve residue in 30-50 ml of alcohol neutralised to
phenolphthalein and titrate with 0.05 N sodium hydroxide.
 Calculate the benzoic acid contents as follows:

14. • Antioxidants are beneficial in preventing rancidity in fats and
foods containing fats.
• Fats exposed to light, moisture, heat or heavy metal ions
become activated and oxidize (reach with available oxygen) to
peroxides.
•The most used antioxidants are
1. Butylated HydroxyAnisole (BHA),
2. Butylated HydroxyToluence (BHT),
3. Propyl Gallate,
4. Natural/Synthetic Tocophelos (Vitamin E)
5. Ascorbic Acid (vitamin C) and
6. Lecithin.