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Chemistry Project

The document discusses chemical preservatives that can be added to foods to prevent spoilage by microorganisms. It focuses on two commonly used preservatives in India - benzoic acid (or sodium benzoate) and sulfur dioxide (or potassium bisulfite). Potassium bisulfite reacts with acids in foods to release sulfur dioxide gas, which kills harmful microbes and prevents spoilage without leaving behind harmful chemicals. The aim of the experiment described is to study the effect of potassium bisulfite as a food preservative under different conditions of temperature, sugar concentration, and potassium bisulfite concentration.

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29 views17 pages

Chemistry Project

The document discusses chemical preservatives that can be added to foods to prevent spoilage by microorganisms. It focuses on two commonly used preservatives in India - benzoic acid (or sodium benzoate) and sulfur dioxide (or potassium bisulfite). Potassium bisulfite reacts with acids in foods to release sulfur dioxide gas, which kills harmful microbes and prevents spoilage without leaving behind harmful chemicals. The aim of the experiment described is to study the effect of potassium bisulfite as a food preservative under different conditions of temperature, sugar concentration, and potassium bisulfite concentration.

Uploaded by

aditisingh71810
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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INTRODUCTION

Growth of microorganisms in a food material can be inhibited by adding


certain chemical substances. However the chemical substances should
not be harmful to the human beings.
Such chemical substances which are added to food materials to
prevent their spoilage are known as chemical preservatives.
In our country, two chemical preservatives which are permitted for
use are:
1.Benzoic acid(or sodium benzoate)
2.Sulphur dioxide(or potassium bisulphite) Benzoic acid or its sodium salt, sodium
benzoate is commonly used for the preservation of food materials. For the preservation of
fruits, fruit juices, squashes and jams sodium benzoate is used as
preservative because it is soluble in water and hence easily mixes with the food product.
Potassium hydrogen sulphite or potassium bisulphite is a chemical
compound with the chemical formula KHSO3. It is used during the production of
alcoholic beverages as a sterilising agent. It is made by the reaction of sulphur dioxide
and potassium carbonate. The sulphur dioxide is passed through a solution of the
potassium carbonate until no more carbon dioxide is given off.
concentrated and then allowed to crystallize.
Potassium bisulphite is used for the preservation of colourless food
materials such as fruit juices, squashes, apples and raw mango
chutney. This is not used for preserving coloured food materials
because Sulphur dioxide produced from this chemical is a bleaching
powder.
Potassium bisulphite on reaction with acid of the juice liberates
Sulphur dioxide which is very effective in killing the harmful microorganisms present
in food and thus prevents it from getting spoiled.
The advantage of this method is that no harmful chemical is left in
the food .The aim of this project is to study the effect of potassium
bisulphite as food preservative.
I. At different temperatures.
ii. At different concentrations of sugar.
iii. For different concentration of KHSO3.
EXPERIMENT
AIM: To study the effect of potassium bisulphite as a food
preservative under various conditions (temperature,
concentration and time).
APPARATUS: Beaker, pestle and mortar, glass bottles,
balance and peeler.

CHEMICAL: Fresh fruits, potassium bisulphite and


sugar.

THEORY: Food materials undergo changes due to time,


temperature and enzymatic action. So these become unfit for
use. These changes can be checked by adding small amounts
of potassium bisulphite. The effectiveness of potassium
bisulphite as preservative depends upon its concentration
under different conditions
PROCEDURE ::

Wash the fresh fruit and peel off their


outer skin. Grind it in a pestle and mortar to a paste. Mix with
sugar and colouring materials. The material so formed is
called fruit jam. This can be used to study the effect of
concentration, temperature and time.
Effect of concentration of sugar: Take three bottles labelled
as A, B and C. Put 100g of fruit jam in each bottle. Now, add
5g, 10g and 15g of sugar to bottle A, B and C. Mix the
contents thoroughly and close the bottle. Keep these bottles
to stand for a week. Note the changes taking place in jam
daily.

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