This document describes two experiments on using potassium bisulphite as a food preservative. The first experiment studied the effect of different concentrations of potassium bisulphite on preserving jam over time. It found that higher concentrations preserved the jam longer by delaying microbial growth. The minimum effective concentration was 1%. The second experiment studied the effect of temperature on preservation. It found that microbial growth occurred earliest in jam kept at room temperature, and preservation was best at lower temperatures of 0-5°C.

1. () at different concentrationsana
(ii) for different intervals of time.
EXPERIMENT 1
IM: To study the effect ofpotasium bisulphite as food preservative under various conditioas
(concentration, time and temperature).
EQUIREMENTS
mtical fiasks (100 mL) a mixer, glass rod, knife, apples, sugar and potassium bisulphite

2. emistry-
Comprehensive Practical Chemist
210
1. Take 500 g fresh apples. Wash them thoroughly and peel off the outer layer. en
and crush the apples in a mixer. Add about 100 g of sugar and heat the conte
about 10 minutes to prepare jam. During heating keep on stirring the contents. [lse syfo
performing the following experiments.
PROCEDURE
aver.
Rermove the
seer
Use this jam. or
Study of Effect of cone. of Potassium Bisulphite and the Effect of Time
onica
1. Take four conical flasks and label them as A, B, Cand D. Add 50 g ofjam in eachofthe f.
2. To flaskA add 0.1 g, flask B 0.2 g, fask C 0.5 g and fiask D1.0gof potassium bisulphite)Mix th
contents in each flask and leave them undisturbed at room temperature.
flasks.
vations
3. Forsome days check for anygrowth ofmicro-organisms after each day and record the obserse.
in a table.
OBSERVATIONS
Growth ofmicro-organisms after
Amount of
Amount of
5 days 6 days
potassium
bisulphite
Sample 1 day 2 days3 days 4 days
jam
50 g 0.1g
50 g 0.2 g
B
50 g 0.58
D 50g 1.0g
RESULT
As the concentration ofpotassium bisulphite is increased, the growth of micro-organisms appears after
more days (longer period). The minimum concentration ofpotassium bisulphite required for preserving
jam is approximately 1%.
Once the
micro-organisms appear their growth increases with the passage of time.
Study of Effect of Temperature
.Take three conical flasks and label them as A, Band C. Add 50 gofjam in each of the threeflasko
e
2 Add 0.5
ofpotassium bisulphite to each of the three conical flasks. Stir the contents wiu
help of glass rod to affect thorough mixing
at
Neep task Ain a
refrigerator, flash Bat room temperature and flask C in an oven maintaie
a
temperature of 60°C, leave them undisturbed for few days.
4. Check for any growth of
micro-organisms: after each day and record the observations.

3. investigatonyProjects
OBSERVATIONS
Amount of
jam
Amount of
PotassiumTemperature
bisulbhite
Growth ofmicro-organismsafte
15 days
10days
Sample
5 days
50g 0.5g
0-5°C
A
0.5g
25-30'C
50g
B 60-70'C
50 g 0.5g
C
RESULT
The growth of
micro-organisms
occurs
earliest in the flask kept at room
temperature.
The preservation
ofjam bypotassium
bisulphite
is
maximum at lower temperature
(0-5°C).