INVESTIGATORY PROJECT CLASS 12 CHEMISTRY

1. INTRODUCTION
PreservationofFood istheprocess of treatingand handlingfoodto
stopor greatlyslow down spoilage (loss of quality, edibility or
nutritivevalue)caused or acceleratedby micro-organisms.
Maintainingorcreatingnutritionalvalue,textureand flavouris
important in preserving itsvalueasfood. Preservationusually
involvespreventingthegrowth of bacteria, fungi,and other
microorganisms, aswellasretarding theoxidation of fats
whichcause rancidity. It alsoincludes processes used toinhibit
naturalageinganddiscolouration thatcan occur during food
preparation such astheenzymatic browning reactionin apples after
theyare cut.Such chemical substances which are added to food
materialsto prevent theirspoilage are known aschemical
preservatives.Inourcountry, twochemical preservativeswhich are
permitted foruseare: 1.Benzoicacid(or sodium benzoate) 2.Sulphur
dioxide(or potassiumbisulphite) Benzoicacidoritssodiumsalt,
sodiumbenzoate iscommonly used,for the preservationof food
materials.Forthe preservationof fruits,fruit juices, squashesand
jamssodium benzoate isusedas preservativebecause it issolublein
waterand hence easilymixes withthefood product. Potassium

2. hydrogen sulfiteorpotassium bisulfiteisa chemical compound with
thechemical formula KHSO3. It isusedduring the production of
alcoholicbeveragesasa sterilisingagent.It ismade by thereaction of
sulfurdioxide andpotassium carbonate. The sulfurdioxide ispassed
through a solutionofthe potassiumcarbonate until no more carbon
dioxide isgiven off.The solutionis concentratedandthenallowed
to crystallize.Potassiumhydrogen sulfiteorpotassiumbisulfite isa
chemical compound withthechemical formula KHSO3. It isused
during theproduction of alcoholic beveragesasa sterilizing agent.
It ismade by thereaction ofsulfurdioxide and potassiumcarbonate.
The sulfurdioxide ispassed through a solutionof thepotassium
carbonate untilno more carbon dioxide isgiven off.The solutionis
concentratedand thenallowed to crystallize. Potassium bisulphite
is used for the preservation ofcolourless food materials, suchasfruit
juices, squashes,apples andraw mangochutney. Thisisnot usedfor
preserving coloured food materials because Sulphur dioxide
produced from this chemical isa bleachingpowder.Potassium
bisulphite on reaction withacid of thejuice liberates Sulphur
dioxide which isvery effectivein killing the harmful
microorganisms present in food and thus preventsit from getting
spoiled.

3. The advantage ofthis method is that no harmful chemical is left in
the food .The aimof this project istostudy the effect of potassium
bisulphate asfoodpreservative.
i . At different temperatures
ii. At differentconcentrationsof sugar.
iii. Fordifferentconcentrationof KHSO3.
iv. At differentTime.