General OutlineWe will be looking at:Food ChemicalsDetergents
Flavorings and Sweeteners
Flour Improvers and Bleaches
Preservatives and nutritional supplements
Natural SweetenerAdds to calories
Natural vs. ArtificialDisadvantages of natural sweeteners:Adds to calories (hence unsuitable for people on a diet)Increases blood sugar levels (hence unsuitable for diabetics)
Natural vs. ArtificialAdvantages of Artificial Sugars:Does not add to caloriesNot metabolized in the bodyInert, harmless
Also known as ortho-sulphobenzimideExcreted in urineInert in body
Methyl ester of aspartic acid-phenylalanine dipeptide
As it is unstable at high temperatures, it is unsuitable for cooking. Hence it is used in cold drinks and foods.
More stable than aspartameAs it is 2000 times sweeter than sucrose control of sweetness difficult
Tri-chloro derivative of sucroseSame taste and appearance as sucroseStable at cooking temperatureDoes not add to calories
Table salt (NaCl)
Preservatives include:Sodium Benzoate
Salts of sorbic acid and propanoic acid
Metabolized in the bodyUsed in limited quantities
Types of detergentsSoapsSynthetic detergents
The general equation for saponification is as follows:Fat + Alkali Soap + Glycerol
SaponificationFatty acids used are:Stearic acidOleic acidPalmitic acid
The soap is precipitated with NaCl (Why?)
Varieties of soapBath Soap
Better quality fat usedExcess alkali removedPerfumes and colors added
Varieties of soapFloating soap
Air bubbles beaten in before hardening
Varieties of soapTransparent soap
Soap dissolved in ethanolExcess solvent evaporated off
Varieties of soapMedicated Soaps:
Medicinal substances added
Varieties of soapShaving soap:
Glycerol added to prevent dryingRosin added which forms sodium rosinate which lathers well
Varieties of soapLaundry soap:
Fillers like sodium rosinate, sodium silicate and sodium carbonate added
Varieties of soapSoap chips:
Melted sheet of soap run into a cool chamber and soap scraped off in small broken pieces
Varieties of soapSoap or scouring powder:It consists of soap, abrasives like powdered pumice or finely divided sand and builders like sodium carbonate and tri-sodium phosphate.
Disadvantages of SoapSoaps cannot work in hard water. This is because hard water contains calcium and magnesium ions. These react with soaps to form insoluble Ca and Mg soaps when soaps are dissolved in hard water.The reaction is as follows:2C17H35COONa + CaCl2 2NaCl + (C17H35COO)2MM = Ca or Mg
Disadvantages of SoapThese separate out as scum and are useless for washing. These make washing harder as they form a gummy mass which adheres to cloth, preventing cleaning action of soap
Other Disadvantages of Hard Water
Hair washed in hard water looks dullDye does not absorb evenly on cloth washed with hard water
Advantages of Synthetic Detergents over soaps
Have all the properties of soapsCan be used in both hard and soft water to give foamGives foam even in ice-cold water
Types of Synthetic DetergentsAnionic DetergentsCationic DetergentsNon-ionic Detergents
Anionic DetergentsSodium salts of sulphonated long chain alcohols or hydrocarbons. Alkyl hydrogensulphates made by treating long chain alcohols with conc. H2SO4 and then neutralized with NaOH
CH3(CH2)10CH2OH H2SO4 CH3(CH2)10CH2OSO3H(Lauryl hydrogensulphate) NaOH (aq) CH3(CH2)10CH2OSO3-Na+(Sodium lauryl sulphate)
Anionic Detergents are mainly used in household cleaning agents
Cationic DetergentsThese are quaternary ammonium salts of amines with acetates, chlorides or bromides as anions.It is called cationic as the cationic part posses long hydrocarbon chains and positive charge on nitrogen atom.
E.g..: Cetyl tri-methyl ammonium bromide
Cationic detergents have germicidal properties and are expensive. These are usually used in hair conditioners.
These detergents do not contain any ion in their constitution.
CH3(CH2)16COOH + HO(CH2CH2O)nCH2CH2OH -H2O CH3(CH2)16COO(CH2CH2O)nCH2CH2OH
These detergents use the same cleaning mechanism as soaps.
Disadvantage of Synthetic Detergents
If the detergent molecule is highly branched, it is difficult to degrade by bacteria, leading to accumulation in the environment, i.e. they are non-biodegradable.