PHYSICAL STATE OF INGREDIENTS IN FOOD SYSTEMS Food Dispersions1.True solution2.Colloidal dispersion3.Emulsion4.Foam5.GelDispersions1.Continuous phase2.Dispersed phase May be solid, liquid, or gas.

True SolutionThe dispersion of particle < 1 nm in liquid.Examples: sugar, lactose, minerals, and vitamins.Colloidal Dispersion (SOL)Dispersion of particle sizes between 10-100 nm in liquid. Common colloids: dispersion of proteins, large molecular salts.Example: milk.

EmulsionsLiquid/liquid systems of 2 immiscible substances are called emulsion. Substances or particle size = 10-100 microns. Examples: butter (w/o), margarine (w/o), mayonnaise (o/w), salad dressing (o/w), milk (o/w), cream (o/w), and chip-dip (o/w). WaterOilOilOilOilOilH OH OH OH OOil/WaterWater/Oil2222OilOilOilOilOilOil

DESTABILIZATION OF THE DISPERSION OilOilOilOilOilOilOilOilOilOilOilOilOilOilOilOilOilOilOilOilOilWaterWaterOilOilOilOilOilWaterOilAggregationOil separation from water

EMULSIFIER OilWaterMayonnaiseWaterOilMargarineEmulsifierHydrophobic groupHydrophilic group

CHEMICAL STRUCTURE OF EMULSIFIERSCH3CH3CH3CH2 O C (CH2)16 CH3OON CH2 CH2 O P O CH2CH O C (CH2)14 CH3OOCH2 O C (CH2)16 CH3HO CHHO CH2OCH2 O C (CH2)16 CH3CH O C (CH2)16 CH3HO CH2OOPhospholipids (Lecithin)Hydrophobic(fat-soluble)Hydrophilic (water-soluble)Mono-Glycerides (mono-stearate)HydrophobicHydrophilicDi-glycerides (di-stearate)HydrophobicHydrophilic-+

Span 60 (sorbitan mono-stearate)HydrophobicHydrophilicTween 60 (polyoxyalkylene sorbitan mono-stearate)HydrophobicHydrophilic

SOME DESIRABLE CHARACTERISTICS OF FOOD EMULSIFIERS Ability to reduce interfacial tension below 10 dynes/cmAbility to be rapidly absorbed at the interfaceAbility to function effectively at low concentrationsResistance to chemical changeLack of odor, color, and toxicityEconomical

FOAM Gas is dispersed in liquid or semi-liquid.Dispersed-phase:gasContinuous-phase:liquidIt requires a 3rd component possessing protective or stabilizing properties to maintain the dispersion.Example:whipped topping

The important foam stability factors are:1.Surface tension2.Concentration of separate phase3.Presence of foaming agent to lower surface tension4.Viscosity of liquid - the higher the viscosity, the more stable the foam.5.Presence and thickness of adsorption layer (a 3rd stabilizing material).

GEL semi-solid state with 2 continuous phases.Continuous phase of interconnected particles and/or macro-molecules intermingled with a continuous phase of liquid phase such as water.Examples: jello, jam

FOOD DISPERSIONS DispersedContinuous Name of ExamplesPhasePhase Dispersion

Solid (S)Liquid (L) Solution, Colloidal dispersionMilkLiquid (L)Liquid (L) EmulsionFrench dressingGas (G)Liquid (L) FoamWhipped toppingGas (G)Solid (S) Solid FoamFoam candySolid (S)Gas (G) Solid AerosolSmoke for flavoring food

STABILITY OF A FOOD DISPERSION 1.Dispersed particle size2.Viscosity of continuous phase3.Dispersed phase concentration4.Density difference between 2 phases