PHYSICAL STATE OF INGREDIENTS IN FOOD SYSTEMS Food Dispersions 1. True solution 2. Colloidal dispersion 3. Emulsion 4. Foam 5. Gel   Dispersions 1. Continuous phase 2. Dispersed phase May be solid, liquid, or gas.

Colloidal Dispersion (SOL) True Solution The 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.

Emulsions Liquid/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). Oil Oil Oil H O H O 2 Oil 2 Oil Oil Oil H O H O 2 Oil 2 Oil Oil Water Oil Oil/Water Water/Oil

DESTABILIZATION OF THE DISPERSION Oil Oil Oil Oil Oil Oil Oil Oil Oil Oil Oil Oil Oil Oil Oil Water Oil Oil Oil Oil Oil Oil Oil Oil Oil Oil Oil Aggregation Water Oil Oil separation from water Water

EMULSIFIER Mayonnaise Emulsifier Margarine Water Oil Hydrophilic group Hydrophobic group Oil Water

CHEMICAL STRUCTURE OF EMULSIFIERS Phospholipids (Lecithin) O CH 2 O C (CH 2 ) 16 CH 3 O CH O CH O C (CH 3 2 ) 14 CH 3 CH + 3 N CH 2 CH 2 O P O CH 2 Hydrophobic CH O 3 - ( fat-soluble) Hydrophilic (water-soluble) Mono- Glycerides (mono- stearate) O CH 2 O C (CH 2 ) 16 CH 3 HO CH Hydrophobic HO CH 2 Hydrophilic Di-glycerides ( di-stearate) O CH 2 O C (CH 2 ) 16 CH 3 O CH O C (CH 2 ) 16 CH 3 HO CH 2 Hydrophobic Hydrophilic

Span 60 (sorbitan mono-stearate) C CH CH 2 O C (CH ) 16 CH 3 C CH C H OH HO O CH Hydrophobic Hydrophilic Tween 60 (polyoxyalkylene sorbitan mono-stearate) Hydrophobic Hydrophilic

SOME DESIRABLE CHARACTERISTICS OF FOOD EMULSIFIERS Ability to reduce interfacial tension below 10 dynes/cm Ability to be rapidly absorbed at the interface Ability to function effectively at low concentrations Resistance to chemical change Lack of odor, color, and toxicity Economical

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

The important foam stability factors are:   1. Surface tension 2. Concentration of separate phase 3. Presence of foaming agent to lower surface tension 4. 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 Dispersed Continuous Name of Examples Phase Phase Dispersion Solid (S) Liquid (L) Solution, Colloidal dispersion Milk Liquid (L) Liquid (L) Emulsion French dressing Gas (G) Liquid (L) Foam Whipped topping Gas (G) Solid (S) Solid Foam Foam candy Solid (S) Gas (G) Solid Aerosol Smoke for flavoring food

STABILITY OF A FOOD DISPERSION 1. Dispersed particle size 2. Viscosity of continuous phase 3. Dispersed phase concentration 4. Density difference between 2 phases