Food dispersions

• intact edible tissues: natural biological systems like plant and animal tissues (ie. fruit, veggie, meat) • food dispersions: complex systems that are usually man-made

system consisting of one or more discontinous phases (dispersed) in a continuous phase

• true solutions/molecular dispersions • colloidal dispersions • suspensions

• molecules and ions are present in their lowest subdivision (ie simple salt or sugar) • particles are < 0.1 um in diameter • transparent (no light scattering) • high osmotic pressure • passes through parchment membrane

• do NOT pass through parchment membranes • does NOT settle under force of gravity (stays in solution) - a macromolecule or an aggregate of a smaller molecule –> may aggregate to form gels - 0.1-1 um - significantly reduced osmotic pressure - may be transparent but is often translucent –> scatters light

• > 1um • generally opaque • suspended material can be filtered out –> settle out of solution by gravity, given enough time • no measurable osmotic pressure

• ungelatinized starch granules will form a suspension when stirred but soon settle out • gelatinized starch forms a colloidal solution or gel depending on concentration

• true solution: uniphasic (you don’t see 2 phases) • colloidal: biphasic

macromolecules

• low charge –> aggregate –> electrostatic interactions, hydrophobic interactions, hydrogen bonding • large charge –> repulse each other (think about caseins)

• colloidal material • colloidal solutions into suspensions • by adding salts to neutralize the charge of the colloids

• electrostatic interactions • hydrogen bonding • hydrophobic interactions • hydrophobic/hydrophilic associations

• liquid in liquid = emulsion • gas in liquid = foam • liquid in solid = solid emulsion (butter) • gas in solid = solid foam (whipping cream)

• unfavorable • high interfacial tension/surface tension can be reduced by emulsifiers or surfactants via hydrophobic/hydrophilic associations

• any compound that has both hydrophilic and hydrophobic groups in its molecular structure • reducing surface tension of water significantly, causing foaming, and can form emulsions

both are the same thing! - but emulsifier = food products - surfactants = non-food applications (like soap)

• surfactants are found near solution surface –> air-water interface = location of lowest free energy state for emulsifiers and surface-active compounds –> hydrophobic ends orient toward hydrophobic air + hydrophilic ends orient themselves into water - this orientation forms transitional region which reduces free energy differential btw hydrophilic water and hydrophobic air - reduces surface tension of water! • if concentration of emulsifier/surfactant is increased beyond surface-covering capacity, then micelles are formed in solution –> formed to reduce the free energy of the solution after the air/water interface is saturated - micelles serve as reservoir of surfactant molecules capable of migrating to new surfaces that are created by mixing

• decrease! • too much –> surface tension doesn’t change substantially bc micelles are formed

• hydrophobic and hydrophilic • amphipathic ex.: phospholipids and monoglycerides

• to incorporate oil into a food system without imparting an oily sensation • to develop a unique texture, enhance viscosity of system or obtain plastic properties • to change optical characteristics of a product (ie white mayo)

• droplet size of the dispersed phase • function of energy put into system

• non-ionic –> most important and widely used group bc they are insensitive to pH • ionic

• glycerol esters (mono and diglycerides) and their non-charged derivatives • use began when glycerol was added to fats with small amount of base to interesterify the fat to produce some monoglycerides –> product was termed superglycerinated shortening containing 3% monoglyceride –> greatly enhances cake volume, especially at high sugar levels

• through interesterification followed by tractional distillation to obtain relatively pure fractions