Elizabeth-Foam

= **__FOAMS__** =


 * Foams if formed from the dispersion of air ( dispersed) in liquid ( continuous)
 * Mostly foam can be found in whipped cream in making of ice cream, marshmallow, meringue, or cakes and also in beer drinks





__ **Structure of foam** __
 * Bubbly foam---> formed when the amount of gas is low for bubbles retain its spherical shape, for example in ice-cream




 * Polyhedral foam---> formed when the amount of gas-to-liquid ratio is large, the bubbles are pressed to each other and will form a honeycomb type structure. Example in beer foam



__Formation of foam__
3 Steps: a.) air must be inserted into liquid by using any mechanical means for example using a mixer b.) large air bubbles must be broken down into smaller ones c.) Small bubbles must be prevented from combine or fusing to each other

__Surface active agent and its role__

 * Essential for formation of stable foam
 * It can lower the surface tension of liquid phase and allow expansion of the surface area
 * Surfactant can form closely packed film around the gas bubbles

__Surface active agent ( protein)__
3 processes involved for stabilization
 * Adsorption of protein foam at gas-liquid interface
 * Surface denaturation
 * Coagulation of protein

__Stability of foam__
factors affecting stability:
 * Drainage -->liquid draining from foam
 * Disproportionation --->Bubble size distribution changes because of gas diffusion( small to large bubbles)
 * Coalescence ---> Fusion of bubbles

__ Egg foam __
Also known as egg white, __Factors prevent foam formation__ __Factors making foam more stable__
 * Protein will lower the surface tension, and denature at the surface
 * Rigidity and stability of the foam can be achieve when the coagulation of protein at gas-liquid interface form a network
 * Globulins is a good foamers by producing small gas bubbles and large volume
 * Ovomucin can stabilize the foam because it denatured on the bubble surface
 * Presence of fat, and egg yolk can give detrimental effect to foam formation
 * Lipids can retard foaming
 * Lecithin in egg yolk can cause the antifoaming behaviour
 * Increase in protein will increase the foamability and foam stability( viscosity effect produce thicker lamella)
 * Egg white pH (6.5) after adding acid ingredients will increase foam stability to heat
 * Sugars enhance foam stability by increase viscosity of lamellar fluid and reduce drainage

__ Problems in foam __

 * Vessel overflowing
 * processing and packaging interference
 * damaging materials and housekeeping issues
 * Silicon dioxide--> used i defoamers ans antifoams--> destroy and suppress processing foams