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A presentation about foam in aerated food such as ice cream, whipped cream, marshmallow, etc.

A presentation about foam in aerated food such as ice cream, whipped cream, marshmallow, etc.

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    Foam Foam Presentation Transcript

    • 1   FOAMS! Photo  courtesy  of  Dan  Phiffer  on  Flickr   Photo  courtesy  of  Leslie  on  Flickr   Photo  courtesy  of  Alpha  on  Flickr   Prof. Abd Karim Alias Universiti Sains MalaysiaThis  work  is  licensed  under  a  Crea=ve  Commons     A@ribu=on-­‐NonCommercial-­‐ShareAlike  3.0  Unported  License.  
    • 2   }  Foam is a two-phase system in which the gas (air) phase is dispersed in a small amount of liquid (water) continuous phase. }  Foam is desirable in beer; it is also promoted in whipped egg white (e.g., for making cakes, meringue, etc.), ice cream, marshmallow, etc. FOAM: DEFINITION & CHARACTERISTICS Abd Karim Alias, 2013
    • 3   }  A bubbly foam (e.g. in ice cream) is formed when the amount of gas incorporated is low enough for bubbles to retain roughly spherical shape. }  Polyhedral foam (e.g., beer foam) – the gas- to-liquid ratio is so large that bubbles are pressed against one another in a honeycomb- type structure. FOAM STRUCTURE Abd Karim Alias, 2013
    • 4   FOAM STRUCTURE Abd Karim Alias, 2013
    • 5   FOAM STRUCTURE Abd Karim Alias, 2013
    • 6   }  Three process steps for foam formation: §  air has to be injected into the liquid (e.g. using a mixer) §  large air bubbles have to be broken up into smaller bubbles §  the smaller bubbles have to be prevented from fusing during the formation of a foam FOAM FORMATION Abd Karim Alias, 2013
    • 7   }  A surface active foaming agent is essential for the formation of stable foam }  The foaming agent lowers the surface tension of the liquid phase & allows expansion of its surface area. }  The surfactant forms a closely packed film around the dispersed gas bubbles. FOAM FORMATION –The role of surface active agent Abd Karim Alias, 2013
    • 8   Three processes involved in the stabilization of protein foams: }  adsorption of the protein at the gas- liquid interface, }  surface denaturation, }  coagulation of protein. FOAM FORMATION –Proteins as surface active agent Abd Karim Alias, 2013
    • 9   FOAM FORMATION –Proteins as surface active agent Abd Karim Alias, 2013
    • 10   Three factors affecting foam stability: §  drainage: the draining of liquid from foam §  disproportionation: the change in foam bubble size distribution caused by gas diffusion from small to large bubbles §  coalescence: the fusion of foam bubbles FOAM STABILITY Abd Karim Alias, 2013
    • 11   •  Water drains from foam under gravity •  A foam drains along lamellae to the curved junction of thin lamellae (plateau borders), where the pressure is lower. FOAM STABILITY : FOAM DRAINAGE Abd Karim Alias, 2013
    • 12   FOAM STABILITY : FOAM DRAINAGE •  As water leaves, faces of film are brought closer together Click picture to view animation Abd Karim Alias, 2013
    • 13   •  The diffusion of gas from small bubbles into big bubbles is referred to as disproportionation. •  In the absence of a stabilizing film of polymer molecules, disproportionation occurs remarkably quickly. •  Probably the most important type of instability in foams. FOAM STABILITY : Disproportionation Abd Karim Alias, 2013
    • 14   }  Egg foams (egg white) are essential in the preparation of angel cakes, sponge cakes, meringues, souffles, etc. }  The proteins not only lower the surface tension of egg white but some are denatured at the surface. }  The coagulation of proteins at the gas-liquid interface form a network that gives some rigidity & stability to the foam. EGG FOAMS Abd Karim Alias, 2013
    • 15   EGG FOAMS Abd Karim Alias, 2013
    • 16   }  Globulins appeared to be good foamers, producing small gas bubbles & a large volume. }  Ovomucin is not a good foamer by itself but stabilised the foam because it is rapidly insolubilised (denatured) at the bubble surface. }  The presence of fat, even in small amounts, and egg yolk, have a detrimental effect on foam formation. EGG FOAMS Abd Karim Alias, 2013
    • 17   }  The presence of lipids retards foaming because the oil molecules migrate to the air-water interface before the protein molecules, inhibiting the unfolding of the protein & thus the formation of foam. }  The antifoaming behavior of egg yolk is partly due to the presence of lecithin, which is believed to bind to egg white proteins, preventing them from associating at the air-water interface, & competitively displacing them from the interface. EGG FOAMS Abd Karim Alias, 2013
    • 18   }  Increase of [protein] increases both the foamability & foam stability, mainly because of viscosity effect which produces a thicker lamella film. }  Adjusting egg white pH to 6.5 by adding an acid ingredient increases foam stability to heat, because the acid makes foam less prone to over-coagulation. }  Sugars enhance foam stability by increasing the viscosity of lamellar fluid which reduces the drainage rate. EGG FOAMS Abd Karim Alias, 2013
    • 19   }  In fact, foams can cause many problems, including vessels overflowing, processing and packaging interference, damaging materials and housekeeping issues }  Silicon dioxide is the most common chemical used in defoamers and antifoams, as it can destroy and suppress processing foams. FOAMS ARE NOT ALWAYS DESIRABLE! Abd Karim Alias, 2013
    • 20   Knowing when to produce foam and when to get rid of it are one of the many keys to product success! Abd Karim Alias, 2013