--Cooking foam -- Food Foam
A foam is
a substance that is formed by trapping many gas bubbles in a liquid
or solid. It can be considered a type of colloid.
Culinary foams are best associated with the Chef Ferran Adria
from El Bulli Restaurant in Spain who began experimenting with
foams consisting of natural flavors mixed with a gelling agent
such as agar (see below). The ingredients are then placed in an
espuma or thermo whip where the foam is forced out with nitrous
oxide. Food foams however are not new with soufflés first
being seen at restaurants in France around the late 1700's.
a foam involves the generation of a protein film surrounding a
gas bubble and the packing of gas bubbles into an overall structure.
Destabilization of protein foams occurs due to creaming, drainage
(from lamellae and plateau boarders), bubble coalescence and disproportionation
of the Basic Food Foams
of Liquid and Solid Foams: Beaten Egg Whites, Milk Foams and Whipped
Cream --gas in liquid; and, Marshmallows -- gas in solid)
of a colloid foam (gas in liquid) used in cooking is egg white
which is a gas dispersed or spread throughout a liquid.
whites are made up of water, protein, and small amounts
of minerals and sugars (see egg
protein composition).. When eggs are beaten, air
is added and the proteins are denatured exposing their
hydrophobic (water hating) and hydrophilic (water
loving) ends of the protein. The proteins align themselves
between air and water forming bubbles with their hydrophilic
chains pointing into the water and dangling their
hydrophobic chains in the air. In addition the proteins
can bond to one another side-to-side as crosslinks
which add to the stability of a foam.
can you stabilize egg white foams?
bowl The copper in a copper bowl assists in creating a tight
bond in reactive sulfur in egg white preventing the sulfurs from
binding other materials. This makes it take longer to form the
foam, but leads to a much more stable foam.
If the foam
is overbeaten in a non-copper bowl, eventually the proteins become
completely denatured and coagulate into clumps. These clumps cannot
be turned back to smooth peaks. If a copper bowl is used, fewer
protein molecules are free to denature and coagulate, because
of the conalbumin-copper complexes. In addition to forming complexes
with conalbumin, the copper may also react with sulfur-containing
groups on other proteins, further stabilizing the egg white foam.
of Tartar - (potassium bitartrate) is an acidic salt that
can be used to change the pH of the egg white to an acidic range
by boosting the number of free-floating hydrogen ions in the egg
white. This has the effect of stabilizing the foam, and is therefore
an alternative to using a copper bowl. 1/8 teaspoon/0.5g cream
of tartar should be used per one egg white to create this effect.
1/2 teaspoon/2ml of lemon juice can also be used to create the
3) Sugar -- Sugar is added during
foam preparation because it creates smooth, stable foam one that
will not collapse and drain quickly.
Why fats kill an egg white foam?
Fat molecules also have both hydrophobic
and hydrophilic parts and will compete with proteins in the hydrophobic/hydrophilic
environment. The difference though is unlike proteins, fats don't
bond to each other side-to-side to form a reinforcing networks
instead they will compete with protein molecules in forming bonds.
So, the addition of any fat e.g,, egg yolks will interfere with
the formation of egg white foam. Note: Once
the protein complex is formed though it is safe to expose fat
molecules to it.
the best type of milk to produce a foam?
As in the
case of egg white foams it is the protein molecules that are responsible
for milk being able to be foamed. And, as in the case of egg whites
addition of fat will minimize the formation of foam. Foam stability
decreases with increasing fat reaching a minimum at about 5% and
then increases rapidly as fat is increased to 10%. At this point
highly stable cream type foams form. Therefore 'skim milk' will
produce the greatest volume and most stable foams, unless of course
you go very high fat (35%) where whipping cream will also produce
a very stable foam.
are two different types of proteins in milk: whey proteins and
caseins with caseins making up 80% of the total protein of milk.
Casein imparts good surface-active properties and thus plays a
role in the functional properties of whipping/foaming. Whey proteins
although offering less surface activity than casein, they offer
far superior foam stabilizing properties creating a more rigid
film at the air/water interface of the foam.
Both proteins are stable up to approximately 140F after which
they become susceptible to denaturation. At this temperature new
proteins are needed for stable foam so more milk must be added.
Effect does Temperature Have on Foaming Ability?
fat milk foams best at low temperatures. This also applies to
both whole milk and cream, although to a lesser extent. At temperatures
about 100F, on up through to 160F the trend is reversed with the
higher fat dairy products consistently exhibiting a greater volume
of foam being produced at any given point. In general temperature
trumps the influence of the fat on foaming.
Why make a
1- Foams can
produce a lighter feel than a to a thick sauce. 2- They can provide
both a tactile and textural aspects. 3- They can provide a visual
aspect to a dish.
How are Foams
You can "make"
foam with a stick blender, but for it to hold, you need a stabilizer
such as agar, gelatin, or lecithin. Many chefs are currently using
the ISI Canisters to
produce a foam. This also requires the presence of a foaming agent
AGENTS -- FOAM STABILIZERS:
agents is a surfactant, which when present in small amounts, facilitates
the formation of a foam, or enhances its stability by inhibiting
the coalescence of bubbles (see Foaming Agents -- Wikipedia)
A foam stabilizer
prevents or retards the coalescence of gas bubbles.
as a foaming agent
is a very efficient foam stabilizer and this property is exploited
in the manufacture of marshmallows. Different gelatins have different
foam stabilizing properties and gelatin for this use needs to
be carefully selected.
as a foaming agent
is classified as an amphoteric surfactant in that it can react
with either an acid or a base. It is ideal for converting juices
and watery liquids to airs and foams. To produce a stable foam,
start with a ration of .6% of lecithin.
making wasabi using lecithin foam video
or agar agar as a foaming agent
agar is a polymer made up of subunits of the sugar galactose.
Agar polysaccharides serve as the primary structural support for
the algae's cell walls.Agar is a gelatinous substance derived
from seaweed. Historically and in a modern context, it is chiefly
used as an ingredient in desserts throughout Japan, but in the
past century has found extensive use as a solid substrate to contain
culture medium for microbiological work. The gelling agent is
an unbranched polysaccharide obtained from the cell membranes
of some species of red algae, primarily from the genera Gelidium
and Gracilaria, or seaweed (Sphaerococcus euchema).
Commercially it is derived primarily from Gelidium amansii.
IN FOOD FOAMS
class II hydrophobin (HFBII)
in Culinary Foams has stimulated interest in researching new
substances that would create more stable foams. The class
II hydrophobin (HFBII) is an ultra low molecular weight protein
that is a highly surface-active protein. It has unique functions
as both superior adsorption on a solid surface and ability
to spread on hydrophobic surface. It has been shown to be
exceptionally stable in food foams compared to present stabilizers
(Cox et.al., 2008)
paper reports the use of a sucrose surfactant which forms
a coating around the air bubbles, but Bee added that others
are being investigated. "The surfactant has to be able to
form a crystalline layer that adsorbs to the surface," he
Polygonal Nanopatterning of Stable Microbubbles Emilie Dressaire,1
Rodney Bee,2 David C. Bell,1 Alex Lips,2 Howard A. Stone1*
Micrometer-sized bubbles are unstable and therefore difficult
to make and store for substantial lengths of time. Short-term
stabilization is achieved by the addition of amphiphilic molecules,
which reduce the driving force for dissolution. When these
molecules crystallize on the air/liquid interface, the lifetime
of individual bubbles may extend over a few months. We demonstrated
low gas-fraction dispersions with mean bubble radii of less
than 1 micrometer and stability lasting more than a year.
An insoluble, self-assembled surfactant layer covers the surface
of the microbubbles, which can result in nanometer-scale hexagonal
patterning that we explain with thermodynamic and molecular
models. The elastic response of the interface arrests the
shrinkage of the bubbles. Our study identifies a route to
fabricate highly stable dispersions of microbubbles.
R. Cox, Deborah L. Aldreda and Andrew B. Russell. Exceptional
stability of food foamsnext term using class II hydrophobin
HFBII , Food Hydrocolloids Volume 23, Issue 2, March 2009,
could extend shelf-life on food foams -- Beveragedaily.com
-- Interfacial polygonal nanopatterning of stable microbubbles
to froth milk -- From Coffee geeks site.
-- Molecular Structure